Father’s Age Is Linked to Risk of Autism and Schizophrenia

Older men are more likely than young ones to father a child who develops autism or schizophrenia, because of random mutations that become more numerous with advancing paternal age, scientists reported on Wednesday, in the first study to quantify the effect as it builds each year. The age of mothers had no bearing on the risk for these disorders, the study found.
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The overall risk to a man in his 40s or older is in the range of 2 percent, at most, and there are other contributing biological factors that are entirely unknown.
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The research team found that the average child born to a 20-year-old father had 25 random mutations that could be traced to paternal genetic material. The number increased steadily by two mutations a year, reaching 65 mutations for offspring of 40-year-old men.

The average number of mutations coming from the mother’s side was 15, no matter her age, the study found.

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Dr. Stefansson said it made sense that de novo mutations would play a significant role in brain disorders. At least 50 percent of active genes play a role in neural development, so that random glitches are more likely to affect the brain than other organs, which have less exposure.

In the end, these kinds of mutations may account for 20 to 30 percent of cases of autism, and perhaps schizophrenia, some experts said. The remainder is probably a result of inherited genetic predisposition and environmental factors that are the subjects of numerous studies.

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