Our study suggests that a man's progeny are going to be healthiest if he has his children during his early 20s. But we know that many men aren't ready for marriage and parenthood at that age. A man may want to wait until he is mature enough and economically stable enough to have children, even though there are health risks involved in having children at an older age. A man has a biological clock, too. And for fathers over the age of 50, two out of three cases of schizophrenia among their children could be attributed to the effects of paternal age.
Schizophrenia is a devastating brain disorder and the most disabling of severe mental illnesses.
About the same percentage are affected in countries around the world, which is one of the puzzles of the disease. If caused by environmental factors, then presumably the disease would only arise in certain parts of the world. No one knows what causes schizophrenia, but it is suspected that many genes contribute to it. The researchers believe that the new study can explain why the incidence of schizophrenia remains fairly constant in all populations over time. They suggest that new mutations are introduced at a constant rate in the disease genes.