Will the psychotherapies yield differential results? A look at assumptions in therapy trials.

Differential results in psychotherapy should be both clinically substantial and attributable to the differences alleged in various treatments. This paper reviews the nonspecific elements of psychotherapy, and inspects cognitive, interpersonal, and analytically oriented therapies to see whether claimed differences are, in fact, sufficient to make differential results likely. It also calls attention to assumptions implicit in most clinical trials about the effectiveness of once-a-week, short-term treatment, and how these assumptions limit the likelihood that research will discriminate differential outcome.