The Stoned Developing Brain
How does adolescent cannabis use impact development? How does this compare to alcohol use? And where do we go from here?
Adolescence is a crucial developmental period. The endocannabinoid system is involved in the release of various neurotransmitters and the maturation of white matter.
As cannabis acts on this system, drug use can lead to lasting neurobiological changes in brain function and behaviour, which adolescents are particularly vulnerable to. There is quite a robust evidence base suggesting adolescent cannabis use contributes to an increased risk in mood disorders and cognitive deficits. There is also fairly consistent evidence that adolescent cannabis use is associated with poorer educational performance.
However, poorer academic attainment may in fact lead to cannabis use, which is also true for mental illness. As we know, unpicking this link, is very difficult and should not be taken at face-value.
Interestingly, cannabis appears to differentially affect adolescents and adults.
A recent study compared cannabis intoxication effects in adolescent and adult users. Adolescents subjectively felt ‘less stoned’ and experienced fewer psychotomimetic symptoms (i.e. feeling delusional). Adults were more anxious and less alert when intoxicated, experiencing greater cognitive impairments. Though, adolescents had more impaired response inhibition and did not show satiety (i.e. they desired more cannabis).
What do these results tell us? It may improve our understanding of adolescent cannabis use, given how differently intoxication is experienced. Adolescents show resistance to the intoxicating effects of cannabis, yet are vulnerable to a lack of satiety and inhibition. This may translate to addiction and problematic use that is seen in adolescence, compared to adulthood.
With this in mind though, how does cannabis compare to alcohol?
A large study examined adolescent and young adult cannabis use, mental health, smoking and alcohol consumption. Cannabis use was associated with mental disorder at all ages. However, alcohol use and smoking significantly contributed to this. So, it is not just cannabis which impacts mental health but psychoactive substances generally, which I think is important to keep in mind.
Other research supports this. Alcohol is an equally problematic drug which we need to address in adolescence.
It is questionable how responsible cannabis is for cognitive impairments reported in adolescence. A study compared daily cannabis users who drank alcohol with alcohol-intake matched non-using controls. There were no differences between the two groups, suggesting cannabis is not what leads to cognitive impairments.
It is incredibly difficult to determine how repeated cannabis use affects the adolescent brain as alcohol is largely used in conjunction, which is also cognitively impairing. We shouldn’t view cannabis as a sole contributor to cognitive deficits in adolescence.
Also, a lot of the research focuses on heavy cannabis use, so what about occasional use? A 10-year follow-up study examined this. Occasional use still predicts higher risks of later substance dependence and use. This goes to show that no drug use is without harm.
Cannabis often brings about the controversial debate for whether it is a gateway drug, is this true?
Gateway drugs increase the risk of abusing ‘harder’ drugs. Cannabis is thought to be one as it often precedes other illicit drug use.
Repeated cannabis use can lead to a blunted response to dopamine neurons. This reduces responses to natural rewarding and motivational stimuli. Naturally, this contributes to an enhanced vulnerability to harmful drug abuse. However, a lot of the research in this area is conducted on rats, so not the most generalisable to humans.
It’s a mistake to think experimenting with cannabis a few times leads to other illicit drug use. Cannabis itself is not a predictor of other drug use, although the media loves it. Most cannabis users do not use other illicit drugs, making this hypothesis rather selective.
Why is cannabis considered a gateway? As it is supplied by the black market in a lot of places, users have more opportunities to try other illicit drugs, compared to non-users. There’s also a degree of personal propensity to use other drugs. If you are a cannabis user, it’s quite probable that you’ll try other psychoactive substances too, for various reasons. But cannabis itself does not cause this.
The gateway hypothesis highlights a key issue with the illicit market, strengthening the argument for decriminalisation and legalisation. Creating a seperate market for cannabis would be a way of limiting this gateway phenomenon. Legalising and monitoring the cannabis market will take it off the streets making it more difficult for adolescents to access the drug.
The takeaway? The differential intoxicating effects cannabis has on adolescents helps explain later risks of drug use. No drug use goes without harm and adolescence is a time of developmental vulnerability. However, cannabis isn’t solely responsible for this and alcohol contributes significantly. And the solution to the gateway phenomenon — legalisation.
