From the Guidelines
The current research findings suggest that Autism Spectrum Disorder (ASD) is caused by a complex interplay of genetic and environmental factors, with environmental chemicals, such as pesticides, heavy metals, and endocrine disruptors, playing a significant role in the etiology of the disorder. The evidence from a 2019 scoping review of human and animal research on environmental chemicals and autism, published in Environmental Health Perspectives 1, highlights the importance of considering the contribution of environmental factors to ASD. This review found that the prenatal period is a sensitive time when the developing brain is particularly susceptible to disruptions from environmental chemicals, and that subtle signs of autism can be detected as early as 9 months.
Some key environmental factors that have been associated with ASD include:
- Exposure to pesticides and heavy metals, which have been shown to affect brain development and function 1
- Endocrine disruptors, such as bisphenol A (BPA) and phthalates, which can interfere with the developing endocrine system and increase the risk of ASD 1
- Maternal infections during pregnancy, which can trigger an immune response and increase the risk of ASD 1
It's also important to note that genetic factors, such as variants in genes involved in the elimination of toxic chemicals from the body, can increase the risk of ASD, particularly when combined with environmental exposures 1. The review highlights the need for further research on the role of environmental chemicals in ASD, particularly in the context of gene-environment interactions.
Overall, the evidence suggests that reducing exposure to environmental chemicals, particularly during the prenatal period, may be an important strategy for preventing or reducing the risk of ASD. Therefore, it is recommended that pregnant women and families with young children take steps to minimize their exposure to environmental chemicals, such as using non-toxic household products and avoiding pesticides and heavy metals.
From the Research
Current Research Findings on the Etiology of Autism Spectrum Disorder (ASD)
The etiology of Autism Spectrum Disorder (ASD) is a complex and multifactorial phenomenon that has been the subject of extensive research. Several studies have investigated the genetic and environmental factors that contribute to the development of ASD.
Genetic Factors
- Genetic susceptibility is a significant factor in the development of ASD, with certain genetic syndromes such as Rett, Fragile X, and tuberous sclerosis accounting for a small proportion of cases 2, 3, 4.
- Recent discoveries have shown that rare variants of large effect size as well as small effect common gene variants all contribute to autism risk 5.
- Genetic polymorphisms of cytochrome P450 enzymes, such as CYP27B1, have also been linked to autism, specifically in relation to vitamin D metabolism 3.
Environmental Factors
- Environmental factors, such as impaired methylation, maternal infection, and exposure to heavy metals, have been implicated in the development of ASD 3.
- Maternally derived antibodies and folic acid supplementation have also been considered as potential environmental factors contributing to ASD 3.
- Epigenetic modifications, which can be influenced by environmental factors, have been shown to play a role in the etiology of ASD, integrating genetic and environmental influences to dysregulate neurodevelopmental processes 4.
Epigenetics
- Epigenetic dysregulation has been associated with the development of ASD, with several genetic syndromes comorbid with ASD demonstrating dysregulation of epigenetic marks or epigenetic mechanisms 4.
- Environmental factors linked to the development of ASD, such as maternal infection and exposure to heavy metals, have also been shown to contribute to epigenetic dysregulation 4.
Current Understanding
- The current understanding of ASD etiology is that it is a multifactorial disorder, with both genetic and environmental factors contributing to its development 2, 3, 4, 5.
- The identification of specific causes and risk factors for ASD is an active area of research, with the goal of achieving a better understanding of the complex interplay between environment and gene regulation 3.