Serum n-3 polyunsaturated fatty acids and psychological distress in early pregnancy: Adjunct Study of Japan Environment and Children's Study

N-3 polyunsaturated fatty acids (PUFAs), especially long-chain types such as docosahexaenoic acid, are important nutrients in pregnancy, but the relationship between n-3 PUFA levels and perinatal and postnatal depression remains controversial. This study examined the possible relationship between serum n-3 PUFA levels and psychological distress among expectant mothers in early pregnancy. Data and specimen samples were obtained in a birth cohort study started at Toyama Regional Center in July 2012 as an adjunct study of the Japan Environment and Children's Study. Blood samples were collected at 9–14 weeks' gestation (75% of samples) or after 15 weeks (25%). Subjects with a Kessler Psychological Distress Scale score (K6) ⩾9 were assigned to the psychological distress group (n=283). The control group (n=283) was matched for age, educational level and family income. Fatty acid composition was determined from serum samples by gas chromatography. Associations between fatty acid levels and incident psychological distress were evaluated by logistic regression. After adjusting for possible confounders, eicosapentaenoic acid showed an inverse association with risk of psychological distress, with an odds ratio of 0.47 (95% confidence interval: 0.30, 0.73) for the highest tertile. This inverse association remained even after applying a higher cutoff score (K6 ⩾13) indicating severe psychological distress (74 pairs). We believe this is the first study to reveal the associations between serum n-3 PUFAs and risk of psychological distress in early pregnancy. Further research is required to verify the causality of these associations.