Aggression in correctional and psychiatric settings is relatively common and has a negative effect on physical and mental health both among inmates/clients and staff, as well as organizational-level functioning. The aim of the present study was to critically review the evidence on the effectiveness of nutritional supplements in reducing aggression and violence to contribute to a better understanding of options available for managing aggressive behaviors in adults. The EMBASE, MEDLINE, PsycINFO, Cochrane Library, and PubMed databases were searched for effectiveness studies published in English anytime up until March 2020. Study quality was assessed using the Mixed Methods Appraisal Tool. Altogether, 14 studies met inclusion criteria; 2 investigated micronutrients, 10 examined macronutrients, while further 2 examined a combination of micro and macronutrients. Out of the 14 studies, 5 reported a beneficial effect of nutritional supplementation (omega-3 fatty acids, vitamins/minerals, S-adenosyl-l-methionine, or tryptophan). Five studies did not report a significant beneficial effect of nutritional supplementation (omega-3 fatty acids, folic acid, tryptophan, broad range supplement containing vitamins and fatty acids, and fatty acids in augmentation with valproic acid), while four studies reported mixed effects (on l-tryptophan, broad-range micronutrient formula, folic acid, and omega-3 fatty acids). The results overall indicated that research in this area is in its infancy: very few studies examined the same composition of nutritional supplementation and when they did so the results were contradictory. The methodological shortcoming of existing studies and directions for future research are discussed to facilitate high-quality research in this evolving area of nutritional psychiatry.
Keywords: aggression; macronutrient; micronutrient; nutritional supplementation; violence.
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