Research reportDepression–anxiety relationships with chronic physical conditions: Results from the World Mental Health surveys☆
Introduction
It is now well established that there is significant comorbidity (co-occurrence) of mental disorders, particularly mood disorders, with chronic physical conditions (Wells et al., 1989a, Wells et al., 1989b, Dew, 1998, Katon and Ciechanowski, 2002, Harter et al., 2003, McWilliams et al., 2003, Buist-Bouwman et al., 2005, Simon et al., 2006, Ortega et al., 2006). These associations have considerable individual and public health significance in their impact on role impairment (Sullivan et al., 1997, Kessler et al., 2003), treatment costs and adherence (Simon et al., 1995, Ciechanowski et al., 2000) and premature mortality risk (Harris and Barraclough, 1998, van Melle et al., 2004, Zhang et al., 2005). However, prior research on the strength of the association between mental disorders and physical conditions has been limited by a preponderance of clinical relative to general population studies, a restricted range of mental or physical conditions explored and an absence of information from developing countries.
There is a further limitation to the earlier research on this topic. Anxiety and depressive disorders often co-occur. Population surveys have found that about half those with a current mood disorder also have a comorbid anxiety disorder (Kessler et al., 1996, Scott et al., 2006). Since prior research has not usually taken this depression–anxiety comorbidity into account, it is not known whether the association of anxiety disorders with chronic physical conditions might be due to comorbid mood disorder, or conversely, whether the association of mood disorders with chronic physical conditions might be due to comorbid anxiety disorder. Additionally, comorbid depression–anxiety is believed to be a more severe and chronic form of psychological disorder than non-comorbid depressive or anxiety disorders (Angst, 1997), so it is of interest to determine if comorbid depressive–anxiety disorder is associated with increased risks of chronic physical conditions. Lastly, since prior research has typically studied single or small numbers of chronic physical conditions, it is not clear whether there are substantial differences in mental–physical comorbidity patterns across different chronic physical conditions.
This paper addresses these issues by using data from 18 surveys participating in the World Mental Health Surveys to investigate the association of 10 chronic physical conditions with depressive and anxiety disorders, taking the comorbidity between depressive and anxiety disorders into account. The objectives of this paper are: 1) to determine whether non-comorbid depressive disorder and/or non-comorbid anxiety disorder are associated with specific physical conditions; 2) to determine whether comorbid depressive–anxiety disorder is more strongly associated than is non-comorbid depressive or anxiety disorder with physical conditions; and 3) to contrast the strength of association of different chronic physical conditions with depressive and anxiety disorders.
Section snippets
Methods
The methods employed in the World Mental Health surveys relevant to this report have been described in detail in prior reports (Kessler et al., 2004). Here we provide a brief overview of the key methodologic features.
Results
Information on sample characteristics is provided in Table 1. The sample size numbers refer to the Part-2 subsample that completed the section of the interview containing the physical condition checklist. The proportion of the sample that was age 60 or greater was higher in the developed countries than the developing countries, and the percent with 12 or more years of education was also generally higher in the developed countries.
The majority of heterogeneity tests assessing whether the
Discussion
Despite great diversity in demographic, socioeconomic and health patterns among the 17 countries surveyed, the pooled cross-national results consistently showed that depressive and anxiety disorders were independently and comparably related to a wide range of chronic physical conditions. Comorbid depressive–anxiety disorder was more strongly associated with several physical conditions than was non-comorbid depression and anxiety. There was considerable variability between physical conditions in
Acknowledgements
The surveys included in this report were carried out in conjunction with the World Health Organization World Mental Health (WMH) Survey Initiative. We thank the WMH staff for assistance with instrumentation, fieldwork, and data analysis. These activities were supported by the United States National Institute of Mental Health (R01MH070884), the John D. and Catherine T. MacArthur Foundation, the Pfizer Foundation, the US Public Health Service (R13-MH066849, R01-MH069864, and R01 DA016558), the
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The funders, detailed in the Acknowledgements section, funded the survey data collection and in some cases have funded the ongoing work of research groups. The funders have had no role in influencing the analysis or interpretation of data, the writing of this report or the decision to submit it for publication.