Introduction to the special issue on the placebo concept in psychotherapy.

As research on the effectiveness of psychotherapy has flourished over the past two decades, scholars have increasingly borrowed various research strategies, including the placebo concept, from medicine. The recent movement toward evidence-based treatment in mental health has also highlighted psychological placebos as control conditions against which to define empirically supported psychotherapies. Nevertheless, the application of the placebo concept to psychotherapy is fraught with both conceptual and pragmatic problems. This special issue brings together leading psychotherapy scholars to explore the concept of the placebo to psychotherapy. Historical, theoretical, ethical, and practical issues are discussed from various perspectives, and recommendations are offered to guide future research.