Comment: The quality of evidence is downgraded by inconsistency (heterogeneity in patients, interventions and results) and imprecise results (most of the trials were small with wide confidence intervals).
A Cochrane review included 26 studies with a total of 1478 subjects. Twenty-five studies (n=1438) investigated the impact of n-3 polyunsaturated fatty acids (n-3PUFA) supplementation vs. placebo and one study (n=40) vs. antidepressant treatment. Studies included individuals who were all receiving therapy for depression at the time of the trial. Treatment duration varied from 4 to 16 weeks. N-3PUFA supplementation resulted in a small to modest benefit for depressive symptomology compared to placebo (SMD -0.32, 95% CI -0.12 to -0.52; 25 studies, n=1373), but this effect is unlikely to be clinically meaningful (an SMD of 0.32 represents a difference between groups in scores on the HDRS (17-item) of approximately 2.2 points (95% CI 0.8 to 3.6)). Although the numbers of individuals experiencing adverse events were similar in intervention and placebo groups (OR 1.24, 95% CI 0.95 to 1.62; 19 studies, n=1207), the CIs include a significant increase in adverse events with n-3PUFAs as well as a small possible decrease. Rates of remission and response, quality of life, and rates of failure to complete studies were also similar between groups. The evidence on which these results are based is very limited. One study was available for the antidepressant comparison (n=40). This study found no differences between treatment with n-3PUFAs and antidepressants in depressive symptomology (MD -0.70, 95% CI -5.88 to 4.48), rates of response to treatment or failure to complete. Adverse events were not reported in a manner suitable for analysis, and rates of depression remission and quality of life were not reported.
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