The Effects of Marijuana on Teens
Your kid’s brain on pot: The real effects of marijuana on teens
ADRIANA BARTON
The Globe and Mail | Published Thursday, Oct. 16 2014
As Canadian youth take advantage of easy access to the street drug, despite law-enforcement efforts, pot’s reputation as “nature’s medicine” continues to grow, fuelling the debate over whether to legalize marijuana use.
Politicians are taking sides on the marijuana issue, with the Liberals championing legalization and regulation, the NDP favouring decriminalization and the Conservatives holding the line on enforcement. But do Canadians actually know how the drug affects users? For teens, whose brains are in a crucial stage of development, is there such thing as a harmless pot habit?
LEARNING PROBLEMS, OVERTAXED BRAINS
While cannabis is not the most dangerous of drugs, as with alcohol “it has a lot of harmful effects,” said Dr. Harold Kalant, a professor of pharmacology at the University of Toronto who has conducted research on alcohol and cannabis since 1959.
Marijuana hijacks normal brain functioning in teens, and many scientists believe the drug may have permanent effects on brain development.
Dr. Andra Smith, an associate professor of psychology at the University of Ottawa, used functional magnetic resonance imaging (fMRI) to compare brain activity in youth ages 19 to 21 who did not smoke pot regularly, and those who had smoked at least one joint a week for three years or more.
In a series of published studies, Smith assessed the youth’s decision-making, planning and meeting long-term goals.
Smith found that the earlier in life a young person smoked pot, the more harmful the effects on the brain.
Earlier studies on rats, conducted by Kalant in the 1980s, suggest cognitive deficits linked to cannabis use may be long-term. Even after the equivalent of nine human years without marijuana exposure, young rats given marijuana showed difficulties in learning and memory that persisted into adulthood. But older rats given marijuana did not develop long-lasting impairments, Kalant said, adding that the cannabis receptors in the brains of humans and rodents work “in very similar ways.”
A more recent study, published in April in the Journal of Neuroscience, found structural changes in the brains of 18- to 25-year-olds who smoked pot at least once per week, compared to those of youth with little history of marijuana use.
Using magnetic resonance imaging (MRI), researchers from Northwestern University detected alterations in brain regions involved in emotion and reward processing. The heavier the marijuana use, the greater the changes in both parts of the brain, they found.
“This study really shows that casual marijuana can be harmful to the brains of young people.” the researchers wrote.
A BLOW TO INTELLIGENCE
Adolescents with a heavy marijuana use risk permanent losses in IQ.
The ongoing study has followed 1,037 people born during 1972-73, from birth to their early 40s.
In a 2012 report, researchers from Duke University analyzed data and found that the earlier and more frequently a person smoked pot, the greater the loss of intelligence by age 38. Compared to their IQs measured at age 13, people who had started using cannabis as teens and maintained a daily pot habit into adulthood had, on average, lower IQ. The decline was not small: By age 38, their average IQ was below that of 70 per cent of their peers.
Individuals who began using cannabis heavily as adults did not show similar losses in IQ, but quitting pot did not seem to restore intellectual functioning in those who had been chronic pot users as teenagers, the researchers found.
A HAZY FUTURE?
Teens who smoke pot everyday are 60 per cent less likely to finish high school or get a university degree than their marijuana-free peers, according to a high-profile study published in September in the Lancet.
The researchers, mainly from Australia, looked at outcomes from three long-term studies conducted in Australia and New Zealand. They compared participants’ life status at age 30 to their patterns of marijuana use before age 17.
Compared to people who had rarely used cannabis, those who were daily users before age 17 had an 18-times greater chance of becoming cannabis dependent. They were eight times more likely to use other illicit drugs in adulthood, and seven times more likely to attempt suicide.
“Delay the use of cannabis in young people is likely to have broad health and social benefits,” they concluded.
Dr. Andra Smith summed it up: “I don’t really care if you smoke at age 35,” she said, “but don’t do it when you’re 13 because you’re just setting yourself up for difficulties.”
