Impairment in Pure and Comorbid Generalized Anxiety Disorder and Major Depression at 12 Months in Two National Surveys

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Abstract
OBJECTIVE: Generalized anxiety disorder might be better conceptualized as a prodrome, residual, or severity marker of major depression or other comorbid disorders than as an independent diagnosis. The authors questioned whether generalized anxiety disorder itself is associated with role impairment or whether the impairment of patients with generalized anxiety disorder is due to depression or other comorbid disorders. METHOD: The authors assessed data from the National Comorbidity Survey and the Midlife Development in the United States Survey for generalized anxiety disorder and major depression at 12 months by using the DSM-III-R criteria with modified versions of the Composite International Diagnostic Interview. RESULTS: The prevalences of generalized anxiety disorder at 12 months were 3.1% and 3.3%, respectively, in the National Comorbidity Survey and the Midlife Development in the United States Survey; the prevalences of major depression at 12 months were 10.3% and 14.1%. The majority of respondents with generalized anxiety disorder at 12 months in the National Comorbidity Survey (58.1%) and the Midlife Development in the United States Survey (69.7%) also met the criteria for major depression at 12 months. Comparisons of respondents with one versus neither disorder showed that both disorders had statistically significant independent associations with impairment that were roughly equal in magnitude. These associations could not be explained by the other comorbid DSM-III-R disorders or by sociodemographic variables. CONCLUSIONS: These results show that a substantial amount of generalized anxiety disorder occurs independently of major depression and that the role impairment of generalized anxiety disorder is comparable to that of major depression.