Objective: The objective of this study is to estimate the comparative associations of mental disorders with three measures of functional impairment: the Global Assessment of Functioning (GAF); the number of days in the past 12 months of total inability to work or carry out normal activities because of emotions, nerves, or mental health (i.e., days out of role); and a modified version of the World Health Organization Disability Assessment Schedule 2.0 (WHODAS 2.0).
Methods: Secondary data analysis of the linked Mental Health Surveillance Study and the National Survey on Drug Use and Health (n = 5653), nationally representative population surveys conducted in the United States. Generalized linear models assessed the independent effects of mental disorders on each measure of functional impairment, controlling for mental disorder comorbidity, physical health disorders, and sociodemographic factors.
Results: The results varied across measures of functional impairment. However, mood disorders generally tended to be associated with the greatest functional impairment, anxiety disorders with intermediate impairment, and substance use disorders with the least impairment. All 15 disorders were significantly associated with the GAF score in multiple regression models, eight disorders were significantly associated with the WHODAS score, and three disorders were significantly associated with days out of role.
Conclusions: Our results highlight the value of complementary measures of functional impairment.
Keywords: Disability; Functional impairment; Global Assessment of Functioning; Mental disorders.