This is a meta-analysis that included randomized trials on psychotherapies from bibliographic databases of Cochrane, Embase, PubMed, and PsychINFO. This analysis included a total of 36,072 patients from 366 trials with 453 comparisons between therapy and control conditions. The primary outcome of the study was the onset of depressive symptoms.

The mean effect sizes for depressive symptoms were much higher in middle-aged adults (g=0.77) than in children (g=0.35). The effect size in young adults (g=0.95) was significantly larger than in middle-aged adults. A significant difference was also found between the effect sizes of older adults (0.66) and older old adults (g=0.97). However, the quality of most studies was optimal and had high levels of heterogeneity.

The trials included in this meta-analysis study included that the effect sizes of psychotherapies were smaller in children than in adults but significantly higher in younger adults than in middle-aged, older, and older old individuals. However, the quality of the trials was suboptimal, and more robust research on the topic is required.