Exploring the Impact of Outdoor Activities and Sibling Compositions on Autism Spectrum Disorder: A Causal Mediation Analysis Using the National Survey of Children's Health in the United States

Exploring the Impact of Outdoor Activities and Sibling Compositions on Autism Spectrum Disorder: A Causal Mediation Analysis Using the National Survey of Children's Health in the United States | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Exploring the Impact of Outdoor Activities and Sibling Compositions on Autism Spectrum Disorder: A Causal Mediation Analysis Using the National Survey of Children's Health in the United States Md Roungu Ahmmad This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7206351/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Purpose Autism Spectrum Disorder (ASD) is a complex neurodevelopmental condition influenced by both environmental and familial factors. This study examined the association between ASD risk and (1) the duration of children's outdoor activities on weekdays and weekends, and (2) sibling composition, specifically the number and gender of siblings. Methods We analyzed cross-sectional data from the 2022 National Survey of Children’s Health (NSCH), including 22,294 children aged 3 to 5 years. Propensity Score Matching (PSM) was used to reduce selection bias by adjusting for covariates such as age, sex, race, anxiety, ADHD, and depression. Weighted logistic regression estimated adjusted odds ratios (wORs), and machine learning models assessed complex interaction effects. Results Outdoor activity was inversely associated with ASD. Compared to ≤ 1 hour, 2 hours of weekend activity reduced ASD odds by 43% (wOR = 0.57; 95% CI: 0.48–0.68), and ≥ 3 hours by 63% (wOR = 0.37; 95% CI: 0.31–0.44). On weekdays, 2 hours reduced odds by 49% (wOR = 0.51), and ≥ 3 hours by 58% (wOR = 0.42; 95% CI: 0.35–0.50). Having one female sibling halved ASD odds (wOR = 0.50), while male siblings increased risk (one: wOR = 2.25; two or more: wOR = 1.87). Machine learning identified highest ASD likelihood among children with no female siblings and limited outdoor activity, and lowest among those with female siblings and ≥ 3 weekend hours outdoors. Conclusion Extended outdoor activity and the presence of female siblings are associated with reduced ASD risk and may inform early prevention efforts. Psychiatry Statistical Epidemiology Autism Spectrum Disorder outdoor activity sibling composition NSCH Machine learning Figures Figure 1 Figure 2 1. Introduction ASD is a complex neurodevelopmental condition characterized by impairments in social communication, restricted interests, and repetitive behaviors (Kuenssberg et al., 2011 ). The global prevalence of ASD has risen significantly, with recent data from the Centers for Disease Control and Prevention (CDC) indicating that approximately 1 in 36 children in the United States are diagnosed with the disorder (Maenner, 2023 ). While genetic factors are well-established contributors to ASD etiology, growing evidence highlights the substantial role of environmental, familial influences, and lifestyle in modulating ASD risk and symptom severity (Bölte et al., 2019 ; Ji et al., 2023 ). Understanding the interplay between these factors is essential for mitigating the health burden associated with ASD, particularly for younger populations. Age, sex, and race are critical demographic factors associated with the diagnosis and prevalence of ASD. Sex differences are among the most consistent findings in ASD epidemiology. Males are significantly more likely to be diagnosed with ASD compared to females, with recent estimates indicating a male-to-female ratio of approximately 4:1 (Maenner, 2023 ). This disparity may reflect both biological differences (e.g., genetic susceptibility and neurodevelopmental pathways) and diagnostic biases, as females with ASD often present with subtler symptoms or more internalizing behaviors, leading to underdiagnosis or delayed diagnosis (Kreiser & White, 2014 ; Mao et al., 2024 ). Age of diagnosis also varies, with most children being identified around age 3–4 years, although early signs may be detectable in infancy (Jin et al., 2025 ; Maenner, 2023 ). Delayed diagnosis can be more common among racial minorities and in populations with limited access to healthcare (Favole et al., 2023 ; Liptak et al., 2008 ). Racial and ethnic disparities in ASD diagnosis have been well documented. Historically, White children in the United States have been more likely to be diagnosed with ASD compared to Black, Hispanic, and Asian children, even when symptom severity is comparable (Jamar, 2013 ; Jo et al., 2015 ). These differences are thought to stem from structural barriers, differences in access to developmental screening, and sociocultural perceptions of behavioral symptoms (Pham & Charles, 2023 ). However, more recent surveillance data from the CDC show a narrowing or even reversal of this gap in some regions, with higher ASD prevalence now reported among Black and Hispanic children in certain states, reflecting potential improvements in outreach and diagnostic equity (Investigators, 2012; Maenner, 2023 ). In addition, ASD frequently co-occurs with other neurodevelopmental and psychiatric conditions, particularly attention-deficit/hyperactivity disorder (ADHD), anxiety disorders, and depression. These comorbidities are not only common but significantly influence the clinical presentation, diagnosis, and outcomes of individuals with ASD (Avni et al., 2018 ; McBride et al., 2020 ). ADHD is among the most prevalent co-occurring conditions, with studies estimating that 30–80% of individuals with ASD meet criteria for ADHD, depending on age and diagnostic approach (Avni et al., 2018 ; Pehlivanidis et al., 2020 ). The two conditions share overlapping cognitive, behavioral, and neurobiological features-such as impairments in executive function, attention regulation, and social behavior-which can complicate differential diagnosis, particularly in early childhood (Tone & Tully, 2014 ). Anxiety disorders also affect a large proportion of individuals with ASD, with prevalence rates ranging from 40–50%, substantially higher than in the general population (Nimmo-Smith et al., 2020 ). Anxiety in ASD can be manifested atypically (e.g., through increased repetitive behaviors or resistance to change) and is often under-recognized, especially in minimally verbal individuals. The mechanisms linking ASD and anxiety are complex, involving shared genetic vulnerabilities, heightened sensory sensitivities, and difficulties with social cognition (Ji et al., 2023 ; White et al., 2014 ). Depression is another prevalent comorbidity, particularly in adolescents and adults with ASD, with estimates suggesting that up to 30% experience clinically significant depressive symptoms (Gotham et al., 2015 ; Hollocks et al., 2019 ). Depression in individuals with ASD is associated with social isolation, low self-esteem, and poor adaptive functioning. Importantly, co-occurring depression and anxiety can exacerbate core ASD symptoms and are linked with increased risk of suicidal ideation, underscoring the need for early screening and targeted intervention (Gupta et al., 2025 ; Hollocks et al., 2019 ). Besides that, ASD is a complex neurodevelopmental condition characterized by deficits in social communication and the presence of restricted and repetitive behaviors. While its etiology involves a combination of genetic and environmental factors, growing attention has been directed toward modifiable lifestyle and environmental exposures, such as outdoor activity, which may influence neurodevelopmental outcomes in children. Outdoor activity-particularly unstructured play in natural environments-is associated with numerous cognitive, emotional, and social benefits, including improved attention regulation, executive functioning, and emotional resilience, all of which are areas commonly affected in ASD (Mason et al., 2022 ). Additionally, outdoor time increases exposure to natural light and physical movement, which may positively impact vitamin D synthesis, circadian rhythm regulation, and reduced screen exposure-factors individually linked to neurodevelopmental outcomes (Sugiyama et al., 2023a ). While some studies have suggested that children with ASD engage in less outdoor activity compared to their neurotypical peers (Coughlan & Lynch, 2024 ; Ziegler & Morrier, 2022 ), the directionality and strength of this association remain underexplored, particularly in large, nationally representative populations. Moreover, few studies differentiate between weekday and weekend outdoor patterns, despite evidence suggesting that lifestyle behaviors and family routines vary significantly across the week and may differentially affect children’s development (Stone et al., 2014 ). Several studies have demonstrated that outdoor activities contribute significantly to children's development by improving motor skills, reducing stress, enhancing social interactions, and supporting sensory regulation (Bhat, 2021 ; Tamblyn et al., 2023 ). Furthermore, outdoor play has been identified as a protective factor that may mitigate the negative effects of excessive screen time on neurodevelopmental outcomes in young children (Sugiyama et al., 2023b ). For children with ASD, access to nature-based outdoor play environments has shown particular promise in fostering positive behavioral and learning outcomes (Haque, 2024 ). Specifically, such environments have been associated with increased engagement, improved communication, and enhanced adaptive functioning among children with ASD (Neville et al., 2021 ). Therefore, there is a pressing need for studies that examine how both weekday and weekend outdoor activity are associated with ASD risk, using robust, population-based data. Understanding these relationships could inform early intervention strategies and public health recommendations aimed at reducing modifiable risk factors for ASD or improving developmental trajectories for children at risk. Furthermore, sibling composition is increasingly being recognized as a potential influence on neurodevelopmental outcomes such as ASD. Siblings play a critical role in shaping early socialization, communication, and emotional development, all of which are core domains affected in ASD (Orsmond & Seltzer, 2007 ; Tsao et al., 2012 ). Existing literature has predominantly explored the genetic and environmental contributions of sibling presence to ASD risk, but findings remain mixed (Orsmond & Seltzer, 2007 ; Rosen, Schiltz, et al., 2022; Tsao et al., 2012 ), and sex-specific patterns in sibling composition have received limited empirical attention. The presence of female siblings may offer a social buffering effect through differences in play styles, communication, and nurturing behaviors, potentially supporting social development and reducing the severity of ASD symptoms (Garrido et al., 2020 ; Walton & Ingersoll, 2015 ). Birth order and sibling interactions have also been linked to variations in diagnostic timing, parental stress, and access to family resources-factors that may indirectly influence ASD risk and presentation (Alvares et al., 2021 ). However, sibling compositions-specifically the presence of male or female siblings within family-may play a significant role in shaping neurodevelopmental outcomes during early childhood. In addition, sibling composition may serve as an important contextual factor in mitigating the risk or indication of ASD in early childhood. Although several factors have been increasingly recognized as contributing to the etiology and indicators of ASD, the specific roles of sibling gender composition and engagement in outdoor activities-both on weekdays and weekends-remain underexplored. The direction and strength of these associations are not yet well established using large-scale population level data. There is a clear need for population-based research utilizing nationally representative datasets to investigate how variations in sibling sex composition and patterns of outdoor activity may independently or interactively influence ASD risk and developmental outcomes. Such research could offer valuable insights into modifiable risk factors associated with ASD, ultimately informing more targeted prevention and intervention strategies. 2. Methods 2.1. Study Population and Framework This study utilizes data from the 2022–2023 National Survey of Children's Health (NSCH), a representative dataset providing extensive information on child health, family dynamics, and social determinants of health in the United States. The target population consists of children aged 3–5 years, with a focus on those diagnosed with ASD or not. Data on outdoor activity levels, sibling composition, and various demographic and psychological factors were extracted for analysis. 2.2. Outcome Variable The primary outcome variable is the diagnosis of ASD, categorized as a binary variable (Yes/No). This information was obtained through parental reports of physician-diagnosed ASD. 2.3 Predictor Variables Outdoor Activity: Measured as the average duration of outdoor play per day on weekdays and weekends. Sibling Composition: Number of siblings in a household and their gender (e.g., presence of older/younger brothers or sisters). 2.4 Demographic Factors: selected subjects age, sex, and race/ethnicity. 2.5 Psychological Factors: Already known predictors with associated ASD psychological factors anxiety, Attention-Deficit/Hyperactivity Disorder (ADHD), and depression. 2.6 Inclusion and Exclusion Criteria: Children aged 3 to 5 years with complete data on ASD diagnosis and key predictor variables are included in this study. Children with missing data on ASD status, outdoor activity, or sibling composition, as well as those with severe comorbid neurodevelopmental conditions that could confound the analysis, are excluded to ensure the accuracy and reliability of the data analysis. 2.7 Statistical Methods Descriptive statistics were computed to summarize the demographic and clinical characteristics of the study population. Bivariate analyses, including chi-square tests, were used to compare children with and without ASD. To address potential selection bias and balance observed covariates, Propensity Score Matching (PSM) was implemented, matching children without ASD to those with ASD based on baseline predictors and known risk factors, including age, sex, race, anxiety, ADHD, and depression. The estimated propensity scores were derived from the following logistic model: $$\:ln\left[\frac{p\left(E\right)}{1-p\left(E\right)}\right]={\beta\:}_{1}\times\:Age+{\beta\:}_{2}\times\:Sex+{\beta\:}_{3}\times\:Race+{\beta\:}_{4}\times\:Anxiety+\:{\beta\:}_{5}\times\:ADHD+\:{\beta\:}_{6}\times\:Depression$$ , where E includes outdoor activity on weekends and weekdays, number of male siblings, and number of female siblings. Following PSM, weighted logistic regression was conducted to evaluate the association between the predictors ( E ) and the likelihood of ASD diagnosis: $$\:logit\left[p(ASD=1)\right]={\beta\:}_{0}+{\beta\:}_{1}\times\:E$$ , producing weighted odds ratios (wORs) and 95% confidence intervals (CIs). Risk ratios (RRs) with corresponding CIs were also calculated for group comparisons. Additionally, machine learning techniques were employed to further assess associations between predictors and ASD. All analyses were conducted in R using MatchIt and survey packages. A two-sided significance level of p < 0.05 was considered statistically significant. 3. Results The study sample consisted of 22,294 children with a mean age of 4.00 years (SD = 0.82), and an even distribution by sex (50.75% male, 49.25% female). Most participants were White (77.01%). The prevalence of ASD was 3.85%, while anxiety and ADHD were reported in 2.83% and 2.46% of children, respectively. Depression was rare (0.15%). More than half of the children (54.73%) engaged in three or more hours of outdoor activity per day on weekends, compared to only 33.02% on weekdays. Regarding sibling composition, 29.60% had no male siblings and 30.77% had no female siblings. Table 1 Descriptive Characteristics of the Study Population (N = 22,294) Characteristics levels Total, N = 22294 (%) Age in Years Mean (SD) 4 (0.82) Sex Female 10979 (49.25) Male 11315 (50.75) Race/Ethnicity Non-White 5126 (22.99) White 17168 (77.01) ASD No 21436 (96.15) Yes 858 (3.85) Anxiety No 21664 (97.17) Yes 630 (2.83) ADHD No 21745 (97.54) Yes 549 (2.46) Depression No 22261 (99.85) Yes 33 (0.15) Outdoor Activity Weekend =3Hours per day 12201 (54.73) Outdoor Activity Weekday =3Hours per day 7361 (33.02) Sibling Composition: Male No male sibling 6600 (29.60) One male sibling 10477 (46.99) Two male or more 5217 (23.40) Sibling Composition: Female No female sibling 6860 (30.77) One female sibling 10588 (47.49) Two female or more 4846 (21.74) Table 2 presents the incidence risk (IR) of ASD across various demographic and clinical subgroups within a sample of 22,294 children. The overall incidence risk of ASD was 3.85% (95% CI: 3.60–4.11%). Sex differences were pronounced, with males showing a significantly higher incidence of ASD (IR: 5.75%; 95% CI: 5.33–6.20%) compared to females (IR: 1.89%; 95% CI: 1.64–2.16%). Racial/ethnic disparities were also observed: Non-White children had a higher ASD incidence (5.19%; 95% CI: 4.60–5.83%) than White children (3.45%; 95% CI: 3.18–3.73%). Children with co-occurring mental health conditions had markedly higher ASD risks. Among those with anxiety, the IR was 24.44% (95% CI: 21.14–27.99%) compared to 3.25% (95% CI: 3.02–3.49%) in those without. Similarly, children with depression showed an IR of 28.96% (95% CI: 25.20–32.95%) versus 3.21% (95% CI: 2.98–3.46%) in those without. Those diagnosed with ADHD also had a significantly elevated risk (18.18%; 95% CI: 6.98–35.46%), though this group had a small sample size. Outdoor activity showed an inverse relationship with ASD incidence. Children who engaged in three or more hours of outdoor activity on weekends had a lower IR (2.62%; 95% CI: 2.35–2.92%) compared to those with one hour or less (7.13%; 95% CI: 6.36–7.96%). Similar patterns were observed on weekdays, where those active for three or more hours had a reduced ASD risk (2.54%; 95% CI: 2.19–2.93%) relative to those active for one hour or less (6.08%; 95% CI: 5.54–6.67%). Regarding sibling composition, children with no male siblings had the lowest ASD risk (1.95%; 95% CI: 1.63–2.32%), while those with one or more male siblings had elevated risks (4.84% and 4.26%, respectively). Likewise, having no female siblings was associated with a higher incidence (6.50%; 95% CI: 5.93–7.11%) compared to having one (2.84%; 95% CI: 2.53–3.18%) or two or more (2.29%; 95% CI: 1.89–2.75%) female siblings. Table 2 Incidence Risk of Autism Spectrum Disorder (ASD) by Population Characteristics with 95% Confidence Intervals Characteristics Levels Autism Spectrum Disorder (ASD) IR (95% CI) Yes No Total Age In Year Mean (SD) 4.00 (0.82) 4.09 (0.79) 4.02 (0.84) 0.97 (0.91 to 1.08) Sex Male 651 10666 11317 5.75 (5.33 to 6.20) Female 207 10772 10979 1.89 (1.64 to 2.16) Total 858 21438 22296 3.85 (3.60 to 4.11) Race Non-White 266 4860 5126 5.19 (4.60 to 5.83) White 592 16576 17168 3.45 (3.18 to 3.73) Total 858 21436 22294 3.85 (3.60 to 4.11) Anxiety Yes 154 476 630 24.44 (21.14 to 27.99) No 704 20960 21664 3.25 (3.02 to 3.49) Total 858 21436 22294 3.85 (3.60 to 4.11) Depression Yes 159 390 549 28.96 (25.20 to 32.95) No 699 21046 21745 3.21 (2.98 to 3.46) Total 858 21436 22294 3.85 (3.60 to 4.11) ADHD Yes 6 27 33 18.18 (6.98 to 35.46) No 852 21409 22261 3.83 (3.58 to 4.09) Total 858 21436 22294 3.85 (3.60 to 4.11) Outdoor Activity: Weekend 2 Hours Per Day 247 5763 6010 4.11 (3.62 to 4.64) = 3 Hours Per Day 320 11881 12201 2.62 (2.35 to 2.92) <= 1 Hour Per Day 291 3792 4083 7.13 (6.36 to 7.96) Total 611 15673 16284 3.75 (3.47 to 4.06) Outdoor Activity: Weekday 2 Hours Per Day 244 7671 7915 3.08 (2.71 to 3.49) = 3 Hours Per Day 187 7174 7361 2.54 (2.19 to 2.93) <= 1 Hour Per Day 427 6591 7018 6.08 (5.54 to 6.67) Total 614 13765 14379 4.27 (3.95 to 4.61) Sibling Composition: Male 1 Male Sibling 507 9970 10477 4.84 (4.44 to 5.27) No Male Sibling 129 6471 6600 1.95 (1.63 to 2.32) Total 636 16441 17077 3.72 (3.45 to 4.02) >= 2 Male Sibling 222 4995 5217 4.26 (3.72 to 4.84) No Male Sibling 129 6471 6600 1.95 (1.63 to 2.32) Total 351 11466 11817 2.97 (2.67 to 3.29) Sibling Composition: Female 1 Female Sibling 301 10287 10588 2.84 (2.53 to 3.18) No Female Sibling 446 6414 6860 6.50 (5.93 to 7.11) Total 747 16701 17448 4.28 (3.99 to 4.59) >= 2 Female Sibling 111 4735 4846 2.29 (1.89 to 2.75) No Female Sibling 446 6414 6860 6.50 (5.93 to 7.11) Total 557 11149 11706 4.76 (4.38 to 5.16) IR: Incidence Risk, CI: Confidence Interval Figure 1 presents the incidence risk ratios (IRRs) and 95% confidence intervals for ASD based on demographic, clinical, environmental, and familial predictors, complementing the findings in Table 2 . Consistent with the descriptive analysis, male sex was associated with a significantly higher risk of ASD compared to female sex (IRR > 2.5), confirming known sex disparities in ASD prevalence. Children from non-White racial/ethnic groups had a slightly higher risk compared to White children. The presence of mental health comorbidities, including depression, anxiety, and ADHD, was associated with markedly elevated ASD risk. Children with depression had the highest IRR, followed by those with anxiety and ADHD, highlighting the strong co-occurrence between ASD and other neurodevelopmental or psychiatric conditions. A protective pattern emerged for outdoor physical activity, with children engaging in ≥ 3 hours of activity per day on both weekdays and weekends showing substantially reduced ASD risk compared to those active for ≤ 1 hour. Regarding sibling composition, having no siblings, particularly no female siblings, was associated with higher ASD risk. In contrast, the presence of one or more male siblings was linked to an increase ASD risk, indicating that sibling interactions may influence early developmental outcomes. Table 3 presents findings from weighted logistic regression models evaluating the associations between outdoor activity, sibling composition, and the risk of ASD, after adjusting for demographic variables and co-occurring psychological conditions using propensity score weighting. Outdoor activity was significantly associated with ASD risk. Compared to children who spent one hour or less outdoors per day, those who engaged in two hours of outdoor activity on weekends had 43% lower odds of ASD (adjusted weighted odds ratio [wOR] = 0.57; 95% CI: 0.48–0.68; p < 0.001). The protective effect was even stronger among children who spent three or more hours outdoors, with 63% reduced odds (wOR = 0.37; 95% CI: 0.31–0.44; p < 0.001). Similar trends were observed for weekday activity: two hours per day was associated with a 49% reduction in odds (wOR = 0.51; 95% CI: 0.43–0.60; p < 0.001), and three or more hours yielded a 58% reduction (wOR = 0.42; 95% CI: 0.35–0.50; p < 0.001). In terms of sibling composition, the presence of male siblings was positively associated with ASD risk. Compared to children with no male siblings, those with one male sibling had more than twice the odds of ASD (wOR = 2.25; 95% CI: 1.85–2.74; p < 0.001), while those with two or more male siblings had 1.87-fold increased odds (wOR = 1.87; 95% CI: 1.44–2.44; p < 0.001). Conversely, the presence of female siblings was inversely associated with ASD. Having one female sibling was associated with 50% lower odds of ASD (wOR = 0.50; 95% CI: 0.42–0.58; p < 0.001), and having two or more female siblings was associated with a 44% reduction in odds (wOR = 0.56; 95% CI: 0.43–0.74; p < 0.001). Table 3 Weighted Logistic Regression Models Estimating the Associations Between Outdoor Activity, Sibling Composition, and autism spectrum disorder (ASD), Adjusted for Demographic and Co-occurring Psychological Factors (NSCH 2022–2023). Predictors Levels wOR 1 95% CI p-value LL UL Outdoor Activities Weekend Less than or equal one hour per day Ref Two hours per day 0.57 0.48 0.68 < 0.001 Three or more hours per day 0.37 0.31 0.44 < 0.001 Weekday Less than or equal one hour per day Ref Two hours per day 0.51 0.43 0.60 < 0.001 Three or more hours per day 0.42 0.35 0.50 < 0.001 Sibling Composition Male Sibling No male sibling Ref One male sibling 2.25 1.85 2.74 < 0.001 Two or more male sibling 1.87 1.44 2.44 < 0.001 Female Sibling No female sibling Ref One female sibling 0.50 0.42 0.58 < 0.001 Two or more female sibling 0.56 0.43 0.74 < 0.001 Note: Results are presented as adjusted weighted odds ratios (wORs) with 95% confidence intervals (CIs), LL: Lower Limit, UL: Upper Limit, and associated p-values. The data was matched using PSM of the confounder factors, age, sex, race/ethnicity, anxiety, ADHD, and depression. All the confounding factors are insignificant in the weighted regression models. Figure 3 illustrates a regression tree model that examines the interaction between sibling composition and outdoor activity patterns in relation to ASD and provides potential subgroup for higher risk of ASD. The model identifies distinct subgroups, or terminal nodes, with varying profiles of ASD. Each node represents a unique combination of predictor variables and highlights patterns of risk across the study population. The most influential predictor was the number of female siblings ( p < 0.001). Children with no female siblings (n = 4,372) had a substantially higher probability of ASD compared to those with at least one female sibling (n = 19,434). Within the group with no female siblings, further stratification by weekday outdoor activity ( p < 0.001) showed that children who spent one hour or less outdoors per weekday were at greater risk profiles. Among them, those who also engaged in two hours or less of weekend outdoor activity had the highest ASD probability at approximately 15% (Node 4). If weekend outdoor time exceeded two hours, the ASD probability decreased to approximately 10% (Node 5). Additionally, children without female siblings who spent 2–3 hours outdoors on weekdays but had limited weekend activity still exhibited a relatively elevated ASD probability of approximately 10% (Node 8). Among children without female siblings who spent more than three hours outdoors on weekdays, the number of male siblings ( p < 0.001) and weekend outdoor activity ( p = 0.003) further influenced ASD risk. Those with one or more male siblings and less than one hour of weekend outdoor time had an ASD probability of 7% (Node 9), while those with greater weekend outdoor engagement had a lower probability of 5% (Node 10). In contrast, among children with at least one female sibling, weekend outdoor activity duration was the key discriminator ( p < 0.001). Those with two or fewer hours of weekend outdoor time and two or more male siblings had an ASD probability of 8% (Node 14), compared to 3% for those with one or no male siblings (Node 13). Furthermore, when weekday outdoor time reached three or more hours among children with at least one female sibling and over two hours of weekend outdoor activity, the ASD probability dropped to 2% (Node 17)-the lowest observed across all subgroups. 4. Discussion This study provides compelling evidence on the influence of outdoor activity duration (weekend and weekday) and sibling composition on children's behavioral and emotional outcomes, based on a nationally representative sample from the 2022–2023 National Survey of Children’s Health (NSCH) data. Our analysis highlights how structured outdoor time-both on weekdays and weekends-and sibling composition are significant predictors of ASD, even after adjusting for demographic and psychological confounders through propensity score weighting and machine learning methodology. A central finding from the regression models is the protective association between increased duration of outdoor activities and reduced odds of ASD. Children who engaged in outdoor activities for two hours or more per day-on both weekdays and weekends-had significantly lower adjusted odds of ASD as compared to those with one hour or less. Specifically, children who spent three or more hours outdoors on weekends had 63% lower odds (OR = 0.37, p < 0.001), and those with similar weekday exposure had 58% reduced odds (OR = 0.42, p < 0.001). These results align with previous findings who emphasized the psychological and developmental benefits of outdoor free play and green space exposure (Haque, 2024 ; Ziegler & Morrier, 2022 ). Outdoor activity promotes not only physical health but also supports emotional regulation, social interaction, and cognitive flexibility-factors associated with reduced behavioral disorders such as ADHD and conduct problems (Haque, 2024 ; Hendrickson, 2019 ; Sugiyama et al., 2023b ). The regression tree model further supports these results by identifying weekday and weekend outdoor activity as primary nodes in classifying children with higher or lower behavioral risk. Among children without female siblings, outdoor activity on weekdays and weekends served as significant split criteria, indicating their critical role in this subgroup. The model demonstrates that even among children with sibling-related risk factors, increased outdoor activity consistently shifts the probability of behavioral problems downward. Sibling composition emerged as another major factor. Notably, having one or more male siblings was associated with increased odds of ASD (e.g., one male sibling: OR = 2.25, p < 0.001), while the presence of female siblings was associated with decreased odds (e.g., one female sibling: OR = 0.50, p < 0.001). This differential pattern may reflect the role of gendered sibling interactions in shaping emotional and social development. Research suggested that male siblings are more likely to engage in competitive or externalizing behavior, which may amplify emotional dysregulation, whereas female siblings often foster prosocial and emotionally supportive dynamics (Dirks et al., 2015 ; Waid et al., 2020 ; Walton & Ingersoll, 2015 ). These dynamics might be particularly influential during middle childhood, a period when peer modeling and familial interactions shape behavioral trajectories (Ladd, 1999 ; Rosen, McCauley, et al., 2022). However, some studies had suggested that the presence of male siblings may contribute positively to the social and psychological development of children (Sang & Nelson, 2017 ). Male siblings often engage in cooperative and task-oriented play, which can foster a supportive and structured environment conducive to developing teamwork, problem-solving, and conflict-resolution skills (Bryant, 1982 ). Such interactions may indirectly support emotional regulation and psychological well-being by encouraging mutual support and shared responsibilities within the family context (Ngai et al., 2021 ). Our findings are consistent with previous research indicating that positive sibling relationships, particularly those involving older or same-gender sisters-can serve as protective factors against internalizing and externalizing disorders in children and adolescents. Some researchers reported that emotionally supportive sibling interactions are linked to lower levels of anxiety, depression, and behavioral difficulties, emphasizing siblings as important sources of emotional regulation and social learning (Feinberg et al., 2012 ; Milevsky, 2005 ). Similarly, found that high-quality sibling relationships are associated with better psychosocial adjustment across developmental stages (Kim et al., 2007 ). Conversely, several studies have shown that sibling conflict, rivalry, and the modeling of aggressive or antisocial behavior-more common among same-gender male siblings-can exacerbate behavioral problems. Researchers noted that coercive or hostile sibling dynamics are predictive of higher levels of externalizing behaviors (Buist et al., 2013 ; Stormshak et al., 1996 ). These findings highlight the complex and bidirectional nature of sibling influences on child development, serving as either protective or risk-enhancing depending on the relational context. Finally, the interaction between outdoor activity and sibling composition suggests that time spent outdoors may attenuate some of the negative effects associated with male sibling presence. The classification tree analysis revealed significant interactions between sibling composition and outdoor activity patterns in relation to ASD diagnosis. The most prominent initial split in the tree was based on the number of female siblings suggesting that the presence of female siblings plays a central role in differentiating ASD outcomes. Among children with no female siblings, weekday outdoor activity emerged as the next critical factor. Those with ≤ 1 hour of outdoor play on weekdays followed by ≤ 2 hours on weekends showed the highest proportion of ASD diagnoses, indicating that limited physical activity may be associated with increased ASD risk in the absence of female sibling support. Conversely, for children with at least one female sibling, outdoor weekend activity were associated with a lower likelihood of ASD, particularly in children with at least one or more female sibling, suggesting a potential protective effect of both increased outdoor engagement and female sibling presence in certain contexts. These findings emphasize the potential value of promoting outdoor play-especially during weekends-and considering sibling dynamics in early screening and intervention efforts for children at risk of ASD. Further research is needed to explore the causal mechanisms and to evaluate whether these factors may serve as modifiable targets for prevention strategies. This study has several strengths, including the use of nationally representative data, adjustment for co-occurring psychological conditions, and the integration of both traditional regression and machine learning methods (e.g., regression trees). However, some limitations must be acknowledged. The cross-sectional nature of the data limits causal inference, and behavioral outcomes were based on parental report, which may introduce bias. Additionally, unmeasured factors such as parenting style, peer relationships, or school environment could confound observed associations. 5. Conclusion The study findings underscore the importance of outdoor activity and sibling compositions in shaping child behavioral health. Public health interventions aimed at promoting regular outdoor engagement-particularly among children with higher familial risk (e.g., presence of male siblings)-could serve as a protective strategy to improve developmental outcomes. Policies that encourage safe outdoor spaces, green schoolyards, and community programs may be particularly impactful. Future longitudinal research is warranted to further explore causal pathways and the role of mediators such as peer interactions, screen time, and parenting practices. Declarations Declaration of generative AI and AI-assisted technologies in the writing process During the preparation of this work the author(s) used chatgpt.com to improve readability and language’s structure formations. After using this tool/service, the author(s) reviewed and edited the content as needed and took(s) full responsibility for the content of the publication. Funding: None Declaration of Interest The authors declare no conflicts of interest relevant to the content of this manuscript. No financial or personal relationships with individuals or organizations have influenced the findings reported in this study. 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Empathy as a “risky strength”: A multilevel examination of empathy and risk for internalizing disorders. Development and Psychopathology , 26 (4pt2), 1547–1565. https://doi.org/10.1017/S0954579414001199 Tsao, L.-L., Davenport, R., & Schmiege, C. (2012). Supporting Siblings of Children with Autism Spectrum Disorders. Early Childhood Education Journal , 40 (1), 47–54. https://doi.org/10.1007/s10643-011-0488-3 Waid, J. D., Tanana, M. J., Vanderloo, M. J., Voit, R., & Kothari, B. H. (2020). The role of siblings in the development of externalizing behaviors during childhood and adolescence: A scoping review. Journal of Family Social Work , 23 (4), 318–337. https://doi.org/10.1080/10522158.2020.1799893 Walton, K. M., & Ingersoll, B. R. (2015). Psychosocial Adjustment and Sibling Relationships in Siblings of Children with Autism Spectrum Disorder: Risk and Protective Factors. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7206351","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":490379042,"identity":"6827d256-662b-4489-a053-0cf55e302889","order_by":0,"name":"Md Roungu Ahmmad","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAArElEQVRIiWNgGAWjYDACCRDBZsPAwHyAgYGHBC1pQJxAmpbDJGjhn92duuFH2fnE+W0MjA/ethFjyZ2z2272nLuduOEYA7PhXGK0MNzI3XaDtw2oRb6BTZqXGC3yQC03/7adAzmM/TdRWgyAWm7zth1IbDjGwMZMlBZDkBaZc8nGG44xNkvOOUeEFjmQw96U2cnOb2M++OFNGRFakABjA2nqR8EoGAWjYBTgBgDrEDuWww1PdwAAAABJRU5ErkJggg==","orcid":"https://orcid.org/0000-0002-3886-5777","institution":"University of South Florida","correspondingAuthor":true,"prefix":"","firstName":"Md","middleName":"Roungu","lastName":"Ahmmad","suffix":""}],"badges":[],"createdAt":"2025-07-24 14:02:28","currentVersionCode":1,"declarations":{"humanSubjects":false,"vertebrateSubjects":false,"conflictsOfInterestStatement":false,"humanSubjectEthicalGuidelines":false,"humanSubjectConsent":false,"humanSubjectClinicalTrial":false,"humanSubjectCaseReport":false,"vertebrateSubjectEthicalGuidelines":false},"doi":"10.21203/rs.3.rs-7206351/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7206351/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":87803971,"identity":"59b15ee0-95c4-4ff4-9f88-2d004f6c30b5","added_by":"auto","created_at":"2025-07-29 08:12:23","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":9081,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eAssociations Between Demographic, Clinical, Environmental, and Familial Predictors and Autism Spectrum Disorder (ASD) Risk: Incidence Rate Ratios (IRR) Based on 2022–2023 National Survey of Children’s Health Data.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-7206351/v1/57053a72e87281eba02c4d0d.png"},{"id":87804633,"identity":"dc3510cf-f0a9-4cb0-9281-3a813525fbe8","added_by":"auto","created_at":"2025-07-29 08:20:23","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":25321,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFigure 3. Exploring the Influence of Sibling Composition and Outdoor Activity Patterns on Autism Spectrum Disorder Risk: Evidence from a Regression Tree Analysis of the NSCH data.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-7206351/v1/21bf74336ea730d6548e3d18.png"},{"id":87805673,"identity":"0987ce57-368e-4cdd-a3b4-c6f22e1d9e11","added_by":"auto","created_at":"2025-07-29 08:28:24","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1109472,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7206351/v1/5844ebb4-bef2-431e-84d3-fe6741398265.pdf"}],"financialInterests":"The authors declare no competing interests.","formattedTitle":"\u003cp\u003e\u003cstrong\u003eExploring the Impact of Outdoor Activities and Sibling Compositions on Autism Spectrum Disorder: A Causal Mediation Analysis Using the National Survey of Children's Health in the United States\u003c/strong\u003e\u003c/p\u003e","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eASD is a complex neurodevelopmental condition characterized by impairments in social communication, restricted interests, and repetitive behaviors (Kuenssberg et al., \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). The global prevalence of ASD has risen significantly, with recent data from the Centers for Disease Control and Prevention (CDC) indicating that approximately 1 in 36 children in the United States are diagnosed with the disorder (Maenner, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). While genetic factors are well-established contributors to ASD etiology, growing evidence highlights the substantial role of environmental, familial influences, and lifestyle in modulating ASD risk and symptom severity (B\u0026ouml;lte et al., \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Ji et al., \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Understanding the interplay between these factors is essential for mitigating the health burden associated with ASD, particularly for younger populations.\u003c/p\u003e\u003cp\u003eAge, sex, and race are critical demographic factors associated with the diagnosis and prevalence of ASD. Sex differences are among the most consistent findings in ASD epidemiology. Males are significantly more likely to be diagnosed with ASD compared to females, with recent estimates indicating a male-to-female ratio of approximately 4:1 (Maenner, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). This disparity may reflect both biological differences (e.g., genetic susceptibility and neurodevelopmental pathways) and diagnostic biases, as females with ASD often present with subtler symptoms or more internalizing behaviors, leading to underdiagnosis or delayed diagnosis (Kreiser \u0026amp; White, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Mao et al., \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Age of diagnosis also varies, with most children being identified around age 3\u0026ndash;4 years, although early signs may be detectable in infancy (Jin et al., \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2025\u003c/span\u003e; Maenner, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Delayed diagnosis can be more common among racial minorities and in populations with limited access to healthcare (Favole et al., \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Liptak et al., \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2008\u003c/span\u003e). Racial and ethnic disparities in ASD diagnosis have been well documented. Historically, White children in the United States have been more likely to be diagnosed with ASD compared to Black, Hispanic, and Asian children, even when symptom severity is comparable (Jamar, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Jo et al., \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). These differences are thought to stem from structural barriers, differences in access to developmental screening, and sociocultural perceptions of behavioral symptoms (Pham \u0026amp; Charles, \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). However, more recent surveillance data from the CDC show a narrowing or even reversal of this gap in some regions, with higher ASD prevalence now reported among Black and Hispanic children in certain states, reflecting potential improvements in outreach and diagnostic equity (Investigators, 2012; Maenner, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2023\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eIn addition, ASD frequently co-occurs with other neurodevelopmental and psychiatric conditions, particularly attention-deficit/hyperactivity disorder (ADHD), anxiety disorders, and depression. These comorbidities are not only common but significantly influence the clinical presentation, diagnosis, and outcomes of individuals with ASD (Avni et al., \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; McBride et al., \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). ADHD is among the most prevalent co-occurring conditions, with studies estimating that 30\u0026ndash;80% of individuals with ASD meet criteria for ADHD, depending on age and diagnostic approach (Avni et al., \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Pehlivanidis et al., \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). The two conditions share overlapping cognitive, behavioral, and neurobiological features-such as impairments in executive function, attention regulation, and social behavior-which can complicate differential diagnosis, particularly in early childhood (Tone \u0026amp; Tully, \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e2014\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eAnxiety disorders also affect a large proportion of individuals with ASD, with prevalence rates ranging from 40\u0026ndash;50%, substantially higher than in the general population (Nimmo-Smith et al., \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Anxiety in ASD can be manifested atypically (e.g., through increased repetitive behaviors or resistance to change) and is often under-recognized, especially in minimally verbal individuals. The mechanisms linking ASD and anxiety are complex, involving shared genetic vulnerabilities, heightened sensory sensitivities, and difficulties with social cognition (Ji et al., \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; White et al., \u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). Depression is another prevalent comorbidity, particularly in adolescents and adults with ASD, with estimates suggesting that up to 30% experience clinically significant depressive symptoms (Gotham et al., \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Hollocks et al., \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Depression in individuals with ASD is associated with social isolation, low self-esteem, and poor adaptive functioning. Importantly, co-occurring depression and anxiety can exacerbate core ASD symptoms and are linked with increased risk of suicidal ideation, underscoring the need for early screening and targeted intervention (Gupta et al., \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2025\u003c/span\u003e; Hollocks et al., \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2019\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eBesides that, ASD is a complex neurodevelopmental condition characterized by deficits in social communication and the presence of restricted and repetitive behaviors. While its etiology involves a combination of genetic and environmental factors, growing attention has been directed toward modifiable lifestyle and environmental exposures, such as outdoor activity, which may influence neurodevelopmental outcomes in children. Outdoor activity-particularly unstructured play in natural environments-is associated with numerous cognitive, emotional, and social benefits, including improved attention regulation, executive functioning, and emotional resilience, all of which are areas commonly affected in ASD (Mason et al., \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). Additionally, outdoor time increases exposure to natural light and physical movement, which may positively impact vitamin D synthesis, circadian rhythm regulation, and reduced screen exposure-factors individually linked to neurodevelopmental outcomes (Sugiyama et al., \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2023a\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eWhile some studies have suggested that children with ASD engage in less outdoor activity compared to their neurotypical peers (Coughlan \u0026amp; Lynch, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2024\u003c/span\u003e; Ziegler \u0026amp; Morrier, \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e2022\u003c/span\u003e), the directionality and strength of this association remain underexplored, particularly in large, nationally representative populations. Moreover, few studies differentiate between weekday and weekend outdoor patterns, despite evidence suggesting that lifestyle behaviors and family routines vary significantly across the week and may differentially affect children\u0026rsquo;s development (Stone et al., \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). Several studies have demonstrated that outdoor activities contribute significantly to children's development by improving motor skills, reducing stress, enhancing social interactions, and supporting sensory regulation (Bhat, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Tamblyn et al., \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Furthermore, outdoor play has been identified as a protective factor that may mitigate the negative effects of excessive screen time on neurodevelopmental outcomes in young children (Sugiyama et al., \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2023b\u003c/span\u003e). For children with ASD, access to nature-based outdoor play environments has shown particular promise in fostering positive behavioral and learning outcomes (Haque, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Specifically, such environments have been associated with increased engagement, improved communication, and enhanced adaptive functioning among children with ASD (Neville et al., \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Therefore, there is a pressing need for studies that examine how both weekday and weekend outdoor activity are associated with ASD risk, using robust, population-based data. Understanding these relationships could inform early intervention strategies and public health recommendations aimed at reducing modifiable risk factors for ASD or improving developmental trajectories for children at risk.\u003c/p\u003e\u003cp\u003eFurthermore, sibling composition is increasingly being recognized as a potential influence on neurodevelopmental outcomes such as ASD. Siblings play a critical role in shaping early socialization, communication, and emotional development, all of which are core domains affected in ASD (Orsmond \u0026amp; Seltzer, \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2007\u003c/span\u003e; Tsao et al., \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). Existing literature has predominantly explored the genetic and environmental contributions of sibling presence to ASD risk, but findings remain mixed (Orsmond \u0026amp; Seltzer, \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2007\u003c/span\u003e; Rosen, Schiltz, et al., 2022; Tsao et al., \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e2012\u003c/span\u003e), and sex-specific patterns in sibling composition have received limited empirical attention. The presence of female siblings may offer a social buffering effect through differences in play styles, communication, and nurturing behaviors, potentially supporting social development and reducing the severity of ASD symptoms (Garrido et al., \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Walton \u0026amp; Ingersoll, \u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). Birth order and sibling interactions have also been linked to variations in diagnostic timing, parental stress, and access to family resources-factors that may indirectly influence ASD risk and presentation (Alvares et al., \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). However, sibling compositions-specifically the presence of male or female siblings within family-may play a significant role in shaping neurodevelopmental outcomes during early childhood. In addition, sibling composition may serve as an important contextual factor in mitigating the risk or indication of ASD in early childhood.\u003c/p\u003e\u003cp\u003eAlthough several factors have been increasingly recognized as contributing to the etiology and indicators of ASD, the specific roles of sibling gender composition and engagement in outdoor activities-both on weekdays and weekends-remain underexplored. The direction and strength of these associations are not yet well established using large-scale population level data. There is a clear need for population-based research utilizing nationally representative datasets to investigate how variations in sibling sex composition and patterns of outdoor activity may independently or interactively influence ASD risk and developmental outcomes. Such research could offer valuable insights into modifiable risk factors associated with ASD, ultimately informing more targeted prevention and intervention strategies.\u003c/p\u003e"},{"header":"2. Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\n \u003ch2\u003e2.1. Study Population and Framework\u003c/h2\u003e\n \u003cp\u003eThis study utilizes data from the 2022\u0026ndash;2023 National Survey of Children\u0026apos;s Health (NSCH), a representative dataset providing extensive information on child health, family dynamics, and social determinants of health in the United States. The target population consists of children aged 3\u0026ndash;5 years, with a focus on those diagnosed with ASD or not. Data on outdoor activity levels, sibling composition, and various demographic and psychological factors were extracted for analysis.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\n \u003ch2\u003e2.2. Outcome Variable\u003c/h2\u003e\n \u003cp\u003eThe primary outcome variable is the diagnosis of ASD, categorized as a binary variable (Yes/No). This information was obtained through parental reports of physician-diagnosed ASD.\u003c/p\u003e\n \u003cp\u003e\u003cspan\u003e2.3 Predictor Variables\u003c/span\u003e\u003c/p\u003e\n \u003cul\u003e\n \u003cli\u003eOutdoor Activity: Measured as the average duration of outdoor play per day on weekdays and weekends.\u003c/li\u003e\n \u003cli\u003eSibling Composition: Number of siblings in a household and their gender (e.g., presence of older/younger brothers or sisters).\u003c/li\u003e\n \u003c/ul\u003e2.4 Demographic Factors: selected subjects age, sex, and race/ethnicity.\u003cbr\u003e\u003cspan\u003e2.5 Psychological Factors: Already known predictors with associated ASD psychological factors anxiety, Attention-Deficit/Hyperactivity Disorder (ADHD), and depression.\u003cbr\u003e\u003c/span\u003e\u003cspan\u003e2.6 Inclusion and Exclusion Criteria: Children aged 3 to 5 years with complete data on ASD diagnosis and key predictor variables are included in this study. Children with missing data on ASD status, outdoor activity, or sibling composition, as well as those with severe comorbid neurodevelopmental conditions that could confound the analysis, are excluded to ensure the accuracy and reliability of the data analysis.\u003cbr\u003e\u003c/span\u003e\u003cspan\u003e2.7 Statistical Methods\u003c/span\u003e\u003cbr\u003e\n \u003cp\u003eDescriptive statistics were computed to summarize the demographic and clinical characteristics of the study population. Bivariate analyses, including chi-square tests, were used to compare children with and without ASD. To address potential selection bias and balance observed covariates, Propensity Score Matching (PSM) was implemented, matching children without ASD to those with ASD based on baseline predictors and known risk factors, including age, sex, race, anxiety, ADHD, and depression. The estimated propensity scores were derived from the following logistic model:\u003c/p\u003e\n \u003cdiv id=\"Equa\" class=\"Equation\"\u003e\n \u003cdiv class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e$$\\:ln\\left[\\frac{p\\left(E\\right)}{1-p\\left(E\\right)}\\right]={\\beta\\:}_{1}\\times\\:Age+{\\beta\\:}_{2}\\times\\:Sex+{\\beta\\:}_{3}\\times\\:Race+{\\beta\\:}_{4}\\times\\:Anxiety+\\:{\\beta\\:}_{5}\\times\\:ADHD+\\:{\\beta\\:}_{6}\\times\\:Depression$$\u003c/div\u003e\n \u003c/div\u003e,\u003cbr\u003e\n \u003cp\u003ewhere \u003cem\u003eE\u003c/em\u003e includes outdoor activity on weekends and weekdays, number of male siblings, and number of female siblings. Following PSM, weighted logistic regression was conducted to evaluate the association between the predictors (\u003cem\u003eE\u003c/em\u003e) and the likelihood of ASD diagnosis:\u003c/p\u003e\n \u003cdiv id=\"Equb\" class=\"Equation\"\u003e\n \u003cdiv class=\"mathdisplay\" id=\"FileID_Equb\" name=\"EquationSource\"\u003e$$\\:logit\\left[p(ASD=1)\\right]={\\beta\\:}_{0}+{\\beta\\:}_{1}\\times\\:E$$\u003c/div\u003e\n \u003c/div\u003e,\u003cbr\u003e\n \u003cp\u003eproducing weighted odds ratios (wORs) and 95% confidence intervals (CIs). Risk ratios (RRs) with corresponding CIs were also calculated for group comparisons. Additionally, machine learning techniques were employed to further assess associations between predictors and ASD. All analyses were conducted in R using MatchIt and \u003cem\u003esurvey\u003c/em\u003e packages. A two-sided significance level of \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05 was considered statistically significant.\u003c/p\u003e\n\u003c/div\u003e"},{"header":"3. Results","content":"\u003cp\u003eThe study sample consisted of 22,294 children with a mean age of 4.00 years (SD\u0026thinsp;=\u0026thinsp;0.82), and an even distribution by sex (50.75% male, 49.25% female). Most participants were White (77.01%). The prevalence of ASD was 3.85%, while anxiety and ADHD were reported in 2.83% and 2.46% of children, respectively. Depression was rare (0.15%). More than half of the children (54.73%) engaged in three or more hours of outdoor activity per day on weekends, compared to only 33.02% on weekdays. Regarding sibling composition, 29.60% had no male siblings and 30.77% had no female siblings.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eDescriptive Characteristics of the Study Population (N\u0026thinsp;=\u0026thinsp;22,294)\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"3\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCharacteristics\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003elevels\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eTotal,\u003c/p\u003e\u003cp\u003eN\u0026thinsp;=\u0026thinsp;22294 (%)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAge in Years\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMean (SD)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e4 (0.82)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSex\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eFemale\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e10979 (49.25)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMale\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e11315 (50.75)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRace/Ethnicity\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNon-White\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e5126 (22.99)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eWhite\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e17168 (77.01)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eASD\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNo\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e21436 (96.15)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eYes\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e858 (3.85)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAnxiety\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNo\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e21664 (97.17)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eYes\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e630 (2.83)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eADHD\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNo\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e21745 (97.54)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eYes\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e549 (2.46)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDepression\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNo\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e22261 (99.85)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eYes\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e33 (0.15)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eOutdoor Activity Weekend\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u0026lt;=1Hour per day\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e4083 (18.31)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e2Hour per day\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e6010 (26.96)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u0026gt;=3Hours per day\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e12201 (54.73)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eOutdoor Activity Weekday\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u0026lt;=1Hour per day\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e7018 (31.48)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e2Hour per day\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e7915 (35.50)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u0026gt;=3Hours per day\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e7361 (33.02)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSibling Composition: Male\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNo male sibling\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e6600 (29.60)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eOne male sibling\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e10477 (46.99)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTwo male or more\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e5217 (23.40)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSibling Composition: Female\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNo female sibling\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e6860 (30.77)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eOne female sibling\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e10588 (47.49)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTwo female or more\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e4846 (21.74)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e presents the incidence risk (IR) of ASD across various demographic and clinical subgroups within a sample of 22,294 children. The overall incidence risk of ASD was 3.85% (95% CI: 3.60\u0026ndash;4.11%). Sex differences were pronounced, with males showing a significantly higher incidence of ASD (IR: 5.75%; 95% CI: 5.33\u0026ndash;6.20%) compared to females (IR: 1.89%; 95% CI: 1.64\u0026ndash;2.16%). Racial/ethnic disparities were also observed: Non-White children had a higher ASD incidence (5.19%; 95% CI: 4.60\u0026ndash;5.83%) than White children (3.45%; 95% CI: 3.18\u0026ndash;3.73%). Children with co-occurring mental health conditions had markedly higher ASD risks. Among those with anxiety, the IR was 24.44% (95% CI: 21.14\u0026ndash;27.99%) compared to 3.25% (95% CI: 3.02\u0026ndash;3.49%) in those without. Similarly, children with depression showed an IR of 28.96% (95% CI: 25.20\u0026ndash;32.95%) versus 3.21% (95% CI: 2.98\u0026ndash;3.46%) in those without. Those diagnosed with ADHD also had a significantly elevated risk (18.18%; 95% CI: 6.98\u0026ndash;35.46%), though this group had a small sample size.\u003c/p\u003e\u003cp\u003eOutdoor activity showed an inverse relationship with ASD incidence. Children who engaged in three or more hours of outdoor activity on weekends had a lower IR (2.62%; 95% CI: 2.35\u0026ndash;2.92%) compared to those with one hour or less (7.13%; 95% CI: 6.36\u0026ndash;7.96%). Similar patterns were observed on weekdays, where those active for three or more hours had a reduced ASD risk (2.54%; 95% CI: 2.19\u0026ndash;2.93%) relative to those active for one hour or less (6.08%; 95% CI: 5.54\u0026ndash;6.67%). Regarding sibling composition, children with no male siblings had the lowest ASD risk (1.95%; 95% CI: 1.63\u0026ndash;2.32%), while those with one or more male siblings had elevated risks (4.84% and 4.26%, respectively). Likewise, having no female siblings was associated with a higher incidence (6.50%; 95% CI: 5.93\u0026ndash;7.11%) compared to having one (2.84%; 95% CI: 2.53\u0026ndash;3.18%) or two or more (2.29%; 95% CI: 1.89\u0026ndash;2.75%) female siblings.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eIncidence Risk of Autism Spectrum Disorder (ASD) by Population Characteristics with 95% Confidence Intervals\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"6\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eCharacteristics\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eLevels\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"3\" nameend=\"c5\" namest=\"c3\"\u003e\u003cp\u003eAutism Spectrum Disorder (ASD)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eIR (95% CI)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eYes\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eNo\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eTotal\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAge In Year\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMean (SD)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e4.00 (0.82)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e4.09 (0.79)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e4.02 (0.84)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.97 (0.91 to 1.08)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e\u003cp\u003eSex\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMale\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e651\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e10666\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e11317\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e5.75 (5.33 to 6.20)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eFemale\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e207\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e10772\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e10979\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e1.89 (1.64 to 2.16)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTotal\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e858\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e21438\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e22296\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e3.85 (3.60 to 4.11)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e\u003cp\u003eRace\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNon-White\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e266\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e4860\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e5126\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e5.19 (4.60 to 5.83)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eWhite\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e592\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e16576\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e17168\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e3.45 (3.18 to 3.73)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTotal\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e858\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e21436\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e22294\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e3.85 (3.60 to 4.11)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e\u003cp\u003eAnxiety\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eYes\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e154\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e476\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e630\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e24.44 (21.14 to 27.99)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNo\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e704\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e20960\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e21664\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e3.25 (3.02 to 3.49)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTotal\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e858\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e21436\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e22294\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e3.85 (3.60 to 4.11)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e\u003cp\u003eDepression\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eYes\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e159\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e390\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e549\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e28.96 (25.20 to 32.95)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNo\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e699\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e21046\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e21745\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e3.21 (2.98 to 3.46)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTotal\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e858\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e21436\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e22294\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e3.85 (3.60 to 4.11)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e\u003cp\u003eADHD\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eYes\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e27\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e33\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e18.18 (6.98 to 35.46)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNo\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e852\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e21409\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e22261\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e3.83 (3.58 to 4.09)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTotal\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e858\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e21436\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e22294\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e3.85 (3.60 to 4.11)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"5\" rowspan=\"6\"\u003e\u003cp\u003eOutdoor Activity: Weekend\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e2 Hours Per Day\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e247\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e5763\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e6010\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e4.11 (3.62 to 4.64)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u0026lt;= 1 Hour Per Day\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e291\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e3792\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e4083\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e7.13 (6.36 to 7.96)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTotal\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e538\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e9555\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e10093\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e5.33 (4.90 to 5.79)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u0026gt;= 3 Hours Per Day\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e320\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e11881\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e12201\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e2.62 (2.35 to 2.92)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u0026lt;= 1 Hour Per Day\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e291\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e3792\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e4083\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e7.13 (6.36 to 7.96)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTotal\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e611\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e15673\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e16284\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e3.75 (3.47 to 4.06)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"5\" rowspan=\"6\"\u003e\u003cp\u003eOutdoor Activity: Weekday\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e2 Hours Per Day\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e244\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e7671\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e7915\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e3.08 (2.71 to 3.49)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u0026lt;= 1 Hour Per Day\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e427\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e6591\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e7018\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e6.08 (5.54 to 6.67)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTotal\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e671\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e14262\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e14933\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e4.49 (4.17 to 4.84)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u0026gt;= 3 Hours Per Day\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e187\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e7174\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e7361\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e2.54 (2.19 to 2.93)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u0026lt;= 1 Hour Per Day\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e427\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e6591\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e7018\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e6.08 (5.54 to 6.67)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTotal\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e614\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e13765\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e14379\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e4.27 (3.95 to 4.61)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"5\" rowspan=\"6\"\u003e\u003cp\u003eSibling Composition: Male\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1 Male Sibling\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e507\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e9970\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e10477\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e4.84 (4.44 to 5.27)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNo Male Sibling\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e129\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e6471\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e6600\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e1.95 (1.63 to 2.32)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTotal\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e636\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e16441\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e17077\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e3.72 (3.45 to 4.02)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u0026gt;= 2 Male Sibling\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e222\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e4995\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e5217\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e4.26 (3.72 to 4.84)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNo Male Sibling\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e129\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e6471\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e6600\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e1.95 (1.63 to 2.32)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTotal\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e351\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e11466\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e11817\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e2.97 (2.67 to 3.29)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"5\" rowspan=\"6\"\u003e\u003cp\u003eSibling Composition: Female\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1 Female Sibling\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e301\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e10287\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e10588\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e2.84 (2.53 to 3.18)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNo Female Sibling\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e446\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e6414\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e6860\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e6.50 (5.93 to 7.11)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTotal\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e747\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e16701\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e17448\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e4.28 (3.99 to 4.59)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u0026gt;= 2 Female Sibling\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e111\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e4735\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e4846\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e2.29 (1.89 to 2.75)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNo Female Sibling\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e446\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e6414\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e6860\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e6.50 (5.93 to 7.11)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTotal\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e557\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e11149\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e11706\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e4.76 (4.38 to 5.16)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"6\" nameend=\"c6\" namest=\"c1\"\u003e\u003cp\u003eIR: Incidence Risk, CI: Confidence Interval\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eFigure \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e presents the incidence risk ratios (IRRs) and 95% confidence intervals for ASD based on demographic, clinical, environmental, and familial predictors, complementing the findings in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. Consistent with the descriptive analysis, male sex was associated with a significantly higher risk of ASD compared to female sex (IRR\u0026thinsp;\u0026gt;\u0026thinsp;2.5), confirming known sex disparities in ASD prevalence. Children from non-White racial/ethnic groups had a slightly higher risk compared to White children. The presence of mental health comorbidities, including depression, anxiety, and ADHD, was associated with markedly elevated ASD risk. Children with depression had the highest IRR, followed by those with anxiety and ADHD, highlighting the strong co-occurrence between ASD and other neurodevelopmental or psychiatric conditions. A protective pattern emerged for outdoor physical activity, with children engaging in \u0026ge;\u0026thinsp;3 hours of activity per day on both weekdays and weekends showing substantially reduced ASD risk compared to those active for \u0026le;\u0026thinsp;1 hour. Regarding sibling composition, having no siblings, particularly no female siblings, was associated with higher ASD risk. In contrast, the presence of one or more male siblings was linked to an increase ASD risk, indicating that sibling interactions may influence early developmental outcomes.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e presents findings from weighted logistic regression models evaluating the associations between outdoor activity, sibling composition, and the risk of ASD, after adjusting for demographic variables and co-occurring psychological conditions using propensity score weighting. Outdoor activity was significantly associated with ASD risk. Compared to children who spent one hour or less outdoors per day, those who engaged in two hours of outdoor activity on weekends had 43% lower odds of ASD (adjusted weighted odds ratio [wOR]\u0026thinsp;=\u0026thinsp;0.57; 95% CI: 0.48\u0026ndash;0.68; p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). The protective effect was even stronger among children who spent three or more hours outdoors, with 63% reduced odds (wOR\u0026thinsp;=\u0026thinsp;0.37; 95% CI: 0.31\u0026ndash;0.44; p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). Similar trends were observed for weekday activity: two hours per day was associated with a 49% reduction in odds (wOR\u0026thinsp;=\u0026thinsp;0.51; 95% CI: 0.43\u0026ndash;0.60; p\u0026thinsp;\u0026lt;\u0026thinsp;0.001), and three or more hours yielded a 58% reduction (wOR\u0026thinsp;=\u0026thinsp;0.42; 95% CI: 0.35\u0026ndash;0.50; p\u0026thinsp;\u0026lt;\u0026thinsp;0.001).\u003c/p\u003e\u003cp\u003eIn terms of sibling composition, the presence of male siblings was positively associated with ASD risk. Compared to children with no male siblings, those with one male sibling had more than twice the odds of ASD (wOR\u0026thinsp;=\u0026thinsp;2.25; 95% CI: 1.85\u0026ndash;2.74; p\u0026thinsp;\u0026lt;\u0026thinsp;0.001), while those with two or more male siblings had 1.87-fold increased odds (wOR\u0026thinsp;=\u0026thinsp;1.87; 95% CI: 1.44\u0026ndash;2.44; p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). Conversely, the presence of female siblings was inversely associated with ASD. Having one female sibling was associated with 50% lower odds of ASD (wOR\u0026thinsp;=\u0026thinsp;0.50; 95% CI: 0.42\u0026ndash;0.58; p\u0026thinsp;\u0026lt;\u0026thinsp;0.001), and having two or more female siblings was associated with a 44% reduction in odds (wOR\u0026thinsp;=\u0026thinsp;0.56; 95% CI: 0.43\u0026ndash;0.74; p\u0026thinsp;\u0026lt;\u0026thinsp;0.001).\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eWeighted Logistic Regression Models Estimating the Associations Between Outdoor Activity, Sibling Composition, and autism spectrum disorder (ASD), Adjusted for Demographic and Co-occurring Psychological Factors (NSCH 2022\u0026ndash;2023).\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"6\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003ePredictors\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eLevels\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003ewOR\u003csup\u003e1\u003c/sup\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e\u003cp\u003e95% CI\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003ep-value\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eLL\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eUL\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colspan=\"6\" nameend=\"c6\" namest=\"c1\"\u003e\u003cp\u003eOutdoor Activities\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eWeekend\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eLess than or equal one hour per day\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eRef\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTwo hours per day\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.57\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.48\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.68\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eThree or more hours per day\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.37\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.31\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.44\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eWeekday\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eLess than or equal one hour per day\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eRef\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTwo hours per day\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.51\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.43\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.60\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eThree or more hours per day\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.42\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.35\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.50\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"6\" nameend=\"c6\" namest=\"c1\"\u003e\u003cp\u003e\u003cb\u003eSibling Composition\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eMale Sibling\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNo male sibling\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eRef\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eOne male sibling\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e2.25\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.85\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e2.74\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTwo or more male sibling\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1.87\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.44\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e2.44\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eFemale Sibling\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNo female sibling\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eRef\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eOne female sibling\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.50\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.42\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.58\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTwo or more female sibling\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.56\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.43\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.74\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"6\" nameend=\"c6\" namest=\"c1\"\u003e\u003cp\u003eNote: Results are presented as adjusted weighted odds ratios (wORs) with 95% confidence intervals (CIs), LL: Lower Limit, UL: Upper Limit, and associated p-values. The data was matched using PSM of the confounder factors, age, sex, race/ethnicity, anxiety, ADHD, and depression. All the confounding factors are insignificant in the weighted regression models.\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eFigure \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e3\u003c/span\u003e illustrates a regression tree model that examines the interaction between sibling composition and outdoor activity patterns in relation to ASD and provides potential subgroup for higher risk of ASD. The model identifies distinct subgroups, or terminal nodes, with varying profiles of ASD. Each node represents a unique combination of predictor variables and highlights patterns of risk across the study population. The most influential predictor was the number of female siblings (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001). Children with no female siblings (n\u0026thinsp;=\u0026thinsp;4,372) had a substantially higher probability of ASD compared to those with at least one female sibling (n\u0026thinsp;=\u0026thinsp;19,434). Within the group with no female siblings, further stratification by weekday outdoor activity (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001) showed that children who spent one hour or less outdoors per weekday were at greater risk profiles. Among them, those who also engaged in two hours or less of weekend outdoor activity had the highest ASD probability at approximately 15% (Node 4). If weekend outdoor time exceeded two hours, the ASD probability decreased to approximately 10% (Node 5). Additionally, children without female siblings who spent 2\u0026ndash;3 hours outdoors on weekdays but had limited weekend activity still exhibited a relatively elevated ASD probability of approximately 10% (Node 8).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eAmong children without female siblings who spent more than three hours outdoors on weekdays, the number of male siblings (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001) and weekend outdoor activity (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.003) further influenced ASD risk. Those with one or more male siblings and less than one hour of weekend outdoor time had an ASD probability of 7% (Node 9), while those with greater weekend outdoor engagement had a lower probability of 5% (Node 10). In contrast, among children with at least one female sibling, weekend outdoor activity duration was the key discriminator (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001). Those with two or fewer hours of weekend outdoor time and two or more male siblings had an ASD probability of 8% (Node 14), compared to 3% for those with one or no male siblings (Node 13). Furthermore, when weekday outdoor time reached three or more hours among children with at least one female sibling and over two hours of weekend outdoor activity, the ASD probability dropped to 2% (Node 17)-the lowest observed across all subgroups.\u003c/p\u003e"},{"header":"4. Discussion","content":"\u003cp\u003eThis study provides compelling evidence on the influence of outdoor activity duration (weekend and weekday) and sibling composition on children's behavioral and emotional outcomes, based on a nationally representative sample from the 2022\u0026ndash;2023 National Survey of Children\u0026rsquo;s Health (NSCH) data. Our analysis highlights how structured outdoor time-both on weekdays and weekends-and sibling composition are significant predictors of ASD, even after adjusting for demographic and psychological confounders through propensity score weighting and machine learning methodology.\u003c/p\u003e\u003cp\u003eA central finding from the regression models is the protective association between increased duration of outdoor activities and reduced odds of ASD. Children who engaged in outdoor activities for two hours or more per day-on both weekdays and weekends-had significantly lower adjusted odds of ASD as compared to those with one hour or less. Specifically, children who spent three or more hours outdoors on weekends had 63% lower odds (OR\u0026thinsp;=\u0026thinsp;0.37, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001), and those with similar weekday exposure had 58% reduced odds (OR\u0026thinsp;=\u0026thinsp;0.42, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001). These results align with previous findings who emphasized the psychological and developmental benefits of outdoor free play and green space exposure (Haque, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2024\u003c/span\u003e; Ziegler \u0026amp; Morrier, \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). Outdoor activity promotes not only physical health but also supports emotional regulation, social interaction, and cognitive flexibility-factors associated with reduced behavioral disorders such as ADHD and conduct problems (Haque, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2024\u003c/span\u003e; Hendrickson, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Sugiyama et al., \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2023b\u003c/span\u003e). The regression tree model further supports these results by identifying weekday and weekend outdoor activity as primary nodes in classifying children with higher or lower behavioral risk. Among children without female siblings, outdoor activity on weekdays and weekends served as significant split criteria, indicating their critical role in this subgroup. The model demonstrates that even among children with sibling-related risk factors, increased outdoor activity consistently shifts the probability of behavioral problems downward.\u003c/p\u003e\u003cp\u003eSibling composition emerged as another major factor. Notably, having one or more male siblings was associated with increased odds of ASD (e.g., one male sibling: OR\u0026thinsp;=\u0026thinsp;2.25, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001), while the presence of female siblings was associated with decreased odds (e.g., one female sibling: OR\u0026thinsp;=\u0026thinsp;0.50, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001). This differential pattern may reflect the role of gendered sibling interactions in shaping emotional and social development. Research suggested that male siblings are more likely to engage in competitive or externalizing behavior, which may amplify emotional dysregulation, whereas female siblings often foster prosocial and emotionally supportive dynamics (Dirks et al., \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Waid et al., \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Walton \u0026amp; Ingersoll, \u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). These dynamics might be particularly influential during middle childhood, a period when peer modeling and familial interactions shape behavioral trajectories (Ladd, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e1999\u003c/span\u003e; Rosen, McCauley, et al., 2022). However, some studies had suggested that the presence of male siblings may contribute positively to the social and psychological development of children (Sang \u0026amp; Nelson, \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). Male siblings often engage in cooperative and task-oriented play, which can foster a supportive and structured environment conducive to developing teamwork, problem-solving, and conflict-resolution skills (Bryant, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e1982\u003c/span\u003e). Such interactions may indirectly support emotional regulation and psychological well-being by encouraging mutual support and shared responsibilities within the family context (Ngai et al., \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2021\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eOur findings are consistent with previous research indicating that positive sibling relationships, particularly those involving older or same-gender sisters-can serve as protective factors against internalizing and externalizing disorders in children and adolescents. Some researchers reported that emotionally supportive sibling interactions are linked to lower levels of anxiety, depression, and behavioral difficulties, emphasizing siblings as important sources of emotional regulation and social learning (Feinberg et al., \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Milevsky, \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2005\u003c/span\u003e). Similarly, found that high-quality sibling relationships are associated with better psychosocial adjustment across developmental stages (Kim et al., \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2007\u003c/span\u003e). Conversely, several studies have shown that sibling conflict, rivalry, and the modeling of aggressive or antisocial behavior-more common among same-gender male siblings-can exacerbate behavioral problems. Researchers noted that coercive or hostile sibling dynamics are predictive of higher levels of externalizing behaviors (Buist et al., \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Stormshak et al., \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e1996\u003c/span\u003e). These findings highlight the complex and bidirectional nature of sibling influences on child development, serving as either protective or risk-enhancing depending on the relational context.\u003c/p\u003e\u003cp\u003eFinally, the interaction between outdoor activity and sibling composition suggests that time spent outdoors may attenuate some of the negative effects associated with male sibling presence. The classification tree analysis revealed significant interactions between sibling composition and outdoor activity patterns in relation to ASD diagnosis. The most prominent initial split in the tree was based on the number of female siblings suggesting that the presence of female siblings plays a central role in differentiating ASD outcomes. Among children with no female siblings, weekday outdoor activity emerged as the next critical factor. Those with \u0026le;\u0026thinsp;1 hour of outdoor play on weekdays followed by \u0026le;\u0026thinsp;2 hours on weekends showed the highest proportion of ASD diagnoses, indicating that limited physical activity may be associated with increased ASD risk in the absence of female sibling support. Conversely, for children with at least one female sibling, outdoor weekend activity were associated with a lower likelihood of ASD, particularly in children with at least one or more female sibling, suggesting a potential protective effect of both increased outdoor engagement and female sibling presence in certain contexts. These findings emphasize the potential value of promoting outdoor play-especially during weekends-and considering sibling dynamics in early screening and intervention efforts for children at risk of ASD. Further research is needed to explore the causal mechanisms and to evaluate whether these factors may serve as modifiable targets for prevention strategies.\u003c/p\u003e\u003cp\u003eThis study has several strengths, including the use of nationally representative data, adjustment for co-occurring psychological conditions, and the integration of both traditional regression and machine learning methods (e.g., regression trees). However, some limitations must be acknowledged. The cross-sectional nature of the data limits causal inference, and behavioral outcomes were based on parental report, which may introduce bias. Additionally, unmeasured factors such as parenting style, peer relationships, or school environment could confound observed associations.\u003c/p\u003e"},{"header":"5. Conclusion","content":"\u003cp\u003eThe study findings underscore the importance of outdoor activity and sibling compositions in shaping child behavioral health. Public health interventions aimed at promoting regular outdoor engagement-particularly among children with higher familial risk (e.g., presence of male siblings)-could serve as a protective strategy to improve developmental outcomes. Policies that encourage safe outdoor spaces, green schoolyards, and community programs may be particularly impactful. Future longitudinal research is warranted to further explore causal pathways and the role of mediators such as peer interactions, screen time, and parenting practices.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eDeclaration of generative AI and AI-assisted technologies in the writing process\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eDuring the preparation of this work the author(s) used chatgpt.com to improve readability and language\u0026rsquo;s structure formations. After using this tool/service, the author(s) reviewed and edited the content as needed and took(s) full responsibility for the content of the publication.\u003c/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eFunding:\u003c/strong\u003e None\u003c/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eDeclaration of Interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no conflicts of interest relevant to the content of this manuscript. No financial or personal relationships with individuals or organizations have influenced the findings reported in this study. All authors have read and approved the final version of the manuscript and agree to be accountable for all aspects of the work.\u003c/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eAcknowledgments:\u003c/strong\u003e Thank to NSCH for giving data access. \u003c/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eData availability:\u003c/strong\u003e Data will be provided upon potential request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAlvares, G. A., Licari, M. K., Stevenson, P. G., Bebbington, K., Cooper, M. N., Glasson, E. J., Tan, D. W., Uljarević, M., Varcin, K. J., Wray, J., \u0026amp; Whitehouse, A. J. O. (2021). Investigating associations between birth order and autism diagnostic phenotypes. \u003cem\u003eJournal of Child Psychology and Psychiatry\u003c/em\u003e, \u003cem\u003e62\u003c/em\u003e(8), 961\u0026ndash;970. https://doi.org/10.1111/jcpp.13349\u003c/li\u003e\n\u003cli\u003eAvni, E., Ben-Itzchak, E., \u0026amp; Zachor, D. A. (2018). 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Increasing Social Interactions of Preschool Children With Autism Through Cooperative Outdoor Play. \u003cem\u003eThe Journal of Special Education\u003c/em\u003e, \u003cem\u003e56\u003c/em\u003e(1), 49\u0026ndash;60. https://doi.org/10.1177/00224669211032556\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"University of South Florida","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Autism Spectrum Disorder, outdoor activity, sibling composition, NSCH, Machine learning","lastPublishedDoi":"10.21203/rs.3.rs-7206351/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7206351/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003ePurpose\u003c/h2\u003e\u003cp\u003eAutism Spectrum Disorder (ASD) is a complex neurodevelopmental condition influenced by both environmental and familial factors. This study examined the association between ASD risk and (1) the duration of children's outdoor activities on weekdays and weekends, and (2) sibling composition, specifically the number and gender of siblings.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e\u003cp\u003eWe analyzed cross-sectional data from the 2022 National Survey of Children\u0026rsquo;s Health (NSCH), including 22,294 children aged 3 to 5 years. Propensity Score Matching (PSM) was used to reduce selection bias by adjusting for covariates such as age, sex, race, anxiety, ADHD, and depression. Weighted logistic regression estimated adjusted odds ratios (wORs), and machine learning models assessed complex interaction effects.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e\u003cp\u003eOutdoor activity was inversely associated with ASD. Compared to \u0026le;\u0026thinsp;1 hour, 2 hours of weekend activity reduced ASD odds by 43% (wOR\u0026thinsp;=\u0026thinsp;0.57; 95% CI: 0.48\u0026ndash;0.68), and \u0026ge;\u0026thinsp;3 hours by 63% (wOR\u0026thinsp;=\u0026thinsp;0.37; 95% CI: 0.31\u0026ndash;0.44). On weekdays, 2 hours reduced odds by 49% (wOR\u0026thinsp;=\u0026thinsp;0.51), and \u0026ge;\u0026thinsp;3 hours by 58% (wOR\u0026thinsp;=\u0026thinsp;0.42; 95% CI: 0.35\u0026ndash;0.50). Having one female sibling halved ASD odds (wOR\u0026thinsp;=\u0026thinsp;0.50), while male siblings increased risk (one: wOR\u0026thinsp;=\u0026thinsp;2.25; two or more: wOR\u0026thinsp;=\u0026thinsp;1.87). Machine learning identified highest ASD likelihood among children with no female siblings and limited outdoor activity, and lowest among those with female siblings and \u0026ge;\u0026thinsp;3 weekend hours outdoors.\u003c/p\u003e\u003ch2\u003eConclusion\u003c/h2\u003e\u003cp\u003eExtended outdoor activity and the presence of female siblings are associated with reduced ASD risk and may inform early prevention efforts.\u003c/p\u003e","manuscriptTitle":"Exploring the Impact of Outdoor Activities and Sibling Compositions on Autism Spectrum Disorder: A Causal Mediation Analysis Using the National Survey of Children's Health in the United States","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-07-29 08:12:19","doi":"10.21203/rs.3.rs-7206351/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"01d3f0ab-5736-4489-accf-88e7a3bb5318","owner":[],"postedDate":"July 29th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":52068789,"name":"Psychiatry"},{"id":52068790,"name":"Statistical Epidemiology"}],"tags":[],"updatedAt":"2025-07-29T08:12:19+00:00","versionOfRecord":[],"versionCreatedAt":"2025-07-29 08:12:19","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7206351","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7206351","identity":"rs-7206351","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}