..After removing duplicates, 16 756 records were screened and 2608 full-text articles were screened. Of these, 366 trials (36 702 patients) with 453 comparisons between a therapy and a control condition were included in the qualitative analysis, including 13 (3.6%) in children (13 years and younger), 24 (6.6%) in adolescents (≥13 to 18 years), 19 (5.2%) in young adults (≥18 to 24 years), 242 (66.1%) in middle-aged adults (≥24 to 55 years), 58 (15.8%) in older adults (≥55 to 75 years), and 10 (2.7%) in older old adults (75 years and older).
The overall effect size of all comparisons across all age groups was g = 0.75 (95% CI, 0.67-0.82), with very high heterogeneity (I2 = 80%; 95% CI: 78-82). Mean effect sizes for depressive symptoms in children (g = 0.35; 95% CI, 0.15-0.55) and adolescents (g = 0.55; 95% CI, 0.34-0.75) were significantly lower than those in middle-aged adults (g = 0.77; 95% CI, 0.67-0.87). The effect sizes in young adults (g = 0.98; 95% CI, 0.79-1.16) were significantly larger than those in middle-aged adults. No significant difference was found between older adults (g = 0.66; 95% CI, 0.51-0.82) and those in older old adults (g = 0.97; 95% CI, 0.42-1.52). The outcomes should be considered with caution because of the suboptimal quality of most of the studies and the high levels of heterogeneity. However, most primary findings proved robust across sensitivity analyses, addressing risk of bias, target populations included, type of therapy, diagnosis of mood disorder, and method of data analysis.
Conclusions and Relevance Trials included in this meta-analysis reported effect sizes of psychotherapies that were smaller in children than in adults, probably also smaller in adolescents, that the effects may be somewhat larger in young adults, and without meaningful differences between middle-aged adults, older adults, and older old adults.