Genetic and environmental factors in major depression.

A study of 48 individuals with major depression in a sample of 443 adoptees has shown that depression is positively but not significantly correlated with a biologic background of affective disorder. Both primary and secondary depression was positively and significantly correlated with several environmental factors. In males, an adoptive home where another individual had an alcohol problem increased depression; in females, death of an adoptive parent prior to adoptee age 19 and an adoptive family where another individual had a behavior disturbance increased depression. Results suggest that the environmental factors occurring prior to adoptees age 18 predisposed to depression.