Egg abnormalities also usually involve larger chromosomal changes, and are therefore easier to test for. The study does not identify what the specific genetic cause of schizophrenia is, but its authors say their results do help to explain why the mental illness remains prevalent. As schizophrenics are less likely to form relationships and have children because of their illness, the researchers say evolution would normally decrease the number with the disease over the course of generations. And because the rate is consistent in different populations, environmental variations, which differ, cannot account for the incidence. Eventually it would seem that the father's sperm is going to turn out to be just as important as the mother's egg.
Schizophrenia is the most common serious mental illness.
A quarter of a million people in Britain have the illness. It affects one person in a hundred at some time in their life, and the rate is the same in every country. Most people are affected when they are in their late teens or early 20s, though it can start at any age. Schizophrenia is a psychotic disorder. Symptoms include hallucinations and delusions.