BACKGROUND: Attainment of remission is viewed as the optimal outcome of acute antidepressant treatment. However, some patients experience subsyndromal symptoms after they achieve remission. This study examines the prognostic significance of subsyndromal symptoms occurring during the first 6 months after remission of late-life depression.

METHOD: Older (age 60-89 years) in-patients and out-patients with unipolar major depression were followed until remission (asymptomatic or almost asymptomatic for 3 consecutive weeks). Two hundred and forty-two achieved remission after uncontrolled antidepressant treatment. This analysis focused on remitted patients who had follow-up data over a 2.5-year period (n = 185).

RESULTS: Approximately 18% of patients relapsed. Of the remainder (n = 152), 42.8% had subsyndromal depressive symptoms during the 6 months following remission. Cox's proportional survival analysis demonstrated that longer duration of subsyndromal symptoms [number of weeks with the Longitudinal Follow-up Examination (LIFE) Psychiatric Status Rating Scale (PSR) score of 3 or 4] in the first 6 months after remission was significantly associated with shorter time to recurrence and higher recurrence rate [hazard ratio (HR) 1.16, 95% confidence interval (CI) 1.08-1.24]. Based on our analysis, patients with 0, 4, 8 and 12 weeks of subsyndromal symptoms in the first 6 months after remission have estimated recurrence rates of 28, 45, 66 and 86% respectively during the ensuing 2 years.

CONCLUSIONS: These findings highlight the clinical importance of subsyndromal symptoms occurring after remission in late-life depression. They also argue that studies of geriatric depression may complement the definition of remission with information on subsyndromal symptoms occurring after the initial asymptomatic period.