Lithium prophylaxis of depression in unipolar, bipolar II, and cyclothymic patients.

The authors assessed lithium's prophylactic effect against depression in unipolar (N = 43), bipolar II (N = 102), and cyclothymic (N = 69) patients using a longitudinal life-table analysis and calculated the probability of remaining free of a depressive episode. The probability of remaining free of one depressive episode after 2 years of taking lithium ranged from 42% to 55% for the bipolar II patients, 31% to 42% for the unipolar patients, and 26% to 36% for the cyclothymic patients. The average probability of suffering one depressive episode severe enough to require either pharmacologic intervention or hospitalization in a 2-year period was 51% for the bipolar II patients, 64% for the unipolar patients, and 69% for the cyclothymic patients.