Twelve inpatients with major depression refractory to at least two
controlled antidepressant trials had tranylcypromine added to ongoing
lithium treatment. Eleven patients showed reliable improvement in nurses'
depression ratings compared with a prior trial of lithium added to an
antidepressant that was not a monoamine oxidase inhibitor (MAOI). Eight
patients were blindly judged much or very much improved, and all 12
patients improved sufficiently to be discharged. Preclinical studies of
conjointly administered lithium and MAOIs suggest that central serotonergic
pathways may mediate this robust clinical effect.