Dietary fish, n-3 polyunsaturated fatty acid consumption, and depression risk in Japan: a population-based prospective cohort study.
Level 3 - non-randomized controlled study
Prospective cohort study with long-term clinical diagnostic follow-up
PubMed 28949340 · doi:10.1038/tp.2017.206
What was done
From a cohort of 12,219 individuals enrolled in 1990 in the Saku area of Japan, researchers analyzed 1,181 participants aged 63-82 years who completed food frequency questionnaires in both 1995 and 2000 and underwent a mental health examination in 2014-2015. The outcome was psychiatrist-diagnosed major depressive disorder (MDD). Odds ratios (ORs) and 95% confidence intervals (CIs) for MDD were calculated across quartiles of fish, n-3 PUFA, and n-6 PUFA intake, with multivariable adjustments including cancer, stroke, myocardial infarction, and diabetes.
What was found
Current MDD was diagnosed in 95 participants. Compared to the lowest intake quartile, significant reductions in MDD risk occurred in: - The third quartile of fish intake (111.1 g/day): OR = 0.44 (95% CI: 0.23-0.84) - The second quartile of eicosapentaenoic acid (EPA) intake (307.7 mg/day): OR = 0.54 (95% CI: 0.30-0.99) - The third quartile of docosapentaenoic acid (DPA) intake (123.1 mg/day): OR = 0.42 (95% CI: 0.22-0.85) Adjusted ORs remained statistically significant for fish and DPA intake. The highest intake quartiles showed no statistically significant reduction in risk.
Why it matters
Unlike studies using self-reported depression scales, this study evaluated psychiatrist-diagnosed MDD in a population with high habitual fish consumption. It supports a non-linear association where moderate, rather than high, fish and marine fatty acid consumption relates to lower depression risk.
Limits
Only 1,181 of 12,219 original participants (under 10%) completed dietary surveys and the psychiatric evaluation 14-19 years later, introducing substantial potential for selection and survivor bias. Dietary intake was not reassessed after 2000. Significant associations were limited to intermediate quartiles without a linear dose-response relationship.
Cited by
- supports Average daily intake of EPA and DHA in Japan is roughly 900 mg per day.