Bipolar disorder is for most patients a life-long illness, associated with a recurrent, chronic course, and functional disability. Primary treatment goals are to stabilize the patient and prevent recurrence of episodes and suicide.

Although bipolar disorder has traditionally been regarded as an illness with good prognosis and most patients returning to normal functioning when a mood episode is over, several longitudinal studies suggest that the long-term outcome is less favorable than previously thought. Combinations of drugs are frequently used in clinical practice for mood stabilization, especially for those who have not responded to monotherapy. Although combination treatments are commonly administered, full interepisode recovery is not achieved in all patients, and as a consequence, bipolar disorder is one of the leading causes of disability.

Among clinicians and in international guidelines, lithium is widely considered as the ‘gold standard’ for long-term treatment. The choice of treatments is undergoing considerable change as new treatments are available, anticonvulsants and atypical antipsychotics are taking a more prominent position. However, the evidence available for the newer treatment options including the various combination treatments varies greatly.

The episodic nature of bipolar disorder requires prophylactic long-term treatment. Many previous worthwhile treatment effects of available mood stabilizing agents and psychotherapeutic interventions on major outcomes in bipolar disorder are only of moderate size and therefore require large-scale studies. Such trials to investigate longer-term outcomes are logistically challenging and expensive, and therefore only feasible within a multisite and multinational approach based on a common documentation system of the illness course.