Geographic and Social Patterning of the Disparate Burden of Comorbidity between Mental and Physical Disorders: An Ecological and Multilevel Analysis

BACKGROUND. Mounting evidence of the comorbidity of mental and physical illness comes from chronic disease literature, with estimates up to 53% of the U.S. population suffering one or more conditions (Merikangas, Ames, Cui, Stang, Ustun, Von Korff, & Kessler, 2007). Although there has been an acknowledgement that these two dimensions are part of an individual's complete experience of health, application of this awareness to inform both policy and practice has been lacking. To separate the mental from the physical may have served to erect barriers to our understanding of a host of diseases and efficacious prevention efforts. Policies aimed at prevention of disease have been approached in social work and public health as prevention of either physical or mental morbidity, not reflecting the complete illness experience. This bifurcated view has influenced primary, secondary, and tertiary prevention efforts.

This investigation examines the covariation of mental and physical health status at both the ecologic and individual levels. Regarding the ecological, this works looks at patterns of comorbidity between several common mental disorders (Major Depression, Dysthymia, GAD, PTSD) and a range of prevalent chronic diseases (e.g., CVD, Diabetes, Cancer). In addition to describing patterns, this work asks whether those individuals who are part of disadvantaged groups suffer a disproportionate burden of comorbidity. Specifically, differential rates of comorbidity by race/ethnicity, SES, and gender will be assessed. For example, poverty's common association with poor mental and physical health indicates that a general susceptibility may be operative (Cassel, 1976); further, this association may be shaped by the social rate of exposure to fundamental causes of poor health. Fundamental causes of the disparate burden of disease stem from economic and political conditions that generate and perpetuate social and economic inequality (Krieger, 1994; Link & Phelan, 1995); common is the notion that poverty is pathogenic to both mental and physical health. The purpose of this study is to: estimate the co-occurrence between mental and physical disorders at both the state and national levels; examine geographic variation in the pattern of results; and investigate the putative differential burden of comorbidity in a multilevel framework, where outcomes are nested within individuals.

METHODS. This study utilizes data from the National Epidemiologic Survey on Alcohol and Related Conditions (NESARC). Face-to-face survey of a non-institutionalized adult general population sample was conducted in the 2001-2002 NESARC (N=43,098). Blacks, Hispanics and young adults were oversampled; overall response rate was 81%. Current and lifetime DSM-IV diagnoses of psychiatric disorders were assessed using AUDADIS-IV; physical disorders were assessed via self-report of a physician confirmed diagnosis.

PRELIMINARY CONCLUSIONS. Initial results reveal a significant overall positive relationship between state-level mental health and physical health, with a wide range of associations. Additionally, there is evidence of geographic clustering, especially regarding the South. Results from this work have implications for social work policy; specifically, a need to address comorbidity in prevention initiatives and health care resource allotments. Findings from this study may inform practice-related activities to explicitly incorporate comorbidity into assessment and treatment approaches to improve the health of disadvantaged groups.