Background: We studied the family psychiatric history of 125 youths with childhood-onset depressive disorder (a portion of whom developed bipolar disorder) and 55 psychiatric controls with nonaffective disorder.
Methods: Probands were classified according to prospectively observed clinical course in childhood. Family psychiatric history was determined by interviewers blind to probands' diagnosis, with mothers typically informing about themselves and about remaining first- and a all second-degree adult relatives.
Results: Families of affectively ill juveniles had 5-fold greater odds of lifetime depressive disorder and 2-fold greater odds of recurrent unipolar depressive disorder than did families of psychiatric controls. The higher risk of depression was most evident in first-degree and female relatives. Mothers of affectively ill youths were younger at onset of depression than were mothers of controls. Alcoholism and substance use disorders were more prevalent in relatives of affectively ill probands than in controls and cosegregated with familial depression. However, other covariates were more important at predicting patterns of familial depression. Familial illness patterns also varied somewhat with proband characteristics.
Conclusions: Child probands with affective disorder identify families enriched with affective disorder (even compared with families of psychiatric controls), suggesting that juvenile- and adult-onset forms of this condition share the same diathesis. Rates of affective illness in the families of depressed youngsters also are notably higher than population-based estimates. The findings therefore indicate that very-early-onset affective disorder is familial and that pedigrees ascertained through affectively ill children are good candidates for family and genetic studies.