Four new studies this week take on the genetics of autism, finding further evidence that older fathers are at increased risk of having an autistic child and suggesting that, overall, the genetic roots of the condition are incredibly complex. Three of the studies, which were published in Nature, looked at new, or de novo, genetic mutations, which are not inherited but occur spontaneously around conception, in autistic children without any affected siblings. The researchers compared these children to each other and in some cases, also to their parents, and found changes in six candidate genes, three of which hadn’t previously been linked to autism. “The basic finding is that new mutations present in sex cells carry substantial risk for autism,” says Dr. Matthew State, a professor of psychiatry at Yale, who led one of the studies. State’s study found that 15% of autism cases in families with no other autistic children were linked to de novo mutations in either the sperm or the egg that joined during conception. The three studies overall confirmed prior research suggesting that older fathers’ sperm is more likely to carry these mutations. In one study, researchers at the University of Washington in Seattle found that the mutations were four times more likely to occur in the fathers than in the mothers — and the risk for men began increasing at age 35. That may be because the older men are, the more times their sperm-creating cells have copied themselves, and each time a cell is copied, there is a chance that a mutation will occur. Previous studies have found that men over 50 have double the risk of having an autistic child, compared with those under 30, and the odds are four times greater for those over 55. (MORE: Researcher Simon Baron-Cohen: Autism’s Lone Wolf) In another of the Nature studies, Harvard researchers found that de novo mutations were slightly higher among autistic people than those in the general population. The findings may help explain the recent rise in autism — a government study last week … Continue reading Autism Studies Confirm Genetic Complexity and Risk for Older Fathers