Teen pot use can lower IQ: study

Teens who start smoking marijuana early and do so frequently risk lowering their IQ scores, according to research from the Canadian Centre on Substance Abuse, which found evidence that early and frequent cannabis use can alter the structure of the developing brain.

The research, part of a larger study due out in June, is to be released Monday — on April 20 — a day that has become a counterculture holiday to celebrate marijuana, as part of a bid to raise awareness about the negative effects of marijuana use among adolescents.

In past years, thousands of people, the majority teenagers and young adults, have flocked to Parliament Hill on April 20 to smoke marijuana. Similar rallies take place around the world.

While use of marijuana among Canadian teens and adults has decreased in recent years, it remains the most commonly used illegal drug among Canadian youth — at about three times the rate of adults. And Canadian youth are the top users of cannabis in the developed world, according to a 2013 UNICEF report.

The growing body of evidence about the effects of cannabis use during adolescence is reason for concern, said Amy Porath-Waller, the CCSA’s lead researcher on the issue.

“I think we should be very concerned. Canada’s ... young people have the highest rate of cannabis use compared to other developed countries. There is a need to take a pause and consider that this is the future of our country. We certainly want to prepare our youth so that they can be productive members of society in terms of employment so there certainly is reason that Canada needs to be concerned about cannabis use among young people.”

Equally concerning, she said, is the perception among many Canadian youth that cannabis is benign and has no effect on their ability to drive or their performance in school.

Canadian teens might be the biggest users of marijuana in the developed world, but they use alcohol at a far greater rate, including binge drinking.

There is growing evidence about the effects of cannabis on teen brains, but more research needs to be done, according to Porath-Waller. The CCSA report The Effects of Cannabis Use during Adolescence, to be released in June, will gather some of that evidence.

A key factor in the impact of cannabis is its potency, which, according to Porath-Waller, has almost quadrupled in the past 25 years.