The results are consistent with the hypothesis that psychiatric patients with substance abuse comorbidity constitute a different group as regards temperament traits and clinical features. The results were consistent with previous research evaluating temperament traits in patients at risk of suicide who had demonstrated a strong relationship between some specific affective temperament-types and suicidal attitudes. The results also confirm previous studies linking irritability with substance abuse disorders. The study strongly supports previous findings in the literature and highlights the importance of assessing temperament traits associated with worse psychopathology in patients with severe mental illness. Patients with severe mental illnesses and comorbidity with substance use disorders typically have a worse outcome, higher psychopathology, and may be at higher risk for suicide. This study sought to evaluate differences between substance abusers and non-abusers in a sample of patients with severe mental illness. 1 table and 49 references