Not All Omega-3s Equal When It Comes to Antidepressant Effects

Kate Johnson

December 08, 2010

December 8, 2010 (Miami Beach, Florida) — Not all omega-3 fatty acids are equal when it comes to their antidepressant effects, according to a meta-analysis presented at the American College of Neuropsychopharmacology 49th Annual Meeting.

In fact, only eicosapentaenoic acid (EPA) — and not docosahexaenoic acid (DHA) — is associated with mood improvement in patients with depression, concluded lead study author John M. Davis, MD, research professor at the University of Illinois in Chicago.

The meta-analysis of 15 randomized, double-blind, placebo-controlled studies clarifies which type of omega-3 fatty acid is effective for depression and why previous findings on the antidepressant effects of omega-3 fatty acids have been contradictory, said Dr. Davis at a press conference.

Omega-3 fatty acids are not synthesized by the body and therefore must be consumed in food (primarily fish and nuts) or supplements. In food, EPA and DHA are found together in a 1:1 ratio, but supplements can contain either fatty acid or a combination of both, he said.

The study concluded that an EPA-predominant formulation is necessary for the full therapeutic antidepressant action, whereas the DHA-predominant formulation has little antidepressant efficacy.

Modern diets may predispose individuals to omega-3 deficiency because changes in farming have resulted in a dietary increase in omega-6 fatty acids, which compete with omega-3 fatty acids in the body, said Dr. Davis.

Although deficiency in omega-3 may predispose individuals to depression and supplementation may have antidepressant benefits, "omega-3 fatty acids are generally not euphoriants in that they do not help people whose mood is normal," he said.

A previous study by Dr. Davis and his colleagues looked at EPA intake among 8000 pregnant women participating in the Avon Longitudinal Study of Parents and Children and found that low intake was associated with high levels of depression (Epidemiology. 2009;20:598-603).

Specifically, compared with women consuming more than 1.5 g of omega-3 from seafood per week, those consuming none were more likely to have high levels of depressive symptoms at 32 weeks' gestation (adjusted odds ratio, 1.54).

François Lespérance, MD, a professor of psychiatry at the Centre Hospitalier de l'Université de Montréal in Quebec, Canada, was the lead investigator on a recently published randomized controlled trial that found a benefit of omega-3 supplementation vs placebo in patients with major depressive disorder (J Clin Psychiatry. June 15, 2010 [Epub ahead of print]).

Reached for comment on Dr. Davis's study Dr. Lespérance said, "This meta-analysis provides additional evidence to what is already known through a limited number of studies in this field. It is therefore a useful summary of several clinical trials that most people may not know in detail."

Dr. Davis has disclosed no relevant financial relationships. Dr. Lespérance received an unrestricted grant from Isodis Natura, a distributor of omega-3 supplements, to conduct his randomized controlled trial but had nothing else to declare.

American College of Neuropsychopharmacology (ACNP) 49th Annual Meeting. Presented December 9, 2010.