Serum folate and depressive symptoms among Japanese men and women: a cross-sectional and prospective study.

Although several studies have reported an association between blood folate concentrations and depressive symptoms, few studies have prospectively examined the association. This study aimed to investigate the cross-sectional and prospective associations between serum folate concentrations and depressive symptoms among Japanese. We analysed data among 545 subjects who participated in a health survey at the time of periodic check-up in 2009 for a cross-sectional association and among 272 subjects without depressive symptoms at baseline (in 2006) who responded to both baseline (2006) and follow-up (2009) surveys for prospective association. Depressive symptoms were assessed using the Center for Epidemiologic Studies Depression (CES-D) scale. In a cross-sectional analysis, serum folate concentrations were significantly associated with a decreased prevalence of depressive symptoms (CES-D scale of ≥16). Moreover, serum folate concentrations at baseline were significantly inversely associated with depressive symptoms after 3 years; the multivariate-adjusted odds ratios (95% confidence intervals) of depressive symptoms for the lowest through highest tertile categories of serum folate concentrations were 1.00 (reference), 0.66 (0.29-1.52) and 0.40 (0.16-0.99) (P for trend=0.047). Our findings suggest that a higher serum folate may be associated with decreased risk of depressive symptoms in Japanese.