A knowledge of the natural history and the future course of mood disorders is crucial when taking treatment decisions, especially those on long-term prophylactic medication.

To describe the course of depressive and bipolar disorders in treated and non-treated subjects differentiated according to gender.

591 subjects, selected by stratified sampling from the community, were studied prospectively from the ages of 19/20 to 49/50 in seven, professionally administered, semi-structured interviews. Course was assessed by seven interviews, nine self-assessments using the SCL-90-R and retrospective annual assessments of the presence of symptoms and treatment. The percentage of symptomatic years in the observation period was computed, as was remission defined as three consecutive symptom-free years without subsequent relapse.

Annual treatment rates for depressive syndromes increased from about 30% at age 20 to over 50% at age 50. Women reported more symptoms of depression over more years and recovered less frequently than men; the gender differences were greater in major depressive than in bipolar disorders. As expected, subjects who sought treatment were more severely ill than those who had never been treated and their illness took a more serious course. At the last individual interview the disorder had remitted in one third of both patients with depression and those with bipolar disorder.

Treatment rates for both major and bipolar depressive disorders increase strongly between 20 and 50 years of age; the high proportion of years with symptoms illustrates the importance of long-term treatment.