Trials in which participants had moderate depressive symptoms at baseline reported a greater efficacy of omega-3 fatty acids when compared to trials in which participants were
only mildly depressed (test for subgroup differences: χ2 = 11.7, df = 1 (P < 0.0006), I2 =
91%). The effect size for omega-3 in trials in which participants were at least moderately
depressed on average at baseline was 0.42 (95% CI: 0.19, 0.65) compared to trials in which
participants had only mild depression on average at baseline (SMD=-0.11, (95% CI: -0.30,
0.09) (see Figure 3).