Boys with an autistic older sister have a 17% risk of developing an autism spectrum disorder in turn.
Parents of a child with autism may wonder, when having a second child, whether the latter is at risk of being autistic in turn. What if it is safe to make a risky choice. Studies had already shown that they were higher in siblings already affected, but a large study carried out at Harvard medical school objectified them all, by differentiating between the sexes.
They have thus shown that the children most at risk are boys who have an older sister with autism spectrum disorders (ASD). They have almost a one in five chance (17%) of developing an ASD in turn. In comparison, in the general population, the risk of autism is only about 1% (1.5% in the United States).
Boys are more at risk
This figure was taken from a database of American mutuals, covering more than 1.5 million families with at least two children, and 3.1 million children. Of these, 39,000 were diagnosed with ASD, or about 1.2% (2% of boys, 0.5% of girls).
Boys with an autistic older brother are also at high risk: 13% of them are autistic. Girls are less affected. Those with an older sister with ASD have a risk of less than 8%. With an older brother, the risk is “only” 4%.
In summary, if the first child with autism is a girl, parents are more likely to have a second child with ASD, especially if it’s a boy.
For an informed choice
“This study is a convincing example of how big data can shed light on trends, and give us information to support parents’ choices and the information provided to pediatricians”, underlines Isaac Kohane, head of the department. of Biomedical Informatics at Harvard Medical School, and lead author of the study.
But, even if the risk of having a second child with autism is very high, the researchers point out that it is not inevitable. “Even for the riskiest group – boys with older sisters with autism – there is still more than four in five chances that the child will not be affected, insists Nathan Palmer, co-author of the study. What we are offering here is a context for families who already have a child with autism or with a similar disorder, so that they have a clearer perspective on risk. “
The origin of autism is still poorly understood. It is the result of a combined influence of genetics, which this study shows again, and environmental factors. It is then manifested by a spectrum of behavioral symptoms that develop in the first years of patients’ life, and which limit the social interactions and communication skills of affected children.
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