Research that points to the causes of Autistic Spectrum Disorder (ASD) has already shown that the condition is associated with genetics. The most recent study, for example, showed that the risk of autism is mostly genetic, around 97%, with heritability of 81%. Only 1% to 3% attributed to environmental factors.
Given this observation, the question arises: what are the chances of a child with autistic siblings also being autistic? Before having a second child, parents of autistic children should know that the chances of the new baby having ASD are high.
Study proves the possibilities
Confirmed by the study by the MIND Institute, the Department of Psychiatry and Behavioral Sciences at the University of California, Davis (UC Davis), and other associated universities. He showed that younger siblings of children already diagnosed with spectrum disorders are about seven times more likely to develop autism.
A number of 664 children from 12 American and Canadian states participated in the study. They assessed from six months of age to 36 months. This is a complete study, based on reliable diagnostic methods and done by a team of specialized researchers. Until then, little known about the relationship between siblings and autism.
According to the research, published in the scientific journal JAMA Pediatrics, 19% of the younger siblings developed the condition, while previous estimates varied between 3% and 10%. The research also showed that when there are two children with ASD in the family, the risk of the third sibling developing autism rises to 32%.
The study also associated the sex of children with autism. The data showed that male children who had an older sibling with autism were three times more likely to have the disease than female babies (26% compared to 9%).
Information already known by researchers is that boys are more susceptible to autism than girls are. Regardless of whether they are firstborn or not. The proportion of ASD incidence among boys and girls is four cases to one.
In light of this, researchers at Harvard University School of Medicine decided to cross-reference the data on the incidence of autism by gender with data that reveal the younger siblings’ chances of having autism.
The researchers reached the following conclusions:
• If the firstborn is a girl and the second child is a boy, the chances are 16.7%;• If both are boys, the chances are 12.9%;• If the firstborn is a boy and the second child is a girl, the chances are 4.2%;• If the two are girls, the chances are 7.6%.
To this end, data from health insurance companies accumulated over eight years analyzed. Almost 1.6 million pairs of brothers identified in the company’s data. Approximately 39,500 in 37,500 families diagnosed with ASD.
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