Review: DHA/EPA Blood Levels Lower in Patients with Depression
Lin, P.. et al., Biol. Psychiatry , in press , 2010
Dept. of Psychiatry, Chang Gung Memorial Hospital , Kaohsiung Medical Ctr., Kaohsiung,Taiwan
Major depressive disorder is anticipated to soon become the second leading cause of disability worldwide after heart disease. Some population studies which monitored fish intakes and some intervention trials which compared EPA/DHA supplementation versus placebo have indicated a reduction in depressive symptomology in patients ingesting much higher levels of EPA/DHA omega-3 fatty acids. Because of some inconsistencies between such studies, it was of interest to perform an overview assessment (via meta-analysis) to compare the blood levels of EPA/DHA and other fatty acids in depressive versus control subjects.
Following extensive assessment of the peer-reviewed literature, 14 major studies were identified that fulfilled the criteria for the statistical analyses. The measured levels of circulating EPA/DHA and other fatty acids were conducted on red blood cell membranes, blood phospholipid , or blood cholesteryl esters. While the overall levels of total omega-6 fatty acids (including AA ,arachidonic acid) were not different , significantly lower levels of EPA, DHA , and total omega-3 (n-3) fatty acids were found in the depressive subjects relative to controls. The authors concluded that their findings imply that omega-3 fatty acids play a role in the pathogenesis of depression while providing a ‘rationale for using n-3 polyunsaturated fatty acids as an alternative treatment for depression’.
It is of interest to note that DHA is a substantial structural component of neuronal membranes while EPA is present in near trace amounts yet EPA-enriched omega-3 concentrates have often been used in controlled clinical trials on depressive patients. Thus, each omega-3 fatty acid may exert benefits by very different mechanisms (modulators of eicosanoid and cytokine production, generation of different patterns of anti-inflammatory .resolvins/protectins,others) operative both within and external to neuronal tissue. Finally, it should be pointed out that the various studies as reviewed herein did not monitor for EPA/DHA intakes . Thus, differences between EPA/DHA intakes in the patients versus controls and/or differences in omega-3 fatty acid metabolic activity/capacity between the two groups could readily contribute to the differences in circulating blood levels of these omega-3 fatty acids.