Distinguishing generalized anxiety disorder from major depression: prevalence and impairment from current pure and comorbid disorders in the US and Ontario

Authors

  • Ronald C. Kessler,

    Corresponding author
    1. Department of Health Care Policy, Harvard Medical School, Boston MA, USA
    • Department of Health Care Policy, Harvard Medical School, 180 Longwood Avenue, Boston, MA 02115.
    Search for more papers by this author
  • Patricia A. Berglund,

    1. Institute for Social Research, University of Michigan, Ann Arbor MI, USA
    Search for more papers by this author
  • David J. Dewit,

    1. Social, Prevention and Health Policy Research Department, Centre for Addiction and Mental Health, London, Ontario, Canada, and Department of Epidemiology and Biostatistics, University of Western Ontario, London, Ontario, Canada
    Search for more papers by this author
  • T. Bedirhan Üstün,

    1. Assessment, Classification and Epidemiology Group, World Health Organization, Geneva, Switzerland
    Search for more papers by this author
  • Philip S. Wang,

    1. Department of Health Care Policy, Harvard Medical School, Boston MA, and Division of Pharmacoepidemiology and Pharmacoeconomics, Brigham and Women's Hospital Boston MA, USA
    Search for more papers by this author
  • Hans-Ulrich Wïttchen

    1. Institute of Clinical Psychology and Psychotherapy, Technical University of Dresden, and Max Planck Institute of Psychiatry, Munich, Germany
    Search for more papers by this author

Abstract

Estimation of comparative disease burden in epidemiological surveys is complicated by the fact that high comorbidities exist among many chronic conditions. The easiest way to take comorbidity into consideration is to distinguish between pure and comorbid conditions and to evaluate the incremental effects of comorbid conditions in prediction equations. This approach is illustrated here in an analysis of the effects of pure and comorbid major depression (MD) and generalized anxiety disorder (GAD) on a number of different measures of role impairment in the US National Comorbidity Survey (NCS) and the Mental Health Supplement to the Ontario (Canada) Health Survey (the Supplement). Pure MD and pure GAD were found to have roughly equal independent associations with role impairments. The incremental effects of having comorbid MD and GAD were found to vary depending on the outcome under investigation. The paper closes with a discussion of the methodological complexities associated with generalizing to comorbidities that involve rare conditions or more than two disorders. Copyright © 2002 Whurr Publishers Ltd.

Ancillary