Cannabis users ‘three times more likely to be violent’

PEOPLE who regularly smoke cannabis are almost three times more likely to commit a violent offence as those who abstain from the drug, new research has discovered.

Scientists involved in a landmark study of almost 300,000 teenagers and young adults believe that over time, prolonged cannabis use profoundly alters the brain, making the user less able to control their temper.

In addition, the research found addicts may also suffer from withdrawal symptoms, making them irritable and prone to lashing out.

Psychiatrist Professor Robin Murray, a world-leading expert on the neurological impact of the drug, said the link between cannabis use and violence was a ‘neglected area’.

‘This is not a surprise for those of us who follow the scientific literature or see patients who heavily use cannabis,’ he added. ‘However, it may be a surprise to the many who think cannabis is a chill-out, anti-violence drug.’

The team from Montreal University in Canada discovered 26 of 30 studies examining the link between the drug and violence showed a tendency towards higher levels of violence among users.

When they pooled the results – meaning they were looking at a combined group of 296,815 teenagers and adults under 30 – they discovered users were more than twice as likely (2.15 times) to have committed a violent offence as non-users.

Among ‘persistent heavy users’, the risk of violence was 2.81 times higher.

Writing in the American Journal Of Psychiatry, they said: ‘This study suggests that cannabis use appears to be a contributing factor in the perpetration of violence.’

Even when accounting for different life circumstances, which might mean cannabis users were more likely to grow up in violent surroundings, they concluded that ‘the effect remained significant’.

Citing neurological research, the team concluded cannabis use during adolescence ‘may cause deterioration of neural structures associated with inhibition and sensation-seeking’.

They added: ‘Such neural deficits are expected to limit one’s ability to suppress the urge to act out violently and heighten the risk of developing antisocial behaviours in adulthood.’