Premature mortality associated with severe mental illness or substance use disorder in an integrated health care system

Research has reported shortened lifespans (by 15–30 years) for those with severe mental illness (SMI) or substance use disorder (SUD), particularly among public mental health treatment consumers. We assessed SMI- and SUD-associated mortality in the understudied setting of a large, nonprofit integrated health care system. This retrospective cohort study examined 2010–2017 health system and death records for 564,592 adult patients. Half had SMI/SUD diagnosis; half were a demographically matched comparison group without SMI, other mental health, or SUD diagnoses. We estimated mortality risks, adjusting for demographic and physical health factors. Having SMI or SUD was associated with higher odds of death (adjusted odds ratio = 1.87) and an average 6.3 years of earlier death relative to comparison individuals. Co-occurring SMI and SUD conferred higher mortality risk from major natural and unnatural causes than did SMI with no SUD. Some indicators of premature mortality were lower than those reported for U.S. public mental health consumers, but risk level varied widely by diagnosis. While patients' having insurance and broad access to care may lower risk, access to care may be insufficient to overcome the many patient-, provider-, and system-level factors contributing to poor physical health in SMI and SUD.