Omega-3 fatty acids reduce depressive symptoms only among the socially stressed: A corollary of the social signal transduction theory of depression.

Abstract

There is mixed evidence about whether omega-3 fatty acids reduce depressive symptoms. We previously reported that 4 months of omega-3 supplementation reduced inflammatory responsivity to a lab-based social stressor. In another study, we showed that those with exaggerated inflammatory responsivity to a social stressor had the greatest depressive symptom increases over time, especially if they experienced frequent social stress. Here we tested whether omega-3 supplementation reduced subthreshold depressive symptoms among those who experienced frequent social stress. METHOD: Healthy, sedentary, generally overweight middle-aged and older adults (N = 138) were randomly assigned to 4 months of pill placebo (n = 46), 1.25 grams per day (g/d) omega-3 (n = 46), or 2.5 g/d omega-3 (n = 46). At a baseline visit and monthly follow-up visits, they reported depressive symptoms and had their blood drawn to assess plasma levels of omega-3 fatty acids. Participants completed the Trier Inventory of Chronic Stress at Visit 2 and the Test of Negative Social Exchange at Visit 3. RESULTS: Among those who were overweight or obese, both doses of omega-3 reduced depressive symptoms only in the context of frequent hostile interactions and social tension, and 2.5 g/d of omega-3 lowered depressive symptoms among those with less social recognition or more performance pressure (ps < .05). Findings were largely corroborated with plasma omega-3 fatty acids. No other social stress or work stress measure moderated omega-3 fatty acids' relationship with depressive symptoms (ps > .05). CONCLUSIONS: Omega-3 fatty acids' antidepressant effect may be most evident among those who experience frequent social stress, perhaps because omega-3 fatty acids reduce inflammatory reactivity to social stressors. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

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