Stress-related disorders, such as post-traumatic stress disorder (PTSD), were significantly associated with an increased risk for developing an autoimmune disease, according to the findings of a recent study published in the Journal of the American Medical Association.
The retrospective cohort study was conducted in Sweden and included 106,464 persons diagnosed with stress-related disorders, 126,652 siblings of individuals with stress-related disorders, 1,064,640 matched controls. Using the National Patient Register, the researchers identified stress-related disorders, defined as a diagnosis of PTSD, acute stress reaction, adjustment disorder, and other stress reactions, and 41 autoimmune diseases, including Crohn disease, systemic lupus erythematosus, and rheumatoid arthritis. The researchers calculated hazard ratios (HR) to estimate the risk of being diagnosed with an autoimmune disease beyond 1 year after a stress-related disorder diagnosis, controlling for multiple risk factors.
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During the mean 10-year follow-up period, the incidence rate of autoimmune diseases among persons with stress-related disorders, siblings, and controls were 9.1, 6.5, and 6.0 per 1000 person-years, respectively. Individuals with stress-related disorders had an increased risk for autoimmune diseases compared with controls (HR 1.36, 95% CI, 1.33-1.4). Among individuals with PTSD, the HR for any autoimmune disease was 1.46 (95% CI, 1.32-1.61) and for 3 or more autoimmune diseases was 2.29 (95% CI, 1.72-3.04). “These associations were consistent in sibling-based comparisons,” the researchers noted.
In addition, the elevated risk associated with stress-related disorders was more pronounced among younger individuals. The hazard ratios were 1.48 for those aged 33 years and younger (95% CI, 1.42-1.55), 1.41 for those aged 34 to 41 years (95% CI, 1.33-1.48), 1.31 for those aged 42 to 50 years (95% CI, 1.24-1.37), and 1.23 for those aged 51 years and older (95% CI, 1.17-1.3).
The researchers found that persistent use of selective serotonin reuptake inhibitors (SSRI) following the first year of PTSD diagnosis attenuated the risk for autoimmune diseases. The risk was highest within the first 179 days (HR 3.64, 95% CI, 2.0-6.62) of SSRI use, however, this increase in risk was lower after 180 to 319 days of use (HR 2.65, 95% CI, 1.57-4.45), and dropped significantly after 320 or more days of use (HR 1.82, 95% CI, 1.09-3.02).
“In this Swedish cohort, exposure to a stress-related disorder was significantly associated with increased risk of subsequent autoimmune disease, compared with matched unexposed individuals and with full siblings,” the researchers concluded. “Further studies are needed to better understand the underlying mechanisms.”
Song H, Fang F, Tomasson G, et al. Association of stress-related disorders with subsequent autoimmune disease [published online June 19, 2018]. JAMA. doi:10.1001/jama.2018.7028.