Effect of long-term supplementation with folic acid and B vitamins on risk of depression in older women.

Homocysteine-lowering nutrients may have preventive/ameliorative roles in depression. To test whether long-term B-vitamin/folate supplementation reduces depression risk. Participants were 4331 women (mean age 63.6 years), without prior depression, from the Women's Antioxidant and Folic Acid Cardiovascular Study - a randomised controlled trial of cardiovascular disease prevention among 5442 women. Participants were randomly assigned to receive a combination of folic acid (2.5 mg/d), vitamin B6 (50 mg/d) and vitamin B12 (1 mg/d) or a matching placebo. Average treatment duration was 7 years. The outcome was incident depression, defined as self-reported physician/clinician-diagnosed depression or clinically significant depressive symptoms. There were 524 incident cases. There was no difference between active v. placebo groups in depression risk (adjusted relative risk 1.02, 95% CI 0.86-1.21, P = 0.81), despite significant homocysteine level reduction. Long-term, high-dose, daily supplementation with folic acid and vitamins B6 and B12 did not reduce overall depression risk in mid-life and older women.