That there were genes involved in the development of autism, was something we knew. However, precisely adding genes associated with autism spectrum disorder (ASD) is more complicated. Now, a fresh look at previous research data has confirmed what many researchers thought: Autism is primarily in the genes. And not only this, the study carried out by scientists at the Icahn School of Medicine at Mount Sinai in New York (USA) has drawn a figure: 83% of autism cases are inherited.
Taking into account that the symptoms are not very clear until the child develops advanced communication skills, that is, at 2 or 3 years of age, this makes it difficult to untangle the genetic and environmental causes of this neurological condition.
The researchers re-analyzed a Swedish longitudinal study with more than 2.6 million pairs of siblings, 37,570 pairs of twins and just under a million pairs of brothers. Of all of them, 14,516 children were diagnosed with autism spectrum disorder.
Twin studies have suggested that as many as 9 out of 10 children with autism inherited the condition through their genetic combination, although other studies put this number well below. Which number is the most accurate?
Researchers were skeptical about the numbers drawn from the studies, so they took the same massive data set on Swedish children and used another method that had previously proven effective in this field.
Its conclusion of 83% of inherited cases is closer to 90% determined by twin studies than 38% of the results of a research carried out in California, and it was estimated with greater precision.
“Like previous twin studies, shared environmental factors contributed minimally to the risk of autism,” the researchers comment in the Journal of the American Medical Association , which just published the scientific study.
While we can be sure that genes play a key role in the development of the traits associated with autism spectrum disorder, we can also be sure that it will not be the last word on the matter.
For one thing, only 1 in 68 children is diagnosed with the disorder. Although not extremely rare, it is difficult to find a sample size large enough to make accurate predictions. In addition , it affects only 1 in 189 girls, while in boys there is a higher incidence: 1 in 42 boys.
We are still a long way from understanding the role genes play in how our brains interact socially and, of course, the environment, the environment, cannot be completely ruled out.
The more we discover, however, the more we become aware that autism spectrum disorder is a more complex condition than we imagined.
Reference: The Heritability of Autism Spectrum Disorder. Sven, Sandin, Paul Lichtenstein, Ralf Kuja-Halkola, et al. JAMA Journal of the American Medical Association. 2017; 318 (12): 1182-1184. doi: 10.1001 / jama.2017.12141
