Objectives: Uncertainty exists regarding whether comorbid substance use disorders (SUDs) in bipolar I disorder are more prevalent among persons with versus without comorbid anxiety disorders. Moreover, the independent contribution of these comorbidities to the burden of bipolar disorder (BD) is unclear.
Methods: The 2001–2002 National Epidemiologic Survey on Alcohol and Related Conditions was used to identify respondents with lifetime BD (n = 1,411). Illness severity was compared across four groups based on the presence of lifetime anxiety disorders, lifetime SUDs, neither, or both. Variables included lifetime prevalence of mixed mania, prolonged mood episodes, BD-related health service utilization, and forensic history, 12-month prevalence of mania and depression, and current general mental health functioning. Diagnoses were generated using the National Institute on Alcohol Abuse and Alcoholism Alcohol Use Disorder and Associated Disabilities Interview Schedule, DSM-IV Version. Analyses were computed separately for males and females.
Results: For females only, the lifetime prevalence of SUDs was significantly greater among those with lifetime anxiety disorders [odds ratio (OR) = 1.41, 95% confidence interval (CI) = 1.08–1.86]; this was not found among males (OR = 1.15, 95% CI = 0.79–1.68). In multiple logistic regression analyses among both males and females, anxiety disorders were significantly associated with mixed episodes, prolonged depressive episodes, 12-month prevalence of depression, BD-related health service utilization, and poorer current mental health functioning. SUDs were significantly associated with mixed episodes among females, 12-month prevalence of depression among males, and with forensic history among both males and females.
Conclusions: Whereas comorbid anxiety disorders appear to confer increased liability towards poor mental health functioning and greater BD-related health service utilization, comorbid SUDs are associated with positive forensic history. Early identification and treatment of these comorbid conditions are of paramount importance. Further representative prospective studies are needed.