Scientists claim genes are to be blamed for violent behavior

Violent thugs aren’t criminalised by society, but may be born that way, researchers claim.

Scientists have identified two genes that may be associated with extremely violent behaviour.

One of them is a variant of cadherin 13 (CDH13), which is involved in neural connectivity, and has been linked to impulse control in extremely violent offenders.

Experts at the Karolinska Institute in Sweden say that the majority of violent crime is committed by a small group of anti-social, repeat offenders and set out to discover why this may be.

Previous studies have linked certain genes to violent crime, including a gene called monoamine oxidase A (MAOA) that contributes to less recycling of the neurotransmitter, dopamine.

Dopamine is a chemical released by nerve cells to send signals to other nerve cells. It plays a major role in reward-motivated behaviour.

Previous studies investigating MAOA’s connection with violence have proved inconclusive.

Professor Jari Tiihonen and colleagues at the Institute analysed the genes of 895 Finnish people found guilty of criminal behaviour, organising them by the crimes they have committed.

These ranged from non-violent offences – such as drug or property crimes – to extremely violent offences, such as homicide and battery.

The researchers found a possible link between violent offences and MAOA, with the strongest association in the extremely violent offending group.
Through additional research, including a genome-wide association study, they identified a gene involved in neural connectivity – a variant of cadherin 13 (CDH13) – that has been linked to impulse control in extremely violent offenders.

‘When compared to the control population, non-violent offenders were not observed to exhibit either variant to a greater degree, indicating that these genetic variants may be specific to extremely violent behaviour,’ Dr Tiihonen said.

The researchers, whose findings were published in the journal Molecular Psychiatry, suggest that the low dopamine recycling, which is associated with the MAOA genotype, may result in higher aggression levels during intoxication, increasing the risk of violent behaviour.