Autoimmune diseases are associated with an increased risk of schizophrenia: A nationwide population-based cohort study.

OBJECTIVES: Studies have suggested a possible autoimmune contribution in a subset of patients with schizophrenia. The purpose of this study was to determine if a history of autoimmune diseases (AD) is associated with an increased risk of later onset of schizophrenia.

METHODS: Taiwan's National Health Insurance Research Database was used to identify a total of 64,817 AD patients and an equal number of age-matched control patients. The incidence rates of schizophrenia with a maximum follow-up period of 10 years between patients with and without AD were compared using a Cox proportional hazard model to estimate the hazard ratio (HR) and 95% confidence interval (95% CI).

RESULTS: The main finding was the discovery of a higher incidence of subsequent schizophrenia in patients with AD (HR: 1.72, 95% CI: 1.23-2.4) after adjustment for other demographic characteristics. Specifically, the risk of schizophrenia was observed to be a significant increase in systemic lupus erythematosus (3.73, 2.07-6.72), rheumatoid arthritis (2.89, 1.97-4.23), dermatomyositis (5.85, 1.32-25.94) and autoimmune vasculitis (2.44, 1.17-5.06). Also, this study revealed some potential risk factors for developing schizophrenia, including younger age (less than or equal to 50 years) and some comorbidities (hypertension, chronic obstructive pulmonary disease, and alcohol use disorder). Conversely, this study found that steroid use was a potential protective factor for the development of schizophrenia.

CONCLUSIONS: This study found that AD were associated with an increased risk of developing schizophrenia, suggesting that the abnormal autoimmune process was associated with an increase in the expression of psychiatric disturbances.