Effects of group-based parent training on oppositional defiant disorder symptoms and irritability in Japanese children

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Although parent training (PT) is the gold standard intervention for ODD, evidence from non-Western contexts is limited, and its effect on irritability—a core emotional dimension of ODD—remains unclear. Methods This open trial examined the effectiveness of a group-based parent training program for parents of children with ODD (PT-ODD). Twelve Japanese mothers who had children aged 7–12 years participated. Outcomes were assessed at pre-treatment, post-treatment, and three-month follow-up using clinician-rated and parent-reported measures. Changes over time were analyzed using linear mixed-effects models, and associations between parenting behaviors and child symptoms were examined. Results Clinician-rated functional impairment and parent-reported oppositional defiant symptoms showed significant and sustained improvements, with large effect sizes. Remission rates increased from 33% post-treatment to 50% at follow-up. Irritability showed no immediate improvement and the overall time effect did not reach statistical significance. However, irritability was significantly lower at follow-up than at baseline, suggesting a potential delayed effect. Changes in positive parenting behaviors were associated with short-term improvements in oppositional defiant symptoms, whereas changes in negative parenting behaviors were observed for longer-term changes in oppositional defiant symptoms. Conclusions These findings suggest that PT-ODD leads to immediate improvements in ODD symptoms and functional impairment, whereas reductions in irritability may emerge more gradually over time. Parent Training Group Intervention Oppositional Defiant Disorder Irritability Parenting Behaviors Introduction Oppositional Defiant Disorder (ODD) is a common disruptive behavior disorder characterized by a persistent pattern of oppositional and defiant behavior and frequent anger and irritability [ 1 ]. A large international meta-analysis estimated the prevalence of ODD to be 3.6%, indicating that ODD is not a rare condition worldwide among children and adolescents [ 2 ]. In Japan, the prevalence of ODD has been reported to be 4.67% [ 3 ], suggesting that ODD represents a clinically significant mental health concern also within the Japanese cultural context. Children with ODD symptoms are at increased risk for a wide range of adverse developmental outcomes, including persistent interpersonal difficulties, impaired family relationships, and reduced occupational opportunities in adulthood [ 4 ]. Given the chronic and impairing nature of ODD, early and effective psychosocial interventions are considered essential to alter maladaptive developmental trajectories. Among evidence-based psychosocial treatments for ODD and related disruptive behavior disorders, parent training (PT) has consistently been regarded as the gold standard intervention [ 5 , 6 ]. PT programs primarily aim to modify coercive parent–child interaction patterns by increasing positive parenting behaviors (e.g., praise, positive involvement) while reducing negative parenting behaviors (e.g., inconsistent discipline, harsh or reactive responses). Meta-analytic reviews have demonstrated robust effects of PT in reducing oppositional and defiant behaviors in children and adolescents [ 7 ]. A large-scale meta-analysis showed that PT is effective across multiple delivery formats, including individual, group-based, and combined parent–child interventions, highlighting its flexibility and broad applicability [ 8 ]. Despite the robust evidence supporting PT for ODD and related problems, important gaps remain in the literature. First, although PT has been extensively studied and validated in Western countries, empirical evidence from non-Western contexts remains limited. In Japan, parent training has been implemented and studied mainly for children with developmental disabilities such as autism spectrum disorder and attention-deficit/hyperactivity disorder [ 9 , 10 ]. In contrast, no study conducted in Japan has evaluated the effectiveness of PT using ODD-related outcomes as the primary endpoint. Given potential cultural differences in parenting practices and family dynamics, the absence of Japanese data limits understanding of the cross-cultural generalizability and applicability of PT. Second, although PT has consistently demonstrated effectiveness in reducing overt oppositional and defiant behaviors, far less attention has been paid to its effects on irritability [ 11 ]. Irritability constitutes a core emotional symptom dimension of ODD and has been identified as a transdiagnostic risk factor. Longitudinal studies indicate that elevated irritability in childhood predicts later anxiety and depressive disorders, as well as the development of ODD [ 12 ]. Despite its developmental and clinical significance, irritability has rarely been examined as a treatment outcome in PT research. Third, PT is based on the assumption that improvements in child behavior occur through changes in parenting behaviors, including increases in positive practices (e.g., praise, warm involvement) and reductions in negative practices (e.g., harsh or inconsistent discipline). However, the mechanisms linking changes in parenting behaviors to changes in children’s oppositional symptoms and irritability remain unclear. Although parenting behaviors are often assumed to mediate treatment effects for externalizing problems, empirical support for these mechanisms is limited and inconsistent [ 13 ]. In Japan, despite the growing implementation of PT [ 9 , 10 ], few studies have directly examined parenting behaviors as outcomes, leaving it unclear whether improvements in child symptoms are accompanied by meaningful changes in parenting practices. The present study aimed to address these gaps by examining the effectiveness of a newly developed group-based parent training program for parents of children with ODD (PT-ODD) using an open trial design with pre-treatment, post-treatment, and three-month follow-up assessments. The study had three objectives. First, we evaluated the effectiveness of group-based parent training for ODD-related outcomes in a Japanese clinical sample, focusing on clinician-rated functional impairment and parent-reported oppositional defiant symptoms. Second, we examined whether the intervention was associated with reductions in irritability, a core emotional symptom dimension of ODD that has rarely been examined as a treatment outcome in prior PT research. Third, we investigated whether changes in parenting behaviors following the intervention were associated with changes in oppositional defiant symptoms and irritability over time. Methods Study Design and Participants This study was an interventional open trial evaluating the effects of a group-based parent training program for parents of children diagnosed with ODD. This study employed an open trial design with pre-treatment, post-treatment, and three-month follow-up assessments. Participants were parents of children who experienced difficulties with ODD. Inclusion criteria were: (a) parents or primary caregivers of children in grades 2 to 6 of elementary school (aged 7–12 years); (b) children meeting diagnostic criteria for ODD; and (c) availability to attend the program sessions on a regular basis. Ethical Approval and Informed Consent The study protocol was approved by the institutional review board of the author’s affiliated university (KG-IRB-23-03). All participating parents received a full explanation of the study procedures and provided written informed consent prior to participation. This study was registered as a clinical trial in the University Hospital Medical Information Network (UMIN) Clinical Trials Registry (UMIN000054295) on May 1, 2024. All procedures involving human participants were performed in accordance with the ethical standards of the institutional research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. Parent Training Program for ODD (PT-ODD) A group-based parent training program for parents of children with ODD (PT-ODD) was delivered in a group format and consisted of eight biweekly sessions, each lasting 120 minutes. The program was grounded in behavioral principles and was informed by the core parent training platform disseminated by the Japanese Parent Training Research Association [ 14 ], as well as established parent training models for children and adolescents with ODD [ 15 , 16 ]. The program aimed to help parents better understand their children’s oppositional behavior and anger-related problems, while teaching practical, evidence-based parenting strategies guided by functional assessment. Session 1 provided an orientation to the program and psychoeducation on ODD, anger-related problems, and parent–child interaction patterns. Session 2 focused on observing and classifying child behavior, with parents learning to identify antecedents, behaviors, and consequences. Session 3 addressed functional assessment, helping parents understand the behavioral functions of oppositional and anger-related behaviors and use this understanding to guide effective parenting responses. Session 4 targeted positive parenting skills, including effective praise, positive attention, and the use of “special time” to strengthen the parent–child relationship. Session 5 introduced planned ignoring as a strategy for reducing minor, non-dangerous oppositional behaviors. Session 6 focused on providing advance notice and clear, consistent instructions to prevent escalation of anger and noncompliance. Session 7 addressed the use of warnings and non-harsh consequences, including time-out and response cost, emphasizing consistent, predictable, and proportionate implementation. Session 8 reviewed all skills, with particular emphasis on the continued importance of praise, positive attention, and special time. Each session included brief lectures by the first author, individual and group exercises, role-play, and homework assignments to promote skill acquisition and generalization to everyday situations. To ensure adequate treatment participation and intervention fidelity, parents who missed a group session were offered an individual make-up session in which the missed content was reviewed. This approach was used to support treatment adherence and to maintain intervention consistency and fidelity across participants. Measures All measures were administered at three time points: pre-treatment, post-treatment, and three-month follow-up. The same assessment procedures were used at each time point. With the exception of the clinician-administered interview, all measures were completed by parents. Clinician-Rated Outcomes Clinician-rated diagnostic status and clinical severity were assessed using the Anxiety Disorders Interview Schedule [ 17 ]. The ADIS was used to evaluate the presence of ODD. ODD-related functional impairment was assessed using the Clinician Severity Rating (CSR), which reflects the degree of interference caused by symptoms in the child’s daily functioning. In addition, overall clinical severity was assessed using the Clinical Global Impression–Severity scale [ 18 ]. The CGI-S is a clinician-rated measure that evaluates the patient’s overall level of psychopathology at the time of assessment, with higher scores indicating greater severity. The ADIS and the CGI-S have been used to assess ODD in previous Japanese research [ 19 ]. Oppositional Defiant Symptoms : Parent-reported oppositional defiant symptoms were assessed using the Disruptive Behavior Disorders Rating Scale (DBDRS) [ 20 ]. The Japanese version of the DBDRS has demonstrated adequate reliability and validity [ 3 ]. The DBDRS assesses four symptom domains: inattention symptoms, hyperactivity symptoms, oppositional defiant symptoms, and conduct problems. Irritability Child irritability reported by parents was assessed using the Japanese version of the Affective Reactivity Index (ARI) [ 21 ]. The reliability and validity of the Japanese version of the ARI have been established previously [ 22 ]. The ARI measures the frequency and severity of irritability, with higher scores indicating greater irritability. Aggressive Behaviors Aggressive behaviors were assessed using the Aggressive Behavior Scale for Children and Adolescents (ABS-CA) [ 23 ]. Although the ABS-CA was originally developed as a self-report measure, in the present study, the scale was administered as a parent-report measure. The ABS-CA includes three subscales assessing physical aggression, verbal aggression, and relational aggression. A total aggressive behaviors score, calculated as the sum of these three subscales, was used in the present study. General Difficulties and Prosocial Behavior General child difficulties and prosocial behavior were assessed using the parent-report version of the Strengths and Difficulties Questionnaire (SDQ) [ 24 ], which served as a general indicator of child functioning. The reliability and validity of the Japanese parent-report SDQ have been established in previous research [ 25 ]. In the present study, the Total Difficulties score and the Prosocial Behavior subscale were analyzed. Parenting Behaviors : Parenting behaviors were assessed using the Parenting Behaviors Questionnaire (PBQ) [ 26 ], for which reliability and validity have been established in the previous research. Positive parenting behaviors were calculated as the total score of four subscales: Positive Attention, Reward, Warmth, and Autonomy Granting. Negative parenting behaviors were calculated as the total score of three subscales: Physical Punishment, Verbal Punishment, and Psychological Control. Higher scores indicated greater use of the respective parenting behaviors. Parental Depressive Symptoms Parental depressive symptoms were assessed using the Quick Inventory of Depressive Symptomatology (QIDS) [ 27 ]. The Japanese version of the QIDS has been developed and its reliability and validity have been examined [ 28 ]. Higher scores indicated greater severity of depressive symptoms. Acceptability To assess program acceptability, a parent-rated acceptability scale was used. This scale was originally developed to measure the acceptability of cognitive behavioral therapy for Japanese children with oppositional defiant disorder (ODD) and their families (Kishida et al., 2024). Parents were asked to rate eight items—enjoyment, satisfaction, willingness to recommend, perceived usefulness, understanding, perceived difficulty, perceived burden, and problem-solving self-efficacy—on a 5-point Likert scale ranging from 0 to 4. Items assessing perceived difficulty and perceived burden were reverse-scored, and the total score was calculated as the acceptability score (possible range: 0–32). Acceptability was assessed at post-intervention. Statistical plan Changes in child and parent outcomes across three time points (pre-treatment [Time 1], post-treatment [Time 2], and three-month follow-up [Time 3]) were analyzed using linear mixed-effects models (LMMs) using Restricted Maximum Likelihood (REML) estimation and Satterthwaite’s approximation, with time specified as a fixed effect and participant intercepts as random effects. To evaluate intervention effects, LMMs were applied to clinician-rated functional impairment for ODD (CSR) and parent-reported oppositional defiant symptoms (DBDRS) and irritability (ARI) as primary outcomes. LMMs were also applied to other outcomes, overall clinical severity (CGI-S), including inattention symptoms, hyperactivity symptoms, and conduct problems (DBDRS), aggressive behaviors (ABS-CA), general difficulties and prosocial behavior (SDQ), parenting behaviors (PBQ), and parental depressive symptoms (QIDS) as secondary outcomes. Effect sizes (Hedges’ g ) were calculated based on descriptive statistics. Associations between changes in positive and negative parenting behaviors and changes in oppositional defiant symptoms and irritability were examined using Pearson correlations, relating changes from Time 1 to Time 2 to changes from Time 1 to Time 2 (short-term correlations) and from Time 1 to Time 3 (long-term correlations). For these correlation analyses only, missing values (one participant at follow-up) were handled using the last observation carried forward (LOCF) method. The significance level was set at p < .10 to reduce the risk of Type II errors given the small sample size. All analyses were conducted using JASP. Results Participant Characteristics Twelve children diagnosed with ODD and their mothers participated in the study and were included in the analyses. The children had a mean age of 10.42 years ( SD = 1.04), and the sample included seven girls and five boys. Among the children, two (16.7%) had a comorbid diagnosis of attention-deficit/hyperactivity disorder (ADHD), as assessed using the ADIS. In addition, autism spectrum disorder (ASD)–related symptoms were assessed using the Social Responsiveness Scale–Second Edition (SRS-2) [ 29 ]. Based on SRS-2 total T-scores, two children (16.7%) were classified as severe, three (25.0%) as moderate, one (8.3%) as mild, and six (50.0%) as within the normal range in terms of ASD symptom severity. The mean age of the mothers was 45.36 years ( SD = 4.21); one mother did not report her age. All participants completed the post-treatment assessment (100%), and 11 participants completed the three-month follow-up assessment (91.7%). Participant characteristics are presented in Table 1. Treatment Attendance, Engagement, and Acceptability With regard to treatment attendance, participants attended an average of 6.67 ( SD = 1.11) of the eight group sessions. Individual make-up sessions were conducted for all participants who missed group sessions, with a mean of 1.33 ( SD = 1.11) sessions per participant, to ensure adequate treatment participation and intervention fidelity. In addition, all mothers completed the assigned homework at each session throughout the program (100%). The mean acceptability score was 26.17 ( SD = 3.24), indicating a high level of program acceptability. Changes in Clinician-Rated Outcomes LMMs revealed a significant main effect of time on clinician-rated functional impairment (CSR), F (2, 21.32) = 9.27, p = .001. Estimated marginal means indicated a significant reduction in CSR from pre-treatment to post-treatment (estimated difference = − 1.75, SE = 0.78, p = .024), with a large effect size (Hedges’ g = − 0.85). This improvement was maintained at the three-month follow-up (estimated difference = − 3.43, SE = 0.98, p < .001), with an even larger effect size (Hedges’ g = − 1.40). Based on clinician ratings, the remission rate following the intervention was 33% (4 of 12 children), which increased to 50% (6 of 12 children) at the three-month follow-up. Descriptive statistics for all outcome variables at pre-treatment (Time 1), post-treatment (Time 2), and three-month follow-up (Time 3) are shown in Table 2. Results of the linear mixed-effects models and effect sizes are presented in Table 3. LMMs also showed a significant main effect of time for overall clinical severity (CGI-S), F (2, 21.14) = 11.25, p < .001. CGI-S scores significantly decreased from pre-treatment to post-treatment (estimated difference = − 1.00, SE = 0.32, p = .002; Hedges’ g = − 0.81) and remained significantly lower at follow-up (estimated difference = − 1.57, SE = 0.33, p < .001; Hedges’ g = − 1.32). Changes in Oppositional Defiant Symptoms and Irritability For parent-reported oppositional defiant symptoms, LMMs showed a significant main effect of time, F (2, 21.11) = 8.70, p = .002. Symptoms significantly decreased from pre-treatment to post-treatment (estimated difference = − 3.08, SE = 1.08, p = .004; Hedges’ g = − 0.59), and this improvement was maintained at the three-month follow-up (estimated difference = − 4.53, SE = 1.12, p < .001; Hedges’ g = − 0.81). Overall, moderate-to-large improvements were observed. No significant main effect of time was observed for inattention symptoms, F (2, 21.09) = 1.52, p = .243, hyperactivity symptoms, F (2, 21.01) = 3.13, p = .065, or conduct problems, F (2, 21.06) = 1.45, p = .257. For irritability, LMMs indicated only a trend-level main effect of time, F (2, 20.97) = 3.26, p = .058, which did not reach statistical significance. Irritability showed no significant change from pre-treatment to post-treatment (estimated difference = − 0.75, SE = 0.76, p = .323; Hedges’ g = − 0.25). Although a reduction was observed at the three-month follow-up (estimated difference = − 1.99, SE = 0.78, p = .022; Hedges’ g = − 0.67), this finding should be interpreted with caution given the absence of a significant overall time effect. Overall, improvements in irritability were small to moderate and emerged gradually rather than immediately following the intervention. Changes in Other Child Outcomes For aggressive behaviors, LMMs indicated only a trend-level main effect of time, F (2, 20.97) = 2.76, p = .086, which did not reach statistical significance. Aggressive behaviors showed no significant reduction from pre-treatment to post-treatment (estimated difference = − 2.50, SE = 1.15, p = .058; Hedges’ g = − 0.34). Although a reduction was observed at the three-month follow-up (estimated difference = − 2.15, SE = 1.18, p = .070; Hedges’ g = − 0.44), this change should be interpreted with caution given the absence of a statistically significant overall time effect. For total difficulties, LMMs revealed a significant main effect of time, F (2, 21.05) = 4.08, p = .032. Total difficulties showed a significant reduction from pre-treatment to post-treatment (estimated difference = − 1.92, SE = 0.68, p = .009; Hedges’ g = − 0.44). However, this improvement was not maintained at the three-month follow-up, as the difference from pre-treatment was no longer statistically significant (estimated difference = − 0.71, SE = 0.70, p = .313; Hedges’ g = − 0.20). No significant main effect of time was observed for prosocial behavior, F (2, 21.11) = 0.14, p = .867. Changes in Parent Outcomes A significant main effect of time was observed for positive parenting behaviors, F (2, 21.07) = 9.27, p = .006. Positive parenting behaviors significantly increased from pre-treatment to post-treatment (estimated difference = 4.00, SE = 1.40, p = .004), with a medium effect size (Hedges’ g = 0.46). This improvement was maintained at the three-month follow-up (estimated difference = 4.82, SE = 1.44, p = .002), with a medium effect size (Hedges’ g = 0.47). For negative parenting behaviors, no significant main effect of time was observed, F (2, 20.87) = 2.57, p = .101. No significant main effect of time was observed for parental depressive symptoms, F (2, 21.19) = 1.55, p = .235. Correlations Between Changes in Parenting Behaviors and Symptom Outcomes Changes in positive parenting behaviors from Time 1 to Time 2 were moderately associated with reductions in oppositional defiant symptoms from Time 1 to Time 2 ( r = − .56, p = 0.06) and weakly associated with reductions in irritability ( r = − .30, p = 0.35). Correlations with symptom changes from Time 1 to Time 3 were negligible ( r = .04, p = 0.91 for oppositional defiant symptoms; r = − .18, p = 0.58 for irritability). Changes in negative parenting behaviors from Time 1 to Time 2 showed moderate positive associations with changes in oppositional defiant symptoms ( r = .44, p = 0.15) and irritability ( r = .20, p = 0.25) from Time 1 to Time 2. Similar correlations were observed for changes in oppositional defiant symptoms ( r = .44, p = 0.10) and irritability ( r = .50, p = 0.15) from Time 1 to Time 3. Short- and long-term correlations between changes in parenting behaviors and changes in child outcomes are shown in Table 4. Discussion The present study examined the effectiveness of a group-based parent training program for parents of children with ODD (PT-ODD). This study makes three primary contributions to the literature: it provides evidence for the effectiveness of parent training when ODD is defined as the primary treatment target in a Japanese clinical context; it offers novel findings regarding the effects of parent training on irritability, a core emotional dimension of ODD; and it provides preliminary insight into parenting behaviors as a potential mechanism linking the intervention to changes in oppositional defiant symptoms. The first contribution is the demonstration that group-based parent training can lead to meaningful improvements in ODD symptoms and functional impairment among Japanese children. Significant and sustained improvements were observed across clinician-rated and parent-reported ODD-related outcomes, with remission rates increasing at follow-up. Although parent training is well established as the gold standard intervention for ODD [ 5 , 6 ], empirical evidence from Japan has been scarce, particularly studies using ODD as the primary outcome [ 9 , 10 ]. The present findings therefore extend the Japanese literature and support the cross-cultural applicability of parent training models originally developed in Western contexts. The second contribution concerns irritability, which is increasingly recognized as a core emotional dimension of ODD and a transdiagnostic risk factor for later emotional and behavioral disorders [ 12 ]. In the present study, irritability did not show significant immediate improvement, and the overall time effect did not reach statistical significance. However, reductions were observed at the three-month follow-up, suggesting a delayed pattern of change. This finding is consistent with the notion that parent training primarily targets parent–child interaction patterns rather than children’s internal emotion regulation processes [ 15 , 16 ], and that emotional symptoms such as irritability may not be directly targeted by parent training but may improve more gradually following sustained changes in the relational environment and child behavior. The third contribution relates to mechanisms of change. Previous reviews have suggested that changes in parenting behaviors may underlie treatment effects for externalizing problems, although empirical evidence remains limited [ 13 ]. In the present study, changes in positive parenting behaviors were associated with short-term improvements in oppositional defiant symptoms, whereas associations involving negative parenting behaviors—despite no significant change during the intervention—were observed for longer-term changes in oppositional defiant symptoms. Although a systematic review has shown that both positive and negative parenting behaviors are associated with externalizing problems, including oppositional defiant symptoms [ 30 ], the present findings suggest that the short-term and long-term influences of these parenting behaviors on oppositional defiant symptoms may differ. In contrast, no significant associations were observed between changes in parenting behaviors and irritability. Therefore, improvements in irritability may not be directly attributable to changes in parenting behaviors but may instead be mediated by changes in other variables, such as the parent–child relationship or child behavior. Changes in aggressive behavior and general difficulties were weaker and less stable, suggesting that these broader outcomes are less directly influenced by ODD-focused interventions. This pattern highlights the specificity of parent training effects and the importance of distinguishing proximal treatment targets from more distal outcomes. In addition, no significant changes were observed in parental depressive symptoms, consistent with the primary focus of parent training on parenting practices and child behavior rather than parental mood. Nevertheless, maintaining stable levels of depressive symptoms may still be clinically meaningful given the substantial parenting burden associated with ODD, and group-based formats may provide indirect benefits through peer support and normalization. Several limitations should be acknowledged. First, the open trial design without a control group limits causal inference. Second, the small sample size reduces statistical power and generalizability, and formal mediation analyses were not conducted. Third, reliance on parent-report measures and the relatively short follow-up period warrant caution. Future studies should employ randomized controlled designs with larger samples and longer follow-up periods to confirm these findings and clarify mechanisms of change. Despite these limitations, the present study provides preliminary evidence that group-based parent training is a feasible and potentially effective intervention for Japanese children with ODD. The findings suggest that core oppositional defiant symptoms may improve relatively quickly, whereas irritability may change more gradually over time, underscoring the importance of integrating both behavioral and emotional perspectives in interventions for ODD. Declarations Ethics approval and consent to participate The study protocol was approved by the Institutional Review Board of Kwansei Gakuin University (Approval No. KG-IRB-23-03). Written informed consent was obtained from all participating parents prior to participation. This study was registered as a clinical trial in the University Hospital Medical Information Network (UMIN) Clinical Trials Registry (UMIN000054295) on May 1, 2024. All procedures involving human participants were performed in accordance with the ethical standards of the institutional research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. Consent for publication Not applicable. Competing interests The authors declare that they have no competing interests. Funding This work was supported by the Japan Society for the Promotion of Science (JSPS) Grants-in-Aid for Scientific Research under Grant Numbers 21K13737 and 24K16861. Author Contribution KK conceptualized the study, conducted the statistical analyses, and drafted the manuscript. YF and MK were involved in the delivery of the intervention. RK and SU contributed to the development of the program. HS supervised the research project. All authors read and approved the final manuscript. Acknowledgement The authors would like to express their sincere gratitude to the children and families who participated in this study. We also thank the staff who supported the implementation of the program in the clinical center. Data Availability The datasets generated and/or analyzed during the current study are not publicly available due to ethical restrictions and participant confidentiality but are available from the corresponding author on reasonable request. References American Psychiatric Association. (2022). Diagnostic and statistical manual of mental disorders (5th ed., text rev.; DSM-5-TR). American Psychiatric Publishing. Polanczyk GV, Salum GA, Sugaya LS, Caye A, Rohde LA. Annual research review: A meta-analysis of the worldwide prevalence of mental disorders in children and adolescents. J Child Psychol Psychiatry. 2015;56(3):345–65. https://doi.org/10.1111/jcpp.12381 . Kishida K, Tsuda M, Ishikawa SI. 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The Affective Reactivity Index: A concise irritability scale for clinical and research settings. J Child Psychol Psychiatry. 2012;53(11):1109–17. https://doi.org/10.1111/j.1469-7610.2012.02561.x . Kishida K, Tsuda M, Takahashi F, Ishikawa SI. Irritability and mental health profiles among children and adolescents: A result of latent profile analysis. J Affect Disord. 2022;300:76–83. https://doi.org/10.1016/j.jad.2021.12.045 . Takahashi F, Sato H, Nagasaku M. Development of an aggressive behavior scale for children: examination of its reliability and validity. Japanese J Cogn Therapy. 2009;2:75–85. Goodman R. The Strengths and Difficulties Questionnaire: A research note. J Child Psychol Psychiatry. 1997;38(5):581–6. https://doi.org/10.1111/j.1469-7610.1997.tb01545.x . Moriwaki A, Kamio Y. Normative data and psychometric properties of the strengths and difficulties questionnaire among Japanese school-aged children. Child Adolesc Psychiatry Mental Health. 2014;8:1. https://doi.org/10.1186/1753-2000-8-1 . Kishida K, Tsuda M, Ishikawa S. (2023). Development and validation of a Parenting Behavior Questionnaire. Poster presented at the 23rd Annual Meeting of the Japanese Association for Cognitive Therapy. Rush, A. J., Trivedi, M. H., Ibrahim, H. M., Carmody, T. J., Arnow, B., Klein, D.N., … Keller, M. B. (2003). The 16-Item Quick Inventory of Depressive Symptomatology(QIDS), clinician rating (QIDS-C), and self-report (QIDS-SR): a psychometric evaluation in patients with chronic major depression. Biological Psychiatry, 54(5), 573–583. https://doi.org/10.1016/S0006-3223(02)01866-8. Fujisawa D, Nakagawa A, Tajima M. Development of the Japanese version of the self-report Quick Inventory of Depressive Symptomatology (QIDS-SR). Japanese J Stress Sci. 2010;25(1):43–52. Constantino JN, Gruber CP. Social Responsiveness Scale–Second Edition (SRS-2) manual. Western Psychological Services; 2012. Pinquart M. Associations of parenting dimensions and styles with externalizing problems of children and adolescents: An updated meta-analysis. Dev Psychol. 2017;53(5):873–932. https://doi.org/10.1037/dev0000295 . Tables Tables are available in the Supplementary Files section. Additional Declarations No competing interests reported. Supplementary Files floatimage1.jpeg floatimage2.jpeg floatimage3.jpeg Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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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-8744950","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":605018358,"identity":"8bc3da5b-5438-4cf1-8e58-1104ea886ac9","order_by":0,"name":"Kohei Kishida","email":"data:image/png;base64,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","orcid":"","institution":"Kobe University","correspondingAuthor":true,"prefix":"","firstName":"Kohei","middleName":"","lastName":"Kishida","suffix":""},{"id":605018360,"identity":"085ef81f-2d83-4726-a47c-939768c677c6","order_by":1,"name":"Yuzaburo Fukuyama","email":"","orcid":"","institution":"Kwansei Gakuin University","correspondingAuthor":false,"prefix":"","firstName":"Yuzaburo","middleName":"","lastName":"Fukuyama","suffix":""},{"id":605018363,"identity":"cf842c03-5f42-4fdf-ac2e-b72e1d6a668c","order_by":2,"name":"Mirena Kitamura","email":"","orcid":"","institution":"Saiseikai Hyogoken Hospital","correspondingAuthor":false,"prefix":"","firstName":"Mirena","middleName":"","lastName":"Kitamura","suffix":""},{"id":605018365,"identity":"be8d4f73-825f-40fb-84a1-4a1b1b86a4e0","order_by":3,"name":"Ryodai Kamioka","email":"","orcid":"","institution":"Kwansei Gakuin University","correspondingAuthor":false,"prefix":"","firstName":"Ryodai","middleName":"","lastName":"Kamioka","suffix":""},{"id":605018366,"identity":"26ea657d-28fa-4ed6-bc7f-c2101e33442c","order_by":4,"name":"Satsuki Ueda","email":"","orcid":"","institution":"Kyoto Bunkyo University","correspondingAuthor":false,"prefix":"","firstName":"Satsuki","middleName":"","lastName":"Ueda","suffix":""},{"id":605018367,"identity":"09c8d814-4f36-4529-b1df-455da4d83ec6","order_by":5,"name":"Hiroshi Sato","email":"","orcid":"","institution":"Kwansei Gakuin University","correspondingAuthor":false,"prefix":"","firstName":"Hiroshi","middleName":"","lastName":"Sato","suffix":""}],"badges":[],"createdAt":"2026-01-30 21:23:49","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8744950/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8744950/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":108085270,"identity":"688d418e-bdaf-461f-8c21-6f35748e9aa8","added_by":"auto","created_at":"2026-04-29 08:26:46","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":257551,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8744950/v1/fbcbc6c8-d1a6-4278-a83a-506b1ace1dea.pdf"},{"id":104749352,"identity":"69ee3ac4-2da4-4454-9965-12e07262a5dc","added_by":"auto","created_at":"2026-03-16 18:57:10","extension":"jpeg","order_by":3,"title":"","display":"","copyAsset":false,"role":"supplement","size":568477,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8744950/v1/afd39227aca2ac431483d694.jpeg"},{"id":104783019,"identity":"a2c3b833-7339-492d-b9d1-9b074cb44839","added_by":"auto","created_at":"2026-03-17 07:58:06","extension":"jpeg","order_by":4,"title":"","display":"","copyAsset":false,"role":"supplement","size":1246346,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage2.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8744950/v1/f41f0e839265bb85c32b29ad.jpeg"},{"id":104749353,"identity":"180aa2d1-e1ef-4075-b5d8-93d87e4e93bd","added_by":"auto","created_at":"2026-03-16 18:57:10","extension":"jpeg","order_by":5,"title":"","display":"","copyAsset":false,"role":"supplement","size":2305553,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage3.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8744950/v1/99477c0a4b89b3ff302ec2c2.jpeg"}],"financialInterests":"No competing interests reported.","formattedTitle":"Effects of group-based parent training on oppositional defiant disorder symptoms and irritability in Japanese children","fulltext":[{"header":"Introduction","content":"\u003cp\u003eOppositional Defiant Disorder (ODD) is a common disruptive behavior disorder characterized by a persistent pattern of oppositional and defiant behavior and frequent anger and irritability [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. A large international meta-analysis estimated the prevalence of ODD to be 3.6%, indicating that ODD is not a rare condition worldwide among children and adolescents [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. In Japan, the prevalence of ODD has been reported to be 4.67% [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e], suggesting that ODD represents a clinically significant mental health concern also within the Japanese cultural context. Children with ODD symptoms are at increased risk for a wide range of adverse developmental outcomes, including persistent interpersonal difficulties, impaired family relationships, and reduced occupational opportunities in adulthood [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Given the chronic and impairing nature of ODD, early and effective psychosocial interventions are considered essential to alter maladaptive developmental trajectories.\u003c/p\u003e \u003cp\u003eAmong evidence-based psychosocial treatments for ODD and related disruptive behavior disorders, parent training (PT) has consistently been regarded as the gold standard intervention [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. PT programs primarily aim to modify coercive parent\u0026ndash;child interaction patterns by increasing positive parenting behaviors (e.g., praise, positive involvement) while reducing negative parenting behaviors (e.g., inconsistent discipline, harsh or reactive responses). Meta-analytic reviews have demonstrated robust effects of PT in reducing oppositional and defiant behaviors in children and adolescents [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. A large-scale meta-analysis showed that PT is effective across multiple delivery formats, including individual, group-based, and combined parent\u0026ndash;child interventions, highlighting its flexibility and broad applicability [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eDespite the robust evidence supporting PT for ODD and related problems, important gaps remain in the literature. First, although PT has been extensively studied and validated in Western countries, empirical evidence from non-Western contexts remains limited. In Japan, parent training has been implemented and studied mainly for children with developmental disabilities such as autism spectrum disorder and attention-deficit/hyperactivity disorder [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. In contrast, no study conducted in Japan has evaluated the effectiveness of PT using ODD-related outcomes as the primary endpoint. Given potential cultural differences in parenting practices and family dynamics, the absence of Japanese data limits understanding of the cross-cultural generalizability and applicability of PT.\u003c/p\u003e \u003cp\u003eSecond, although PT has consistently demonstrated effectiveness in reducing overt oppositional and defiant behaviors, far less attention has been paid to its effects on irritability [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Irritability constitutes a core emotional symptom dimension of ODD and has been identified as a transdiagnostic risk factor. Longitudinal studies indicate that elevated irritability in childhood predicts later anxiety and depressive disorders, as well as the development of ODD [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Despite its developmental and clinical significance, irritability has rarely been examined as a treatment outcome in PT research.\u003c/p\u003e \u003cp\u003eThird, PT is based on the assumption that improvements in child behavior occur through changes in parenting behaviors, including increases in positive practices (e.g., praise, warm involvement) and reductions in negative practices (e.g., harsh or inconsistent discipline). However, the mechanisms linking changes in parenting behaviors to changes in children\u0026rsquo;s oppositional symptoms and irritability remain unclear. Although parenting behaviors are often assumed to mediate treatment effects for externalizing problems, empirical support for these mechanisms is limited and inconsistent [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. In Japan, despite the growing implementation of PT [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e], few studies have directly examined parenting behaviors as outcomes, leaving it unclear whether improvements in child symptoms are accompanied by meaningful changes in parenting practices.\u003c/p\u003e \u003cp\u003eThe present study aimed to address these gaps by examining the effectiveness of a newly developed group-based parent training program for parents of children with ODD (PT-ODD) using an open trial design with pre-treatment, post-treatment, and three-month follow-up assessments. The study had three objectives. First, we evaluated the effectiveness of group-based parent training for ODD-related outcomes in a Japanese clinical sample, focusing on clinician-rated functional impairment and parent-reported oppositional defiant symptoms. Second, we examined whether the intervention was associated with reductions in irritability, a core emotional symptom dimension of ODD that has rarely been examined as a treatment outcome in prior PT research. Third, we investigated whether changes in parenting behaviors following the intervention were associated with changes in oppositional defiant symptoms and irritability over time.\u003c/p\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStudy Design and Participants\u003c/h2\u003e \u003cp\u003eThis study was an interventional open trial evaluating the effects of a group-based parent training program for parents of children diagnosed with ODD. This study employed an open trial design with pre-treatment, post-treatment, and three-month follow-up assessments. Participants were parents of children who experienced difficulties with ODD. Inclusion criteria were: (a) parents or primary caregivers of children in grades 2 to 6 of elementary school (aged 7\u0026ndash;12 years); (b) children meeting diagnostic criteria for ODD; and (c) availability to attend the program sessions on a regular basis.\u003c/p\u003e \u003cp\u003e \u003cstrong\u003eEthical Approval\u003c/strong\u003e \u003cp\u003e \u003cb\u003eand Informed Consent\u003c/b\u003e \u003c/p\u003e \u003c/p\u003e \u003cp\u003eThe study protocol was approved by the institutional review board of the author\u0026rsquo;s affiliated university (KG-IRB-23-03). All participating parents received a full explanation of the study procedures and provided written informed consent prior to participation. This study was registered as a clinical trial in the University Hospital Medical Information Network (UMIN) Clinical Trials Registry (UMIN000054295) on May 1, 2024. All procedures involving human participants were performed in accordance with the ethical standards of the institutional research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eParent Training Program for ODD (PT-ODD)\u003c/h3\u003e\n\u003cp\u003eA group-based parent training program for parents of children with ODD (PT-ODD) was delivered in a group format and consisted of eight biweekly sessions, each lasting 120 minutes. The program was grounded in behavioral principles and was informed by the core parent training platform disseminated by the Japanese Parent Training Research Association [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e], as well as established parent training models for children and adolescents with ODD [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. The program aimed to help parents better understand their children\u0026rsquo;s oppositional behavior and anger-related problems, while teaching practical, evidence-based parenting strategies guided by functional assessment.\u003c/p\u003e \u003cp\u003eSession 1 provided an orientation to the program and psychoeducation on ODD, anger-related problems, and parent\u0026ndash;child interaction patterns. Session 2 focused on observing and classifying child behavior, with parents learning to identify antecedents, behaviors, and consequences. Session 3 addressed functional assessment, helping parents understand the behavioral functions of oppositional and anger-related behaviors and use this understanding to guide effective parenting responses. Session 4 targeted positive parenting skills, including effective praise, positive attention, and the use of \u0026ldquo;special time\u0026rdquo; to strengthen the parent\u0026ndash;child relationship. Session 5 introduced planned ignoring as a strategy for reducing minor, non-dangerous oppositional behaviors. Session 6 focused on providing advance notice and clear, consistent instructions to prevent escalation of anger and noncompliance. Session 7 addressed the use of warnings and non-harsh consequences, including time-out and response cost, emphasizing consistent, predictable, and proportionate implementation. Session 8 reviewed all skills, with particular emphasis on the continued importance of praise, positive attention, and special time.\u003c/p\u003e \u003cp\u003eEach session included brief lectures by the first author, individual and group exercises, role-play, and homework assignments to promote skill acquisition and generalization to everyday situations. To ensure adequate treatment participation and intervention fidelity, parents who missed a group session were offered an individual make-up session in which the missed content was reviewed. This approach was used to support treatment adherence and to maintain intervention consistency and fidelity across participants.\u003c/p\u003e\n\u003ch3\u003eMeasures\u003c/h3\u003e\n\u003cp\u003eAll measures were administered at three time points: pre-treatment, post-treatment, and three-month follow-up. The same assessment procedures were used at each time point. With the exception of the clinician-administered interview, all measures were completed by parents.\u003c/p\u003e \u003cp\u003e \u003cstrong\u003eClinician-Rated Outcomes\u003c/strong\u003e \u003cp\u003eClinician-rated diagnostic status and clinical severity were assessed using the Anxiety Disorders Interview Schedule [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. The ADIS was used to evaluate the presence of ODD. ODD-related functional impairment was assessed using the Clinician Severity Rating (CSR), which reflects the degree of interference caused by symptoms in the child\u0026rsquo;s daily functioning. In addition, overall clinical severity was assessed using the Clinical Global Impression\u0026ndash;Severity scale [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. The CGI-S is a clinician-rated measure that evaluates the patient\u0026rsquo;s overall level of psychopathology at the time of assessment, with higher scores indicating greater severity. The ADIS and the CGI-S have been used to assess ODD in previous Japanese research [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e].\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cb\u003eOppositional Defiant Symptoms\u003c/b\u003e: Parent-reported oppositional defiant symptoms were assessed using the Disruptive Behavior Disorders Rating Scale (DBDRS) [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. The Japanese version of the DBDRS has demonstrated adequate reliability and validity [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. The DBDRS assesses four symptom domains: inattention symptoms, hyperactivity symptoms, oppositional defiant symptoms, and conduct problems.\u003c/p\u003e \u003cp\u003e \u003cstrong\u003eIrritability\u003c/strong\u003e \u003cp\u003eChild irritability reported by parents was assessed using the Japanese version of the Affective Reactivity Index (ARI) [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. The reliability and validity of the Japanese version of the ARI have been established previously [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. The ARI measures the frequency and severity of irritability, with higher scores indicating greater irritability.\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eAggressive Behaviors\u003c/strong\u003e \u003cp\u003eAggressive behaviors were assessed using the Aggressive Behavior Scale for Children and Adolescents (ABS-CA) [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. Although the ABS-CA was originally developed as a self-report measure, in the present study, the scale was administered as a parent-report measure. The ABS-CA includes three subscales assessing physical aggression, verbal aggression, and relational aggression. A total aggressive behaviors score, calculated as the sum of these three subscales, was used in the present study.\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eGeneral Difficulties and Prosocial Behavior\u003c/strong\u003e \u003cp\u003eGeneral child difficulties and prosocial behavior were assessed using the parent-report version of the Strengths and Difficulties Questionnaire (SDQ) [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e], which served as a general indicator of child functioning. The reliability and validity of the Japanese parent-report SDQ have been established in previous research [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. In the present study, the Total Difficulties score and the Prosocial Behavior subscale were analyzed.\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cb\u003eParenting Behaviors\u003c/b\u003e: Parenting behaviors were assessed using the Parenting Behaviors Questionnaire (PBQ) [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e], for which reliability and validity have been established in the previous research. Positive parenting behaviors were calculated as the total score of four subscales: Positive Attention, Reward, Warmth, and Autonomy Granting. Negative parenting behaviors were calculated as the total score of three subscales: Physical Punishment, Verbal Punishment, and Psychological Control. Higher scores indicated greater use of the respective parenting behaviors.\u003c/p\u003e \u003cp\u003e \u003cstrong\u003eParental Depressive Symptoms\u003c/strong\u003e \u003cp\u003eParental depressive symptoms were assessed using the Quick Inventory of Depressive Symptomatology (QIDS) [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. The Japanese version of the QIDS has been developed and its reliability and validity have been examined [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. Higher scores indicated greater severity of depressive symptoms.\u003c/p\u003e \u003c/p\u003e\n\u003ch3\u003eAcceptability\u003c/h3\u003e\n\u003cp\u003eTo assess program acceptability, a parent-rated acceptability scale was used. This scale was originally developed to measure the acceptability of cognitive behavioral therapy for Japanese children with oppositional defiant disorder (ODD) and their families (Kishida et al., 2024). Parents were asked to rate eight items\u0026mdash;enjoyment, satisfaction, willingness to recommend, perceived usefulness, understanding, perceived difficulty, perceived burden, and problem-solving self-efficacy\u0026mdash;on a 5-point Likert scale ranging from 0 to 4. Items assessing perceived difficulty and perceived burden were reverse-scored, and the total score was calculated as the acceptability score (possible range: 0\u0026ndash;32). Acceptability was assessed at post-intervention.\u003c/p\u003e\n\u003ch3\u003eStatistical plan\u003c/h3\u003e\n\u003cp\u003eChanges in child and parent outcomes across three time points (pre-treatment [Time 1], post-treatment [Time 2], and three-month follow-up [Time 3]) were analyzed using linear mixed-effects models (LMMs) using Restricted Maximum Likelihood (REML) estimation and Satterthwaite\u0026rsquo;s approximation, with time specified as a fixed effect and participant intercepts as random effects. To evaluate intervention effects, LMMs were applied to clinician-rated functional impairment for ODD (CSR) and parent-reported oppositional defiant symptoms (DBDRS) and irritability (ARI) as primary outcomes. LMMs were also applied to other outcomes, overall clinical severity (CGI-S), including inattention symptoms, hyperactivity symptoms, and conduct problems (DBDRS), aggressive behaviors (ABS-CA), general difficulties and prosocial behavior (SDQ), parenting behaviors (PBQ), and parental depressive symptoms (QIDS) as secondary outcomes. Effect sizes (Hedges\u0026rsquo; \u003cem\u003eg\u003c/em\u003e) were calculated based on descriptive statistics. Associations between changes in positive and negative parenting behaviors and changes in oppositional defiant symptoms and irritability were examined using Pearson correlations, relating changes from Time 1 to Time 2 to changes from Time 1 to Time 2 (short-term correlations) and from Time 1 to Time 3 (long-term correlations). For these correlation analyses only, missing values (one participant at follow-up) were handled using the last observation carried forward (LOCF) method. The significance level was set at \u003cem\u003ep\u003c/em\u003e \u0026lt; .10 to reduce the risk of Type II errors given the small sample size. All analyses were conducted using JASP.\u003c/p\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003eParticipant Characteristics\u003c/h2\u003e \u003cp\u003eTwelve children diagnosed with ODD and their mothers participated in the study and were included in the analyses. The children had a mean age of 10.42 years (\u003cem\u003eSD\u003c/em\u003e\u0026thinsp;=\u0026thinsp;1.04), and the sample included seven girls and five boys. Among the children, two (16.7%) had a comorbid diagnosis of attention-deficit/hyperactivity disorder (ADHD), as assessed using the ADIS. In addition, autism spectrum disorder (ASD)\u0026ndash;related symptoms were assessed using the Social Responsiveness Scale\u0026ndash;Second Edition (SRS-2) [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. Based on SRS-2 total T-scores, two children (16.7%) were classified as severe, three (25.0%) as moderate, one (8.3%) as mild, and six (50.0%) as within the normal range in terms of ASD symptom severity.\u003c/p\u003e \u003cp\u003eThe mean age of the mothers was 45.36 years (\u003cem\u003eSD\u003c/em\u003e\u0026thinsp;=\u0026thinsp;4.21); one mother did not report her age. All participants completed the post-treatment assessment (100%), and 11 participants completed the three-month follow-up assessment (91.7%). Participant characteristics are presented in Table\u0026nbsp;1.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eTreatment Attendance, Engagement, and Acceptability\u003c/h3\u003e\n\u003cp\u003eWith regard to treatment attendance, participants attended an average of 6.67 (\u003cem\u003eSD\u003c/em\u003e\u0026thinsp;=\u0026thinsp;1.11) of the eight group sessions. Individual make-up sessions were conducted for all participants who missed group sessions, with a mean of 1.33 (\u003cem\u003eSD\u003c/em\u003e\u0026thinsp;=\u0026thinsp;1.11) sessions per participant, to ensure adequate treatment participation and intervention fidelity. In addition, all mothers completed the assigned homework at each session throughout the program (100%). The mean acceptability score was 26.17 (\u003cem\u003eSD\u003c/em\u003e\u0026thinsp;=\u0026thinsp;3.24), indicating a high level of program acceptability.\u003c/p\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eChanges in Clinician-Rated Outcomes\u003c/h2\u003e \u003cp\u003eLMMs revealed a significant main effect of time on clinician-rated functional impairment (CSR), \u003cem\u003eF\u003c/em\u003e (2, 21.32)\u0026thinsp;=\u0026thinsp;9.27, \u003cem\u003ep\u003c/em\u003e = .001. Estimated marginal means indicated a significant reduction in CSR from pre-treatment to post-treatment (estimated difference\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;1.75, \u003cem\u003eSE\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.78, \u003cem\u003ep\u003c/em\u003e = .024), with a large effect size (Hedges\u0026rsquo; \u003cem\u003eg\u003c/em\u003e\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.85). This improvement was maintained at the three-month follow-up (estimated difference\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;3.43, \u003cem\u003eSE\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.98, \u003cem\u003ep\u003c/em\u003e \u0026lt; .001), with an even larger effect size (Hedges\u0026rsquo; \u003cem\u003eg\u003c/em\u003e\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;1.40). Based on clinician ratings, the remission rate following the intervention was 33% (4 of 12 children), which increased to 50% (6 of 12 children) at the three-month follow-up. Descriptive statistics for all outcome variables at pre-treatment (Time 1), post-treatment (Time 2), and three-month follow-up (Time 3) are shown in Table\u0026nbsp;2. Results of the linear mixed-effects models and effect sizes are presented in Table\u0026nbsp;3.\u003c/p\u003e \u003cp\u003eLMMs also showed a significant main effect of time for overall clinical severity (CGI-S), \u003cem\u003eF\u003c/em\u003e (2, 21.14)\u0026thinsp;=\u0026thinsp;11.25, \u003cem\u003ep\u003c/em\u003e \u0026lt; .001. CGI-S scores significantly decreased from pre-treatment to post-treatment (estimated difference\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;1.00, \u003cem\u003eSE\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.32, \u003cem\u003ep\u003c/em\u003e = .002; Hedges\u0026rsquo; \u003cem\u003eg\u003c/em\u003e\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.81) and remained significantly lower at follow-up (estimated difference\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;1.57, \u003cem\u003eSE\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.33, \u003cem\u003ep\u003c/em\u003e \u0026lt; .001; Hedges\u0026rsquo; \u003cem\u003eg\u003c/em\u003e\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;1.32).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003eChanges in Oppositional Defiant Symptoms and Irritability\u003c/h2\u003e \u003cp\u003eFor parent-reported oppositional defiant symptoms, LMMs showed a significant main effect of time, \u003cem\u003eF\u003c/em\u003e (2, 21.11)\u0026thinsp;=\u0026thinsp;8.70, \u003cem\u003ep\u003c/em\u003e = .002. Symptoms significantly decreased from pre-treatment to post-treatment (estimated difference\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;3.08, \u003cem\u003eSE\u003c/em\u003e\u0026thinsp;=\u0026thinsp;1.08, \u003cem\u003ep\u003c/em\u003e = .004; Hedges\u0026rsquo; \u003cem\u003eg\u003c/em\u003e\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.59), and this improvement was maintained at the three-month follow-up (estimated difference\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;4.53, \u003cem\u003eSE\u003c/em\u003e\u0026thinsp;=\u0026thinsp;1.12, \u003cem\u003ep\u003c/em\u003e \u0026lt; .001; Hedges\u0026rsquo; \u003cem\u003eg\u003c/em\u003e\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.81). Overall, moderate-to-large improvements were observed. No significant main effect of time was observed for inattention symptoms, \u003cem\u003eF\u003c/em\u003e (2, 21.09)\u0026thinsp;=\u0026thinsp;1.52, \u003cem\u003ep\u003c/em\u003e = .243, hyperactivity symptoms, \u003cem\u003eF\u003c/em\u003e (2, 21.01)\u0026thinsp;=\u0026thinsp;3.13, \u003cem\u003ep\u003c/em\u003e = .065, or conduct problems, \u003cem\u003eF\u003c/em\u003e (2, 21.06)\u0026thinsp;=\u0026thinsp;1.45, \u003cem\u003ep\u003c/em\u003e = .257.\u003c/p\u003e \u003cp\u003eFor irritability, LMMs indicated only a trend-level main effect of time, \u003cem\u003eF\u003c/em\u003e (2, 20.97)\u0026thinsp;=\u0026thinsp;3.26, \u003cem\u003ep\u003c/em\u003e = .058, which did not reach statistical significance. Irritability showed no significant change from pre-treatment to post-treatment (estimated difference\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.75, \u003cem\u003eSE\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.76, \u003cem\u003ep\u003c/em\u003e = .323; Hedges\u0026rsquo; \u003cem\u003eg\u003c/em\u003e\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.25). Although a reduction was observed at the three-month follow-up (estimated difference\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;1.99, SE\u0026thinsp;=\u0026thinsp;0.78, \u003cem\u003ep\u003c/em\u003e = .022; Hedges\u0026rsquo; \u003cem\u003eg\u003c/em\u003e\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.67), this finding should be interpreted with caution given the absence of a significant overall time effect. Overall, improvements in irritability were small to moderate and emerged gradually rather than immediately following the intervention.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003eChanges in Other Child Outcomes\u003c/h2\u003e \u003cp\u003eFor aggressive behaviors, LMMs indicated only a trend-level main effect of time, \u003cem\u003eF\u003c/em\u003e (2, 20.97)\u0026thinsp;=\u0026thinsp;2.76, \u003cem\u003ep\u003c/em\u003e = .086, which did not reach statistical significance. Aggressive behaviors showed no significant reduction from pre-treatment to post-treatment (estimated difference\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;2.50, \u003cem\u003eSE\u003c/em\u003e\u0026thinsp;=\u0026thinsp;1.15, \u003cem\u003ep\u003c/em\u003e = .058; Hedges\u0026rsquo; \u003cem\u003eg\u003c/em\u003e\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.34). Although a reduction was observed at the three-month follow-up (estimated difference\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;2.15, \u003cem\u003eSE\u003c/em\u003e\u0026thinsp;=\u0026thinsp;1.18, \u003cem\u003ep\u003c/em\u003e = .070; Hedges\u0026rsquo; \u003cem\u003eg\u003c/em\u003e\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.44), this change should be interpreted with caution given the absence of a statistically significant overall time effect.\u003c/p\u003e \u003cp\u003eFor total difficulties, LMMs revealed a significant main effect of time, \u003cem\u003eF\u003c/em\u003e (2, 21.05)\u0026thinsp;=\u0026thinsp;4.08, \u003cem\u003ep\u003c/em\u003e = .032. Total difficulties showed a significant reduction from pre-treatment to post-treatment (estimated difference\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;1.92, \u003cem\u003eSE\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.68, \u003cem\u003ep\u003c/em\u003e = .009; Hedges\u0026rsquo; \u003cem\u003eg\u003c/em\u003e\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.44). However, this improvement was not maintained at the three-month follow-up, as the difference from pre-treatment was no longer statistically significant (estimated difference\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.71, \u003cem\u003eSE\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.70, \u003cem\u003ep\u003c/em\u003e = .313; Hedges\u0026rsquo; \u003cem\u003eg\u003c/em\u003e\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.20). No significant main effect of time was observed for prosocial behavior, \u003cem\u003eF\u003c/em\u003e (2, 21.11)\u0026thinsp;=\u0026thinsp;0.14, \u003cem\u003ep\u003c/em\u003e = .867.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003eChanges in Parent Outcomes\u003c/h2\u003e \u003cp\u003eA significant main effect of time was observed for positive parenting behaviors, \u003cem\u003eF\u003c/em\u003e (2, 21.07)\u0026thinsp;=\u0026thinsp;9.27, \u003cem\u003ep\u003c/em\u003e = .006. Positive parenting behaviors significantly increased from pre-treatment to post-treatment (estimated difference\u0026thinsp;=\u0026thinsp;4.00, \u003cem\u003eSE\u003c/em\u003e\u0026thinsp;=\u0026thinsp;1.40, \u003cem\u003ep\u003c/em\u003e = .004), with a medium effect size (Hedges\u0026rsquo; \u003cem\u003eg\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.46). This improvement was maintained at the three-month follow-up (estimated difference\u0026thinsp;=\u0026thinsp;4.82, \u003cem\u003eSE\u003c/em\u003e\u0026thinsp;=\u0026thinsp;1.44, \u003cem\u003ep\u003c/em\u003e = .002), with a medium effect size (Hedges\u0026rsquo; \u003cem\u003eg\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.47). For negative parenting behaviors, no significant main effect of time was observed, \u003cem\u003eF\u003c/em\u003e (2, 20.87)\u0026thinsp;=\u0026thinsp;2.57, \u003cem\u003ep\u003c/em\u003e = .101. No significant main effect of time was observed for parental depressive symptoms, \u003cem\u003eF\u003c/em\u003e (2, 21.19)\u0026thinsp;=\u0026thinsp;1.55, \u003cem\u003ep\u003c/em\u003e = .235.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003eCorrelations Between Changes in Parenting Behaviors and Symptom Outcomes\u003c/h2\u003e \u003cp\u003eChanges in positive parenting behaviors from Time 1 to Time 2 were moderately associated with reductions in oppositional defiant symptoms from Time 1 to Time 2 (\u003cem\u003er\u003c/em\u003e\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;.56, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.06) and weakly associated with reductions in irritability (\u003cem\u003er\u003c/em\u003e\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;.30, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.35). Correlations with symptom changes from Time 1 to Time 3 were negligible (\u003cem\u003er\u003c/em\u003e = .04, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.91 for oppositional defiant symptoms; \u003cem\u003er\u003c/em\u003e\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;.18, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.58 for irritability). Changes in negative parenting behaviors from Time 1 to Time 2 showed moderate positive associations with changes in oppositional defiant symptoms (\u003cem\u003er\u003c/em\u003e = .44, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.15) and irritability (\u003cem\u003er\u003c/em\u003e = .20, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.25) from Time 1 to Time 2. Similar correlations were observed for changes in oppositional defiant symptoms (\u003cem\u003er\u003c/em\u003e = .44, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.10) and irritability (\u003cem\u003er\u003c/em\u003e = .50, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.15) from Time 1 to Time 3. Short- and long-term correlations between changes in parenting behaviors and changes in child outcomes are shown in Table\u0026nbsp;4.\u003c/p\u003e \u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe present study examined the effectiveness of a group-based parent training program for parents of children with ODD (PT-ODD). This study makes three primary contributions to the literature: it provides evidence for the effectiveness of parent training when ODD is defined as the primary treatment target in a Japanese clinical context; it offers novel findings regarding the effects of parent training on irritability, a core emotional dimension of ODD; and it provides preliminary insight into parenting behaviors as a potential mechanism linking the intervention to changes in oppositional defiant symptoms.\u003c/p\u003e \u003cp\u003eThe first contribution is the demonstration that group-based parent training can lead to meaningful improvements in ODD symptoms and functional impairment among Japanese children. Significant and sustained improvements were observed across clinician-rated and parent-reported ODD-related outcomes, with remission rates increasing at follow-up. Although parent training is well established as the gold standard intervention for ODD [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e], empirical evidence from Japan has been scarce, particularly studies using ODD as the primary outcome [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. The present findings therefore extend the Japanese literature and support the cross-cultural applicability of parent training models originally developed in Western contexts.\u003c/p\u003e \u003cp\u003eThe second contribution concerns irritability, which is increasingly recognized as a core emotional dimension of ODD and a transdiagnostic risk factor for later emotional and behavioral disorders [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. In the present study, irritability did not show significant immediate improvement, and the overall time effect did not reach statistical significance. However, reductions were observed at the three-month follow-up, suggesting a delayed pattern of change. This finding is consistent with the notion that parent training primarily targets parent\u0026ndash;child interaction patterns rather than children\u0026rsquo;s internal emotion regulation processes [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e], and that emotional symptoms such as irritability may not be directly targeted by parent training but may improve more gradually following sustained changes in the relational environment and child behavior.\u003c/p\u003e \u003cp\u003eThe third contribution relates to mechanisms of change. Previous reviews have suggested that changes in parenting behaviors may underlie treatment effects for externalizing problems, although empirical evidence remains limited [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. In the present study, changes in positive parenting behaviors were associated with short-term improvements in oppositional defiant symptoms, whereas associations involving negative parenting behaviors\u0026mdash;despite no significant change during the intervention\u0026mdash;were observed for longer-term changes in oppositional defiant symptoms. Although a systematic review has shown that both positive and negative parenting behaviors are associated with externalizing problems, including oppositional defiant symptoms [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e], the present findings suggest that the short-term and long-term influences of these parenting behaviors on oppositional defiant symptoms may differ. In contrast, no significant associations were observed between changes in parenting behaviors and irritability. Therefore, improvements in irritability may not be directly attributable to changes in parenting behaviors but may instead be mediated by changes in other variables, such as the parent\u0026ndash;child relationship or child behavior.\u003c/p\u003e \u003cp\u003eChanges in aggressive behavior and general difficulties were weaker and less stable, suggesting that these broader outcomes are less directly influenced by ODD-focused interventions. This pattern highlights the specificity of parent training effects and the importance of distinguishing proximal treatment targets from more distal outcomes. In addition, no significant changes were observed in parental depressive symptoms, consistent with the primary focus of parent training on parenting practices and child behavior rather than parental mood. Nevertheless, maintaining stable levels of depressive symptoms may still be clinically meaningful given the substantial parenting burden associated with ODD, and group-based formats may provide indirect benefits through peer support and normalization.\u003c/p\u003e \u003cp\u003eSeveral limitations should be acknowledged. First, the open trial design without a control group limits causal inference. Second, the small sample size reduces statistical power and generalizability, and formal mediation analyses were not conducted. Third, reliance on parent-report measures and the relatively short follow-up period warrant caution. Future studies should employ randomized controlled designs with larger samples and longer follow-up periods to confirm these findings and clarify mechanisms of change.\u003c/p\u003e \u003cp\u003eDespite these limitations, the present study provides preliminary evidence that group-based parent training is a feasible and potentially effective intervention for Japanese children with ODD. The findings suggest that core oppositional defiant symptoms may improve relatively quickly, whereas irritability may change more gradually over time, underscoring the importance of integrating both behavioral and emotional perspectives in interventions for ODD.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e \u003ch2\u003eEthics approval and consent to participate\u003c/h2\u003e \u003cp\u003eThe study protocol was approved by the Institutional Review Board of Kwansei Gakuin University (Approval No. KG-IRB-23-03). Written informed consent was obtained from all participating parents prior to participation. This study was registered as a clinical trial in the University Hospital Medical Information Network (UMIN) Clinical Trials Registry (UMIN000054295) on May 1, 2024. All procedures involving human participants were performed in accordance with the ethical standards of the institutional research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eConsent for publication\u003c/strong\u003e \u003cp\u003eNot applicable.\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eCompeting interests\u003c/strong\u003e \u003cp\u003eThe authors declare that they have no competing interests.\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eFunding\u003c/h2\u003e \u003cp\u003eThis work was supported by the Japan Society for the Promotion of Science (JSPS) Grants-in-Aid for Scientific Research under Grant Numbers 21K13737 and 24K16861.\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eKK conceptualized the study, conducted the statistical analyses, and drafted the manuscript. YF and MK were involved in the delivery of the intervention. RK and SU contributed to the development of the program. HS supervised the research project. All authors read and approved the final manuscript.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eThe authors would like to express their sincere gratitude to the children and families who participated in this study. We also thank the staff who supported the implementation of the program in the clinical center.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eThe datasets generated and/or analyzed during the current study are not publicly available due to ethical restrictions and participant confidentiality but are available from the corresponding author on reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eAmerican Psychiatric Association. (2022). 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Dev Psychol. 2017;53(5):873\u0026ndash;932. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1037/dev0000295\u003c/span\u003e\u003cspan address=\"10.1037/dev0000295\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"},{"header":"Tables","content":"\u003cp\u003eTables are available in the Supplementary Files section.\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","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":"Parent Training, Group Intervention, Oppositional Defiant Disorder, Irritability, Parenting Behaviors","lastPublishedDoi":"10.21203/rs.3.rs-8744950/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8744950/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e \u003cp\u003eOppositional defiant disorder (ODD) is a childhood disorder associated with substantial functional impairment. Although parent training (PT) is the gold standard intervention for ODD, evidence from non-Western contexts is limited, and its effect on irritability\u0026mdash;a core emotional dimension of ODD\u0026mdash;remains unclear.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eThis open trial examined the effectiveness of a group-based parent training program for parents of children with ODD (PT-ODD). Twelve Japanese mothers who had children aged 7\u0026ndash;12 years participated. Outcomes were assessed at pre-treatment, post-treatment, and three-month follow-up using clinician-rated and parent-reported measures. Changes over time were analyzed using linear mixed-effects models, and associations between parenting behaviors and child symptoms were examined.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eClinician-rated functional impairment and parent-reported oppositional defiant symptoms showed significant and sustained improvements, with large effect sizes. Remission rates increased from 33% post-treatment to 50% at follow-up. Irritability showed no immediate improvement and the overall time effect did not reach statistical significance. However, irritability was significantly lower at follow-up than at baseline, suggesting a potential delayed effect. Changes in positive parenting behaviors were associated with short-term improvements in oppositional defiant symptoms, whereas changes in negative parenting behaviors were observed for longer-term changes in oppositional defiant symptoms.\u003c/p\u003e\u003ch2\u003eConclusions\u003c/h2\u003e \u003cp\u003eThese findings suggest that PT-ODD leads to immediate improvements in ODD symptoms and functional impairment, whereas reductions in irritability may emerge more gradually over time.\u003c/p\u003e","manuscriptTitle":"Effects of group-based parent training on oppositional defiant disorder symptoms and irritability in Japanese children","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-03-16 18:57:05","doi":"10.21203/rs.3.rs-8744950/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":"be124a59-4b39-4958-b49a-ec4089eb00ae","owner":[],"postedDate":"March 16th, 2026","published":true,"recentEditorialEvents":[{"type":"decision","content":"Withdrawn","date":"2026-04-29T08:11:05+00:00","index":"","fulltext":""}],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-04-29T08:26:34+00:00","versionOfRecord":[],"versionCreatedAt":"2026-03-16 18:57:05","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8744950","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8744950","identity":"rs-8744950","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}