Cannabis ‘linked to aggression’

Smoking cannabis is strongly associated with delinquent and aggressive behaviour in young teenagers, a major study has found.

Researchers in the Netherlands revealed the link after surveying more than 5,500 adolescents aged 12 to 16.

The results showed that “externalising” problem behaviour, such as criminality and aggression, increased with higher use of cannabis. No similar association was found with “internalising” problems of withdrawal and depression.

The scientists, led by Ms Karin Monshouwer, from the Trimbos Institute in Utrecht, accounted for confounding influences including social background, regular smoking and alcohol consumption.

They wrote in the British Journal of Psychiatry: “This study shows that at young ages the use of cannabis is already strongly associated with delinquent and aggressive behaviour, even after controlling for strong confounders such as alcohol use and smoking.

“The strength of the associations increased with higher frequency of use, and significant associations were only present among those who had used cannabis recently.”

Cannabis users who had not taken the drug in the preceding year did not show any more signs of delinquency than teenagers who had never smoked a joint. “Heavy” cannabis use was also associated with thought and attention problems.

Marjorie Wallace, chief executive of the mental health charity Sane, said: “In the past, it has been claimed that cannabis is of less concern than it might be because it can make people withdrawn rather than aggressive.

“Some recent studies, however, have been linking aggressive behaviour with heavy use of cannabis, particularly among young people.

“Aggression can worsen the symptoms and outcomes of those who may be developing mental illness.”
Source: 6.2.06

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