Anders Gilliand was only 17 years old when he started to lose touch with reality.
“He thought there were higher beings communicating with him to tell him what to do or who he was,” said his mother, Kristin Gilliand, who lives in Nashville.
Her son, who had used marijuana since he was 14, was diagnosed with schizophrenia, a chronic psychiatric disorder that can include symptoms such as delusions, hallucinations and disorganized speech.
He started taking antipsychotic medications, but eventually stopped because of the side effects he was experiencing. To suppress the voices in his head, he started using heroin and died of an accidental drug overdose in 2019, at the age of 22.
“If he had never started using cannabis, he might still be here,” said Gilliand, a neuroscientist at Vanderbilt University. Although there is a family history of schizophrenia, she believes her son’s marijuana use led to psychotic episodes and caused the condition.
Anders was among a growing number of young adults, especially men, who are at increased risk of developing psychosis from marijuana use. Evidence from separate Danish and British studies, among others, suggests a link between heavy marijuana use and psychiatric disorders such as depression, bipolar disorder and schizophrenia. Researchers believe that high concentrations of THC – the psychoactive component in the cannabis plant that causes the high – may cause these conditions in people at genetic risk. The THC content in marijuana has been increasing for decades.
“We are definitely seeing an increase in cannabis-induced psychosis among teens,” says child psychiatrist Dr. Christian Thurstone, an addiction specialist at the University of Colorado School of Medicine in Denver.
Is higher potency marijuana more dangerous?
The more potent the cannabis products, the more likely users are to experience adverse effects, says Nora Volkow, director of the National Institute on Drug Abuse.
“Those who consume the highest doses are at greatest risk of becoming psychotic,” she said.
There has been limited research on the adverse effects of high THC levels, although a European study published in 2020 found that high-potency cannabis products carried a greater risk of hallucinations and delusions compared to lower-potency types.
“It appears there is a link between cannabis strength and an increased risk of psychosis, but more work needs to be done,” said Ziva Cooper, director of the Center for Cannabis and Cannabinoids at UCLA.
As many as half of people with cannabis-induced psychosis may develop schizophrenia or bipolar disorder, research shows.
Young adults and teens should be especially concerned, Thurstone said
“The studies we have so far clearly indicate that the risk of psychosis is dose-dependent, meaning that the more marijuana someone is exposed to, especially in adolescence, the greater the risk of developing psychosis, schizophrenia and serious mental illness ,” he said.
Another problem with higher strength products is the potential for developing a cannabis use disorder, or an addiction to marijuana. When people are regularly exposed to higher strengths of cannabis, they are more likely to develop a cannabis use disorder, although further research is still needed to make definitive statements.
“There is no longer any scientific debate that marijuana can not only be psychologically addictive or habit-forming, but can also be physically addictive,” Thurstone said. “It is a substance that produces tolerance, so people have to use more and more of it to get the same effect.”
According to the Centers for Disease Control, about 1 in 10 people who start using cannabis become addicted.
How cannabis potency may be linked to psychosis
Marijuana overactivates molecules in our brain known as cannabinoid receptors, which cause the high. When these brain receptors are stimulated, it can cause problems with thinking and problem solving, as well as impaired memory.
How marijuana use can cause psychosis isn’t yet fully understood, although scientists think it disrupts our brain’s ability to distinguish between what’s happening in our heads and what’s happening in the real world.
“Marijuana in the 60s, 70s, 80s and early 90s contained about 2% to 3% THC,” says Thurstone, who has followed the rise of high-potency THC products in smoke shops and pharmacies. “Today, commercialized products are routinely over 20 percent – so about 10 times more powerful.”
Patrick Johnson, assistant store manager at Frost Exotic dispensary in Colorado, has been in the cannabis industry since 2009 and has seen its potency soar firsthand. Johnson said THC levels really took off after marijuana became legal for recreational use in Colorado in 2014.
Since then, 24 states, two territories and Washington DC have legalized marijuana for medical and recreational use.
As more people across the country use pot legally, there’s greater consumer demand for more potent pot, experts say.
“After recreational [legalization] is when I’ve personally seen it go from like 19 or 20% to like 30 or 35%,” Johnson said.
Currently in his store they have varieties from only 14% to 30%. Most customers prefer the strong stuff, Johnson said.
One reason the potency of cannabis products has become stronger over the years is because customers can build up a tolerance to the drug, says Mahmoud ElSohly, a professor of pharmacy and cannabis researcher at the University of Mississippi. He has studied this problem in collaboration with the National Institute of Drug Abuse and found that the average potency increased from 3% to 15% between 1995 and 2021.
“People need more and more powerful products to get the level of high they are looking for,” he said.
In the past, a 2% THC joint might have been enough to get most people high, ElSohly says. With heavier use, many people have now built up a tolerance and may need to smoke multiple 2% THC joints or purchase a single 6% THC joint to get a similar feeling.
Is One Form of Marijuana Safer?
The potency of cannabis mainly refers to the THC content in the marijuana flower or bud, the smokable part of the plant.
While the THC content in the flower can be close to 40%, other products, such as concentrates or oils, can contain amounts as high as 95%.
The problem, says Cooper of UCLA, is that there isn’t yet a universally accepted standard dose like there is with alcohol, so predicting how someone will react to different cannabis products can be difficult.
It is also a challenge to develop a unit dose for inhaled combusted products. While a typical joint may contain between 100 and 200 milligrams of THC, that doesn’t tell the whole story, Cooper said.
How much THC a marijuana smoker is exposed to can vary. How long and how deeply do they inhale? Or how long do they wait between puffs, because a lot of THC is lost between puffs due to “sidestream” smoke coming from the burning end of the joint.
By comparison, edible marijuana products such as gummies, cookies and brownies are typically 5 to 10 milligrams per dose. There is a move toward establishing a unit dose for edibles and limiting the amount of THC that can be consumed at one time. For example, in New York State that number is 10 mg per serving.
How high can the THC go?
“I don’t necessarily think it will do much more,” says Volkow of the National Institute on Drug Abuse. “There may be a level where too much can sometimes become aversive, so that people smoke and become very agitated or paranoid.”
She is optimistic that the THC content of available marijuana flowers will not rise as high as 50%.
There is a limit to the amount of THC the plant can produce, although manufacturers are finding clever ways to boost the chemical, Cooper said.
“The industry is adding more THC to the botanicals,” including infusing pre-rolled cannabis cigarettes with extra THC, she said. “We’re starting to see people being exposed to THC levels that we haven’t seen in the past.
This article was originally published on NBCNews.com