Prevalence and risk of atopic disorders among schizophrenia patients: A nationwide population based study

Objective: Although a body of evidence indicates a link between psychiatric illnesses and allergies, no one has investigated the association between schizophrenia and atopic disorders. The objective of this nationwide population-based study was to examine the prevalence and risk of atopic disorders (asthma, allergic rhinitis, urticaria, and atopic dermatitis) among schizophrenia patients. Method: This study used data from the Taiwan National Health Insurance Research Database covering the years 2000 to 2002. A total of 44,187 patients diagnosed with schizophrenia in the year 2000 were included, together with 132,561 matched non-psychiatric controls. Follow up until the end of 2002 identified concurrent diagnoses of atopic disorders. Logistic regression analyses were performed after controlling for the covariates of socio-demographic characteristics. Results: Findings indicated high comorbidity, with 20.2% of schizophrenia patients (approximately one in five) experiencing concurrent atopic disorders. Moreover, schizophrenia in patients was independently associated with a 1.3-fold increased risk (95%CI = 1.24-1.39) of concurrent asthma, after adjusting for socio-demographic characteristics. Yet the risk of diagnosed allergic rhinitis and urticaria was 23% (95%CI=0.74-0.81) and 26% (95%CI=0.72-0.77) lower respectively, among schizophrenia patients compared to people without any psychiatric disease. Conclusion: Data suggests an increased risk of asthma and decreased risk of allergic rhinitis and urticaria among schizophrenia patients. Future studies on the identification of common etiologic pathways for schizophrenia and asthma could be significant for developing innovative treatments that target both illnesses concurrently. (C) 2009 Elsevier B.V. All rights reserved.