The genetics of affective disorder: data, theory, and clinical applications

A genetic factor in the etiology of the affective disorders has been a subject of considerable interest and investigation during the last five decades. Data from twin studies, family studies, and adoption studies strongly support three major findings: genetic factors are significant in the etiology of both bipolar and unipolar affective disorder; bipolar and unipolar affective disorder tend to breed true and are genetically distinct diseases; and both bipolar and unipolar affective disorder are genetically distinct from schizophrenia. While the mode of transmission for the affective disorders remains unclear, the genetic data already afford clinical applications pertinent to diagnosis, prognosis, treatment response, and both immediate and longitudinal clinical course. Pharmacogenetic factors unrelated to the illness are also relevant to the management of antidepressant pharmacotherapy.