States that legalized marijuana now researching mental health risks of high-potency cannabis

Products like wax and shatter can have THC levels up to 90 percent, and states like Washington and Colorado are looking at potency caps and product warnings.

With national cannabis legalization poised to be introduced in the Senate, states that legalized recreational marijuana 10 years ago are now studying the public health implications of a variety of new high-potency products amid questions about a possible link to psychosis.

The newer products are called marijuana concentrates and are commonly known as wax and shatter. They can have levels of THC, the psychoactive component of marijuana, as high as 85 percent to 90 percent. By comparison, researchers say, the marijuana level in a typical joint 20 years ago was closer to 5 percent. States like Washington and Colorado are now considering product warnings or potency caps to limit access.

At a January forum, the director of the National Institute on Drug Abuse, Dr. Nora Volkow, raised concerns that teens are increasingly vaping high-potency cannabis.

Volkow said she worries that “huge concentrations” of THC could have serious consequences.

“We are seeing a very significant rise in psychosis associated with the consumption of marijuana,” she said.

“And the higher the content of THC, the higher the likelihood of a psychotic episode.”

She said it remains an ongoing research question whether or not such psychotic episodes can lead to permanent schizophrenia.

In a statement to NBC News, Bethany Moore, a spokesperson for the National Cannabis Industry Association, said, “The best way to address these concerns is through proper testing and labeling, as well as ensuring cannabis products are only sold to fully-informed adults through licensed facilities that are required by law to verify legal age for purchase.”

Moore said public safety measures can be imposed effectively only when underground markets are replaced with regulated markets.

But some public health experts have complained that industry backers of legalizing marijuana focus on the cannabis plant and fail to mention that legalization will be accompanied by a flood of cannabis concentrates.

“We were not aware when we were voting [in 2012] that we were voting on anything but the plant,” said Dr. Beatriz Carlini, a research scientist at the University of Washington’s Addictions, Drug & Alcohol Institute. She has led the effort in Washington state to research high-potency pot and is now exploring policy options to limit access. Her team concluded in 2020 that “high-potency cannabis can have lifelong mental health consequences.”

Carlini said there’s widespread understanding that the cannabis plant “is not that scary and it has some benefits, but this [concentrated] product is just a totally different animal.”

She likened it to the marketing of strawberry icing. “Strawberries are healthy, but a Pop-Tart with strawberry icing is not.” 

The new high-THC products aren’t legal for those under 21 in states with recreational marijuana, but teenagers say they’re easily accessible.

Jasmin Block, 19, of Denver, told NBC News’ Steve Patterson that high-potency cannabis products were so easy to get that she was first offered a “wax pen” between classes in her school bathroom. She said she was unable to grasp “how much was too much” and came away “too high.” She said the high-potency products were a gateway to stronger drugs.

Her mother, Sydney Block, said that she had her own struggles with addiction and that when she saw her daughter high from marijuana concentrates and slurring her words she was in disbelief, thinking, “There’s no way that this is just weed.”

Will Brown, 18, also of Colorado, said he started out smoking regular weed and soon moved on to high-potency marijuana and “crazy dabs” that left him lying on his bedroom floor unable to talk. He said he didn’t realize it was a problem until two years into his usage.

“My life was falling apart around me,” he told Patterson.

His mother, Janet Corneil, said she began to suspect something was going on with her son because he stopped showing up for sports practice.

“And I was like, ‘What is wrong with you?’ you know? Because I didn’t smell it, you know? I couldn’t smell it on him. And he was acting erratic. And I had no idea what was going on.”

Both teens, who are now sober, found support at a Denver public high school called 5280 dedicated to helping kids in recovery.  

Melissa Mouton, the school’s founder, said, “There is a perception among teens that marijuana is safe, and what we’re finding out now is that actually there are a lot of harmful impacts that marijuana has on the teenage brain — because it’s still developing and growing.”

State legislative efforts

National cannabis legalization has already passed the House. Senate Majority Leader Chuck Schumer, D-N.Y., promised cannabis lobbyists on April 22 that he would introduce a Senate version by August. He’s facing some resistance from Republicans. 

But in Colorado after emergency room doctors testified last year that they were seeing increasing cases of psychosis connected to marijuana concentrates, a bill that curbed access to high-potency products passed the Legislature unanimously.

One of the legislation’s components directed the University of Colorado’s medical school to do a comprehensive review of more than 800 scientific articles on the physical and mental health impacts of high-potency THC. The report is due in July.

The review team met this week. Dr. Jon Samet, the dean of the Colorado School of Public Health, is overseeing the effort. He said the studies aren’t uniform in their methods or results and that it will be challenging to characterize the “messy data,” but he said he anticipates creating a public database of research that will be kept up to date.

In Washington state, researchers are further along, having completed a six-month review in 2020 led by 11 scientists who concluded that THC has a “dose response.” That means the more THC consumed, the worse the negative effects. The work began after concentrate sales soared, rising from 9 percent of the state's legal cannabis market in 2014 to 35 percent in 2020.

The Washington researchers, led by Carlini, concluded that young people were particularly vulnerable to addiction and negative effects from high-potency marijuana and that “there is an urgent need for policy considerations and deliberations to support public health and well-being.”

Since the work was published in 2020, she said, she has heard from other states that want guidance. “Our mistakes are there for everyone to see, and people are trying to learn from our mistakes.”

Researchers from the two state teams are consulting one another. In Seattle, researchers are exploring ways to reduce access to the products, including a cap on potency or a possible tax based on the potency level, as is already in use in Illinois and New York.

The Washington team is also looking at product warning labels like those used in Canada, which say: “WARNING: Frequent and prolonged use of cannabis containing THC can contribute to mental health problems over time. Daily or near-daily use increases the risk of dependence and may bring on or worsen disorders related to anxiety and depression.” The team’s next report is due at the end of 2022.

State efforts to impose potency caps have been mixed.

Vermont is the only state with legal recreational marijuana that has a potency cap. Other efforts failed in South Dakota and Massachusetts.

The cannabis industry has strongly pushed back against efforts to curtail marijuana concentrates, saying the products are popular with consumers and that there is “scant clinical or epidemiological evidence to suggest significant or widespread risk associated with those products for the vast majority of consumers.”

Carlini said she’s used to the industry’s downplaying the risks. And she said that’s why her team stated its conclusion clearly in its 2020 report — “The greater the potency of cannabis products, the greater the likelihood of adverse health events.” She said, “We really stand by this consensus.”