IBS is a relatively frequent disorder with about twice as many female patients as male patients. Gender role theories propose that aspects of the female gender role which may lead to increased vulnerability may also induce higher levels of co-morbid psychopathology among females.

Gender roles differ systematically among cultures, in particular in the degree of differentiation between genders. The objective is to investigate possible gender and cultural differences in the relation between IBS and psychopathology.

To test whether both gender and cultural factors such as degree of gender differentiation are associated with variation in the incidence of comorbid psychopathology of people with IBS.

Results from a corpus of 141 studies were analysed by means of a random-effects model in terms of odds ratios between IBS and comparison groups for psychological factors which are indicative of dysfunction (the procedure was analogous to that employed for laterality by Martin et al., Psychological Bulletin, 2010). Meta-regression was used to test for the moderating effects of gender and of the Hofstede cultural factors of masculinity (i.e., gender differentiation), individualism, uncertainty avoidance, and power distance.

Counter to expectations, higher IBS psychopathology odds ratios were associated with samples containing more males and lower gender differentiation. Further, higher levels of psychopathology were found in cultures with lower individualism and uncertainty avoidance, and higher power distance.

Cultural factors and gender are systematically predictive of psychopathology co-morbidity rates in IBS, but the detailed patterns revealed do not support existing gender role theories.