MedWire News: Postmortem study demonstrates a selective deficit in the omega-3 fatty acid docosahexaenoic acid (DHA) in the orbitofrontal cortex of patients with major depressive disorder (MDD), researchers report.
These findings suggest a role for omega-3 fatty acid deficiency in the pathophysiology and, potentially, pathogenesis of MDD, Robert McNamara (University of Cincinnati College of Medicine, Ohio, USA) and colleagues say.
Previous epidemiological surveys and studies of plasma fatty acid levels have suggested a link between omega-3 fatty acid deficiency and MDD.
In the current study, McNamara and team analyzed the total fatty acid composition of post-mortem orbitofrontal cortex from 15 patients diagnosed with MDD and 27 age-matched controls, using gas chromatography.
After multiple comparison tests, DHA was the only fatty acid which levels differed significantly in the post-mortem orbitofrontal cortex from patients with MDD, compared with controls, being 22% lower in MDD patients.
These differences were greater in female MDD patients (–32%) but lower in male MDD patients (–16%). This could not be attributed to lifestyle factors or post-mortem tissue variables, the team notes.
DHA levels negatively correlated with concentrations of the main monounsaturated fatty acids – oleic acid and vaccenic acid – and this suggests that DHA loss is compensated for by elevations in these fatty acids. In contrast, DHA levels positively correlated with arachidonic acid levels, suggesting concomitant loss.
McNamara et al comment that, as previous studies have observed reductions in gray matter volume in the orbitofrontal cortex of patients with MDD, it would be of interest to determine whether chronic omega-3 fatty acid treatment can normalize these volume reductions."