Silymarin (Milk Thistle) Treatment of Adults With Gambling Disorder: A Double-Blind, Placebo-Controlled Trial.

Objective: Data on the pharmacological treatment of gambling disorder are limited. Silymarin (derived from milk thistle) has antioxidant properties. The goal of the current study was to determine the efficacy and tolerability of silymarin in adults with gambling disorder.

Methods: Forty-three individuals (18 [41.9%] women; mean age=49.61 [±13.1] years) with gambling disorder entered an 8-week, double-blind, placebo-controlled study. Dosing of silymarin ranged from 150 to 300 mg twice a day. The primary outcome measure was the Yale Brown Obsessive Compulsive Scale Modified for Pathological Gambling (PG-YBOCS). Secondary outcome measures comprised the Gambling Symptom Assessment Scale and measures of depression and anxiety. Outcomes were examined using mixed-effect models.

Results: Silymarin did not statistically differentiate from the placebo on any of the outcome measures of interest, in terms of treatment group×time interactions. There was a robust response in the placebo group (57% reduction on the PG-YBOCS), and on average there was a 56% reduction in YBOCS score for the milk thistle.

Conclusions: The findings of this study do not support the use of silymarin/milk thistle in the treatment of gambling disorder but highlight the large placebo response seen in gambling disorder. Treatment interventions for gambling disorder need to better understand and address the placebo response.

Trial registration: ClinicalTrials.gov identifier: NCT02337634.