Early-onset affective disorder is associated with obstetric complications and a high familial risk of psychiatric illness, in particular psychosis. In a matched case-control study, we investigated 47 adult in-patients with major depressive disorder or bipolar 1 disorder, who had earlier in life presented to a child psychiatry department. Cases were matched on sex, social class and ethnic group with 47 controls, who were admitted to hospital for affective disorders in adult life but had no psychiatric contact before the age of 21. We found that both psychiatric disorder in first-degree relatives and a history of obstetric complications were associated with early onset. Childhood symptoms did not predict the type of adult affective disorder.