Say you did a study and the results disappointed — would you publish it? If you said no you’ve got some company. The National Institutes of Health funded 55 clinical trials of psychological treatments for depression between 1972 and 2008, researchers found. Only 42 of the trials published results. That meant that the data representing the effectiveness of treatment was incomplete — absent results from a full 13 out of 55 trials. When a group of researchers rounded up the unpublished 13, the efficacy of psychotherapy looked a little different. Turns out, as you might have guessed, the people with the better results had a higher publication rate. So the results were skewed in favor of success — it’s called a “publication bias.” Sort of the opposite of what happens with angry diners who publish bad reviews on Yelp! That segment skews negative.
The results of the study were published in the journal PLOS ONE. They follow a similar revelation from a 2008 study on the effectiveness of drugs in treating depression, which was also found to be overstated. “The efficacy of psychological interventions for depression has been overestimated in the published literature, just as it has been for pharmacotherapy,” reads the report. Psychotherapy works, the study shows — but it shoots a few more blanks than you’d think from reading the literature.