TAIPEI, TAIWAN. Major depressive disorder (MDD) is a serious illness that by 2020 is expected to be the second leading cause of disability, second only to heart disease. Numerous studies have been done to elucidate the possible connection between depression and blood levels of omega-3 and omega-6 long-chain polyunsaturated fatty acids (PUFAs), more specifically eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and arachidonic acid (AA). EPA and DHA are the main components of fish oils and there is evidence that societies with a high fish consumption tend to have a lower incidence of MDD. In addition, several, but not all, clinical trials have found that fish oil supplementation is as effective in treating MDD as is medication with standard antidepressants such as fluoxetine (Prozac).
A group of Chinese researchers report the results of a meta-analysis of 14 studies dealing with the association between depression and intake of long-chain PUFAs. Their main finding is that patients with depression have significantly lower levels of EPA and DHA and moderately lower levels of total omega-3 PUFAs than do non- depressed control subjects. The levels of AA and total omega-6 PUFAs were not significantly different between controls and patients. Limiting the analysis to patients diagnosed with major depressive disorder further strengthened the association between low levels of EPA and DHA and depression.
The authors conclude that long-chain omega-3 PUFAs play an important role in the etiology of depression and suggest that this provides a rationale for using fish oils in the treatment of patients with depression.
Lin, PY, et al. A meta-analytic review of polyunsaturated fatty acid compositions in patients with depression. Biological Psychiatry, Vol. 68, 2010, pp. 140-47