Increased Risk of Depressive Disorders in Ankylosing Spondylitis

Ankylosing spondylitis (AS) can cause significant functional impairments and lead to decreased quality of life.  Patients with AS have a higher prevalence of comorbidities, including psychiatric conditions.

A recent study published in The Journal of Rheumatology found that patients with AS have an increased risk of developing certain depressive disorders following their diagnosis, with risk persisting more than 5 years in some cases.¹

“Our nationwide population-based retrospective cohort study showed that AS may increase the risk of subsequent newly diagnosed depression, anxiety disorders, and sleep disorders,” Shih-Jen Tsai, MD, lead researcher and section chief of the Adult Psychiatry Section in the Department of Psychiatry at the Taipei Veterans General Hospital in Taipei, Taiwan, told Rheumatology Advisor. “But we did not find it to increase the risk of schizophrenia or bipolar disorder,” Dr Tsai added.

The study included 2331 patients with AS and 9324 control patients without AS who were enrolled in Taiwan’s mandatory National Health Insurance (NHI) program between January 1, 2000 and December 31, 2008. Patients were followed until death, withdrawal from the NHI system, or until December 31, 2009. All patients with AS were diagnosed by an orthopedist or rheumatologist and had at least 2 consensus diagnoses.

During the study period, 190 patients with AS (8.15%) and 467 controls (5.01%) received a psychiatric disorders diagnosis (P < .001). Among those with AS, the most common diagnoses were depressive disorders (n=73; 3.1%), anxiety disorders (n= 64; 2.7%), and sleep disorders (n=39; 1.7%).

Using Cox proportional hazards regression analysis adjusted for age, sex, comorbidities, urbanization, and monthly income, the researchers found that, compared with matched controls, patients with AS had a markedly higher risk of developing subsequent depressive disorders (adjusted hazard ratio [HR], 1.718; 95% confidence interval [CI], 1.303–2.265), anxiety disorders (adjusted HR, 1.848; 95% CI, 1.369–2.494), and sleep disorders (adjusted HR, 1.494; 95% CI, 1.031–2.162).

A subanalysis based on the duration of follow-up showed that the risk of developing a newly diagnosed depressive disorder persisted for more than 5 years following the AS diagnosis, whereas the risk of a newly diagnosed anxiety disorder only increased the first year after the AS diagnosis.

The researchers speculated that several factors might be responsible for the persistent increased risk of depressive disorders in patients with AS, including a potentially shared genetic background that involves systemic inflammation and the long-term psychological stress that accompany AS.

Summary and Clinical Applicability

Dr Tsai and colleagues’ study had several strengths, including its large sample size, stringent criteria for diagnosing AS and psychiatric disorders, and longitudinal perspective. 

The investigators also reported several limitations, including the NHI’s lack of comprehensive patient information (e.g., on tobacco and alcohol use), limiting the researchers’ ability to control for other potentially confounding factors; the possibility of underestimating psychiatric conditions due to reliance on billing codes and patients’ potential avoidance of seeking care for such conditions; and an inability to account for the heterogeneity of certain disorders, particularly anxiety disorders.

Nevertheless, the findings add to the growing body of literature showing an association between AS and psychiatric disorders.

“Because depression, anxiety disorders, and sleep disorders are treatable conditions that have a great impact on the quality of life of AS patients, clinicians should be alert to the possibility of these conditions,” said Dr Tsai. “Additionally, further exploration of the association between AS and psychiatric disorders is warranted to improve our understanding of the mechanisms underlying mental illness, which may be helpful for providing more comprehensive care to patients with AS experiencing comorbidities or subsequent psychiatric disorders.”

Reference

1. Shen CC, Hu LY, Yang AC, Kuo BI, Chiang YY, Tsai SJ. Risk of psychiatric disorders following ankylosing spondylitis: a nationwide population-based retrospective cohort study. J Rheumatol. 2016;43(3):625-631.