Ten double-blind, placebo-controlled studies (329 participants) were included in the review.
The results showed there was a moderate antidepressant effect of omega-3 PUFAs in comparison with placebo (SMD 0.61, 95% CI: 0.21, 1.01, p=0.003; 10 studies). However, there was evidence of significant heterogeneity (p=0.004). The sensitivity analysis showed that none of the included studies strongly affected the positive effect of the treatment (data not presented).
Subgroup analysis of studies that examined clearly defined depression using HAM-D criteria showed a significant antidepressant effect of omega-3 PUFAs compared with placebo (SMD 0.69, 95% CI: 0.24, 1.13, p=0.002; 8 studies, 222 participants). However, there was again evidence of significant heterogeneity (p=0.03).
Further subgroup analysis showed a significant antidepressant effect of omega-3 PUFAs compared with placebo in participants with bipolar disorder (ES 0.69, 95% CI: 0.28, 1.0, p=0.0009; 2 studies, 67 participants).
Subgroup analysis dividing studies by different dosage of eicosapentaenoic acid showed no statistically significant differences between the low-, medium- and high-dosage groups.
There was evidence of significant publication bias (p<0.025).