Sex offending is written in the genes, an unprecedented study has shown, with the brothers of men convicted of sex crimes five times more likely to commit a rape or assault than the general public.
The controversial finding, published recently in the International Journal of Epidemiology, suggests that some men are born with an increased risk of molesting children or carrying out a violent sexual attack.
Researchers at Oxford University and the Karolinska Institute in Sweden say the fathers and brothers of sex offenders could be offered psychotherapy to teach them relationship skills such as respecting boundaries and curbing aggression as a way of protecting the public.
Around 40 per cent of the risk of committing a sex crime is genetic, the research found, with the remaining 60 per cent down to personal and environmental factors, such as being abused as a child, upbringing, wealth and education.
“We are definitely not saying that we have found a gene for sexual offending’ or anything of the kind,” said Professor Seena Fazel, of Oxford University’s Department of Psychiatry.
“What we have found is high quality evidence from a large population study that genetic factors have a substantial influence on an increased risk of being convicted of sexual offences.
“At the moment genetic factors are typically ignored when it comes to making risk assessments of those at high risk of sexual offending.
“Many of the families we are talking about may already be known to social services for other reasons, and if we can predict those at high risk of offending with greater accuracy then it may be possible to shape these interventions and target education and preventative therapies where they could do the most good.”
The study analysed data from all 21,566 men convicted for sex crimes in Sweden between 1973 and 2009.
Having a brother convicted of a sexual offence raised the risk of a man also being convicted of a sex crime by five times, from 0.5 per cent, to 2.3 per cent. Fathers of convicted sex offenders were also four times more likely to have also carried out a sexual assault.
In February it emerged that Jimmy Savile’s brother Jonny had also molested women at a mental health home.
The researchers found that half-brothers of sex offenders were far less likely to carry out sex attacks than full brothers, even if they had grown up in the same household, suggesting that a shared environment had little impact.
Genetic factors are already recognised as influencing normal sexual behaviour such as arousal, desire and sexual preference. Although it is not clear which genes are responsible for raising the risk, the academics suggest that those linked to increased impulsivity, egotism and decreased intellectual ability could be responsible.
“Importantly, this does not imply that sons or brothers of sex offenders inevitably become offenders too,” said Niklas Langstrom, Professor of Psychiatric Epidemiology at the Karolinska Institute in Sweden.
“But although sex crime convictions are relatively few overall, our study shows that the family risk increase is substantial.
“Preventative treatment for families at risk could possible reduce the number of future victims.”
However the researchers ruled out the possibility of creating a biological test to for sex offenders or screening out the risk in babies born through IVF.
Figures released in January show that 48,934 sexual offences were recorded by police last year, a 19 per cent rise from 2013. The annual Victim Crime Survey suggests around 1.3 per cent of people have been the victim of a sexual crime in Britain, a similar percentage as in Sweden.
The National Organisation for the Treatment of Abusers (NOTA), a charity which looks at ways to prevent sexual offending, said that targeting those at risk of committing sex crimes could prevent attacks.
“The possibility of carefully targeted interventions and support for families in which the relative risks are higher is an exciting prospect,” said a spokesman for NOTA.
Dr Rajan Darjee, a consultant forensic psychiatrist based in Edinburgh, said many sex offenders have underlying psychological problems such as impulsivity, problematic attitudes to children and difficulties relating to others.
“Genes influence brain development and brain functioning underpins psychological functioning, so it should not be surprising to find that genetic factors play a role in sexual offending.
“The fact that genes play such a role does not mean that a person is less responsible for their offending or that offending is inevitable in someone at higher genetic risk, it just emphasises that genes are an important part of a complicated jigsaw.”
Source: The Telegraph