Researchers have produced strong evidence that older fathers are more likely to have children who develop schizophrenia.
Having an older father may be a risk
The finding adds weight to the theory that accumulating mutations in the sperm are to blame.
Sweden's Karolinska Institute and Bristol University estimate older fathers could account for 710 cases in England and Wales in 2002.
The study is published in the online edition of the British Medical Journal.
The researchers analysed the medical records of over 700,000 people born between 1973 and 1980.
They found that, even after taking into consideration other factors, people born to older fathers were at increased risk of developing schizophrenia.
They calculated that overall 15.5% of cases of schizophrenia seen in the group may have been due to the patient having a father who was aged over 30 years at their birth.
The association seemed to be relatively specific to schizophrenia compared with other related forms of psychosis.
It was also stronger in those with no family history of the disorder.
The researchers argue that the key is the accumulation of mutations in older fathers' sperm.
It is known that spontaneous genetic errors are more likely to occur in sperm and egg cells produced by older people - a phenomenon known as age-related aneuploidy.
In England and Wales the average paternal age has increased from 29.2 years in 1980 to 32.1 in 2002.
Based on their data, the authors estimate that this increase could have led to an additional 710 cases of schizophrenia in 2002 over and above the 5,923 cases due to the background incidence rate.
Paul Corry, of the schizophrenia charity Rethink, said: "Anyone looking for a single 'Big Bang' theory for the development of schizophrenia is likely to be disappointed.
"Schizophrenia remains poorly understood, but is almost certainly an umbrella term covering a range of conditions with a number of common symptoms.
"Blaming older fathers for their children's mental health helps no-one.
"What this research underlines is that schizophrenia is a very complex condition involving an interaction of various genes and environmental factors in ways that have not yet been defined."
There are around 250,000 people living with schizophrenia in Britain today.