A systematic review including 25 studies with a total of 2124 subjects was abstracted in DARE. For anxiety, 19 trials had a combined effect size of 0.42 (95% CI 0.08 to 0.74), and were strongly heterogeneous. For depression, 20 trials had a combined effect size of 0.36 (95% CI 0.08 to 0.66), and were also heterogeneous. After removal of 3 studies with very large effect sizes the effect size was weak (0.19).
Comment: The quality of evidence is downgraded by study quality (limitations in review methodology)