A systematic review of the association between allergic asthma and autism

INTRODUCTION: Autism Spectrum Disorder represents a burdensome condition in early childhood, with a number of risk factors proposed to explain its pathogenesis, most of which without a reliable scientific basis. Allergic asthma is likely to be one of the possible comorbilities of autism. EVIDENCE ACQUISITION: In this paper, the relationship between autism and allergic asthma was analyzed through a systematic literature review, conducted according to the PRISMA Guidelines. The review was performed on PubMed and Science Direct database and covered the period January 1, 2004-July 9, 2016. The search was limited to articles published in peer-reviewed journals. The obtained results were sorted by relevance and the most significant case-control, epidemiological and nationwide-based works associating autism and allergic asthma in humans were selected. EVIDENCE SYNTHESIS: A slight correlation between these conditions has been found in more than a half studies selected, suggesting a possible association between the two diseases. Small sample sizes of some works and some methodological limitations rise uncertainty about this link. CONCLUSIONS: Autism Spectrum Disorder and asthma could be associated conditions, as evidenced by the higher prevalence of asthma in autistic children with respect to typically developed controls, with also a verisimilar biological basis. Despite that, future studies are required to provide more reliable data, also by employing animal models, to better clarify this, still unsure, relationship. Methods for study selection and inclusion criteria were specified in advance and documented in PROSPERO protocol #CRD42014012851.