Effects of psychotherapy in treating depression overestimated

Psychotherapy is an effective treatment for depression, but less so than has previously been suggested in the scientific literature. This is because research that demonstrates the effectiveness of psychotherapy is more likely to be published than studies that show the effects to be less significant. This is the conclusion of an international study to which Claudi Bockting, Professor of Clinical Psychology at Utrecht University, contributed. The results have been published in the scientific journal PLOS ONE.

For the study, the researchers analysed 55 studies conducted between 1972 and 2008. A quarter of all of these studies were never published. In the light of the authors’ meta-analysis of both published and unpublished studies, psychotherapy proved to be less effective than previously thought. One of the co-authors, Pim Cuijpers from VU University Amsterdam, pointed out that the effectiveness of psychotherapy in reducing symptoms of depression has been overestimated by approximately a quarter.

Effects of antidepressants

Researcher Eric Turner had already demonstrated in 2008 that the effects of antidepressants had been overestimated as a result of publication bias – the distortion created when positive results of scientific research get published, but negative or unclear results do not. “This was the reason for investigating whether this was also the case for treating depression with psychotherapy”, says Bockting. 

Publication bias

However, Utrecht-based Bockting stresses that psychotherapy is still always an effective treatment for depression. “But it is less effective than the scientific literature has so far shown.”
The authors of the PLOS ONE article suggest that the original research proposals and the raw data from both published and unpublished studies should be archived. “That will enable this type of publication bias to be prevented or corrected in future.”

The study has received coverage both nationally and internationally and even featured in the NY Times.
The main author of the PLOS ONE article is Ellen Driessen (VU University Amsterdam).