The biology of folate in depression: implications for nutritional hypotheses of the psychoses.

Folate deficiency is a common occurrence in psychiatric disorders, whether organic or functional, particularly in depressive illness. We have shown that folate deficiency is a common association of depressive symptoms in a variety of settings including primary endogenous or non-endogenous depression, and in alcoholic, lithium-treated and anorexic patients. Possible pathogenetic mediating mechanisms for this association are methylation and hydroxylation and the implications for nutritional hypotheses of the psychoses are discussed. We suggest that folate deficiency, with or without deficiencies of other nutritional factors such as monoamine precursors, vitamins B6, B12 and C, may predispose to or aggravate psychiatric disturbances, particularly depression and a model for these interactions is proposed.