Objectives: The purpose of this study was to conduct a systematic review of the scientificmedical literature to identify, appraise and synthesize the evidence for the effects of omega-3 fatty acids in mental health. Evidence was sought to permit the investigation of three basic questions: the efficacy and safety of omega-3 fatty acids as (primary or supplemental) treatment of psychiatric disorders or conditions (e.g., symptoms alone); the association between intake of omega-3 fatty acids and the onset, continuation or recurrence of psychiatric disorders or conditions; and, the association between the fatty acid content of biomarkers and the onset, continuation or recurrence of psychiatric disorders or conditions. The latter two questions examined the protective value of omega-3 fatty acid content in the diet and/or blood lipid biomarkers. The impact of effect modifiers was examined as well. The results will be used largely to inform a research agenda