Heavy Marijuana Use Linked to Brain Damage in Teens

The marijuana debate has quite literally gone – to pot.?Pro-legalization forces have managed to convince about half the states in the country to pass laws?decriminalizing if not outright legalizing marijuana smoking.?Marijuana is safe to use recreationally and too many people are serving ridiculously long criminal sentences for using it, advocates say. If adults can use alcohol and tobacco, they should be free to use marijuana, too.?

It’s my body -- and I’ll puff if I want to.???

But heavy pot use may not be safe after all – especially not for our youth, especially our youngest teens. Missing in much of the current debate is more careful science about the effects of heavy marijuana use on different age groups. Young developing brains are especially vulnerable to disruption from exposure to many of the chemicals found in marijuana, especially THC, the psychoactive ingredient that gets users "high." That concern has only heightened as the lethality of pot -- and the proportion of THC contained in a single marijuana leaf - has skyrocketed in recent years.

The “new” marijuana

Many of today’s older pot smokers remember fondly the cheap, relatively mild marijuana they consumed recreationally in the 1960s and 1970s. Typically sourced in nearby Mexico, back then, a “dime bag” of marijuana was cheap, maybe just $10. It was often filled with plant stems and seeds and usually required more than a single hand-rolled “joint” or two to give the user a modest "high." In small amounts, the mind-altering effects were pleasant, but hardly debilitating. One could work, play and function quite "normally."

Pot in 2025 – often sourced in Colombia, Hawaii, South Asia and other exotic locales – is potentially far more mind-bending. As recently as the 1980s, marijuana sold on the streets contained no more than 4% of THC. That’s one reason it took so much of it to “get off.” By contrast, tests performed in Colorado in 2015 where marijuana has been legalized, found rates as high as 20% and even 30%.? A more common estimate used by public health specialists is 15%, about four times the level recorded four decades ago. But other tests have confirmed THC levels as high as 75%, nearly 20 times the potency of bygone years.

Pot and youth brain development?

Public health officials warn that developing young adult brains are highly susceptible to damage from exposure to such high levels of THC. But there is little agreement on how permanent that damage might be, especially if use is moderate or light and if the user refrains from pot for significant periods. It could be that temporary cessation allows the vulnerable brain to “naturally” heal and recuperate from heavy pot use. The issue is still in dispute.

What does the current science tell us?

In a number of studies dating to 2008, frequent marijuana use by teenagers is associated with changes in parts of the brain that are involved with attention, memory, decision-making and motivation. For example, in 2019, Jodi Gilman director of neuroscience at the Massachusetts General Hospital Center for Addiction found that the specific age at which teenagers began using marijuana could determine whether pot use affected their memory. In her study, those who began smoking pot at age 17 to 18 years old did not appear to suffer any significant memory deficits but those in the 14–15-year-old cohort did – and in fact, their memory loss was quite substantial. Whether you were a beginning user in your early teens or late teens – at different stages of early brain development – really mattered, her study found.

And it’s not just memory.?The powerful THC that makes its way to the brain can interrupt “normal” brain development, shrinking the prefrontal cortex and disrupting neurotransmitters.?Teens using pot heavily may encounter difficulty thinking and problem-solving, maintaining attention and deeper concentration, and reduced coordination. School attendance will suffer and the effects on learning and academic performance can be severe.

Another growing danger to teens is “synthetic” marijuana, often sold under cute names like “Scooby” or “Black Mamba.” It’s not really marijuana. It may be a leafy substance that’s sprayed with synthetic chemicals, including dangerous hallucinogens. Liquids laced with dangerous synthetic chemicals can also be sold separately to youth as convenience outlets, gas stations and drug paraphernalia stores. Kids that vape are starting to put Scooby and other legal but toxic substances in their vaping pens, along with marijuana, and some are landing in the ER, suffering from severe bleeding, vomiting and nausea.

Much of the recent evidence on synthetic marijuana use is anecdotal.?However, available research is already pointing to major warning signs. A 2020 study in Wisconsin found that “chronic” synthetic pot use was damaging not just memory and executive functioning but also leading to heightened depression, anxiety and even symptoms of schizophrenia.

Finally, while pot use may not be physically addictive in the same way that alcohol and illicit drugs are, there is widespread acceptance of the idea that marijuana use can lead to a psychological dependency that makes voluntary cessation extremely difficult for the chronic user, especially youth.

While most marijuana users may not develop a deep dependence, some do – about 10% overall, but 17% for those who start using in their teens, according to federal statistics (NIDA, 2016). Moreover, just because the dependency and withdrawal symptoms do not appear as severe as they might in the case of heroin, for example, some form of physical addiction -- requiring a debilitating "withdrawal" period -- may still be present, many researchers now believe.?

According to the DSM-5, which categorizes mental illnesses, extreme dependence on marijuana is now classified as “cannabis abuse disorder.” As with alcohol addiction, there is a recognized checklist of behaviors that indicate whether a marijuana user might be addicted. Experiencing just two or more of the identified symptoms within a 12-month period is considered a sign that the pot user is suffering from “cannabis use disorder.”

Is teen pot use rising?

Despite the growing evidence that chronic marijuana use by teens is indeed damaging, anti-pot prevention campaigns are not having much effect -- not yet at least.?In fact, actual pot use by youngsters is still rising annually.??

A massive study conducted by the Oregon Health and Science University in 2022, and published in the journal Clinical Toxicology, examined various forms of drug use by youth between 2000 and 2020. The research team found that teen pot use had skyrocketed by a rate of 240% over this period. The youth group most susceptible? 10-14 year olds, a cohort especially vulnerable to the brain altering effects of chronic pot use.?

Current prevalence rates for pot use point to its widespread adoption. In?2022. 30.7% of 12th graders reported using cannabis in the past year, and 6.3% reported using cannabis daily in the past 30 days, according to the CDC. Of the 52.5 million marijuana users under 25, 10.5% are in the highly vulnerable 14-17 year-old old cohort.

It’s worth noting that the past 20-year increase in teen pot use has not been accompanied by increases in either alcohol or tobacco use. In fact, the prevalence rates for both substances have declined sharply.?The idea that various forms of drug use are co-occurring – or that one is a “gateway” drug – is not unequivocally supported by the research evidence.

However, some studies do find evidence that early cannabis users who were first exposed to tobacco and alcohol are also more likely to experiment with harder illicit drugs, including cocaine, heroin and methamphetamines. Moreover, consuming alcohol while smoking weed has been shown to increase dramatically the effects of THC on the user’s “high,” making chronic pot use especially debilitating to developing brain.?

The adult bias?

Why do 6 in 10 Americans support marijuana legalization??Mainly because pro-legalization advocates have done a good job of conflating the promising medicinal aspects of medical" marijuana -- which doesn't contain THC -- with its recreational use, ignoring the age-based vulnerabilities of chronic pot use by youth.??

In theory, legalization of pot is only for adults, but the legalization movement has created an unusually permissive social climate around pot use by all age groups. Pot is much easier to find and acquire and the increase in other pot consumption methods, including cooking, eating (so-called "edibles") and vaping has made pot consumption among youth more widespread than ever.

Pro-marijuana groups welcome the spread of pot use to the youngest age groups as a means of inculcating in future generations the joys of marijuana. If anything, the idea of crackdowns on youth pot use – or even new public health advisories – are perceived as a threat to their movement’s forward march. Anti-pot youth health prevention campaigns are branded and even ridiculed as a form of reactionary “hysteria” that threatens individual freedom.

In 2020, the U.S. Surgeon General issued a national advisory warning of the dangers of marijuana use to pregnant mothers and youth. It was a long overdue recognition that despite changing social mores about marijuana use generally, the health effects of rampant recreational pot use are still a potential threat to our youth and children.

But the campaign to limit pot use will continue to face an uphill battle. Teens don’t vote, but adults do, and politicians in both parties are becoming increasingly susceptible to supporting marijuana legalization bills on behalf of recreational users, many of them wealthy campaign donors well into their 60s and 70s.

Furthermore, legalized pot is now big business, with annual revenues nearing $10 billion. It’s becoming an enormous revenue-generating opportunity not just for entrepreneurs but for fiscally strapped governments looking to tax and profit from a burgeoning consumer market.?

Even if our nation’s youngsters will continue to pay a heavy price.