Irritable Bowel Syndrome (IBS) and Smoking: An Evaluation of IBS symptom severity and anxiety sensitivity among adults in the United States.

Participants were recruited from across the United States (US) using Qualtrics Panels, an online survey management system. The name of the study and inclusion/exclusion criteria were listed in the Qualtrics Panels Management system and adults were able to self-select into the study if they believed they may be eligible. Participants who self-selected into the study first completed a brief eligibility screening form. If deemed eligible, participants were asked to provide informed consent and were directed to the study survey. Participants could opt to receive the equivalent of $10.75 in compensation via cash-based incentives (i.e., gift cards), reward miles, or reward points. To ensure quality responses, a speeding check (i.e., one-half the median survey completion time) was included and IP addresses were recorded to prevent multiple attempts to complete the survey by the same respondent. The study was approved by the Institutional Review Board of the university where the study took place. A total of 2,858 individuals responded to the study advertisement, of which 2,141 were excluded because they did not meet self-reported ROME-IV criteria for IBS ( Palsson et al., 2016 ), 181 were excluded because they reported smoking less than 5 cigarettes per day, 84 were excluded because they did not meet the age criteria, and 189 were excluded because they did not pass data quality checks, resulting in a final sample of 263 individuals for the current analyses. A total of 263 (52.1% female; M age = 44.1 years, SD = 12.71) adults who met criteria for IBS and reported smoking at least 5 cigarettes per day were included. Inclusion criteria was as follows: 1) being between the ages of 18 and 75, 2) endorsing current daily smoking (≥ 5 cigarettes per day), 3) meeting criteria for IBS based on self-reported symptoms on the ROME-IV (i.e., recurrent abdominal pain occurring at least weekly; two or more of the following at least 30% of occasions: pain related to defecation, pain associated with a change in frequency of stool, pain associated with a change in the appearance of stool; and symptom onset at least 6 months ago), and 4) having access to a computer or mobile device (to ensure ability to complete the study survey). Exclusionary criteria included: 1) an inability to complete self-report surveys, 2) lack of proficiency in English (to ensure comprehension of survey items), and 3) an inability to provide voluntary informed consent. Demographic information collected included sex, age, sexual orientation, gender, race, ethnicity, annual income, and highest level of education. Sex and age were included as covariates. The Chronic Overlapping Pain Conditions Screener (COPCS; Schrepf et al., 2024 ) is designed to identify the presence of nociplastic pain conditions that frequently co-occur in an individual. Respondents are presented with a body map and asked to indicate areas in which they experience chronic pain. Based on the indicated area(s), they respond to a series of diagnostic questions corresponding to a relevant pain condition (i.e. if an individual marks jaw pain on the body map, they will be presented with questions corresponding to the criteria for temporomandibular disorder [TMD]). As the COPCS provides a comprehensive assessment of 10 different chronic pain conditions, it was used in this study to describe the sample in terms of reporting prevalence of specific pain conditions, including but not limited to TMD, IBS, and fibromyalgia (FM). The Smoking History Questionnaire (SHQ; Brown et al., 2002 ) is used to assess quit problems and patterns of smoking. This measure records issues an individual may experience while attempting to quit smoking. It also seeks to understand the products and methods used to smoke. In this study, respondents were given 17 structured questions that asked whether they noticed specific issues arising when they quit smoking in the past. The SHWQ was used to describe smoking history and the composite score for the severity of problems when quitting (α = .95). The Fagerström Test for Cigarette Dependence-Revised (FTCD-R; Korte et al., 2013 ) is a 6-item self-report measure of cigarette dependence. Items on the FTCD-R vary in scale and grading (e.g., “What cigarette would you most hate to give up? 1 = first in the morning, 0 = all others” and “How soon after you wake up do you have your first cigarette? 3 = within 5 minutes, 2 = 6–30 minutes, 1 = 21–30 minutes, 0 = after 60 minutes”). All items are summed for a total score and higher scores indicate a greater degree of cigarette dependence. In the current study, the FTCD-R was utilized as criterion variable (α = .51); the lower alpha for this scale is common and a product of the descriptive nature of the item content ( Berlin et al., 2016 ). The Irritable Bowel Syndrome Symptom Severity Scale (IBS-SSS; Francis et al., 1997 ) was utilized to assess the degree to which individuals experience GI symptoms. This scale consists of five items evaluating pain, distension, bowel dysfunction, and quality of life/global well-being, and classifies respondents’ symptoms as mild, moderate, or severe. In the current study, IBS symptom severity was used as a predictor for smoking outcomes, with a higher score indicating higher symptom severity (α =.82). The Short Scale Anxiety Sensitivity Index (SSASI; Zvolensky et al., 2018 ) is a 5-item self-report measure of sensitivity to and fear of anxiety and arousal-related sensations. This survey employs the use of a 5-point Likert-type scale (0 = “ very little ” to 4 = “ very much ”), the degree to which they are concerned about the consequences of these sensations. In this study, the sum of the SSASI score was used as a predictor variable, wherein higher scores were evident of greater anxiety sensitivity (α = .91). The Barriers to Cessation Scale (BCS; Macnee & Talsma, 1995 ) is a 19-item self-report questionnaire that measures perceived barriers to smoking cessation. Responses are provided using a 4-point Likert scale (0 = ‘not a barrier’ to 3 = ‘large barrier’ ). The BCS has strong psychometric properties ( Garey et al., 2017 ). In the current study, the total score was used as a predictor variable, higher scores indicated greater difficulty in smoking cessation (α = .95). The Short-Form Smoking Consequences Questionnaire (S-SCQ; Myers et al., 2003 ) is a 21-item self-report measure that assesses individuals’ beliefs about the outcomes of smoking behavior. Items are rated on a scale from 0 ( completely unlikely ) to 9 ( completely likely ). This study uses a negative reinforcement subscale (S-SCQ-NR), which refers to individuals’ beliefs that cigarette use will help them cope with uncomfortable moods or sensations. The mean S-SCQ-NR score was computed, with a higher score indicating higher NR expectancies; the mean score was utilized as a smoking outcome variable and demonstrated excellent internal consistency (α = .95). SPSS version 29.0 was used. First, zero-order correlations were examined among study variables along with descriptive analyses. Then, three separate three-step hierarchical regression analyses were conducted for the following continuous criterion variables: 1) perceived barriers for smoking cessation, 2) severity of problems experienced during past attempts to quit smoking, and 3) negative reinforcement smoking expectancies. In the first step, covariates were entered into the model and included age, race/ethnicity, and cigarette dependence. Sex was coded as follows: 0 = male, 1 = female. Race/ethnicity was coded as follows: 1 = Hispanic/Latino Alaska Native/American Indian, 2 =Not Hispanic/Latino Alaska Native/American Indian, 3 = Hispanic/Latino Asian, 4 =Not Hispanic/Latino Asian, 5 = Hispanic/Latino Black/African American, 6 =Not Hispanic/Latino Black/African American, 7 = Hispanic/Latino Native Hawaiian or other Pacific Islander, 8 =Not Hispanic/Latino Native Hawaiian or other Pacific Islander, 9 = Hispanic/Latino White, 0 =Not Hispanic/Latino White, 11 = Hispanic/Latino more than one race, 12 =Not Hispanic/Latino more than one race, 13 = Hispanic/Latino Other, 4 =Not Hispanic/Latino Other. In the second step, IBS symptom severity and anxiety sensitivity was added to the model. In the third step, the interaction of IBS symptom severity and anxiety sensitivity was added to the model. For each model, the F statistic was utilized to measure model fit and squared semi-partial correlations ( sr 2 ) were utilized as an indicator of effect size, with effects of .02, .13, and .26 indicating small, moderate, and large effect size ( Cohen et al., 2013 ), respectively.

Detailed descriptive information for the sample is presented in Table 1 . The largest self-identified racial/ethnic group in the sample was White and non-Hispanic/Latino ( N = 29; 69.6%), followed by Hispanic/Latino White ( N = 25; 11.0%) and non-Hispanic/Latino Black (9.5%). The most common co-occurring chronic pain condition in the sample was chronic fatigue syndrome ( N = 103; 39.2%), followed by chronic low back pain ( N = 102; 38.8%). Most of the sample completed high school or higher (95.8%) and approximately half (49.0%) of the sample completed a bachelor’s degree or higher. About one-third of participants (30.8%) reported earning an income of $100,000 or higher. Participants reported smoking an average of 18.49 ( SD =16.42) cigarettes per day. The average age of smoking onset in the sample was 17.8 years ( SD = 6.93). The average level of cigarette in the sample, as measured by the FTCD-R ( Korte et al., 2013 ), was in the moderate range ( M = 5.54; SD = 2.01). In addition to smoking combustible cigarettes, 51.0% reported current cigar use, 38.4% reported current smokeless tobacco use, 30.0% reported pipe tobacco use, and 24.3% reported daily use of electronic cigarettes. Bivariate correlations are presented in Table 2 . IBS symptom severity was statistically significantly and positively correlated with cigarette dependence ( r = .34), anxiety sensitivity ( r = .35), perceived barriers for smoking cessation ( r = .44), severity of problems experienced during past attempts to quit smoking ( r = .30), and negative reinforcement smoking expectancies ( r = .46). Anxiety sensitivity was statistically significantly and negatively correlated with age ( r = −.28) and positively correlated with cigarette dependence ( r = .27), perceived barriers for smoking cessation ( r = .56), severity of problems experienced during past attempts to quit smoking ( r = .46), and negative reinforcement smoking expectancies ( r = .33). The three criterion variables were statistically significant and positively correlated with one another ( r range: .27 – .58). Hierarchical regression results are presented in Table 3 . For perceived barriers for smoking cessation, step 1 of the model with covariates was statistically significant ( R 2 = .20, F (4, 258) = 16.46, p < .001). Age and cigarette dependence were statistically significant predictors. At step 2 (Δ R 2 = .23, F [2, 256] = 52.08, p < .001) a statistically significant main effect emerged for IBS symptom severity and anxiety sensitivity. There was not a statistically significant interaction ( R 2 <.001, F (1, 255) = .01, p = .937). For severity of problems experienced during past attempts to quit smoking, step 1 of the model with covariates was statistically significant ( R 2 = .11, F (4, 258) = 8.33, p < .001). Age and cigarette dependence were statistically significant predictors. At step 2 (Δ R 2 = .15, F [2, 256] = 26.24, p < .001), a statistically significant main effect emerged for IBS symptom severity and anxiety sensitivity. There was not interaction between IBS symptom severity and anxiety sensitivity (Δ R 2 < .001, F (1, 255) = 0.05, p = .826). For negative reinforcement smoking expectancies, step 1 of the model with covariates was statistically significant ( R 2 = .07, F (4, 258) = 4.89, p < .001). Cigarette dependence was a statistically significant predictor. At step 2 (Δ R 2 = .20, F [2, 256] = 35.62, p <.001), a statistically significant main effect emerged for IBS symptom severity and anxiety sensitivity. There also was a statistically significant interaction at step 3 (Δ R 2 = .02, F (1, 255) = 6.90, p = .019). Inspection of the form of the interaction (see Figure 1 ) showed that while IBS symptom severity was statistically significantly and positively related to negative reinforcement smoking expectancies across the entire sample, the magnitude of this effect was higher for those with higher compared to lower levels of anxiety sensitivity (higher: b = .01, SE = .002, p < .001; lower: b = .004, SE = .002, p = .020).

IBS is widely recognized as a high impact pain condition that exacts a pernicious toll measured in human and financial methods of analysis ( Oka et al., 2020 ). Although smoking is one of the most common and destructive forms of substance use behavior ( Samet, 2013 ), surprisingly little effort has sought to integrate the IBS and smoking literatures to understand the interplay between these behavioral health problems. As an initial step in this domain, the present investigation explored IBS symptom severity and anxiety sensitivity (an established individual difference factor in the IBS and other chronic health conditions and smoking populations, respectively; Kauffman et al., 2024 ) as concurrent and interactive predictors of a range of clinically significant smoking processes among adults with IBS who smoke cigarettes. As hypothesized, IBS symptom severity and anxiety sensitivity were each associated with greater perceived barriers for smoking cessation, severity of problems experienced during quitting, and negative reinforcement smoking expectancies. Thus, after accounting for their shared variance with one another (12%), IBS symptom severity and anxiety sensitivity were each independently related to the studied smoking-related processes. Across models, observed effects ranged from small to medium and revealed an interesting set of findings. Namely, anxiety sensitivity accounted for more variance relative to IBS symptom severity for perceived barriers for smoking cessation (anxiety sensitivity = 13% versus IBS symptom severity = 4%), whereas the opposite pattern was evident for severity of problems experienced during quitting (IBS symptom severity = 11% versus anxiety sensitivity = 4%) and negative reinforcement smoking expectancies (IBS symptom severity = 11% versus anxiety sensitivity = 4%). Importantly, the observed effects were evident after accounting for variance explained by age, sex, race/ethnicity, and cigarette dependence. Collectively, these data make clear that IBS symptom severity and anxiety sensitivity are both important vulnerability factors for continued smoking among adults with IBS. Evaluation of tests focused on the interaction between IBS symptom severity and anxiety sensitivity indicated a statistically significant interaction only for negative reinforcement smoking expectancies. As hypothesized, IBS symptom severity was more strongly associated with negative reinforcement smoking expectancies among individuals with higher compared to lower levels of anxiety sensitivity. Although the same interaction was not apparent for perceived barriers for smoking cessation and severity of problems experienced during prior quit attempts, these data highlight synergistic interplay between IBS symptom severity and anxiety sensitivity for smoking-related negative reinforcement cognition. Such findings are in line with integrated theoretical models of smoking and interoceptive vigilance that highlight the potential amplifying effects of anxiety sensitivity for coping-oriented substance use ( Redmond et al., in press ). Future research is needed to evaluate the explanatory parameters of the interactive effects of IBS symptom severity and anxiety sensitivity for other smoking processes that tap into the downregulation of interoceptive perturbation such as lapse and relapse during a quit attempt ( Zvolensky et al., 2009 ) and smoking-based experiential avoidance ( Farris et al., 2016 ). This future work could inform an IBS-specific theoretical conceptualization of smoking, thereby engendering novel integrated treatment approaches for smoking cessation among this vulnerable and understudied population. Medical and psychiatric comorbidities and their reciprocal and interactive relationship represent ( Druss & Walker, 2011 ) one of the most vexing obstacles to advance public health efforts to reduce the negative impact of smoking in the general population in the US ( Rojewski et al., 2016 ). The present findings highlight IBS as another prevalent yet underrecognized contributor to the maintenance of tobacco smoking behavior. Clinically, these results highlight the importance of screening for IBS symptoms and cognitive-based vulnerabilities for interoceptive threat among adults who smoke. To the extent these vulnerability factors continue to be identified among the IBS population, targeted interventions could be developed to offset smoking-related risks that augment the public health burden of IBS. Presently, no specialized smoking cessation programs exist for individuals with IBS (or other functional GI disorders), ensuring this population will continue to experience challenges in quitting and experiencing negative health consequences related to smoking ( U.S Department of Health & Human Services, 2014 ). Such integrated smoking cessation programs could be developed that draw upon existing evidenced based tactics for managing IBS symptoms ( Lackner et al., 2004 , 2018 ) and reducing anxiety sensitivity ( Zvolensky, Garey, Allan, et al., 2018 ). There are several limitations to the present investigation. First, the study design was cross-sectional. Therefore, causal and directional inferences cannot be inferred. Future research should build from this initial work using longitudinal or experimental methodologies. Second, the nationally recruited sex-balanced sample was majority non-Hispanic White (69%). To test the generalizability of the model to other racial/ethnic groups, research could sample a more racially/ethnically group of individuals. This effort is important as smoking is not equally distributed in the US population ( Nguyen-Grozavu et al., 2020 ) and health inequities are also apparent for IBS ( Sasegbon & Vasant, 2021 ). Third, the assessment approach that was employed was unidimensional and based on self-report measures potentially vulnerable to response bias. Although scientifically valid and well-established tools were utilized, future research could broaden our understanding of smoking among the IBS population by using multimethod assessment protocols for smoking (e.g., CO analysis; Mattes et al., 2014 ) and the diagnosis of IBS (e.g., physical examination including digital rectal examination, and screening tests; Camilleri, 2021 ). Fourth, although daily smoking behavior was an inclusionary criterion, the sample was not treatment seeking nor engaged in a quit attempt for smoking cessation. A direct extension of the present research could be to model IBS symptom severity and anxiety sensitivity in terms of quit success among individuals attempting to quit smoking. Fifth, we modeled anxiety sensitivity as one candidate mechanism at a cognitive level of analysis because it is one of the few constructs linked to IBS ( Lackner & Jaccard, 2021 ) and smoking ( Zvolensky, Bakhshaie, et al., 2017 ). Still, there could be advantage to exploring domain specific sensitivity constructs in the future such as visceral sensitivity ( Zhou & Verne, 2011 ); some work suggests that this more focused index of sensitivity to GI symptoms may be particularly useful in understanding IBS and related disorders ( Mertz, 2003 ). Finally, the present research was oriented on smoking processes as the focal point. However, it should not be overlooked that IBS outcomes could be equally important. Consequently, research could build from a small literature in this domain ( Gudleski et al., 2017 ) to better characterize the IBS-smoking ecosystem by evaluating how smoking cognition and behavior impacts IBS clinical outcomes. Overall, the current investigation found that both IBS symptom severity and anxiety sensitivity each were unique explanatory variables in adjusted models for perceived barriers for smoking cessation, severity of problems experienced during prior quit attempts, and negative reinforcement smoking expectancies. These data are the first to identify vulnerability factors among adults with IBS to better understand smoking behavior. There is a continued need to further scientific understanding of smoking among IBS samples and to identify novel methods that can improve quitting among this vulnerable population.