Autism spectrum disorder (ASD) is a neurodevelopmental disorder that affects an estimated 1 in 36 children in the United States (CDC, 2023). It is characterized by difficulties in communication, social interaction, and repetitive behaviors. The cause of autism is still not fully understood, and there is no known cure. But research on autism has come a long way in recent years, giving us new information about the condition and possible ways to treat it. In this blog, let us delve into some of the latest research findings into the causes of autism.
Genetics and Autism
The etiology of ASD is complex and recent research has shed light on the role of genetic factors in the development of ASD.
One of the most significant findings in ASD research is the high heritability of the disorder. Twin studies have consistently shown that ASD has a strong genetic component, with heritability estimates ranging from 64% to 91% (Hallmayer et al., 2011, Tick et al., 2016). Several large-scale genome-wide association studies (GWAS) have identified multiple common genetic variants associated with ASD, including variants in genes involved in neuronal development, synapse formation, and immune system function (Gaugler et al, 2014, Grove et al 2019)
Other research has also focused on rare genetic variants, such as copy number variations (CNVs) and de novo mutations, which are present in a small percentage of individuals with ASD but have a large effect on ASD risk. Several studies have identified specific CNVs and de novo mutations that are strongly associated with ASD, including deletions or duplications in the 16p11.2 and 22q11.2 regions and mutations in the CHD8 and SCN2A genes (Sander et al., 2015).
Environmental Factors and Autism
Research by other scientists has pointed to environmental factors that may play a role in the This study suggests that reducing exposure to air pollution during pregnancy may be an important public health strategy for preventing autism.This study shows that limiting the amount of air pollution a pregnant woman is exposed to may be an important public health measure for preventing autism.
Finally, there is growing evidence that exposure to pesticides may be a risk factor for autism. A study by Shelton et al. (2014) found that children whose mothers lived within a mile of agricultural fields where pesticides were applied had a higher risk of ASD. This study suggests that reducing exposure to pesticides, particularly during pregnancy, may be an important way to reduce the risk of autism.
Maternal Factors and Autism
One such environmental factor that has been investigated is maternal factors, including age, health, and lifestyle choices.
A recent study conducted by Lyall et al. (2021) examined the association between maternal age and ASD in a large population-based cohort of children. The study found that children born to mothers who were younger than 20 years old or older than 35 years old had a higher risk of ASD compared to those born to mothers between the ages of 25 and 29 years old. The researchers suggest that advanced maternal age may be associated with increased genetic mutations and alterations in epigenetic regulation, which may contribute to the development of ASD.
Another study by Li et al. (2020) investigated the relationship between maternal health and the risk of ASD in offspring. The study found that maternal hypertension and gestational diabetes were associated with an increased risk of ASD in offspring. The authors suggest that these conditions may lead to increased inflammation and oxidative stress in the developing fetal brain, which may contribute to the development of ASD.
Yet another factor that has been linked to autism is maternal obesity. A study by Krakowiak et al. (2012) found that children born to mothers who were obese during pregnancy had a significantly higher risk of developing ASD. This association may be due to the effects of maternal obesity on fetal brain development, as well as the increased inflammation and oxidative stress associated with obesity.
In addition to maternal health, maternal lifestyle factors have also been investigated in relation to the risk of ASD. A study by Lyall et al. (2017) examined the association between maternal smoking during pregnancy and the risk of ASD in offspring. The study found that children born to mothers who smoked during pregnancy had a higher risk of ASD compared to those born to non-smoking mothers. The authors suggest that smoking during pregnancy may lead to alterations in brain development and function, which may contribute to the development of ASD.
Other medical conditions and autism
Recent studies have examined the association between autism and various other medical conditions in children. One such study conducted by Benevides and colleagues (2021) found a higher prevalence of gastrointestinal symptoms in children with autism spectrum disorder (ASD) compared to neurotypical children. The study concluded that gastrointestinal problems may contribute to the behavioral symptoms associated with ASD, and that interventions to address gastrointestinal symptoms may improve ASD-related outcomes. Another study by Yoshimura and colleagues (2021) found a significant association between asthma and ASD in children. The study suggests that asthma may be a risk factor for the development of ASD, and that monitoring and managing asthma may be an important aspect of early intervention for children with ASD.
ASD has been looked at in terms of both medical conditions and environmental factors. A recent study by Hertz-Picciotto and colleagues (2020) examined the relationship between exposure to air pollution during pregnancy and the risk of autism in children. The study found that exposure to fine particulate matter and nitrogen dioxide during pregnancy was associated with an increased risk of ASD in offspring. The study shows how environmental factors may play a role in the cause of ASD and how important it is to take environmental factors into account when trying to stop ASD.
The latest research findings on autism have shed new light on our understanding of this complex neurodevelopmental disorder. Through advances in genetics, brain imaging, and behavioral studies, researchers have made significant progress in identifying the underlying biological mechanisms and environmental factors that contribute to the development of autism. These findings have also led to the development of new interventions and therapies aimed at improving outcomes for individuals with autism. While there is still much to be learned about autism, the latest research provides hope for improved understanding and treatment of this condition in the future.
- Benevides, T. W., Carretta, H. J., Lane, S. J., Smith, C. B., Latimer, M. M., Fleming, K., & Coleman, G. G. (2021). Gastrointestinal symptoms are associated with increased repetitive behaviors and sensory sensitivities in children with autism spectrum disorder. Autism Research, 14 (2), 316-324.
- Gaugler, T., Klei, L., Sanders, S. J., Bodea, C. A., Goldberg, A. P., Lee, A. B., … & Reitz, C. (2014). Most genetic risk for autism resides with common variation. Nature genetics, 46(8), 881-885.
- Grove, J., Ripke, S., Als, T. D., Mattheisen, M., Walters, R. K., Won, H., … & Neale, B. M. (2019). Identification of common genetic risk variants for autism spectrum disorder. Nature genetics, 51(3), 431-444.
- Hallmayer, J., Cleveland, S., Torres, A., Phillips, J., Cohen, B., Torigoe, T., … & Risch, N. (2011). Genetic heritability and shared environmental factors among twin pairs with autism. Archives of general psychiatry, 68(11), 1095-1102.
- Hertz-Picciotto, I., Schmidt, R. J., Walker, C. K., Bennett, D. H., Oliver, M., Shedd-Wise, K. M., … & Iosif, A. M. (2020). A prospective study of environmental exposures and early biomarkers in autism spectrum disorder: Design, protocols, and preliminary data from the MARBLES study. Environmental Health Perspectives, 128(8), 87002.
- Krakowiak, P., Walker, C. K., Bremer, A. A., Baker, A. S., Ozonoff, S., Hansen, R. L., & Hertz-Picciotto, I. (2012). Maternal metabolic conditions and risk for autism and other neurodevelopmental disorders. Pediatrics, 129(5), e1121-e1128
- Li, M., Fallin, M. D., Riley, A., Landa, R., & Walker, S. O. (2020). Maternal medical conditions during pregnancy and risk of autism spectrum disorder in offspring: A systematic review and meta-analysis. Autism Research, 13(3), 374-384.
- Lyall, K., Croen, L. A., Sjödin, A., Yoshida, C. K., Zerbo, O., Kharrazi, M., … & Newschaffer, C. J. (2017). Polychlorinated biphenyl and organochlorine pesticide concentrations in maternal mid-pregnancy serum samples: Association with autism spectrum disorder and intellectual disability. Environmental Health Perspectives, 125(3), 474-480.
- Lyall, K., Schmidt, R. J., Hertz-Picciotto, I., & Newschaffer, C. J. (2021). Maternal age and risk of autism spectrum disorder in offspring: A population-based cohort study. Journal of Autism and Developmental Disorders, 51(1), 121-130.
- Raz, R., Roberts, A. L., Lyall, K., Hart, J. E., Just, A. C., Laden, F., & Weisskopf, M. G. (2021). Autism spectrum disorder and particulate matter air pollution before, during, and after pregnancy: a nested case-control analysis within the Nurses’ Health Study II Cohort. Environmental Health Perspectives, 129(2), 027006.
- Sanders, S. J., He, X., Willsey, A. J., Ercan-Sencicek, A. G., Samocha, K. E., Cicek, A. E., … & State, M. W. (2015). Insights into autism spectrum disorder genomic architecture and biology from 71 risk loci. Neuron, 87(6), 1215-1233.
- Shelton, J. F., Geraghty, E. M., Tancredi, D. J., Delwiche, L. D., Schmidt, R. J., Ritz, B., … & Hertz-Picciotto, I. (2014). Neurodevelopmental disorders and prenatal residential proximity to agricultural pesticides: the CHARGE study. Environmental Health Perspectives, 122(10), 1103-1109.
- Tick, B., Bolton, P., Happé, F., Rutter, M., & Rijsdijk, F. (2016). Heritability of autism spectrum disorders: a meta-analysis of twin studies. Journal of child psychology and psychiatry, 57(5), 585-595
- Yoshimura, S., Oshima, T., Matsuoka, Y. J., Hashimoto, R., Yamamori, H., Yasuda, Y., … & Kishimoto, T. (2021). Asthma is associated with autism spectrum disorder: A population-based case–control study in Japan. Journal of Autism and Developmental Disorders, 51(5), 1565-1576.