Tryptophan depletion in recently manic patients treated with lithium

Background: Serotonin has been repeatedly implicated in the mechanism of action of lithium against acute mania. Its role, however, has never been directly confirmed. Methods: We studied recently manic patients successfully treated with lithium using a tryptophan depletion methodology. Results: Patients remained euthymic despite a confirmed decrease in serum tryptophan levels. Conclusions: These data do not suggest that serotonin plays a critical role in the acute antimanic effect of lithium.