Led by Marie-Pierre Sylvestre, a professor at the School of Public Health at the Université de Montréal, the researchers draw on Quebec data from COMPASS, a pan-Canadian longitudinal study on the health behaviours of secondary-school students.
Published in the journal Addiction, the analysis looks at 1,768 students from 11 Quebec schools who were followed between 2017 and 2019. All were non-users of cannabis at the start of the study.
The researchers examined the extent to which two factors, having friends who use cannabis and perceiving cannabis as easy to obtain, contributed to initiation among those teens.
The results show that the two factors act in synergy: having friends who use cannabis but not perceiving cannabis as accessible does not significantly multiply the risk, the researchers found.
On the other hand, believing that cannabis is easy to obtain, even without friends who use it, already increases the risk in a notable way. It is the combination of both that has the most pronounced effect.
Specifically, these adolescents had a 21.6-percentage-point higher risk of initiating cannabis use than youth who had no friends who used cannabis and perceived access as difficult.
"Adolescents who had friends who used cannabis and who perceived cannabis as easy to obtain had the highest probability of initiating use," said Sylvestre, the study's lead author.
