Omega-3 fatty acid biomarkers and subsequent depressive symptoms

We sought to determine the relationship between the omega-3 fatty acid content of red blood cell membranes (RBC), in particular docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), and baseline and new-onset depressive symptoms in post-menopausal women. We secondarily sought to characterize the association between dietary omega-3 fatty acid intake and depressive symptomatology.

Study participants included 7086 members of the Women's Health Initiative Memory Study (aged 63-81 years) who had an assessment of RBC omega-3 fatty acid concentrations at the baseline screening visit. Depressive symptoms at baseline and follow-up were characterized using the Burnam eight-item scale for depressive disorders (Center for Epidemiologic Studies Depression Scale/Diagnostic Interview Schedule short form) and secondarily additionally inferred by antidepressant medication use.

In multivariable-adjusted models, our primary exposure, RBC DHA + EPA, was not related to depressive symptoms by any measure at baseline or follow-up, nor were RBC total omega-3, DHA, or EPA (all p > 0.2). In contrast, dietary intake of omega-3 was positively associated with depressive symptoms at baseline (adjusted odds ratio 1.082, 95% confidence interval 1.004-1.166; p = 0.04 for dietary DHA + EPA and Burnam score ≥0.06), although this generally did not persist at follow-up.

No relationship between RBC omega-3 levels and subsequent depressive symptoms was evident, and associations between dietary omega-3 and depressive symptoms were variable. Biomarkers of omega-3 status do not appear to be related to risk of new depression in post-menopausal women.