Impact of support on the effectiveness of written cognitive behavioural self-help: A systematic review and meta-analysis of randomised controlled trials

► Written CBT self-help results in a medium effect size. ► Effectiveness did not vary by type of support. ► Effectiveness may vary by mental health condition with different types of support. ► Larger effect sizes were associated with higher baseline severity for depression. ► There were a number of significant clinical and methodological moderators.