Primary and secondary affective disorders: Unipolar patients compared on familial aggregation

We examined rates of mental disorders in relatives of 569 unipolar depressed patients. Probands were divided into three groups: primary depression (never secondary; N = 327), secondary depression (never primary; N = 191), and complicated depression (both primary and secondary episodes of depression; N = 51). We obtained blind family study diagnoses (direct interview) for 1,152 relatives and family history diagnoses (information from proband, with or without information from another relative) for 3,617 relatives. There was no increase in risk for major affective disorder in relatives of probands with primary depression as compared to the other two groups. The risks for several nonaffective diagnoses were increased in the families of patients with secondary depression (as were the risks for secondary depression). The family data for patients with complicated depressions were similar to those with secondary depression. We may conclude that secondary depression is a common finding in patients with nonaffective mental disorders, and shows no increased familial aggregation except increased frequency of nonaffective disorders which themselves are associated with secondary depression.