Clinical importance of inter-episode symptoms in patients with bipolar affective disorder.

A literature review was performed to determine whether inter-episode symptoms are of clinical importance in the management of bipolar disorder. Inter-episode symptoms are easy to miss but observational studies confirm that they are related to impaired function and reduced survival to full relapse. Randomised, controlled trials with lithium carbonate, and two studies exploring psychological treatments to recognise and treat prodromal symptoms of manic or depressive relapse, suggest some inter-episode symptoms are worth recognising because they are associated with reduced manic relapse and improved function. A classification is proposed to inform attempts at management of inter-episode symptoms in bipolar disorder patients, both clinically, and for future research. However, promotion of well-being in bipolar disorder patients does not require all symptoms to be treated. In other patients, the presence of inter-episode symptoms may be a marker of resistance to treatment. Finally, the mechanism by which inter-episode symptoms might lead to relapse, or even lead directly to functional impairment, awaits convincing explanation and empirical support.