RESUMO
BACKGROUND: Disturbance of lipid, particularly omega-3 polyunsaturated fatty acid (PUFA), metabolism is associated with the etiology and symptoms of schizophrenia. Numerous clinical studies have tried to evaluate whether omega-3 PUFA supplementation can ameliorate the disorder, but the results are inconclusive. OBJECTIVES: This systematic review integrates and refines the research evidence of the effectiveness of omega-3 PUFA nutritional supplementation on schizophrenia during the different developmental phases of the disease (prodromal, first-episode, and chronic phases) and examines whether different developmental stages modulate the efficacy of omega-3 PUFA supplementation. DATA SOURCES: Scientific articles from 2000 to 2020 in PubMed/Medline, Allied Health Literature, PsychINFO, and SCOPUS following the Preferred Reporting Items for Systematic Reviews guidelines. METHODS: A systematic review was performed. We reviewed electronic databases and identified 1,266 clinical studies. Of these, 26 met the inclusion criteria. RESULTS: The effectiveness of omega-3 dietary supplementation on symptoms varies among different phases of illness. Omega-3 supplementation significantly improves positive and negative symptoms at the prodromal phase, improves mainly the negative symptoms in patients with the first-episode, and effects symptoms partly in patients with chronic schizophrenia. DISCUSSION: The effectiveness of omega-3 PUFA dietary supplementation is modulated by age, duration of untreated psychosis and illness, baseline levels of omega-3 fatty acids, and status of antioxidant capacity of patients. The important implications for psychiatric research and clinical practice developments as well as nursing care are presented and discussed.