The older a man is when he conceives a child, the more likely that child is to develop autism or schizophrenia, a study released today concluded. The finding lends credence to the theory that the recent surge in autism diagnoses is caused in part by the trend toward having children at an older age, the New York Times reports. It also refutes the conventional wisdom that the key factor was the mother's age; researchers found it actually had no effect at all.
Older parents have children with more genetic mutations, researchers explained. The average child of a 20-year-old dad had 25 random mutations, compared to 65 for the child of a 40-year-old. "It is absolutely stunning that the father's age accounted for all this added risk," says the study's senior author, "and it's stunning that so little is contributed by the age of the mother." Still, researchers say would-be parents shouldn't let the risks deter them; dads 40 and older have only a 2% risk at most. "The vast majority of these mutations have no consequences, (and) there are tons of guys in their 50s who have healthy children," says one. (Read more autism stories.)