Limitations of this study include the retrospective data gathering on substance use. Further, we included subjects with regular to heavy substance use, but not necessarily having an Axis I diagnosis of abuse or dependence. We carefully scoured the medical records, as this was the primary study aim; however, we do not have specific use patterns including frequency, amount and duration. Subjects were identified by having an inpatient hospitalization in state facilities, thus representing a group who likely received medical assistance, had more severe mental illness at the start of mortality follow-up, were less likely to be dependent or regular abusers of substances at the start of follow-up, and who may have been more or less likely to receive adequate medical treatment. Given the inclusion criteria, these subjects identified through inpatient hospitalization records may not be representative of patients treated entirely in the outpatient sector. Also, the average life expectancy of the general population in the USA is 76 years and we analyzed only people until 55 years. But in schizophrenia the average life expectancy is 51–61 years (Newman & Bland
