- Researchers say cannabis has become more potent over the years as THC concentrations have increased.
- Experts say the stronger varieties of cannabis are raising concerns that it may have higher addiction potential.
- There are also concerns about the health effects, especially on the brain, that cannabis use can have on people under age 18.
“This is not your dad’s cannabis.”
That’s one expert’s response to a new U.K. study that reported that street cannabis across the world has become substantially stronger over the past 50 years.
“Kids need to know and parents need to know,” said Deni Carise, PhD, a clinical psychologist and chief scientific officer of Recovery Centers of America, as well as an adjunct assistant professor at University of Pennsylvania.
“This is not what you smoked in 1970,” Carise said. “This is completely different.”
The research, published in the journal Addiction, doesn’t particularly surprise many experts, but they said it brings up the need for important discussions about the risk of addiction.
“I think what’s unique about this paper is that it’s trying to capture internationally what’s been going on, but we’ve known the potency of cannabis has been going up steadily for quite a long time and for very good reason,” said Margaret Haney, PhD, a professor of neurobiology (in psychiatry) at the Columbia University Irving Medical Center in New York, where she’s the director of the Cannabis Research Laboratory and co-director of the Substance Use Research Center.
“You just get more money for the stronger stuff so there’s an incentive to increase THC,” Haney added.
Carise sees the work as mounting evidence that cannabis is a significant drug.
“The other piece is, depending upon where you get your [cannabis], you will not know how much THC is in it, particularly if you buy it on the street,” she told Healthline.
With four more states voting to legalize recreational cannabis in the November election, Healthline asked experts for their thoughts on the new research, whether cannabis that’s more potent can lead to addiction, and what experts want you to know before you smoke.
For their study, researchers at the University of Bath in England synthesized data from more than 80,000 street samples of cannabis collected in the United States, United Kingdom, Netherlands, France, Denmark, Italy, and New Zealand over the past 50 years.
They studied how concentrations of tetrahydrocannabinol — also known as THC, the psychoactive component of cannabis that gets users high — has changed over time.
They found that THC concentrations increased by 14 percent from 1970 to 2017 in herbal cannabis.
They found significant increases in THC for cannabis resin, with concentrations rising by 24 percent between 1975 and 2017.
Cannabis resin extracted from herbal cannabis is now typically stronger than herbal cannabis, the researchers said. The team found no changes in cannabidiol (CBD) in cannabis.
There’s more information out there to support their findings.
In 2016, a study published in the journal Biological Psychiatry reported that the potency of illicit cannabis had consistently risen from approximately 4 percent in 1995 to about 12 percent in 2014.
Last year, the U.S. Surgeon General released an advisory emphasizing the health risks of cannabis and how it has changed over time.
Haney believes the research highlights a need for mature conversations about the risks and benefits of cannabis use, including that there’s potential for misuse.
“Anybody in the field knows that cannabis’ potency has been increasing over time. Consumers should be aware of the risks and know what their behavior could lead to,” she told Healthline.
“I honestly find that most Americans do not think that cannabis can produce dependence, and so I think that’s the first step, knowing that there’s that potential,” Haney added. “I think getting that message out is really important.”
The researchers in Bath said in a statement that their findings highlight the need for wider strategies to reduce harm, such as methods of measuring intake.
“As the strength of cannabis has risen, consumers are faced with limited information to help them monitor their intake and guide decisions about relative benefits and risks. The introduction of a standard unit system for cannabis — similar to standard alcohol units — could help people to limit their consumption and use it more safely,” said Tom Freeman, PhD, BSc, the lead author of the study and a senior lecturer at the University of Bath.
“The findings support what many of us in the addiction treatment industry have known for years,” said Dr. Mark Calarco, the national medical director for clinical diagnostics for American Addiction Centers.
Calaraco noted that his organization isn’t seeing a spike in people seeking treatment for cannabis use disorder right now, but he sees some danger looming.
“[Cannabis] has become more potent because people are developing cannabis plants that represent nothing that has ever existed in nature,” he told Healthline. “They are not only manipulating THC levels but also other psychoactives. These semi-synthetic variations can bind longer to certain cannabinoid receptors in the brain and cause a higher dopamine spike followed by a greater crash.”
Haney explained that cannabis can change areas of the brain associated with reward and reinforcement.
“Things associated with that drug can take on larger importance. You can see something that reminds you of the drug and the probability of your behavior is greatly shifted,” she said.
“There is consequence in the brain with chronic exposure to any drug of abuse and that’s true for cannabis as well. It has an impact,” she added.
Of great concern to Haney is the impact of cannabis on the developing brain.
“Cannabis binds to a particular protein in the brain called the cannabinoid receptor. That receptor is everywhere in the brain and extremely important in a lot of different brain function and synaptic development,” she explained.
“Exposing that young brain to daily cannabis, the impact on that system is really something we don’t know or understand, but it’s certainly biologically plausible that it’s going to have a longer term outcome,” Haney said.
Last year, the National Institute on Drug Abuse released data that suggested 30 percent of cannabis users may have some degree of cannabis use disorder.
People who use before age 18 are 4–7 times more likely to develop this use disorder than adults, the data reported.
“People have been smoking cannabis for a long time and people have been smoking cannabis as adolescents, so the effects are likely more subtle than not. We know it’s not going to kill you,” Haney said. “But with my own children I just kind of emphasize that point, smoking cannabis at 14 versus when you’re 34, it has really different implications.”
Addiction is also listed, with approximately 1 in 10 cannabis users experiencing signs of addiction.
Haney pointed to memory effects, the increased likelihood of developing bronchitis and certain respiratory illnesses, the increased risk of driving accidents, and “there’s the risk of developing cannabis use disorder where it takes on a larger role in your life than you might have wanted from the beginning.”
It’s not definitively clear whether potency plays a role in addiction issues, she noted, but it makes sense that it would.
“Cannabis use disorder is well recognized as an issue, particularly given the number of people who are currently smoking and the societal acceptance of it. We’re expecting those numbers to just continue to rise, and they have been rising in young adults but thankfully not in adolescents,” Haney said.
A study from Columbia University in New York did find that the prevalence of cannabis use disorder decreased between 2002 and 2016 among frequent users.
However, concerns remain.
“We don’t have definitive data suggesting (an impact of potency), but based on what we know about most other drugs of abuse, it wouldn’t be surprising that it’s going to increase the speed in which somebody develops a problem,” Haney said.
“As the strength of cannabis has increased, so too has the number of people entering treatment for cannabis use problems,” Freeman said in a press statement for the new research. “More Europeans are now entering drug treatment because of cannabis than heroin or cocaine.”
According to Haney, stronger messaging on cannabis use disorder is needed.
“I don’t think the general public knows that cannabis use disorder really exists. They don’t know the risks of developing it. Psychosis I’m still agnostic on, but there is certainly an association,” she added.
Calarco said that for a subset of people, especially those who are predisposed to addiction, higher THC could lead to more addiction potential.
“They can find themselves craving the drug or seeking out more powerful substances,” he said. “It’s important to note that [cannabis] can be a gateway drug for some people.”
“In addition to the primary addiction, chronic use can also have a negative impact on the brain and can cause lung issues if smoked or inhaled. For people with depression, bipolar disorder, or other mental health issues, [cannabis] can exacerbate their condition,” he continued.
Dr. Kevin Hill, an addiction psychiatrist and director of the division of addiction psychiatry at Beth Israel Deaconess Medical Center in Boston and associate professor of psychiatry at Harvard Medical School, told Healthline that there’s a demand for more potent cannabis.
“As more people sell cannabis — now more often through legal businesses as opposed to illegal sales — vendors want to differentiate themselves from others by offering stronger or different cannabis products,” Hill said.
“Most consumers who buy cannabis in dispensaries or retail stores want cannabis with a high THC content. Improvements in technology have helped make that possible,” he added.
Paul Armentano, deputy director of the National Organization for the Reform of Marijuana Laws, a nonprofit that advocates legalization policy, told Healthline that consumers are more informed when products are sold legally.
“In a legally regulated market, the potency of cannabis products is lab tested and labeled, so that the consumer is aware of the potency and can adjust their consumption accordingly,” he said. “Regulators can also impose limits on the maximum potency of regulated products and such caps exist in some states.”
“By contrast, illicit products are of unknown potency to the consumer, much like illegally produced moonshine,” he added.
Experts note that more potent products could potentially take you somewhere you don’t want to go.
“While consumers are happy with more potent cannabis, it comes with a downside. Users are more likely to experience the adverse effects of cannabis as potency rises,” Hill explained. “Research has shown that as potency rises, so does the likelihood of addiction or developing psychotic symptoms.”
Research from last year found that addiction had increased among young people who lived in states where recreational cannabis is legal, although it still remained low overall.
“While only a minority of cannabis users experience these problems, we are seeing this happen more often,” Hill explained. “Many people still do not believe that cannabis use can lead to addiction and others are unaware of the extent of psychotic symptoms that cannabis can trigger, so sensible cannabis education about both risks and benefits remains crucial.”
Haney agreed that it’s important for people to know that cannabis can be a drug of misuse.
“People would be surprised at the number of people seeking treatment for cannabis use disorder,” she said. “I think what is important to note is again, developing this disorder doesn’t necessarily lead to the same consequences as alcohol or opioid or cocaine addiction, but it is distressing to these individuals, and they’re seeking treatment because it’s very difficult for them to stop.”
It’s also critical to know, Haney said, how cannabis use disorder impacts lives.
“This is a real phenomenon, that adults on their own initiative are seeking treatment for cannabis use disorder and it is because they try to quit, they can’t, they’re undergoing withdrawal,” she said. “They’re preoccupied with using, people in their lives are finding it upsetting that they’re using to that degree, so when they try to quit on their own they’re not succeeding, so they seek treatment.”
“This is not something most people are aware of,” she added. “But given the number of people using cannabis, there’s a steady number of people seeking treatment.”