Cannabis use among youth linked to lower income and education, say researchers

Young cannabis users may earn less income than their peers, are less likely to earn university degrees and may have poorer health outcomes, according to research.

These are some of the findings from psychology professors Kara Thompson of St. Francis Xavier University in Antigonish, N.S., and Bonnie Leadbeater of University of Victoria that were published in the Canadian Journal of Behavioral Science and Prevention Science.

Researchers studied a decade of data from the Victoria Healthy Youth Survey, which followed 662 youth ages 12-to-18, observing how cannabis use unfolded over time.

The subjects were interviewed every two years about their substance use, mental health, accomplishments and general well-being.

On average, one in 10 of the young people in the study was identified as a chronic user — a person who used cannabis more than once a week by age 13 and into young adulthood.

Researchers identified several differences between this group and peers who used occasionally, or abstained altogether. 

"These young people were four times less likely to have bachelor degrees," Thompson told CBC's Information Morning. "In their 20s, they were earning $6,500 less in annual salary, they had two times more debt and they also reported much higher symptoms of depression and anxiety in young adulthood, as well as oppositional behaviours and symptoms of ADHD."

Some youth in the chronic group also used alcohol, other substances, came from lower socio-economic backgrounds and had pre-existing mental health conditions. However, Thompson said the study controlled the impact of those factors.

"I think it highlights that cannabis is kind of part of a constellation of risks for some people," she said. "But this risk starts very, very early."

An effective public health approach to reducing youth cannabis use needs to also address these other factors, Thompson said.

She said there exists a limited understanding of the patterns and consequences of cannabis use in youth over time, something this large data set could help explain.

Call for youth-targeted warnings

With legalization of cannabis in Canada expected later this year, Thompson hopes the study will help shape health messages that will lead young people to make more informed decisions.

"We have warnings about hot tubs, we have warnings about cigarettes and opiates, we have warnings about side effects of medicine, like antibiotics. And so we need warnings for marijuana use as well."

Thompson said some of the impacts of chronic cannabis use are well established.

"We know that it can be addictive," she said. "We know that it can aggravate symptoms of anxiety and depression and psychosis.

"We know that you shouldn't mix it with alcohol or use while driving or operating machinery."

Researchers hope the findings will help inform future government and public health cannabis policies.