title: Expanded conceptualization of multimorbidity to encompass substance use disorders and other psychiatric illness.
abstract: Traditionally, the study of medicine has focused on individual diseases. In reality, however, diseases tend to co-occur in individual patients, a concept known as multimorbidity. Multimorbidity most often is seen in geriatric practice. Empirical data on patients with multiple chronic disorders and clinical care guidelines based on single conditions are insufficient to inform medical care of patients with >1 medical condition.
  
  
  
  This article reviews concepts of multimorbidity in the published literature in the context of substance use disorders, other psychiatric disorders, and associated social and environmental problems in other populations, including public sector service populations.
  
  
  
  Besides historically recognized co-occurrence of 3 dimensions of illness, including multiple medical illnesses, psychiatric disorders, and substance use disorders in varying combinations with one another, a fourth dimension of multimorbidity that includes associated social and environmental conditions fits within this construction.
  
  
  
  Additional steps are needed to address more effectively the needs of patients with substance use and other psychiatric disorders in the public sector psychiatric systems of care. These efforts will need to address the systems theory approach to multimorbidity that entails the socioeconomic and environmental aspects of their conditions.
authors.affiliation: The Altshuler Center for Education and Research, Metrocare Services, The University of Texas Southwestern Medical Center, Department of Psychiatry, Dallas, TX USA. E-mail: carol.north@southwestern.edu.
authors.forename: Carol S
authors.initials: CS
authors.lastname: North
authors.forename: E Sherwood
authors.initials: ES
authors.lastname: Brown
authors.forename: David E
authors.initials: DE
authors.lastname: Pollio
mesh_terms: D000368:Aged; D005260:Female; D006801:Humans; D008297:Male; D001523:Mental Disorders / Q000453:epidemiology*; D000076322:Multimorbidity; D017150:Public Sector; D019966:Substance-Related Disorders / Q000453:epidemiology*