Change in folate status with antidepressant treatment.

Ninety-nine consecutive unmedicated outpatients with a major depressive illness had blood drawn for measurement of serum folate (SF), red cell folate (RCF), and vitamin B12 within 24 hours of completion of ratings of severity of depression at the beginning and ending of a 5-week trial of desmethylimipramine (mean dose = 149.2 mg/day, range = 75-225 mg). As compared with nonresponders, responders had a significantly higher mean SF at baseline (nonresponders = 13.8 nmol/l; responders = 17.7 nmol/l) and RCF showed a significant inverse correlation with severity of depression and a significant positive correlation with age of onset of illness. At week 5, change in severity of depression was significantly correlated with change in RCF, and significantly more responders than nonresponders had an increase in RCF. The possible role of folate status in the regulation of mood and response to treatment is discussed.