BACKGROUND: Chronic forms of depression are associated with significant functional and psychosocial impairments. To date, no study has measured psychosocial functioning in this population during long-term maintenance antidepressant treatment or following the double-blind discontinuation of treatment. METHODS: Patients with chronic major or double depression completed 12 weeks of short-term treatment followed by 16 weeks of continuation treatment with sertraline hydrochloride. Responders at the end of the continuation phase were randomized, double-blind, to 18 months of maintenance therapy with either sertraline (n = 77) or placebo (n = 84). Multiple domains of psychosocial functioning were assessed during double-blind therapy. RESULTS: Substantial worsening in psychosocial function measures occurred in patients taking placebo compared with sertraline during maintenance. Patients with reemergence of depression lost psychosocial gains regardless of treatment. In the subsample of patients who remained in remission throughout maintenance, most of the observed improvement in psychosocial functioning occurred during short-term treatment. By maintenance end point, normalization of functioning was achieved by 58% to 84% of remitters, depending on the outcome measure used. CONCLUSIONS: These results indicate that long-term treatment of chronic forms of depression can result in sustained psychosocial benefits. Discontinuation of treatment results in frequent reemergence of symptoms and loss of psychosocial gains. Long-term treatment resulted in only modest further improvement of psychosocial measures over that achieved in the short-term phase.