Fifteen RCTs (1,310 participants) were included in the review.
Internalising outcomes: Overall there was a significant reduction in anxiety and depression following treatment of internalising disorders compared to placebo (effect size 0.32, 95% CI 0.17 to 0.47). There was no evidence of statistical heterogeneity for this analysis (I2=8%). Subgroup analysis reported a larger effect size for CBT than for pharmacological treatment (p=0.032) and for treatment of anxiety compared with depression (p=0.044). There was evidence of significant publication bias (p<0.05) and the trim-and-fill analysis estimated that the degree of bias was small.
Alcohol outcomes: Treatment of internalising symptoms significantly improved overall alcohol use (effect size 0.22, 95% CI 0.02 to 0.42), frequency (effect size 0.34, 95% CI 0.13 to 0.56) and quantity (effect size 0.36, 95% CI 0.16 to 0.56), but had no significant effect on abstinence or intensity. Heterogeneity was significant for the analysis of intensity (I2=53%). Subgroup analysis found no significant differences for alcohol outcomes for CBT compared with pharmacological treatment, anxiety compared with depression and for larger effect sizes compared with smaller effect sizes for internalising outcome. There was no evidence of publication bias.