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Evolutionary explanations for the rise of Autism Spectrum Disorders

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Autism Spectrum Disorders(ASD) have steadily been on the rise in the United States for the past 30 years.

Over the past few years, the United States has reported the highest rate of Autism Spectrum Disorder(ASD) and the greatest number of cases worldwide for any country.

This has been baffling to many scientists and epidemiologists. Many public health officials and experts have scrambled to undercover the primary causative agents. In fact, over half of all papers published on Autism have occurred since 2008. Experts attribute the increasing number of cases partially to a more encompassing definition for ASD that includes other forms of neurodevelopment disorders.

The term “Autism” has been used for over a hundred years and comes from the Greek word “autos,” meaning self. It describes the medical condition where a person is detached from social interactions. While most research indicates that genetic factors dominate, newer promising research has assessed the role of environmental factors in the etiology of ASD. Most researchers acknowledge that there is most likely not a single cause of autism, however, there may be highly conserved risk factors across ASD.

The field of Evolutionary Medicine presents many evolutionary reasons as to why different states of disease exist. Some believe that the field can shed light on understanding ASD. Most experts in ASD research claim that it is caused by a combination of genetic predispositions and environmental causes. However, the age of parents is becoming an issue that is increasingly studied. What are Evolutionary reasons for wanting young and fit parents?

In most countries, ASD is relatively rare in nature, and many of the gene variants and mutations typically associated with ASD are critical to human survival and development. Therefore, these genes remain prevalent in the population, despite the fact that exposure to many chemicals, viral agents, and environmental toxins during pregnancy can substantially increase the risk of developing ASD.

Understanding the evolutionary foundations for psychiatric diseases is more complicated than typical diseases. There is a fundamental distinction in the evolution of psychiatric diseases including the symptoms and the diseases that cause the symptoms.

Geneticists typically consider a condition to be a genetic condition if the heritability is high. Research early in the field suggested that the heritability of ASD is pretty high. Twin and family studies have elucidated a high heritability with ASD. Due to the recent distinction between Autism and schizophrenia, autism has a relatively short recorded natural history and has been used since the 1900s to broadly specify a host of neuropsychological conditions. However, its recent distinction from schizophrenia came in the 1960s and psychiatrists noticed distinct symptoms and time of onset.

Traditional mendelian inheritance and exposure to environmental factors cannot adequately explain the prevalence and presence of many neurological diseases. Multiple genes can be involved to develop any of the symptoms of those with ASD. This is true of many behavioral disorders as well. While certain environmental factors such as obesity and enhanced paternal and maternal aging are exacerbating and causing changes this does not guarantee the development of autism. Due to the complexity of the disease and the cost of developing drugs, understanding environmental causes may be a better way to perturb the increased prevalence of ASD.

Advancing paternal and maternal age has both been associated with risk for autism spectrum disorders (ASD). The shape of the association remains unclear, and results on the joint associations are still lacking. However, after surveying literature in the field and using autism databases it is most reasonable to suggest that a combination of prenatal stresses and genetic susceptibilities lead to increased risk for the development of Autism Spectrum Disorders.

Insights into how ASD has presented over many generations can be understood with the notion that conflicting actions of natural selection can maintain any disease in a population. The complexity of ASD continues to make it challenging for researchers to study.



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This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

© 2020 Michael Mannen