Early Childhood Allergy Linked With Development of Attention Deficit Hyperactivity Disorder and Autism Spectrum Disorder

Abstract

Background: Previous studies reported controversial results regarding the association between allergic disorders and ADHD/ASD. The aim of this article is to investigate whether allergic disorders are associated with ADHD/ASD in a large cohort of pediatric patients. Methods: A retrospective study using the pediatric (0-18 year) database (ICD-9-CM codes) of Clalit Health Services during the years (2000-2018). Diagnosis of all disorders was made by specialist physicians. Results: 117,022 consecutive non-selective allergic children diagnosed with one or more allergic disorder (asthma, rhinitis. conjunctivitis, skin, food, or drug allergy) and 116,968 non-allergic children were enrolled to our study. The mean follow-up period was 11±6 years. The presence of allergic disorders in early childhood (mean age of allergic diagnosis 4.5± 4.3 years) in boys as well as in girls, significantly increased the risk to develop ADHD (O.R 2.45, CI 2.39-2.51; P<0.0001), ASD (O.R 1.17, CI 1.08-1.27; P<0.0001) or both ADHD+ASD (O.R 1.5, CI 1.35-1.79; P<0.0001). Children with more than one allergic comorbidity revealed a much higher risk. In a multivariable analysis (adjusted for age at study entry, number of yearly visits and gender) the risk of allergic children to develop ADHD and ADHD+ASD, but not ASD alone, remained significantly higher. Conclusion: Allergic disorder in early childhood significantly increased the risk to develop ADHD, and to a less extend ASD, in later life.