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Disability in depression and back pain
Abstract
The World Health Organization Disability Assessment Schedule (WHO DAS II) is a new measure of disability based on the ICIDH-2 model of functioning and disability. This study evaluates the measurement properties of the WHO DAS II in two disorders commonly encountered in the primary care setting. Seventy-three patients with depression and 76 patients with back pain were interviewed at baseline and after 3 months of usual primary care. Internal validity, convergent validity, and responsiveness to change of the WHO DAS II were evaluated. The WHO DAS II had excellent internal validity and convergent validity in the primary care setting. The responsiveness to change of the WHO DAS II was comparable to that of the SF-36. The WHO DAS II appears to be a useful health status instrument for measuring the disability associated with both physical and mental disorders in the primary care setting. This instrument facilitates the use of the ICIDH-2 as a framework for evaluating activity limitations and participation.
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“It has also demonstrated adequate psychometric properties (Chwastiak & Von Korff, 2003; McKibbin, Patterson, & Jeste, 2004; Cronbach’s α = .94).”
From An Integrated, Acceptance-Based Behavioral Approach for Depression With Social Anxiety: Preliminary Results (2014) · cites this paper as Chwastiak & Von Korff, 2003
Citations
Cites
(1992) · PubMed · Cited by 33,716
The MOS 36-ltem Short-Form Health Survey (SF-36): I. Conceptual Framework and Item Selection
Ware, J. E., & Sherbourne, C. D. (1992) · Medical Care · doi:10.1097/00005650-199206000-00002 · Cited by 30,033
Spitzer, R. L. (1999) · JAMA · doi:10.1001/jama.282.18.1737 · Cited by 9,802
Murray, C. J. L., & López, A. D. (1997) · The Lancet · doi:10.1016/s0140-6736(96)07492-2 · Cited by 7,007
A Study of the Natural History of Back Pain: Part I
ROLAND, M., & MORRIS, R. (1983) · Spine · doi:10.1097/00007632-198303000-00004 · Cited by 3,395
Effect Sizes for Interpreting Changes in Health Status
Kazis, L. E., Anderson, J. J., & Meenan, R. F. (1989) · Medical Care · doi:10.1097/00005650-198903001-00015 · Cited by 2,401
The convergent and discriminant validity of subjective fit perceptions.
Cable, D. M., & DeRue, D. S. (2002) · Journal of Applied Psychology · doi:10.1037/0021-9010.87.5.875 · Cited by 2,224
Ware, J. E., Kosinski, M. R., Bayliss, M. S., McHorney, C. A., Rogers, W. H., & Raczek, A. E. (1995) · PubMed · Cited by 1,734
Methods for assessing responsiveness
Husted, J., Cook, R. J., Farewell, V. T., & Gladman, D. (2000) · Journal of Clinical Epidemiology · doi:10.1016/s0895-4356(99)00206-1 · Cited by 1,543
Deyo, R. A., Diehr, P. H., & Patrick, D. L. (1991) · Controlled Clinical Trials · doi:10.1016/s0197-2456(05)80019-4 · Cited by 1,369
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Charlson, M. E., Mittleman, I., Ramos, R., Cassells, A. N., Lin, T., Eggleston, A., Wells, M. T., Hollenberg, J. P., Pirraglia, P. A., Winston, G. J., et al. (2025) · Contemporary Clinical Trials · doi:10.1016/j.cct.2025.107865 · Cited by 2
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Awoke, W., Alene, G. D., Admasie, A., & Ambaw, F. (2025) · BMJ Open · doi:10.1136/bmjopen-2025-104693 · Cited by 1
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Martin, D. (2006) · CRC Press eBooks · doi:10.1201/b14657-17
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Metadata
- Authors
- Chwastiak, L. A., & Von Korff, M.
- Affiliations
- University of Washington (US)
- Corresponding author
- Chwastiak, Lydia A.
- ORCID
- Chwastiak, Lydia A.
- Venue
- Journal of Clinical Epidemiology
- Publisher
- Elsevier BV
- Published
- 2003-06
- Volume
- 56
- Issue
- 6
- Pages
- 507-514
- ISSN
- 0895-4356 (ISSN-L)
- OpenAlex
- W2058879410
- Cited by
- 280
- References
- 47
- Citations by year
- 2026: 3 · 2025: 7 · 2024: 2 · 2023: 8 · 2022: 10 · 2021: 12 · 2020: 12 · 2019: 14 · 2018: 12 · 2017: 14 · 2016: 17 · 2015: 13 · 2014: 15 · 2013: 19 · 2012: 18
- FWCI
- 18.58
- Type
- journal article
- Language
- en
- Open access
- closed
- Locations
- Journal of Clinical Epidemiology (publishedVersion)
- PubMed (publishedVersion)
- Topics
- Social Sciences › Economics, Econometrics and Finance › Economics and Econometrics › Health Systems, Economic Evaluations, Quality of Life
- Health Sciences › Health Professions › Physical Therapy, Sports Therapy and Rehabilitation › Musculoskeletal pain and rehabilitation
- Health Sciences › Health Professions › Physical Therapy, Sports Therapy and Rehabilitation › Medical Practices and Rehabilitation
- Keywords
- WHO Disability Assessment Schedule II, disability assessment, depression, back pain, functioning and disability, internal validity, convergent validity, responsiveness to change, SF-36, primary care, health assessment, activity limitation, participation
- MeSH terms
- Adult, Back Pain, Depressive Disorder, Disability Evaluation, Female, Follow-Up Studies, Health Services Research, Health Status Indicators, Humans, Male, Middle Aged, Primary Health Care, Washington, Reproducibility of Results
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