Addiction Policy Forum Blog

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Now What? THC Exposure and the Adolescent Brain

By Mark Gold, MD on August 29, 2019

As more states move to decriminalize or legalize marijuana and THC-related products, researching potential harms associated with cannabis use is an even more important field of study. In certain cases, such as marijuana-related medications, there is sound evidence. Usually, the manufacturer of a drug has to do clinical trials, called FDA trials, to demonstrate dose, safety, and efficacy for a particular problem or illness. The FDA did approve the first drug comprised of an active ingredient derived from marijuana to treat rare, severe forms of epilepsy. This was a well-conceived and logical trial and process. It resulted in the approval of Epidiolex (cannabidiol, or CBD) oral solution for the treatment of seizures associated with two rare and severe forms of epilepsy, Lennox-Gastaut syndrome and Dravet syndrome, in patients two years of age and older. This was the first FDA-approved drug that contains a purified drug substance derived from marijuana. It was also the first FDA approval of a drug for the treatment of patients with Dravet syndrome. Notably, however, the FDA did not approve a crude plant or marijuana, but CBD. CBD does not cause intoxication or euphoria, the “high” that comes from marijuana’s tetrahydrocannabinol (THC). In this case, we know that the medication is safe, we know its formulation and composition, and we know the dose. We also know that before this treatment, there were no good alternatives.

According to pediatricians and research scientists, there’s no scientific evidence supporting the acceptability of adolescent marijuana use, and products sold in dispensaries pose considerable risks to children and teens.1 The situation with cannabis, vaping THC, and other preparations is considerably different from that of an FDA-approved medication. In these cases, sadly, we are doing the research after the fact. We know that laws are meant to prevent children from using and smoking marijuana, but the public appears confused about safety warnings when children and adolescents seem like they are safely given cannabis for seizures. Recent data shows that use is increasing among young people. A SAMHSA report found that marijuana is teens’ most widely used illicit drug.2 Frequent marijuana use, in both youth (aged 12-17 years) and young adults, appears to be associated with risk for opioid use, heavy alcohol use, and major depressive episodes. Youth have access to the legal cannabis and related product markets, as well as the thriving illicit marketplace for drugs. Health problems linked to vaping may be in the headlines, as many of those with reported lung damage have vaped THC, but it is not the only problem facing teen users.3 

What does the latest research tell us about the effects of cannabis on the adolescent brain, and do we know enough to make recommendations? 

Science has not shown that cannabis is performance-enhancing like amphetamines, psychostimulants, or medications like methylphenidate given to people with learning problems. Research has clearly shown that adult cannabis use can affect a person’s memory, performance and ability to learn. Recently, Gorey et. al. conducted a systematic review of 21 human and animal studies to investigate whether age influenced the effects of cannabis on the brain, and found preliminary evidence that suggested it does. Further understanding the differences between how cannabis affects the adult brain versus the adolescent one could help us create better messaging and education for youth about how cannabis could affect them.  

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