Children whose fathers are “highly intelligent” are more at risk of autism than those whose fathers are of “average intelligence”, a new study has revealed.

The research, published by the Karolinska Institute in Stockholm, found that the risk increases by almost a third (31 per cent).

“High intelligence” was categorised by a father having an IQ of 111 or more, while the “average” father scored around 100.

The work supports observations that date back as far as the 1940s, and more recently in 2012, where a highly-educated region in the Netherlands also saw a higher frequency of autism.

The Stockholm research, which looked at around 310,000 children, also found a greater risk (around 65 per cent higher) of ADHD in children whose fathers had below-average intelligence (categorised by an IQ score of 75 or lower).

However, the researchers warned that one half of the genetic puzzle was missing – the mothers’ intelligence.

As the IQ data was sourced from the Swedish military database, not all mothers’ IQ could be observed.