The importance of role disability, that is, inability to work or carry out usual activities, has become increasingly recognized as a major source of indirect costs of illness because of its high economic impact on ill workers, their employers, and society. However, there is limited information on the amount of disability associated with a wide range of specific physical and mental conditions.
New findings published by Drs. Kathleen Merikangas from the National Institute of Mental Health (NIMH) and Ronald Kessler from Harvard Medical School and colleagues in the October 2007 issue of the Archives of General Psychiatry show that more than half of U.S. adults have a mental or physical condition that influences their role functioning.
In addition, more than 1.3 billion days out of role performance are lost each year in the U.S. due to mental disorders, and major depression is the mental disorder associated with the largest number of days out of role. The study also found that the number of days out of role due to mental disorders is roughly half as large as the number of days associated with all chronic physical conditions combined.
These results are based on the National Comorbidity Survey-Replication (NCS-R), a nation-wide survey of 9,282 Americans ages 18 and older funded by the NIMH. Respondents in the survey were asked how many days they were completely unable to work or carry out their usual activities as a result of problems with their physical or mental health.
A wide range of physical and mental disorders were included in the study. The associations between each of the individual physical and mental disorders with days of role disability were examined using innovative methods to sort out the relative effects of co-occurring conditions among people who reported having multiple health problems.
The findings showed that more than half of U.S. adults have a mental or physical condition that is associated with excess days out of role, leading to an estimated 3.7 billion days per year out of role associated with the conditions studied. Nationwide, about 2.4 billion disability days resulted from the chronic physical conditions studied and about 1.3 billion disability days resulted from the mental conditions studied. The effects of individual mental conditions were as large as those of most chronic physical conditions. Chronic back-neck pain was the condition associated with the largest number of days out of role (1.2 billion), followed by major depression resulting in the second largest number of days out of role (387 million).
The researchers suggest that, in light of these results, health care resource allocation decisions may need to be rethought. "Previous research has found that, on the whole, the least amount of health resources are spent on research and treatment of musculoskeletal disorders and depression, even though these are the most prevalent and disabling conditions," said Dr. Merikangas. "These results illuminate the discrepancy between how we allocate our health care resources, and which illnesses have the most impact."
This research was funded by the National Institute of Mental Health.
Citation: Archives of General Psychiatry, Vol. 65: No. 9, October 2007, "The Impact of Comorbidity of Mental and Physical Conditions on Role Disability in the US Adult Household Population", Kathleen Merikangas, PhD; Minnie Ames, PhD; Lihong Cui, MS; Paul E. Stang, PhD; T. Bedirhan Ustun, MD; Michael Von Korff, PhD; Ronald Kessler, PhD
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