The effects of psychotherapy: A reevaluation based on dosage

Abstract

In 1952, Hans Eysenck published “The Effects of Psychotherapy: An Evaluation” in which he concluded that the effect of psychotherapy is no greater than that of spontaneous remission. In the present paper, we tested this conclusion using Eysenck's original panel of “untreated” patients. A probit analysis of rates of improvement by time of assessed improvement was conducted on these data, and results were compared to a probit analysis conducted on a panel of patients who had received psychotherapy. Treatment was associated with significantly higher rates of improvement when compared to the effects of spontaneous remission. In fact, 50% of psychotherapy patients were estimated to improve after 8 weeks, whereas only 2% of untreated patient were estimated to improve in this time. Probit analysis showed that the 50% improvement rate for Eysenck's spontaneous remission group occurred at a much later time than the 50% improvement rate for psychotherapy. According to his % improvement estimates, psychotherapy accomplishes in about 15 scssions what spontaneous remission takes two years to do. Thus, Eysenck's data reveal that psychotherapy is very effective.