Risk of Psychiatric Disorders following Ankylosing Spondylitis: A Nationwide Population-based Retrospective Cohort Study

Objective. Ankylosing spondylitis (AS) is a common inflammatory rheumatic disease. A higher prevalence of psychiatric comorbidities, including depressive disorder, has been proven in patients with AS. However, a clear temporal causal relationship between AS and psychiatric disorders has not been well established. We performed a nationwide population-based retrospective cohort study to analyze the relationship between AS and the subsequent development of psychiatric disorders, including schizophrenia, bipolar disorder, depressive disorders, anxiety disorders, and sleep disorders. Methods. We identified subjects who were newly diagnosed with AS between January 1, 2000, and December 31, 2008, in the Taiwan National Health Insurance (NHI) Research Database. A comparison cohort was constructed of patients without AS who were matched according to age and sex. All patients with AS and control patients were observed until diagnosed with psychiatric disorders, or until death or withdrawal from the NHI system, or until December 31, 2009. Results. The AS cohort consisted of 2331 patients and the comparison cohort consisted of 9324 matched control patients without AS. The adjusted HR for depressive disorders, anxiety disorders, and sleep disorders in subjects with AS were higher than those of the controls during followup (HR 1.718, 95% CI 1.303-2.265; HR 1.848, 95% CI 1.369-2.494; and HR 1.494, 95% CI 1.031-2.162, respectively). Conclusion. AS might increase the risk of a subsequent newly diagnosed depressive disorder, anxiety disorder, or sleep disorder, but not schizophrenia or bipolar disorder. These observations highlight the need for psychiatric evaluation and intervention for patients with AS.