Teenagers especially need to be made aware that the drug isn't benign.

In two decades of supporting people who have drug and alcohol addictions, I've been astonished how rarely cannabis has come in for criticism. I couldn't count the number of times I've heard the contradictory declaration "I don't use drugs" from a person who is an inveterate cannabis smoker.

It's a widely held perception (certainly among people under 40) that marijuana, spliff, ganja, hooch, wacky tobaccy - call it what you will - is a substance no more deleterious than caffeine. I'm tired of hearing about the drug's beneficial powers, as though it were yoga in a bong.

Perhaps it's marijuana's enduring association with the 1960s peace movement, rock'n'roll and hippie culture that has helped to make it the most popular illicit drug in Australia. Just one more thing to thank the baby boomers for.

Consider this: while only 1.4 per cent of Australians have tried heroin, 33.6 per cent (yes, one-third) of our population admits to having used cannabis.