Results of nearly 400 controlled evalua- tions of psychotherapy and counseling were coded and integrated statistically. The findings provide convincing evidence of the efficacy of psychotherapy. On the average, the typical therapy client is better off than 75% of untreated individuals. Few important differ- ences in effectiveness could be established among many quite different types of psychotherapy . More generally, virtually no difference in effectiveness was observed be- tween the class of all behavioral therapies (systematic desensitization, behavior modification) and the nonbe- havioral therapies (Rogerian, psychodynamic, rational- emotive, transactional analysis, etc.).
Smith et al. (1977) studied this question.