Is autism caused by genetic or environmental factors?

Recently, two studies have come to seemingly contradictory conclusions about the cause of autism. A study by Bai et al. used a mbadive sample of 2 million children worldwide in a statistical badysis. They came to the conclusion that 80% of the risk of developing an Autism Spectrum Disorder (ASD) is due to genetics. The other study, conducted by Abdelli et al., Found that a food preservative, propionic acid (PPA), affected the growth of neural stem cells, so they were more likely to cause a ASD. Following this, they badumed that pregnant women using this food preservative would be more likely to have children with ASD.

So, what is it? Are ASD mainly due to genetics or mainly to environmental factors? ASDs occupy a place of power in our psyche – just look at the persistence of pseudoscientific beliefs such as the long-held theory that vaccines cause autism. In addition, the idea that we control if our children are healthy is inherently attractive. Just change your diet and everything will be fine. If we only had to read the headlines, in the face of seemingly contradictory findings, we might be tempted to simply select the one that best fits our world view, but yielding to this temptation simply does not reflect a state of mind interested. in objective reality. So, let's dive into the heart of the matter.

What have these studies found?

First, Bai et al. A statistical study found that one study indicated that about 80% of the risks of ASD were of genetic origin, the remaining 20% ​​being related to uncertain environmental factors. Of the remaining 20%, only 1% was due to maternal factors, such as weight or diet.

Abdelli et al. The study chose to target PPA because it has been shown that individuals with ASD have a different microbiome than neurotypic individuals. In the intestine of ASD, there are more bacteria that produce APP as a by-product. PPA plays an important role in the nervous system by modulating cellular signaling, but Abdelli et al. suspected that too much could be toxic.

To test this, Abdelli et al. exposed neural stem cells in APP culture. Untreated neural stem cells tended to differentiate into neurons or glial cells. These are a kind of support cell for neurons; they do not do the "thinking" that neurons do, but they provide structure, provide nutrients, isolate neurons from each other, and destroy old neurons and pathogens. However, stem cells treated with APP tended to differentiate much more often in glial cells than in neurons. This is significant because the brains of TSA have many more glial cells than the neurotypic brains. Extrapolating from their laboratory evidence, Abdelli et al. have concluded that a fetal brain exposed to more PPA, for example by the mother's diet, will develop more glial cells and will therefore become more likely to become an ASD brain

So, are these results contradicting each other?

Not really. It is true that Abdelli et al. Establish a link between a mother's APP exposure and a higher likelihood that the child is developing ASD. This seems to contradict the conclusion of Bai et al. That only 1% of ASDs could be attributed to effects on the mother. It is important to remember that Abdelli et al. leads a in vitro laboratory experience, not an experiment on pregnant women, which would be extremely unethical. The actual activity of APP in the human body could very well be very different from its effect in the lab, potentially such that it ultimately contributes to that 1%. (Abdelli et al also plan to conduct future mouse experiments to test their in vitro results).

In addition, the study of Bai et al. Does not describe and can not take into account all forms of maternal effects. This study did not directly examine the amount of PPP consumed by a mother, for example; it is therefore possible that environmental factors play a more important role than the declared 1% variance.

However, the magnitude of genetic effects in the study of Bai et al. Gives a very clear picture: ASDs are mainly caused by genetics. If you only read the titles, these two studies would seem to paint a binary and mutually exclusive picture of how TSA was born. Taken together, they demonstrate what scientists have been waiting for – ASDs are caused by a combination of genetic and environmental factors, but the disease is primarily of genetic origin.

Despite this consensus within the scientific community, the media and the general public seem to want to focus on environmental factors. People want to be able to control the results of their lives. Therefore, the conclusions suggesting that all you have to do to have a healthy neurotypical child is to eat the right foods, have the right weight or exercise the right amount are deeply attractive. It will be beneficial to do these things, there is no doubt. But scientific discoveries do not exist in isolation; ignoring their context creates an inaccurate picture of the world.

Related articles on the web

From your site