The association between autoimmune diseases and schizophrenia has rarely been systematically investigated.

To investigate the association between schizophrenia and a variety of autoimmune diseases and to explore possible gender variation in any such association.

Taiwan's National Health Insurance Research Database was used to identify 10 811 hospital in-patients with schizophrenia and 108 110 age-matched controls. Univariate and multiple logistic regression analyses were performed, separately, to evaluate the association between autoimmune diseases and schizophrenia. We applied the false discovery rate to correct for multiple testing.

When compared with the control group, the in-patients with schizophrenia had an increased risk of Graves' disease (odds ratio (OR) = 1.32, 95% CI 1.04–1.67), psoriasis (OR = 1.48, 95% CI 1.07–2.04), pernicious anaemia (OR = 1.71, 95% CI 1.04–2.80), celiac disease (OR = 2.43, 95% CI 1.12–5.27) and hypersensitivity vasculitis (OR = 5.00, 95% CI 1.64–15.26), whereas a reverse association with rheumatoid arthritis (OR = 0.52, 95% CI 0.35–0.76) was also observed. Gender-specific variation was found for Sjögren syndrome, hereditary haemolytic anaemia, myasthenia gravis, polymyalgia rheumatica and dermatomyositis.

Schizophrenia was associated with a greater variety of autoimmune diseases than was anticipated. Further investigation is needed to gain a better understanding of the aetiology of schizophrenia and autoimmune diseases.