All antidepressants are more efficacious than placebo in adults with major depressive disorder, a systematic review and meta-analysis has found. Double-blind, randomised controlled trials were identified from the Cochrane Central Register of Controlled Trials and other large databases. Placebo-controlled and head-to-head trials of 21 antidepressants (a selection of first-generation and all approved second-generation antidepressants) were included.