[Folates in the treatment of depression]

Depression is an important and often recurrent illness. An initial antidepressant trial is effective at achieving remission for about 30 % of patients when prescribed as monotherapy, with the majority of patients returning as partial or non-responders. Suboptimal serum and red blood cell folate levels have been associated with a poorer response to antidepressant therapy, a greater severity of symptoms, later onset of clinical improvement, and overall treatment resistance. This article reviews the evidence for L-methylfolate and folic acid as antidepressive agents in depression and discusses their clinical use.