Adding lithium to antidepressant therapy: factors related to therapeutic potentiation.

Lithium augmentation of antidepressant drugs was studied in 51 patients with endogenous refractory depression. The remission after 28 days of lithium was obtained in 28 patients (55%). Better effect of lithium was shown in bipolar than unipolar patients, with subjects with lower pre-lithium severity of depression and in those with rapid improvement (within 7 days) on lithium addition. Factors such as age, gender, number of prior antidepressant (or ECT) treatments, type of preceding antidepressant, mean plasma lithium concentration and the results of DST did not show any association with the outcome of lithium augmentation. The 'priming' effect of lithium may contribute to the mechanism of lithium potentiation in a proportion of depressed patients.