Marijuana damages teen brains, top doctors say as they call for the drug to be banned for under-25s

Two top doctors say legal marijuana should be banned for Americans under 25 years old because the drug hampers the developing brain. 

Cannabis is legal medically in over half of the US, and recreationally in 10 states and Canada – with other states expected to follow in the coming years, including New York and New Jersey.  

We still know very little about what the drug does to humans because it has been illegal, making it difficult for scientists to get access to study it. 

But Dr Kenneth L Davis, CEO of Mount Sinai Health System, and Dr Mary Jeanne Kreek, head of the Laboratory of the Biology of Addictive Diseases at Rockefeller University, warn that the few studies we do have all suggest weed deals a heavy blow to teen brains. 

Writing in an op-ed for the New York Times, Drs Davis and Kreek call on lawmakers to focus their attention on imposing an age limit to protect young people, before considering how to tax the incredibly lucrative product, or how to ‘breathalyze’ high drivers (which is nowhere near as simple as with booze).  

Dr Kenneth L Davis, CEO of Mount Sinai Health System, and Dr Mary Jeanne Kreek, of Rockefeller University, warn the studies we do have all show weed deals a blow to teen brains

‘It’s tempting to think marijuana is a harmless substance that poses no threat to teens and young adults. The medical facts, however, reveal a different reality,’ they write.  

In 2010, marijuana was barely legal, marginally available via prescription in 17 states.

But in the last eight years, that has changed: legalization has swept North America, partly in response to the opioid epidemic, amid soaring demand for alternatives to addictive painkillers. 

Now, it is legal in recreationally in 10 states, and medically in 33. In Canada, where marijuana was legalized recreationally in October 2018, anyone over 18 can consume weed. In most states, the age limit is 21, as would be the case for New York and New Jersey.  

To get here, the drug has been successfully marketed as a ‘natural’ medicine, with claims it can work as a numbing agent, anxiety treatment, or sleep aid. 

Now, more than two-thirds of Americans support legalizing recreational marijuana, and data show teens are increasingly trying weed before they try alcohol. 

But Drs Davis and Kreek warn ‘natural’ does not mean ‘harmless’, particularly for the youngest users. 

They cite eight peer-reviewed studies suggesting that 25 would be a better cut-off limit.  

‘Researchers who tracked subjects from childhood through age 38 found a consequential I.Q. decline over the 25-year period among adolescents who consistently used marijuana every week,’ they wrote. 

‘In addition, studies have shown that substantial adolescent exposure to marijuana may be a predictor of opioid use disorders.’  

One of the studies found THC (the psychoactive part of the drug) altered brain connections in teen users, impacting ‘cognition, including learning, attention and emotional responses.’  

‘Simply because society has become more accepting of marijuana use doesn’t make it safe for high school and college students.’

As for benefits of cannabis, evidence supports four:

  1. For those that like to feel high, THC (the psychoactive property in the marijuana plant) does make you feel high.
  2. The National Academy of Medicine says medical marijuana has been shown to ease pain and nausea for patients on chemotherapy – but that more trials are needed before they could properly endorse that.
  3. The National Academy of Medicine says that CBD (the non-psychoactive part of cannabis) has provided relief for some epilepsy patients, but scientists have struggled to replicate those findings widely so they stopped short of a thumbs up.
  4. The drug may offer some relief for the growing number of people with anxiety, the Academy said, but more studies are needed.

Beyond that, there isn’t sufficient research beyond anecdotal evidence, and there is no research to support the myth that cannabis could cure cancer. 

US Surgeon General Jerome Adams has widespread support in his call for more research, not necessarily broader use of the drug.

Drs Kreek and Davis agree, and call for a slow-down to the fast-paced legalization wave

‘Cigarettes and alcohol, both legal, have caused great harm in society as well as to people’s health, and have ruined many lives. Marijuana may do the same,’ they write.