A model of placebo responses in antidepressant clinical trials

A substantial proportion of the observed response to clinical treatment with antidepressants is not attributable to specific effects of the medication but rather to placebo responses. This chapter proposes a conceptual model for understanding placebo responses in antidepressant randomized clinical trials. It specifies factors contributing to placebo responses and focuses on those conceptualized as contributing to the therapeutic effect of placebos: expectancy and contact with the physician. It synthesizes the literature on each factor, with a special focus on whether and how each can be manipulated. A thorough understanding of the factors contributing to placebo responses, their neurobiological underpinning, and the manners in which they can be manipulated may result in the ability to optimize placebo response to the diverging needs of pharmacotherapy research and clinical practice: minimizing it in clinical trials and maximizing it in clinical practice.