Autism Spectrum Disorder Causes. Dr Nadeem Ghayas
October 21, 2024
The causes of Autism Spectrum Disorder are well studied, but Autism Spectrum Disorder ASD is a complicated neurodevelopmental disorder that is caused by many factors. ASD has implications on communication, social skills and behavior and its occurrence has been on the rise in the world over the last two decades. ASD has been reported to affect 1 in 36 children in the United States CDC, 2023.
Autism Spectrum Disorder.
Autism Spectrum Disorder is a developmental condition that is distinguished by difficulties in social communication and limited, monotonous behavioral patterns, interest, or activities American Psychiatric Association, 2013. The word spectrum is the mark of the broad range of symptoms and levels of severity. Others are heavily dependent in their day-to-day lives whereas others are self-reliant and portray extraordinary abilities in some fields like memory, music or mathematics.
ASD normally manifests itself at an early age, usually at the age of less than three years. The symptoms may be manifested by early childhood impairments like inadequate speech development, poor eye contact, non-response to name, and repetitive actions. Although the behavioral features are clear, it is more complicated to find out the precise causes of Autism Spectrum Disorder.
Genetic Etiology of Autism Spectrum Disorder.
Inherited Genetic Factor Role.
Genetic factors are said to be the biggest causes of Autism Spectrum Disorder. Family and twin studies prove a great hereditary factor. Studies indicate that the concordance rate of ASD is much higher in identical twins than in fraternal twins, implying a major role of genetic factors National Institute of Mental Health NIMH, 2022.
Children that have an autistic sibling are more likely to develop ASD. Research shows that between 10 and 20 percent of families having one of their children with an affected individual have the recurrence of it Ozonoff et al., 2011. These results confirm the hypothesis that inherited genetic variations are a key contributor to the risk of autism.
Mutations in Genes and Chromosomal Abnormalities.
The development of molecular genetics has helped in the identification of a few gene mutations related to ASD. Fluctuations in genes that govern the development of the brain, synaptic activity, and neural linkage are usually noticed. As an example, SHANK3, CHD8, and SCN2A gene mutations have been associated with autism spectrum disorder risk Lord et al., 2020.
Some genetic syndromes also have increased likelihood of autism such as Fragile X syndrome and Rett syndrome. The conditions influence the development of the brain and may cause the autism like behavior. Nevertheless, there is no single gene that causes the occurrence of all cases of ASD. Rather, autism has been viewed as a polygenic disorder, i.e. it is a combination of multiple genes interacting to heighten susceptibility.
Autism Spectrum Disorder is Environmentally caused.
Environmental Prenatal Risk Factors.
Through environmental factors especially in pregnancy, they also play a vital role in determining the cause of the autism spectrum disorder. It has been suggested that potential causes of autism could be related to prenatal exposure to some infections, including rubella or cytomegalovirus World Health Organization WHO, 2023.
Mother health diseases like diabetes, obesity, and autoimmune diseases can also be the cause of disturbed fetal brain development. Prenatal exposure to some drugs, such as valproic acid, has been identified as a risk of developing ASD in children Christensen et al., 2013.
Advanced Parental Age
Maternal and paternal advanced age has always been found as one of the risk factors of ASD. Research indicates that parents who are older might have a marginally higher risk of having a child with autism, potentially because of genetic mutation or epigenetic alteration with age Sandin et al., 2016.
Pollutants and Environmental Toxins.
Prenatal exposure to air pollution, heavy metals, and pesticides has been examined as a possible risk factor to autism. There is some research indicating that high air pollution levels are linked with high prevalence of ASD, but the results are not conclusive yet CDC, 2023. Notably, vaccination has undergone a lot of research and could not be attributed to Autism Spectrum Disorder. Extensive studies have identified no scientific data to support the association between vaccines and ASD CDC, 2023.
Autism Spectrum Disorder has neurobiological Etiology.
Structural and Connectedness of the Brain.
Neuroimaging evidence demonstrates that individuals with ASD differ in brain structure and brain connection. It has been found that there is a non-typical development of the cerebral cortex, amygdala, and cerebellum, which are social behavior, emotion regulation, and motor coordination related areas (Lord et al., 2020).
Deviant neural connectivity can be related to communication challenges and compulsory behaviors. Other studies indicate early overgrowth of the brain of children who eventually develop autism and consequently experience deviant developmental carriers.
Imbalances of neurotransmitters.
Autism Spectrum Disorder can also be caused by neurochemical factors. Serotonin, dopamine, and gamma aminobutyric receptors systems have been found to differ in people with ASD. They are neurotransmitters that are essential in mood, social behavior, and sensory processing NIMH, 2022.
Birth and Pregnancy complications.
Pregnancy complications or birth complications are related to high risk of autism. The earlier birth, the poor weight of the baby at birth and loss of oxygen during the delivery have been indicated to increase the risk of developing ASD Gardener et al., 2011. These factors do not cause autism directly, but they can have an interactive effect with genetic vulnerability to alter development of the brain.
Genetic x Environmental Interaction.
The scientific current opinion is to adopt a multifactorial model of the causes of Autism Spectrum Disorder. This implies that autism is a product of both a complicated interplay between environmental factors and genetic predisposition. It is also possible that genetic factors predisposition cause some individuals to be more vulnerable to environmental cues at a critical stage of brain development.
One of the new fields of study is epigenetics, or the modification of the expression of genes without any alteration in the sequence. The exposures of the environment can have an effect on the activation or inactivation of genes, which could be a cause of autism.
Myths and Misconceptions of Autism Causes.
The fact that vaccines cause autism is one of the most detrimental myths. Millions of studies on children have strongly proved that there is no connection between vaccination and Autism Spectrum Disorder CDC, 2023. The initial research which proposed such a relationship has been invalidated and withdrawn.
The other myth is that the style of parenting is the cause of autism. No scientific evidence can prove this assertion. Autism is a neurodevelopmental disorder that has biological basis but not the behavior of parents.
Significance of Early Detection and Study.
Even though the true causes of Autism Spectrum Disorder are still not thoroughly known, the current study is still making its mark. The outcome of development is highly enhanced by early diagnosis and early intervention. Communication skills and adaptive functioning can be improved by means of behavioral therapy, speech therapy, occupational therapy, and family support programs.
Learning the causes of autism spectrum disorder assists in the reduction of stigma, enhancing early screening, and supporting the evidence based support strategies. The organizations like CDC, WHO, and NIMH continue to conduct research to define risk factors and enhance prevention measures.
Conclusion
The etiology of Autism Spectrum Disorders is multifactorial. There is strong scientific evidence that ASD is caused by a mix of genetic, environmental, neurobiological and prenatal factors. There is no one cause that describes all the cases. Genetic studies, brain scanning and environmental health studies are bringing in more knowledge. This can help the society to assist the people with autism and their parents and this can be done by creating awareness and relying on evidence provided by credible scientists.
References
The American Psychiatric Association. 2013. Diagnostic and statistical manual of mental disorders 5th edition. Washington, DC: Author.
Centers of Disease Control and Prevention. 2023. Autism spectrum disorder data and statistics. Published by the Centers of Disease and Protection, 2017.
Christensen, J., Gronborg, T. K., Sorensen, M. J., Schendel, D., Parner, E. T., Pedersen, L. H., and Vestergaard, M. 2013. Autism spectrum disorders and childhood autism. The American Medical Association, 309, 1696 to 1703.
Gardener, H., Spiegelman, D., and Buka, S. L. 2011. Prenatal risk factors of autism: Literature review of meta-analyses. British Journal of Psychiatry, 195, 7 to 14.
Lord, C., Brugha, T. S., Charman, T., Cusack, J., Dumas, G., Frazier, T., and Veenstra VanderWeele, J. 2020. Autism spectrum disorder. Nature Reviews Disease Primers, 6, 5.
National Institute of Mental Health. 2022. Autism spectrum disorder. Accessed on 1st January 2019.
Ozonoff, S., Young, G. S., Carter, A., Messinger, D., Yirmiya, N., Zwaigenbaum, L., and Stone, W. L. 2011. Repeat risk of autism spectrum disorders: A Baby Siblings Research Consortium study. Pediatrics, 128, e488 to e495.
Sandin, Sandin, S., Lichtenstein, P., Kuja Halkola, R., Larsson, H., Hultman, C. M., and Reichenberg, A. 2016. The familial risk of autism. Editorial Board of Journal of the American Medical Association, 311, 1770-1777.
World Health Organization. 2023. Autism. Obtained on 21st July, 2020 at the end of the page under the heading Access to health services.