Fish contains high concentrations of omega-3 polyunsaturated fatty acids. Several studies have reported depletions of omega-3 fats among depressed patients, and a cross-national comparison has revealed a significant inverse correlation between annual prevalence of major depression and fish consumption.

In a sample of 3,204 Finnish adults, depressive symptoms were estimated with the Beck Depression Inventory. A frequency question was used to measure fish consumption. Multiple logistic regression analysis was conducted to assess the association between depression and fish consumption.

After the analysis adjusted for potential confounders, the likelihood of having depressive symptoms was significantly higher among infrequent fish consumers than among frequent consumers.