REFERENCE: Roberts, A. H., Kewman, D. G., Mercier, L., Hovell, M. (1993). The power of nonspecific effects in healing: Implications for psychosocial and biological treatments. Clinical Psychology Review, 13, 375-391.

We evaluated the hypothesis that the power of nonspecific effects may account for as much as two thirds of successful treatment outcomes when both the healer and the patient believe in the efficacy of a treatment. Five medical and surgical treatments, once considered to be efficacious by their proponents but no longer considered effective based upon later controlled trials, were selected according to strict inclusion criteria. A search of the English literature was conducted for all studies published for each treatment area. The results of the these studies were categorized, where possible, into excellent, good, and poor outcomes. For these five treatments combined, 40 % excellent, 30 % good, and 30 % poor results were reported by proponents. We conclude that, under conditions of heightened expectations, the power of nonspecific effects far exceeds that commonly reported in the literature. The implications of the results in evaluating the relative efficacy of biological and psychosocial treatments is discussed.


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