Plasma lithium levels and therapeutic outcome in the prophylaxis of affective disorders: a retrospective study.

Patients receiving prophylactic lithium therapy for primary affective disorder during a four year period were studied for recurrence of affective illness. Patients who had affective episodes during this period did not differ from those who remained well in age, sex or diagnosis. Those with a favourable outcome had spent significantly less time at serum lithium levels above 0.9 mmol/litre than those who had a recurrence of affective episodes.