Genetics of psychiatric disorders

The major psychiatric disorders are common disorders with a complex genetics, similar to other common medical disorders such as diabetes and hypertension. For most of these disorders, linkage studies in families with multiple cases have revealed chromosomal areas that contain susceptibility genes. In recent years, specific single genes have begun to be identified for disorders such as schizophrenia (e.g., DISC1, neuregulin), bipolar affective disorder (G72, BDNF), autism (neuroligins), attention-deficit disorder (DAT, DRD4), AND alcohol dependence (GABRA2, ADH4). Genome-wide association studies in large case-control data sets are now in progress, which may confirm and extend such reports. Genetic studies of Alzheimer's disease (APOE) and several forms of mental retardation (Down's syndrome, Fragile X) are already well advanced. Functional studies related to single gene vulnerability factors are now beginning. Important clues are emerging from gene expression studies and epigenetics. It is anticipated that new diagnostic tools and therapeutic strategies will result from this work.