Yutaka Matsuoka, M.D., Ph.D.

Chief, Division of Health Care Research, Center for Public Health Sciences, National Cancer Center Japan

Visiting Associate Professor, China Medical University, Taichung, Taiwan

Previous studies have revealed that n-3 polyunsaturated fatty acids (PUFAs) have been critical in the development and management of depression. Systematic review of observational studies has revealed that fish consumption and levels of PUFAs such as eicosapentaenoic acid (EPA) and docosahexaenoic acid are associated with a reduced risk of depression. However, there is limited evidence from populations with high fish consumption and no studies have used a standard psychiatrist-based diagnosis of depression. 

We traced the lifestyles of 1,181 residents of the Saku district of Nagano Prefecture, who were aged between 40 and 59 in 1990, for 25 years beginning in that year. We looked at the subjects' consumption of 19 different types of fish and other seafood and if there was an association with the presence of current depression in 2014-2015. Trained psychiatrists assessed whether the participants currently met the DSM-IV criteria for depression. Odds ratios and 95% confidence intervals for depression according to fish intake and PUFAs quartiles were calculated.

The participants were divided into four groups depending on their daily consumption, and when compared to the group with the lowest median intake of 57 grams, the group that ate the second-most amount of fish and other seafood at a median of 111 grams was 56 percent less likely to develop depression. In addition, when the subjects' consumption of PUFA was calculated, reduced risk was observed if the person also had high levels of EPA and docosapentaenoic acid. These findings recommend moderate fish intake for the prevention of depression in aged Japanese individuals.