Relationship between Autism Spectrum Disorder and Pesticides: A Systematic Review of Human and Preclinical Models

Abstract

Autism spectrum disorder (ASD) is a complex set of neurodevelopmental pathologies characterized by impoverished social and communicative abilities and stereotyped behaviors. Although its genetic basis is unquestionable, the involvement of environmental factors such as exposure to pesticides has also been proposed. Despite the systematic analyses of this relationship in humans, there are no specific reviews including both human and preclinical models. The present systematic review summarizes, analyzes, and discusses recent advances in preclinical and epidemiological studies. We included 45 human and 16 preclinical studies. These studies focused on Organophosphates (OP), Organochlorine (OC), Pyrethroid (PT), Neonicotinoid (NN), Carbamate (CM), and mixed exposures. Preclinical studies, where the OP Chlorpyrifos (CPF) compound is the one most studied, pointed to an association between gestational exposure and increased ASD-like behaviors, although the data are inconclusive with regard to other ages or pesticides. Studies in humans focused on prenatal exposure to OP and OC agents, and report cognitive and behavioral alterations related to ASD symptomatology. The results of both suggest that gestational exposure to certain OP agents could be linked to the clinical signs of ASD. Future experimental studies should focus on extending the analysis of ASD-like behaviors in preclinical models and include exposure patterns similar to those observed in human studies.

Keywords: autism spectrum disorder; carbamates; chlorpyrifos; organochlorine; organophosphate; pesticide; sociability.

Figure 1

Flow Diagram. From top to bottom, the total number of outputs from Scopus and PubMed searches (n = 464). Selection based on year, language (n = 308) and exclusion of duplicates (n = 194), the total number of studies that successfully passed the selection checklist (n = 50), and the total number of accepted studies after parallel searching (n = 61).