Recent developments in genetics of manic-depressive illness.

Bipolar affective disorder appears to be a heterogeneous disorder with multiple independently inherited disease genes, each giving similar clinical results (bipolar, unipolar, and other disorders). This conclusion derives from the recent findings of separate forms of illness linked to single gene markers, with the preponderance of cases in several studies not linked to any of them. At this time, reports of linkage to chromosome 11 and to the color-blindness region of X chromosome are widely accepted, but reports of linkage of the HLA region of chromosome 6 have been criticized and are considered controversial. Persons born in successive decades of the 20th century have progressively greater risks for bipolar and unipolar affective disorders, suicide, and alcoholism but not schizophrenia. This multinational trend begins with persons born in the 1930s and extends to the present time (or possibly until the present decade). For affective disorders, this trend has greater effect in families of affective disorder patients than in the population as a whole, implying a genetic-environment interaction.