Longitudinal studies in the third world demonstrate an increase in immunological disorders as a country grows more affluent and, it is presumed, cleaner.
In the past, functional bowel disorders such as irritable bowel syndrome (IBS) which produced symptoms of bloating were attributed to increased production of intestinal gas.
The spectrum of autistic disorders is notable for its significant gender disparity, with the incidence of autism in males greatly exceeding the incidence in females.
