Docosahexaenoic acid (DHA) is an omega-3 essential fatty acid found primarily in fish oil and has been linked in multiple studies to mood and cognitive function. Earlier research has suggested that low omega-3 levels may be associated with depression. A study published in Biological Psychiatry (July 1, 2007; Volume 62, Issue 1, pages 17–24) examined DHA levels in the frontal lobes of deceased patients with major depressive disorder and compared them with those of individuals without depression. Of all the fatty acids measured, DHA was the only one that differed significantly between the two groups. DHA levels in the frontal lobes of patients with depression were approximately 22% lower than in those without depression.