The genetics of affective disorder and genetic counseling

Abstract

Affective disorders—depression and mania—occurring with no preexisting psychiatric condition, severe physical illness, or recent personal loss can be divided into unipolar (depression only) and bipolar (both manic and depressive episodes) disorders. Bipolar illness is transmitted in some families as an X‐linked dominant factor. In other families, X‐linked transmission does not occur. Hence, bipolar illness may be similar to retinitis pigmentosa. This makes some types of genetic counseling difficult to apply to bipolar families. There is no evidence that unipolar depressive illness is transmitted by an X‐linked factor. Family studies indicate that there might be more than one type of unipolar illness. Limited prediction of risk of depression and other psychiatric conditions in other family members can be based on family studies which show that alcoholism and personality disorder occur frequently in families of early onset depressives but much less frequently in families of late onset depressives (age 40 or older).