Is there a link between childhood and parental asthma and risk of schizophrenia?
• A previous longitudinal cohort study found that both children and adolescents with asthma are at increased risk of schizophrenia 
• Acute asthma during pregnancy is associated with systemic increases in inflammation
• A variety of prenatal exposures linked to inflammation, in turn, are associated with increased risk of schizophrenia
• Wu and colleagues  conducted a longitudinal cohort study of the association between asthma and severe mental illness
• The authors investigated relationships between childhood asthma and maternal asthma (before and during pregnancy) and risk of schizophrenia-spectrum disorders
• The authors performed a study of all children born in Sweden from 1973 to 1995 and their parents
• Childhood asthma was grouped by age of first hospitalization (<5, 6-10, and 11-15)
• Both maternal and paternal hospitalizations for asthma before offspring birth were also identified
• The authors considered multiple potential confounding factors, including sex, birth order, SES, urban residence, preterm delivery, antenatal infections, childhood respiratory infections, parental age, maternal smoking, and parental history of asthma and mental illness
• Cox proportional hazard regression model was used to estimate the risk of schizophrenia
• The cohort consisted of 2.26 million individuals; including 40,187 children with hospitalization for asthma before age 15, and 9,892 children born to mothers with hospitalizations for asthma before birth
• After adjustment for potential confounders, first asthma admission aged 11 to 15 years was associated with significant increased risk for schizophrenia-spectrum disorders (HR=1.62, 95% CI 1.08-2.42)
• The authors concluded that adolescent asthma is associated with schizophrenia-spectrum disorder
• They found less evidence for an association between maternal asthma, and no association between paternal asthma and schizophrenia risk
• Findings raise the possibility of shared genetic architecture for asthma and mental illness
• The use of national registry data is an important strength of the study
Take Home Point
• This study strengthens the evidence that severe asthma during adolescence increases the risk of schizophrenia-spectrum disorders
1. Pedersen MS, Benros ME, Agerbo E, et al. Schizophrenia in patients with atopic disorders with particular emphasis on asthma: a Danish population-based study. Schizophr Res. 2012;138:58–62.
2. Wu Q, Dalman C, Karlsson H, et al. Childhood and Parental Asthma, Future Risk of Bipolar Disorder and Schizophrenia Spectrum Disorders: A Population-Based Cohort Study. Schiz Bull. 2018 Mar 9. doi: 10.1093/schbul/sby023.