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Review finds inadequate evidence of efficacy of omega-3 supplements for MDD

A recent Cochrane review found insufficient evidence for efficacy of omega-3 supplements for treatment of major depressive disorder when compared with placebo or antidepressant treatment.

“One emerging potential treatment for [major depressive disorder (MDD)] is n-3 polyunsaturated fatty acids (n-3PUFAs), also known as omega-3 oils, naturally found in fatty fish, some other seafood and some nuts and seeds,” Katherine M. Appleton, PhD, of Bournemouth University, Poole, United Kingdom, and colleagues wrote. “Various lines of evidence suggest a role for n-3PUFAs in MDD, but the evidence is far from conclusive. Reviews and meta-analyses clearly demonstrate heterogeneity between studies. Investigations of heterogeneity suggest differential effects of n-3PUFAs, depending on severity of depressive symptoms.”

To evaluate efficacy of omega-3 supplements for MDD, researchers analyzed 25 randomized controlled trials (n = 1,438) that compared them with placebo and one randomized trial that compared omega-3 supplements with an antidepressant treatment (n = 40).

Compared with placebo, omega-3 supplements resulted in a small-to-modest benefit for depressive symptoms, with a standardized mean difference of –0.32 (95% CI, –0.12 to –0.52). The observed effect is unlikely to be clinically meaningful, according to researchers, as there was very low quality evidence.

The study that compared omega-3 supplements with antidepressant treatment found no differences between the two regarding depressive symptoms (mean difference = –0.7 (95% CI, –5.88 to 4.48), rates of treatment response and failure to complete.

Adverse events, depression remission rates and quality of life were not reported or not suitable for analysis.

“We found a small-to-modest positive effect of omega-3 fatty acids compared to placebo, but the size of this effect is unlikely to be meaningful to people with depression, and we considered the evidence to be of low or very low quality. All studies contributing to our analyses were of direct relevance to our research question, but most of these studies are small and of low quality,” Appleton said in a press release. “At present, we just don’t have enough high quality evidence to determine the effects of omega-3 fatty acids as a treatment for major depressive disorder. It’s important that people who suffer from depression are aware of this, so that they can make more informed choices about treatment.” – by Amanda Oldt

Disclosure: The researchers report no relevant financial disclosures.