New research has found a connection between cannabis use during adolescence and decreased chances of completing higher education in adulthood. The research, drawing on over two decades of data, suggests that those who used cannabis during their teenage years are less likely to attain college and graduate degrees compared to their peers who abstained. The findings have been published in Economics & Human Biology.
“The recent wave of marijuana legalizations may result in a greater use by adolescents. Yet, we do not know much about the causal effect of adolescent marijuana use on future degree attainment. This study contributes to estimating this effect using a nationally representative dataset from the United States,” said study author Aliaksandr Amialchuk, a professor at the University of Toledo.
The researchers analyzed data from the National Longitudinal Study of Adolescent to Adult Health (Add Health), a survey that followed approximately 90,000 respondents from their school days in the mid-90s into adulthood. The final analysis focused on a subset of these participants, those who were re-interviewed as adults between 2016 and 2018, when they were aged 33 to 43, resulting in a final sample size of 8,953 individuals after excluding those with missing data on key variables of interest.
The researchers employed a rigorous methodological framework to examine the relationship between adolescent cannabis use and later educational outcomes. This included using statistical models that account for various individual and family characteristics that might influence both drug use and education, as well as an innovative instrumental variable technique to tackle potential biases in their analysis.
The results showed that teenagers who used cannabis had a notably higher chance of continuing its use into adulthood. Moreover, these adolescent users were approximately 10 percentage points less likely to attain a college degree and 3 percentage points less likely to achieve a graduate degree compared to their peers who did not use cannabis during their teenage years.
An interesting feature of the study’s methodology was the use of an instrumental variable approach, a statistical technique used to estimate causal relationships when controlled experiments are not feasible.
Imagine you’re trying to understand if eating candy directly leads to cavities, but you know kids who eat candy often also tend to skip brushing their teeth. To truly figure out if candy is the culprit, you need to find a way to isolate candy’s effect from the habit of not brushing.
This is similar to what the researchers faced in their study on adolescent cannabis use and educational outcomes. They needed to ensure that the link they observed between cannabis use and lower educational achievement wasn’t muddled by other factors that could influence both, like a student’s family background or personal characteristics.
To tackle this challenge, the researchers examined the cannabis use status of “friends once removed” (friends of the respondent’s friends who are not directly connected to the respondent).
They first looked at whether these friends once removed were using cannabis and if that made the teenagers in the study more likely to use it too, while controlling for other variables. This stage essentially isolated the part of an individual’s cannabis use that can be explained by the social influence of their wider peer network, independent of their own characteristics or other influences that might also affect their educational outcomes.
Then, the researchers used this information to see if teenagers’ cannabis use influenced their education, like finishing college. Since this cannabis use is now only connected to the influence from friends once removed (and not directly tied to the teenagers’ other traits or their environment), it gives a clearer picture of cannabis’s effect on education.
Through this methodology, the researchers found that the negative impact of adolescent cannabis use on educational attainment could be significantly greater than previously estimated. The instrumental variable model suggested that the likelihood of completing college could decrease by as much as 44 percentage points for adolescent cannabis users, with a 13 percentage points decrease in the likelihood of obtaining a graduate degree.
“These results suggest that initiating marijuana use in adolescence is much more detrimental to these academic outcomes than what is suggested by the unadjusted differences between the users and non-users,” the researchers wrote.
The researchers also explored various adjustments to their analysis, such as the intensity of cannabis use and the age of first use, finding that their primary conclusions remained consistent across these different models. This consistency further strengthens the argument that early cannabis use has a pervasive and detrimental effect on educational outcomes.
Despite the compelling evidence presented, the researchers acknowledge certain limitations to their study. The instrumental variable technique, while innovative, relies on assumptions that may not hold in every context, and the study’s focus on adolescent cannabis use does not account for those who may start using the drug later in life. Furthermore, the mechanisms through which cannabis use affects educational outcomes—whether through cognitive impairment, motivational changes, or social dynamics—are not directly addressed in this research, presenting avenues for future investigation.
Nevertheless, the findings suggest the need for targeted interventions to prevent cannabis use among teenagers and highlights the importance of conveying the potential risks associated with early drug use.
“This research suggests that age restrictions on the purchase of marijuana products make a lot of sense and should not be lifted,” Amialchuk said. “Also, because this is a school-based study, it informs school-based policies that target prevention.”
The study, “The effect of marijuana use in adolescence on college and graduate degree attainment,” was authored by Aliaksandr A. Amialchuk and Brooke M. Buckingham.
