Folate, B12, and life course of depressive illness.

Forty-four consecutive, unmedicated outpatients with a major depressive disorder were evaluated to determine the relationships in life course, severity of depressive illness, and serum folate and B12 levels. Duration of current episode was significantly inversely correlated with folate levels. Age at onset of illness was significantly correlated with B12. In a subgroup of recurrent depressives, current age and age at onset of depressive illness were positively correlated with folate. The findings are discussed in light of the current hypotheses regarding the association of folate and mood.