Depression in the community: an investigation into age of onset.

Age of onset of any lifetime depressive disorder was investigated to identify periods of the life course associated with increased risk of depression. In this large community-based sample of adults, one fourth of those with a major depressive disorder at some point in their lives reported onset during childhood or adolescence; over one half reported onset by age 25. Women were likely to have an earlier onset of depression than were men; non-Hispanic Whites and Mexican Americans born in the United States reported earlier onset than did Mexican-American immigrants. Age of onset did not appear to be consequential in terms of the number, type, or severity of the symptoms occurring during the worst depressive episode or with the probability of relapse. These findings imply that age of onset may contribute to group differences in prevalence rates.