Omega-3 fatty acids and depression: scientific evidence and biological mechanisms

Abstract

The changing of omega-6/omega-3 polyunsaturated fatty acids (PUFA) in the food supply of Western societies occurred over the last 150 years is thought to promote the pathogenesis of many inflammatory-related diseases, including depressive disorders. Several epidemiological studies reported a significant inverse correlation between intake of oily fish and depression or bipolar disorders. Studies conducted specifically on the association between omega-3 intake and depression reported contrasting results, suggesting that the preventive role of omega-3 PUFA may depend also on other factors, such as overall diet quality and the social environment. Accordingly, tertiary prevention with omega-3 PUFA supplement in depressed patients has reached greater effectiveness during the last recent years, although definitive statements on their use in depression therapy cannot be yet freely asserted. Among the biological properties of omega-3 PUFA, their anti-inflammatory effects and their important role on the structural changing of the brain should be taken into account to better understand the possible pathway through which they can be effective both in preventing or treating depression. However, the problem of how to correct the inadequate supply of omega-3 PUFA in the Westernized countries' diet is a priority in order to set food and health policies and also dietary recommendations for individuals and population groups.

Figure 1

Biosynthesis of the principal polyunsaturated fatty acids and their metabolism.

Figure 2

Per capita annual fish consumption and age-standardized disability-adjusted life year for unipolar disorder distribution across countries. DALY rates by gender are also reported per all World Health Organization regions (year 2004). High-income regions reported higher rates of DALY despite their increased consumption of fish, suggesting the role of social environment in the establishment of unipolar depressive disorder. Source: Consumption of Fish and Fishery Products, Fishery and Aquaculture Department 2011, Food and Agriculture Organization of the United Nations (FAOSTAT); the Global Burden of Disease: 2004 Update, World Health Organization, Geneva, 2008.

Figure 3

(a) Association between per capita annual fish consumption and age-standardized disability-adjusted life year for unipolar and bipolar disorders by country (year 2004). (b) Countries ordered by increasing fish consumption and relative depressive disorders trends. Both types of graphs demonstrate that DALY rates for unipolar and bipolar disorders are decreased in countries with increased fish consumption. Source: Consumption of Fish and Fishery Products, Fishery and Aquaculture Department 2011, Food and Agriculture Organization of the United Nations (FAOSTAT); the Global Burden of Disease: 2004 Update, World Health Organization, Geneva, 2008.

Figure 4

Trend over time (1999–2007) of per capita annual fish consumption and mixed anxiety and depressive disorders in the United Kingdom. Despite a diametric-shaped distribution of cases and relative fish consumption, a significant increasing trend has been found. Source: Consumption of Fish and Fishery Products, Fishery and Aquaculture Department 2011, Food and Agriculture Organization of the United Nations (FAOSTAT); to Walters et al. [3].