A new study has found that older men are more likely to have a child who suffers from autism or schizophrenia. Scientists say that the increasing average age of fathers is responsible for up to 30 percent of autism cases. But the new study found that the overall risk to a man over age 40 is about 2 percent, so scientists say this is no reason for older men to stop having children. The findings have long been suspected, but this is the first time the risk has been quantified. The study was carried out by Icelandic firm deCODE Genetics.