Paedophiles may owe their sexual urges to faulty connections in the brain, research has suggested.

A study in which the brains of convicted child sex abusers were scanned and compared with criminals who were not sex offenders has revealed striking differences that could point to a neurological origin for paedophilia.

Scientists in Canada used magnetic resonance imaging (MRI) and sophisticated computer analysis of the results to show that the paedophiles had significantly less of a brain tissue called white matter than the other criminals.

As white matter is responsible for holding the different parts of the brain together, the researchers said the results could mean that faulty connections in the wiring of the brain could explain paedophile impulses.

However, James Cantor, of the Canadian Centre for Addiction and Mental Health, in Toronto, who led the study, said that if the finding were confirmed, it would in no way excuse paedophiles who abuse children.

Even if paedophiles’ sexual attraction to children is determined or influenced by underlying brain structure, that did not mean that people who actually attempted to have sex with children were not culpable. “There is nothing in this research that says paedophiles shouldn’t be held criminally responsible for their actions,” he said. “Not being able to choose your sexual interests doesn’t mean you can’t choose what you do.”

Dr Cantor said the study, which is published in the ournal of Psychiatry Research, builds on previous research that he has carried out, demonstrating significant biological differences between paedophiles and people with normal sexual tastes.

Paedophiles, he said, were three times more likely to be left-handed, and also on average 2cm shorter than other people. They tended to have lower IQs and low educational achievements, and they were also more likely to have suffered head injuries as children.

He added that while traditional explanations rooted paedophilia in childhood trauma or abuse, there was little solid evidence for this. He preferred the theory that conditions in the womb lead to the abnormal brain structures that predispose people to paedophilia.

Dr Cantor took MRI scans of the brains of 127 subjects, half of whom had been convicted for paedophile offences. The paedophiles were found to have significantly lower volumes of white matter.

He said that he hoped his research would help to develop treatments for paedophiles to stop them feeling sexually attracted to children.The study authors said that their expectation that paedophiles “would exhibit additional symptoms of poor brain functioning” was borne out by the men with low white matter volumes having lower IQs and poor verbal memory. “The most straightforward explanation of the results is that low white matter volumes increase the risk of developing paedophilia,” the researchers said.

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