Older dads linked to rise in mental illness

A genetic study has added to evidence that the increase in some mental disorders may be due to men having children later in life.

An Icelandic company found the number of genetic mutations in children was directly related to the age of their father when they were conceived.

One prominent researcher suggested young men should consider freezing their sperm if they wanted to have a family in later life.

The research is published in Nature.

According to Dr Kari Stefansson, of Decode Genetics, who led the research, the results show it is the age of men, rather than women, that is likely to have an effect on the health of the child.



"Society has been very focused on the age of the mother. But apart from [Down's Syndrome] it seems that disorders such as schizophrenia and autism are influenced by the age of the father and not the mother".

Male driven

Dr Stefansson's team sequenced the DNA of 78 parents and their children.

This revealed a direct correlation between the number of mutations or slight alterations to the DNA, of the child and the age of their father.

The results indicate that a father aged 20 passes, on average, approximately 25 mutations, while a 40-year-old father passes on about 65. The study suggests that for every year a man delays fatherhood, they risk passing two more mutations on to their child.

What this means in terms of the impact on the health of the child is unclear. But it does back studies that also show fathers are responsible for mutations and that these mutations increase with age.

And, for the first time, these results have been quantified and they show that 97% of all mutations passed on to children are from older fathers.

The reason that men rather than women drive the mutation rate is that women are born with all their eggs whereas men produce new sperm throughout their adult life. It is during sperm production that genetic errors creep in, especially as men get older.

The findings should not alarm older fathers. The occurrence of many of these disorders in the population is very low and so the possible doubling in risk by having a child later in life will still be a very low risk.


Dr Stefansson, however, told BBC News that from a long-term perspective the decision by some men to have children later in life might well be speeding up the evolution of our species.

"The high rate of mutations is dangerous for the next generation but is generating diversity from which nature can select and further refine this product we call man," he said.

"So what is bad for the next generation may be good for our species in general."

- BBC.co.uk