Munder, T., Fluckiger, C., Leichsenring, F, Abbass, A.A., Hilsenroth, M.J., … Wampold, B.E. (2018). Is psychotherapy effective? A re-analysis of treatments for depression. Epidemiology and Psychiatric Sciences, 1-7.
Based on a deeply flawed review in 1952, Hans Eysenck declared that psychotherapy was no more effective than custodial care for treating mental disorders. Later, he qualified this by stating that behaviour therapy was effective and other forms of psychotherapy were not. These statements touched off decades of angst and debate in the psychotherapy community, and also resulted in a great deal of research about psychotherapy’s effectiveness. By the 1970s the new research technique of meta-analysis was developed and was applied to psychotherapy research. In their seminal meta analysis of controlled studies, Smith and Glass found that psychotherapy was useful and with large effects compared to no treatment. And yet the debate continues. In 2018, Cuijpers argued that waitlist control groups (i.e., a common control condition in psychotherapy studies in which patients receive no treatment) are an inappropriate comparison leading to exaggerated estimates of the effects of psychotherapy. Recently, Munder and colleagues argued that waitlist controls are a way of estimating the natural course of the disorder (what would happen with no treatment) plus the effect of expecting to receive treatment (client expectations of receiving treatment tend to have a positive impact on symptoms). In fact, research shows that pre- to post-study effect sizes for the waiting period is approximately g = .40, or a medium effect. In other words, waiting for therapy in a study results in a moderate proportion of individuals getting better on their own without treatment. Therefore, Munder and colleagues argued that comparing psychotherapy to a waitlist control is appropriate and may be a conservative estimate of psychotherapy’s effects (i.e., psychotherapy has to outperform the effects of clients expecting treatment to help them). In their meta analysis, Munder and colleagues re-analysed 71 studies of psychotherapy for depression compared to a waitlist control condition. They found that the effect size in favour of psychotherapy was g = 0.75 (SE = 0.09) indicating a moderate to large effect. Psychotherapy was also more effective than care as usual (i.e., compared to another intervention that was not psychotherapy), g = 0.31 (SE = 0.11). There were no differences between types of psychotherapy (CBT, IPT, PDT, etc.) for depression outcomes.
Despite various attempts during the history of psychotherapy to downplay or disparage its efficacy, research continues to show that psychotherapy is in fact effective. The average effect size compared to the natural history of depression is moderate to large (and that is likely an under-estimate). Again, there is no evidence that one type of psychotherapy is superior to another for treating depression. It is time for the field to move beyond questions of efficacy of psychotherapy and of the relative efficacy of different treatments, and look to understanding therapist interpersonal stances, client characteristics, and relationship factors that may improve outcomes from psychotherapy.