The cause of Autism Spectrum Disorder (ASD) has been a question asked for years. Many have speculated yet the definite cause has yet to be articulated. Genes have been a large focus for researchers. However, with the increasing knowledge of epigenetics the role of the environment must also be researched. Resulting in the classic question how much nature versus nature?
In a review article by Andreas Grabrucker, a professor at the Nuerocenter of Ulm University in Germany, potential environmental factors were discussed. Although there were many factors mentioned such as prenatal viral infections, maternal diabetes, abnormal melatonin synthesis and toxins, they all seemed to center around two key environmental factors: immune dysfunction and zinc deficiency.
Many environmental factors lead to the dysfunction of the immune system. Some of the risk factors discussed in the article were prenatal viral infections, prenatal stress, maternal diabetes, parental age and gastrointestinal abnormalities. It was hypothesized that factors would lead to the increase inflammatory cytokines, such as IL-6, which leads to the dysregulation of gene expression in the P38 MAPK and ERK pathways. This may result in glutamate synapse dysfunction which will result in an imbalance of excitatory and inhibitory signals, therefore causing an individual to develop ASD.
Another environmental factor that may lead to ASD is zinc deficiency. Low levels of zinc can be found in individuals with abnormal melatonin synthesis, gastrointestinal abnormalities and those who have poor eating habits. Low levels of zinc will also follow the same path of immune dysfunction by resulting in a glutamate synapse dysfunction.
The places that have the highest rates of zinc deficiency are third world countries where their populations often suffer from malnutrition. By following the link between zinc deficiency and ASD, a logical assumption could be made that there is probably more autism in third world countries. However, according to studies this is not the case. Most studies on ASD in third world countries report lower findings of it than in the USA. This may be a misrepresentation due to lack of medical records in developing countries or this could indicate the although environment plays a role in ASD, genetics play a larger role. These findings bring forth the question of how much nature and how much nurture goes into the development of ASD.
For continued reading about environmental factors in ASD check out:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3548163/
For continued reading about rates of ASD in developing countries check out:
http://www.who.int/mediacentre/factsheets/autism-spectrum-disorders/en/
https://spectrumnews.org/news/researchers-track-down-autism-rates-across-the-globe/
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https://youinc.com/content/leadership/nature-vs-nurture
Nature Versus Nurture: Environmental Factors in Autism
