Omega-3 polyunsaturated fatty acids and mood disorders

Abstract

The hypothesis of a role of n-3 polyunsaturated fatty acids (PUFA) in the pathophysiology of depression has emerged from the observation that depressed patients had decreased levels of n-3 long-chain PUFA (especially eicosapentaenoic acid, EPA, and docosahexaenoic acid, DHA) in plasma, erythrocytes, or adipose tissue, as compared to healthy controls, a decrease which was not observed with n-6 PUFA. Suicide attempters have much lower levels of EPA and DHA in red blood cells than hospital controls. Recently, a decreased level of DHA has also been observed in the post-mortem brain cortex of patients with major depression. The fact that these changes were specific of the n-3 family suggests that a low n-3 PUFA status or intake predisposes to depression. International ecological studies show a strong negative correlation between apparent fish consumption and the prevalence of depression or of bipolar disorder, as well as between DHA content of maternal milk and the prevalence of postpartum depression. In cross-sectional studies in several countries, a higher risk of depression or of depressive symptoms has been found in subjects with a lower fish consumption. In a French cohort of adults, habitual fatty fish consumption or a higher n-3 PUFA intake were associated with a lower risk of depression, especially of recurrent depression. Randomized, placebo-controlled trials have been conducted to test the effects of long-chain n-3 PUFA in depressive or bipolar patients. EPA as an adjunct to a standard treatment appears to improve depressive patients or bipolar patients in depressive phase when given at the dose of 1-2 g/day, and fish oil prevents depressive recurrences in bipolar patients. Recently, a mixture of EPA plus DHA has proven efficiency in untreated depressive children. In summary, many epidemiological and clinical works in the last ten years have abundantly documented the existence of an association between a low n-3 PUFA intake or status and a greater risk of mood disorder, as well as a therapeutic potential of n-3 PUFA in depressed or bipolar patients. Other works are necessary in order to establish a causal relation between n-3 PUFA deficiency and depression, and to further explore their preventive or therapeutic use.