Scientists say distinct differences in the brain activity of pedophiles have been found using scanning technology.
A Yale University team found activity in parts of pedophiles' brains were lower than in other volunteers when shown adult, erotic material.
The journal Biological Psychiatry said this was the first real-time evidence of differences in thought patterns.
A forensic psychologist from the UK said drug treatments for pedophilia might be possible.
This deficit may predispose individuals who are vulnerable to pedophilia to seek other forms of stimulation
Dr John Krystal, Editor, Biological Psychiatry
There is increasing evidence that problems in certain areas of the brain may contribute to feelings of sexual attraction towards children.
In a few cases, patients with a brain tumor in a particular part of the brain have developed such feelings, only for them to go away when the tumor was removed.
The Yale study used functional Magnetic Resonance Imaging (fMRI), a technique which allows the activity within the brain to be recorded as the patient is thinking.
They found that when known patients with pedophilia feelings were asked to look at adult pornography, a part of the brain called the hypothalamus, which is known to be involved in arousal and hormone release, was less active than in other volunteers.
More generally, the more extreme the pedophilia behavior was rated, the lower the activation in a part of the brain called the "frontal cortex".
However, Dr John Krystal, the journal's editor, said he didn't know whether this particular pattern of brain activity could be used to predict someone's risk of pedophilia.
But he said: "The findings provide clues to the complexity of this disorder, and this deficit may predispose individuals who are vulnerable to pedophilia to seek other forms of stimulation."
Lead researcher Dr Georg Northoff added: "Our results may thus be seen as the first step towards establishing a neurobiology of pedophilia which ultimately may contribute to the development of new and effective means of therapies for this debilitating disorder."
In the UK, many experts are looking to the biology of the brain to explain not just pedophilia, but other types of compulsive criminality.
Dr Keith Ashcroft, a forensic psychologist at the Center for Forensic Neuroscience, in Lancashire, said that other evidence pointed to problems in the pre-frontal cortex of the brain being linked to pedophilia thoughts.
He said: "Sexual behavior is very complex, especially as some people are not aroused by visual stimuli, but by touch instead.
"I am campaigning for the use of anti-schizophrenia drugs in pedophilia, as these act on a similar part of the brain and may be useful."
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