Genetic studies of affective disorders: should we be starting with childhood onset probands?

The objective of this study is to test whether the presence of childhood onset affective disorder identifies families with increased incidence and severity of affective disorders.

Family history information was collected on the first and second degree relatives and first cousins age > or = 15 years of 22 children with bipolar affective disorder, 54 children with major depressive disorder, and 31 psychiatrically normal children.

Compared with the relatives of normal children, relatives identified through children with bipolar affective disorder or major depressive disorder had elevated rates of affective disorders and increased severity of affective disorders as judged by earlier age of onset and increased suicide attempts. Segregation analyses could reject purely environmental transmission of illness.

Ascertaining families through childhood onset affective disorder probands identifies extended pedigrees with high incidence and severity of affective disorders. These families may be more appropriate for genetic analyses than are families of adult probands.