While there is some disagreement on the subject, most medical scientists would agree that Autism rates are on the rise in the U.S. and in many other parts of the world. What’s the reason for this increase? Like most medical issues, there are probably a variety of reasons. Some have suggested that the increase in autism can be linked to childhood vaccination, but the data argue strongly against it. Most likely, there are a series of genetic and environmental factors that play a role in the increase.
For quite some time now, there has been strong evidence that the age of the father has a significant effect on the chance of his child having autism.1 There has been evidence that the mother’s age also plays a role, but its effect is much smaller.2 However, these studies simply demonstrate a correlation between parental age and autism. They do not show that increased parental age plays a direct role in the cause of autism. However, a recent study published in the journal Nature has changed that. It seems to provide a direct link between the age of the father and autism in the child.
The authors of the study examined the entire genomes of 78 parent-offspring trios (mother, father, and child) to directly determine what mutations the child received from the father’s sperm cell and what mutations the child received from the mother’s egg cell. Because they were specifically interested in the cause of neurological disorders, they used a large number of trios that contained a child with either autism or schizophrenia. In the end, 44 of the children had autism spectrum disorder, and 21 were schizophrenic. In addition, the genomes of 1,859 other people were sequenced to serve as a population comparison.
The authors focused on the de novo mutations in the children. These are mutations that do not exist in either parent but do exist in the child. Thus, they must arise from a mutation that occurred when the father made his sperm or the mother made her egg. Such mutations happen in every production of egg and sperm cells, and the authors wanted to know which parent (if either) was more responsible for them. The results were surprising, to say the least!
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