Emergency department use of persons with comorbid psychiatric and substance abuse disorders

Study objective: This study assesses the relationship between substance abuse comorbidity and emergency department use among patients with psychiatric disorders in a large academic medical center. Methods: Data were obtained from an administrative database including every patient visit to the ED of a large, academically affiliated county hospital from January 1994 through June 1998. This study focuses on 12,212 patients who were given a diagnosis of a primary psychiatric disorder in the ED. Diagnoses, assigned during ED visits, were made according to the Diagnostic and Statistical Manual of Mental Disorders III-R or IV. Results: Primary psychiatric patients with substance use comorbidity had a significantly higher mean number of ED visits across the span of the study (mean 5.2; SD 7.4) than primary psychiatric patients without substance use comorbidity (mean 2.8; SD 3.9). In multiple logistic regression analyses predicting several categorizations of heavier use of the ED (either 4+, 8+, 12+, 16+, or 20+ visits over the span of the study), psychiatric patients with a comorbid substance use disorder had adjusted odds ratios of 2.8 to 4.9 (reference group was defined as patients with a psychiatric disorder but no substance use disorder; models controlled for age, race, and sex). Conclusion: Substance use comorbidity among patients presenting to an ED with a psychiatric disorder is associated with substantially increased ED service use. Improved detection, referral, and treatment of substance use disorders in this population could result in decreased ED use and improved patient outcomes.