Fig. 2.

Model of underlying structure for shared predisposing genetic and environmental factors and co-morbidities. The specific syndromes appear primarily to be due to particular environmental influences , e.g. the development of irritable bowel syndrome (IBS) subsequent to a bacterial gastrointestinal infection. A-D are specific symptom clusters, e.g. cardiopulmonary, gastrointestinal, etc. UGF = unique genetic factors, UEF = unique environmental factors