Placebo response in depression: a search for predictors

Although 30-40% of depressed patients respond to placebo treatment, few predictors of placebo response have been identified. We evaluated patients with moderate to severe depression who had received placebo for 3-6 weeks in multicenter clinical trials (Study 1, n = 125; Study 2, n = 88). Placebo response rates (greater than 50% improvement in Hamilton total depression score) were 38.4% and 30.7%, respectively. Despite differences in treatment outcome, baseline clinical and demographic characteristics were similar for responders and nonresponders. The studies confirmed the substantial placebo response in moderately to severely depressed patients and suggested chronicity may be a predictor.