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Does Eating More Fish Cure or Prevent Depression?

Walk into any health food shop and you would think that  omega-3 highly unsaturated fatty acids (HUFAs) were a panacea for all ills - the hype for these dietary supplements arises from recent research which appeared to find various benefits but now a study published by Brian Hallahan and colleagues attempts to pool all the data accumulated on the subject and cut through to the truth.

From the original recently published paper by Brian Hallahan and colleagues

Efficacy of omega-3 highly unsaturated fatty acids in the treatment of depression* Brian Hallahan, Timothy Ryan, Joseph R. Hibbeln, Ivan T. Murray, Shauna Glynn, Christopher E. Ramsden, John Paul SanGiovanni and John M. Davis

The British Journal of Psychiatry 1–10. doi: 10.1192/bjp.bp.114.160242

Many randomised controlled trials (RCTs) have reported beneficial effects for omega-3 highly unsaturated fatty acids (HUFAs) in bipolar and major depressive disorder, but others have reported essentially no effect.... possible explanatory factors: (a) that only eicosapentaenoic acid (EPA)-predominant formulations of omega-3 HUFA have an antidepressant effect;37,38 and (b) that the putative antidepressant effects of omega-3 HUFAs only occur in episodes of diagnosed clinical depression...

The study found that:  

Among participants with diagnosed depression, eicosapentaenoic acid (EPA)-predominant formulations (450% EPA) demonstrated clinical benefits compared with placebo... whereas docosahexaenoic acid (DHA)-predominant formulations (450% DHA) did not. EPA failed to prevent depressive symptoms among populations not diagnosed for depression.