al. (2004) followed up the Northern Finland 1966 Birth Cohort prospectively from pregnancy to 31 years of age. Members of the cohort were sent questionnaires, invited to undergo a clinical examination to assess indices of depression, and asked to estimate seafood consumption in the previous six months (presumably related to the lifetime pattern of seafood consumption). The study found that females who rarely consumed fish showed greater incidences of life-time depression than regular consumers of fish, based on the Hopkins Symptom Check List (HSCL-25) depression subscale alone (cutoff-point 2.01) (OR=1.4; 95% confidence interval [CI] 1.1-1.9) and the HSCL-25 depression subscale (cutoff-point 2.01) with a doctor diagnosis (OR=2.6; 95% CI 1.4-5.1), but not based on doctor diagnosis alone (OR=1.3; 95% CI 0.9-1.9) or suicidal ideation. This study, however, did not show causation and did not address postpartum depression specifically.
Otto et al. (2003) investigated the relationship between postpartum depression and changes in maternal plasma phospholipid-associated fatty acid (DHA and docosapentaenoic acid [DPA]) status by measurement at 36 weeks of pregnancy, at delivery, and 32 weeks postpartum in women in the Netherlands. Postpartum depression was assessed using the Edinburgh Postnatal Depression Scale (EPDS), developed as a screening and monitoring tool for postpartum depression (Cox et al., 1987). Only relative plasma fatty acid levels (percent of total fatty acids, wt/wt) were reported because total absolute amounts of plasma phospholipid-associated fatty acids at delivery and changes that occurred postpartum were not significantly different between the “possibly depressed” and “non-depressed” groups. The conclusion from this study was that the ratio of 22:6 n-3 (DHA) to 22:5 n-6 (DPA) becomes reduced during pregnancy and the difference is significant (p<0.04) compared to increased EPDS scores, while DHA status at delivery did not correlate with depressive symptoms (p=0.563) (Otto et al., 2003).
In contrast to the above-mentioned studies, Llorente et al. (2003) examined a cohort of 44 women who consumed 200 mg of DHA per day during the first 4 months of lactation compared to a placebo control group (n=45) for indices of postpartum depression and information processing (cognition). Both groups were analyzed for symptoms of depression using a self-rating questionnaire, the Beck Depression Inventory (BDI). Additionally, a subgroup of the population was administered the EPDS and the Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Axis I Disorders—Clinical Version. A positive and statistically significant correlation was found between the BDI questionnaire at 4 months and the EPDS scores at 18 months (p<0.0001), which validated use of the BDI for assessment of symptoms. However, no difference was found between the supplemented and control groups for diagnostic measures of postpartum depression or information processing (see Appendix Table B-1b).