To review the clinical evidence supporting complementary and alternative medicine interventions for treating major depressive disorder.

PubMed was searched from January 1966 to February 2010 using the term depressive disorder in combination with St John’s wort, S-adenosylmethionine (SAM-e), exercise, acupuncture, omega-3 fatty acids, and folate. Only relevant human trials were selected.

In a large meta-analysis, St John’s wort was found to be equivalent to antidepressant drugs with fewer side effects. Exercise reduced depressive scores in 3 meta-analyses. Omega-3 fatty acids reduced depressive scores in a meta-analysis of 16 trials, but publication bias was identified. Oral SAM-e monotherapy reduced depressive scores in 4 of 5 small randomized controlled trials. Folate deficiency is associated with more severe and refractory depression, and supplementation reduced depressive scores in 2 of 3 randomized controlled trials. Acupuncture demonstrated limited efficacy in 1 meta-analysis and 5 other trials.

St John’s wort and regular exercise appear effective in the treatment of depression. Acupuncture appears ineffective for depression, but it might offer other health benefits. Other promising therapies include SAM-e, omega-3 fatty acid, and folic acid supplementation in selected patients; further study is warranted.