The purpose of this study is to determine whether the administration of omega-3 polyunsaturated fatty acids, particularly eicosapentaenoic acid (EPA), can be useful both to reduce coronary artery disease (CAD) risk and illness severity in clinically-stable patients with schizophrenia (or schizoaffective disorder), major depression or bipolar disorder (depressed phase) being treated with lipid lowering drugs (e.g., statins).