What causes autism? What we know, don’t know and suspect

To date, no study has been able to examine the thousands of people necessary to identify with accuracy all of the small mutations that might lead to autism.

With more than 3 billion building blocks in the DNA chain that forms our chromosomes, it’s difficult for scientists to isolate genes that could cause autism.

However, with genetic technologies improving at an astronomical pace, as well as global scientific cooperation that will lead to large numbers of people being studied, major advances in the understanding of the causes of autism are likely in the very near future.

A likely prospect is that many cases of autism will be related to what is called “common genetic variation”. This refers to differences in genes that are also found in many individuals who do not have autism and which by themselves are not sufficient to lead to autism. However, when multiple genetic risk factors are found in the same person, they combine to have a major effect on how the brain develops.


A small proportion of autism cases are also likely to be caused by what are known as de novo (“new”) mutations. Most often, the egg and sperm that create a baby contain genetic material that is present in the mother and father, respectively. However, in rare cases, the egg and sperm may contain genetic material that is not found in either parent. There is now good evidence that some people with autism may have inherited de novogenetic mutations that have an effect on brain development.



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