Big genes, little genes, affective disorder, and anxiety. A commentary

This article offers a brief explanation of the methods used for studying the genetic epidemiology of psychiatric disorder and comments on three articles in this issue of the Archives. Although the methods have had success in detecting genes of major effect for enzymes involved in neurotransmitter synthesis and degradation, they have not produced compelling evidence for a major locus in affective disorder. At the same time, simpler modes of transmission do not fully explain familial data on bipolar disorder or early-onset unipolar disorder. The problem of familial comorbidity of anxiety and depression is discussed, and an illustration is given of how assumptions about psychiatric classification and familial models can obscure the issue of comorbidity.