Studies that included at least one group, or a subset, of adults with unipolar depressive disorder treated with antidepressants or not treated with antidepressants were eligible for inclusion provided that they had at least 10 years of follow-up, with at least one follow-up after 1988 (for antidepressant studies only), and reported at least one clinical or psychosocial outcome, other than suicide or mortality. Studies that fulfilled the inclusion criteria for both antidepressant and non-antidepressant treatment were only included in the analysis for antidepressant treatment.
The included studies for antidepressant treatment were conducted in seven countries; the earliest began in 1947 and the follow-up ranged from 10 to 50 years. The number of follow-up assessments ranged from one to 25, and duration between follow-up assessments ranged from six months to 25 years. Participants had symptoms of unipolar depression, dysthymic disorder, mood disorder, or were hospitalised as former in-patients with a depressive disorder. Eight studies enrolled consecutive patients from psychiatric or medical clinics, one study reviewed patient records, and the remaining three studies recruited community samples. Data on antidepressant treatment was limited; most participants had received antidepressants during the index episode or later. Most participants in the included studies were white women with at least one in-patient stay. The primary outcomes were symptom status including recurrence, relapse, remission, or recovery.