Environmental risk factors for autism

Abstract

Autism is a devastating childhood condition that has emerged as an increasing social concern just as it has increased in prevalence in recent decades. Autism and the broader category of autism spectrum disorders are among the increasingly seen examples in which there is a fetal basis for later disease or disorder. Environmental, genetic, and epigenetic factors all play a role in determining the risk of autism and some of these effects appear to be transgenerational. Identification of the most critical windows of developmental vulnerability is paramount to understanding when and under what circumstances a child is at elevated risk for autism. No single environmental factor explains the increased prevalence of autism. While a handful of environmental risk factors have been suggested based on data from human studies and animal research, it is clear that many more, and perhaps the most significant risk factors, remain to be identified. The most promising risk factors identified to date fall within the categories of drugs, environmental chemicals, infectious agents, dietary factors, and other physical/psychological stressors. However, the rate at which environmental risk factors for autism have been identified via research and safety testing has not kept pace with the emerging health threat posed by this condition. For the way forward, it seems clear that additional focused research is needed. But more importantly, successful risk reduction strategies for autism will require more extensive and relevant developmental safety testing of drugs and chemicals.

Does the Human Gut Microbiota Contribute to the Etiology of Autism Spectrum Disorders?

“…Several studies have revealed immune and neuronal dysregulation in autistic subjects [4,5]. The underlying causes remain unclear, but both genetic and environmental factors appear to play a role [5][6][7]. The rapid increase in autism in recent years is unlikely to be explained by an increase in awareness and diagnosis of the condition alone, which also points to the environment as a contributing factor [7].…”

“…The underlying causes remain unclear, but both genetic and environmental factors appear to play a role [5][6][7]. The rapid increase in autism in recent years is unlikely to be explained by an increase in awareness and diagnosis of the condition alone, which also points to the environment as a contributing factor [7]. Environmental factors that may contribute to the etiology of ASD include pre-or postnatal exposure to certain environmental chemicals and drugs, stress, maternal infection, and dietary factors [7].…”

“…The rapid increase in autism in recent years is unlikely to be explained by an increase in awareness and diagnosis of the condition alone, which also points to the environment as a contributing factor [7]. Environmental factors that may contribute to the etiology of ASD include pre-or postnatal exposure to certain environmental chemicals and drugs, stress, maternal infection, and dietary factors [7]. It has to be kept in mind that ASD envelops a range of disorders with great heterogeneity between subjects, and it may be necessary to investigate specific subgroups to identify the biological processes underlying these diseases.…”

The Role of Heavy Metal Pollution in Neurobehavioral Disorders: a Focus on Autism

“…Therefore, exposure to environmental chemicals during the early fetal development can cause brain injury at levels much lower than those affecting adult brain function (Grandjean and Landrigan 2006). Environmentally mediated changes in fetal programming may be limited to an individual's prenatal period of development or, alternatively, alteration in control of gene expression may appear later in adulthood (Dietert et al 2011). Epigenetic mechanisms (e.g., DNA methylation, histone modifications, and expression of non-coding microRNAs) produce heritable modifications in gene expression without changes in DNA sequence (Chuang and Jones 2007;Cedar and Bergman 2009;Svoboda and Flemr 2010).…”

A Randomized Comparison of Two Instructional Sequences for Imitation Intervention for Children with Autism Spectrum Disorders

“…Additionally, presence of genetic or chromosomal conditions, such as fragile X syndrome or tuberous sclerosis can also increase the risk of being diagnosed with ASD (CDC, 2014;Numis et al, 2011). There are also various environmental risk factors such as premature or low birth weight, maternal stress (prior to 32 weeks of gestation), paternal age, and exposure to heavy metals, pesticides, and specific pharmacological drugs (Dietert, Dietert, & Dewitt, 2011;Gardener, Spiegelman, & Buka, 2011).…”