Cannabis and the Teenage Brain

By Chris Bond
Published: August 14, 2020 | Last updated: April 9, 2021 05:52:02
Key Takeaways

New research suggests cannabis use as a teen does not necessarily affect cognitive abilities short-term, but more information is needed to determine long-term effects. Chris Bond cites the latest studies on how cannabis affects the teenage brain.

Despite widespread legalization of cannabis in the Western world, both medicinal and recreational, the use of cannabis by teenagers remains illegal under almost all instances. There is very good reason for this ban on underage consumption. The brains of these young people are still developing and being hard-wired, so cannabis use at this stage may have lifelong negative effects. The studies are not all entirely conclusive, and there is still a lot of room for debate and further study, but until we know conclusively about the full range of potential side effects of cannabis use and the teenage brain, caution about its usage is likely the prudent course of action.


Cognitive and Developmental Risks of Teenage Cannabis Use

The number of teenagers that likely use cannabis or have used it is hard to pin down. Like any illicit substance, not all users are inclined to admit their use for fear of punishment. Some studies lowball it at less than 25 per cent; others suggest it is more than 50 per cent. Whatever the real incidence may be, it is not an insignificant number of teenagers that use or have used cannabis. Conclusive evidence suggests cannabis use is a health risk during adolescent years.

A 2018 article published by the National Center for Biotechnology Information claims cannabis use by adolescents likely poses a threat to psychosocial adjustment and at its extreme may even prove to be neurotoxic to the developing brain. It can disrupt the brain’s reward system. It has been shown to impair memory in some test subjects and impede other cognitive functions which can cause or exacerbate learning disorders. A common and oft-used technique to determine the cognitive function of individuals is called the Iowa Gambling Task (IGT).


Read also: Treating Alzheimer’s with High-THC Cannabis Strains

The IGT, sometimes referred to as Bechara’s Gambling Task (BGT) is administered in a laboratory or clinical setting and simulates a card game. Researchers can study the decision-making processes of life’s everyday uncertainties. The “game” is comprised of four decks. Some of these decks are full of cards that reward the player and other decks penalize the player. Teenagers that do not use cannabis or have never used cannabis tend to make more reasonable and rational decisions than those who may be displaying a compromised cognition due to excessive cannabis consumption. Those individuals with perceived impairments caused by developmental or cognitive damage typically select cards from “disadvantageous” decks and fail to anticipate the consequences of their selections as compared to those teens that have not used cannabis with any frequency. The IGT is becoming an increasingly useful diagnostic tool to not only assess potential cognitive damage from excessive cannabis or other substance abuse, but it is more often used to ascertain the severity of such conditions as schizophrenia and obsessive-compulsive disorder (OCD).

Like any substance that is smoked and a potential respiratory irritant, cannabis is, of course, a risk to the pulmonary system as well as the cardiovascular system. The same range of physical risks of regular cigarette or tobacco smoking are present for those that consume cannabis regularly by smoking, vaping, or otherwise inhaling.


IQ and Teenage Cannabis Use

In what may be viewed as good news, teenage cannabis use does not seem to have any statistically significant impact on IQ, or so several recent studies suggest. In fact, teenagers that use tobacco on a regular basis and use cannabis infrequently (or never), have a higher chance of sustaining lower IQ according to the British Avon Longitudinal Study of Parents and Children. They further report teenagers that have used cannabis more than 50 times in their lives do not seem to differ in IQ or educational performance from their peers who have used it fewer than 50 times or never. The study goes on to say, “modest cannabis use in teenagers may have less cognitive impact than epidemiological surveys of older cohorts have previously suggested.” It should be noted, however, this study did yield a correlation between those tested who had used cannabis before their teenage years and a lower IQ when tested as a teenager. Cannabis usage among preteens does seem to affect cognitive function and IQ into the teenage years, but more study on this is still required to draw accurate conclusions.

Read also: The Effects of CBD on the Endocannabinoid System


A separate study published in a 2016 article in the Journal of Psychopharmacology came to similar conclusions as the Avon Longitudinal Study. The preliminary results found a correlation between teenage cannabis users and both lower IQs as well as poor educational performance as compared to teenagers that had never used cannabis. What they further discovered was that once other factors such as behavioral problems, childhood depression, maternal use of cannabis during pregnancy, and other substance abuse were factored in with teens who both did and did not use cannabis, that cannabis usage by the age of 15 did not predict either lower IQ scores or poorer school performance. The results of these findings, like many others, show that at least minimal to modest use of cannabis by teenagers does not likely cause the kinds of cognitive impairment previously believed. This is not necessarily all good news though.

The study did not link infrequent to moderate teenage cannabis use to lower IQ in teens, it did, however, find a positive correlation between persistent cannabis use starting during the teenage years and a decline in IQ by middle age. The study does stress that totality of circumstances, especially cigarette smoking among teenagers, needs to be factored into poor cognitive performance by teens and lower IQs as well as the numerous other factors that can contribute to a lower IQ by middle age apart from cannabis use.


The oft repeated notion teens smoking pot are “dumber” than their non-cannabis using peers does not seem to hold up to scrutiny, at least not according to several peer-reviewed studies. No study or studies are, however, infallible. Researchers of the very trials and studies referenced above caution there are limitations to their conclusions. Further investigations on larger groups of teens and young adults that consider a wide range of factors including assessments prior to cannabis usage, during usage, and after ceasing to consume cannabis still need to be undertaken using increasingly objective measures. A wider “net” also needs to be cast to gain a better understanding of potential causal factors ranging beyond behavioral and substance abuse to see the whole picture and drill down what exactly the real risks are.

Adolescence into the teenage years is inarguably a period of continued and critical brain development. Cannabis use at these ages does convey more risks than consumption during adult years. Though it may not be the detriment to their cognitive ability it was once thought to be, there is still credible concern that moderate to heavy cannabis consumption can produce a range of potentially irreversible problems to both mental and physical health. Unless prescribed by a health care professional for an ailment or disease, cannabis use by teenagers and those who have not yet reached the legal age of majority should not be encouraged to consume it.


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Written by Chris Bond | Certified Permaculture Designer, Nursery Technician, Nursery Professional

Profile Picture of Chris Bond

Chris Bond’s research interests are with sustainable agriculture, biological pest control, and alternative growing methods. He is a certified permaculture designer and certified nursery technician in Ohio and a certified nursery professional in New York, where he got his start in growing.


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