Recent research suggests that there is not enough evidence to support the use of omega-3 fatty acid supplements for the treatment of major depressive disorder (MDD).

Omega-3 fatty acids are naturally found in fatty fish, such as tuna, seafood, and some nuts and seeds. Supplements are available over-the-counter and its use has grown over the last decade.

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A new Cochrane review analyzed the use of omega-3 fatty acids against a comparator (eg, placebo, antidepressant, standard care, no treatment, wait-list control) for MDD in adults. Twenty-five studies (n=1,438) evaluating the impact of omega-3 supplementation vs. placebo, and one study (n=40) evaluating the impact of omega-3 supplementation vs. antidepressant treatment were included in the review.

Compared to placebo, omega-3 fatty acids showed a small-to-modest positive effect for depressive symptoms: standardized mean difference (SMD) -0.32 (95% CI: -0.12 to -0.52; very low-quality evidence). However, this effect is unlikely to be clinically meaningful as the SMD reflects a difference of approximately 2.2 points (95% CI: 0.8 to 3.6) between the two groups. The amount of patients that experienced adverse events were similar (OR 1.24, 95% CI: 0.95 to 1.62, very low-quality evidence).

The study comparing omega-3 fatty acids to antidepressants found no difference in depressive symptomology: mean difference (MD) -0.70 (95% CI: -5.88 to 4.48), rates of response to treatment or failure to complete. Rates of depression remission and quality of life were not reported.

Even though recent research shows a slightly positive effect for omega-3 fatty acids vs. placebo, these results are not likely clinically meaningful and are of low quality evidence, researchers concluded.  Further studies are needed to make conclusions about the efficacy and safety of omega-3 supplements for the treatment of MDD. 

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