“…Adoption studies have also con®rmed an important role for genetic risk factors in the development of MDD [Mendlewicz and Rainer, 1977;Cadoret, 1978;Wender et al, 1986]. Consistent with these results, a large number of family studies have demonstrated an increased risk of MDD among relatives of MDD probands, with about a twofold increased risk to ®rst-degree relatives [Baron et al, 1982;Gershon et al, 1982;Weissman et al, 1984a;Bland et al, 1986, Stancer et al, 1987McGuf®n et al, 1988;Kupfer et al, 1989;Moldin et al, 1991]. Early age of onset of the ®rst major depressive episode [Mendlewicz and Baron, 1981;Weissman et al, 1984bWeissman et al, , 1986aBland et al, 1986;Price et al, 1987;Kupfer et al, 1989] as well as recurrence [Bland et al, 1986;Rice et al, 1987;Kendler et al, 1993bKendler et al, , 1994 are independent factors that increase the morbid risk of MDD among family members.…”