Researchers conducted a population-matched, sibling-matched retrospective Swedish cohort study to identify whether a link exists between stress-related disorders (including post-traumatic stress disorder (PTSD) and acute stress reaction) and subsequent autoimmune disease. Patients with stress-related disorders were at increased risk of developing autoimmune disease compared with population-matched individuals (HR 1.36 (95% CI 1.33-1.40)). Treatment with selective serotonin reuptake inhibitors during the first year following a diagnosis of PTSD was associated with attenuated relative risk of autoimmune disease.