Prescribing Tamoxifen in Patients with Mood Disorders

Tamoxifen is a selective estrogen receptor modulator widely used for treatment and prevention of estrogenic receptor-positive breast cancer. Tamoxifen is an object of growing interest in psychopharmacology as an antimanic drug, because it inhibits the protein kinase C, a molecular target of bipolar disorder. Consistently, the potential depressive effect of tamoxifen has been repeatedly reported.This article systematically reviews studies examining tamoxifen impact on mood, exploring either its potential therapeutic use as antimanic agent or its potential depressive effect.Eight studies explored tamoxifen antimanic properties, all, but one, reported a rapid and efficacious antimanic action. As to the depressive effect, 9 cohort studies emerged among which 4 pointed out an increased risk of depression. Seven case reports described the onset or exacerbation of depressive episodes besides 1 case series study reported a high rate of depressive symptoms. In addition, 1 case report study described a tamoxifen-induced manic episode.The present review highlights tamoxifen treatment as a possible trigger of mood symptoms onset or exacerbation in vulnerable patients. Accordingly, patients with a history of mood disorders may require a close clinical surveillance during tamoxifen use. At the same time, the use of tamoxifen as an antimanic agent in psychiatric settings requires caution, as available evidence came from small-sample studies with short observation time. More studies are needed to define how long-term tamoxifen use may affect the course of bipolar disorder.