Objective: It is not known whether irritable bowel syndrome (IBS) fluctuates with the seasons. We aimed to determine whether seasonal changes in symptoms occur in IBS and to examine the relationships between IBS, seasonality, and psychological factors.
Methods: A random sample of the community (n = 99) and hospital staff volunteers (n = 163) in Sydney, Australia, completed a previously validated questionnaire that measured bowel symptoms, psychosocial factors, and seasonality.
Results: IBS (n = 60; 23%) was significantly associated with somatization (by the Psychosomatic Symptom Checklist) and lifetime depression but not neuroticism (by the Eysenck Personality Questionnaire) or psychological morbidity (by the General Health Questionnaire). A seasonal variation in behavior score (measuring sleep, eating, including carbohydrate craving, weight gain, socializing, energy level, and mood by the Seasonal Pattern Assessment Questionnaire) was associated with somatization (p < 0.001) and IBS (p < 0.05) in a stepwise multiple regression model. Of those with IBS, 23% reported moderate or greater seasonal change in bowel symptoms. Subjects with IBS (vs subjects with some bowel symptoms) were significantly more likely to report seasonal changes in pain and/or disturbed defecation (odds ratio = 3.2; 95% CI = 1.25-8.23); the latter was significantly associated with somatization but not the other psychological variables.
Conclusions: A subset of IBS may be seasonally determined, and this is explained in part by somatization.