Quantity and quality of psychotherapy trials for depression in the past five decades

Over the years randomized controlled trials (RCTs) of various psychotherapies for treating depression have provided evidence to demonstrate the interventions' efficacy/effectiveness. However, recent researches suggest that the quality of some RCTs were actually less than ideal, which could hence have biased their results. The present study aims to assess (1) the changes in characteristics of RCTs of psychotherapies for treating adult depression; (2) the temporal changes in their trial quality, and (3) the quality differences among different therapeutic approaches.

We included 135 RCTs of psychotherapies treating adult depression published from year 1969 to 2011. Temporal changes in trials' characteristics including their quantity and quality were assessed at study-level and arm-level. Quality differences among different schools of psychotherapy were assessed at arm-level.

Changes in quantity and improvements in methodological quality were found at study-level. Positive changes in trial quality at arm-level were observed in most aspects. Comparisons made across different schools of psychotherapy revealed statistically significant differences among them, with earlier behavior therapy trials doing worst and more recent third wave cognitive-behavior therapy doing best.

We could not determine whether the observed changes in quality resulted from actual improvement in trial quality and/or from improved reporting. The relatively smaller number of arms for several types of interventions could weaken the representativeness when making comparisons across psychotherapeutic approaches.

Our study revealed positive temporal changes in both trial quantity and quality over the past five decades and has also spotted possible areas for further improvement.