Genetics of mood disorders

The enormous public health importance of mood disorders, when considered alongside their substantial heritabilities, has stimulated much work, predominantly in bipolar disorder but increasingly in unipolar depression, aimed at identifying susceptibility genes using molecular genetic approaches. Several chromosomal regions of interest have emerged in linkage studies and, recently, evidence implicating specific genes has been reported; the best supported include BDNF and DAOA but further replications are required and phenotypic relationships and biological mechanisms need investigation. The complexity of psychiatric phenotypes is demonstrated by (a) the evidence accumulating for an overlap in genetic susceptibility across the traditional classification systems that divide disorders into schizophrenia and mood disorders, and (b) evidence suggestive of gene–environment interactions.