Two joints a week can make teens addicts, claims poll

April 7 2003

Teenagers who smoke cannabis more than once a week are at risk of developing an addiction to the drug by the time they hit their early twenties, a study has found.

A survey of 2,000 teenagers by the Centre for Adolescent Health at the Murdoch Children's Research Institute in Melbourne found people who smoked cannabis more than once a week between the ages of 14-17 were 20 times more likely to form a habit as young adults than those who smoked less often.

The centre's director, Professor George Patton, said it was time for the notion that cannabis was a benign, non-addictive drug to be laid to rest.

"In clinical populations we have had, for about ten years, younger people presenting with symptoms of cannabis dependence and that problem appears to be increasing," he said.

Symptoms of dependence and addiction included cravings, preoccupations with obtaining the drug and withdrawal symptoms 12-24 hours after the last use, Prof Patton said.


He said withdrawal symptoms could be characterised by anxiety, irritability, disturbed sleep and appetite or hot and cold sweats.

"There is a psychological and social dimension but beyond that we think these symptoms of withdrawal are indicative of a physical dependence," he said.

The study, published in the latest issue of the British Journal of Psychiatry, tracked the group of teenagers between the ages of 14-17 and interviewed them again at 20-21.

Prof Patton said the study showed almost two thirds of teenagers used cannabis and about seven per cent showed clear signs of dependence.

Risks of future dependence shot up as teenagers moved to weekly or more frequent use.

"Those kids had twenty times the risk of later cannabis dependance compared to kids who hadn't experimented with cannabis during the teens," he said.

Thirty per cent of the teenagers who used cannabis at least once a week had become dependant by the age of 20-21, he said.

Prof Patton said cannabis dependence was more marked in boys and young men than girls and young women.

He said the reason for this was unclear, but it may be that women were more likely than men to experience depression and anxiety as a result of cannabis, which may encourage them to stop using it.

He also said teenagers who drank heavily appeared to be less likely to develop a problem with cannabis.

Prof Patton said more research needed to be channelled into treatment and detoxification strategies for cannabis dependence.

He said there had been an increase in cannabis use in Australia during the 1990s with the result that more young people were using the drug more frequently than ever before.

"We've seen a dominant attitude that this is a soft drug, it doesn't have harms, and I think we need to get the message out that it ain't that simple and that cannabis use, particularly at the more frequent end of things, is associated with very substantial harms," he said.

AAP