A team from the USA and Australia assessed the relative contribution of genetic and environmental influences on the development of irritable bowel syndrome (IBS).
They did this by comparing concordance rates in monozygotic and dizygotic twins to concordance between mothers and their children.
Questionnaires were sent to both members of 11,986 twin pairs. These solicited information on the occurrence of more than 80 health problems, including IBS, in self and other family members.
A total of 10,699 individuals responded, representing 6060 twin pairs.
| More than 6000 twin pairs were questioned.
| Gastroenterology |
Concordance for IBS was significantly greater in monozygotic (17.2%) than in dizygotic (8.4%) twins, supporting a genetic contribution to IBS.
However, the proportion of dizygotic twins with IBS who have mothers with IBS was 15.2%. This was greater than the proportion of dizygotic twins with IBS who have co-twins with IBS (6.7%).
Logistic regression analysis showed that having a mother with IBS and having a father with IBS are independent predictors of irritable bowel status. Both are stronger predictors than having a twin with IBS.
Addition of information about the other twin accounted for little additional predictive power.
Rona L. Levy, of the University of Washington, Seattle, concluded on behalf of fellow authors, "Heredity contributes to development of IBS. However, social learning (what an individual learns from those in his or her environment) has an equal or greater influence."