Abstract The literature has succeeded in showing that psychotherapy in general is more effective than no-treatment conditions, but it has not clearly demonstrated differences in outcome efficacy between psychotherapies. One prominent explanation for equivalent treatment outcome efficacy is the placebo effect. The origins of the placebo effect, its evolution, and the debate surrounding it are discussed. It is argued that the placebo effect is not useful for the understanding and advancement of psychotherapy. It is proposed that examination of specific and nonspecific factors with regard to individual therapies will be of more utility. Specific factors refer to elements clearly delineated by proponents of a given therapy as the active causes of change. Nonspecific factors refer to possible elements in one therapy that contribute to improvement but which are not specified in the theoretical or practical delineation of the therapy. Cognitive therapy for depression is posited to be a suitable vehicle for examining specific and nonspecific factors in psychotherapy. Therefore, evidence for specific factors and nonspecific factors is considered in the context of Beck's cognitive models and therapy. The literature appears to suggest that both specific and nonspecific factors are influential. Our own study suggests that specific factors are more influential in the change occurring in cognitive therapy. However, action of these specific factors are not unique to cognitive therapy. Until evidence is forthcoming to show presence of elements both specific and unique to differing psychotherapies, the issue of reasons for treatment efficacy will remain controversial.