Depression and depressive symptoms in pregnant women are frequent and have a great need to be addressed because they can have adverse physical and mental effects on both the woman and her child, but most pregnant women do not wish to receive drug therapy due to safety concerns. Among nutrients, omega-3 fatty acids have accumulated the most evidence for their antidepressant effects, and we conducted a randomized controlled trial to evaluate the efficacy of omega-3 fatty acids on depressive symptoms in pregnant women in a two-country collaboration with Taiwan.
A total of 108 pregnant women at three institutions (two in Japan and one in Taiwan) participated in the study and were administered a supplement containing eicosapentaenoic acid (EPA) as the main ingredient for 12 weeks. Study results showed no benefit of omega-3 fatty acids, but a subgroup analysis by site showed a relatively high effect size (0.72) only at one site in Japan. Participants at that site had higher plasma estradiol (E2) levels than participants at the other two sites, and in the intervention group, increases in blood EPA and E2 were significantly associated with fewer depressive symptoms. This suggests that supplementation with omega-3 fatty acids during mid- to late pregnancy, when E2 is elevated in pregnant women, may have a greater antidepressant effect.