As Marijuana Use Among Teenagers Rises, so Does the Risk of Mental Illness and Psychosis

Customers shop for marijuana products at a cannabis dispensary in Santa Ana, Calif., on Feb. 18, 2021. John Fredricks/The Epoch Times

In 2012, Colorado and Washington became the first two states to legalize nonmedical marijuana for adults over the age of 21. Since then, 22 states have followed suit.

In November, the Journal of the American Academy of Child and Adolescent Psychiatry published a study that found the legalization of cannabis had “shifted societal beliefs throughout the United States,” resulting in a 13 percent increase in past-month marijuana use for youth aged 12 to 17.

The study further found a 22 percent increase in past-month marijuana use among young adults aged 18 to 25.

But the notion that marijuana use is benign and acceptable is a cause for concern, according to some experts.

Ken C. Winters is a senior scientist at the Oregon Research Institute, a consultant for the Native Center for Behavioral Health at the University of Iowa, and a former professor at the University of Minnesota’s Department of Psychiatry. He is also the founder and former director of the Center for Adolescent Substance Abuse Research.

“With the opioid crisis in America, the outcomes are terrible, and it’s easy to see,” Winters told The Epoch Times. "With cannabis, it’s a lot slower acting, and not everyone is at high risk. Some people are at very high risk, some are at moderate risk, and some are at low risk.

“But it devastates when it has a negative impact.”

Lea List, a school counselor at The Classical Academy, one of the largest K–12 charter schools in Colorado, said that legalization is sending the wrong message to youth.

“Students tell me all the time that they can get access to marijuana easier than alcohol,” she said.

She added that when you remove the word “illegal” from a substance, youth and young adults who haven’t fully developed their abstract reasoning skills see things in “black and white.”

“If it’s not illegal, then that means it’s OK,” List said.

Specifically, Winters said tetrahydrocannabinol (THC), the substance in cannabis that’s primarily responsible for the psychoactive effects, is insidious, especially for youth and young adults, because of how it affects undeveloped brains.

The Brain and Mental Health

When Johnny Stack was 14, he started using THC as a freshman in high school. In 2019, at the age of 19, Stack died by suicide.

Three days before his passing, he told his mom, Laura Stack, “I need to tell you that you were right. You told me weed would hurt my brain, and it’s ruined my mind and my life.”

After his passing, Laura Stack started a nonprofit aimed at youth THC prevention called Johnny’s Ambassadors.

“Five years ago, on November 20, 2019, my beloved 19-year-old son, Johnny, took his life. As many of you know, he had a psychotic episode from using high-potency THC concentrates,” Laura Stack states on her nonprofit’s website.

“Sadly, after he died, we learned so much more about the connection between youth THC use, brain development, addiction, psychosis, and suicide.”

Research indicates that THC is a "possible trigger," or "aggravating factor," for psychosis. PA

Unlike a mature brain, where there’s not as much concern for long-term structural changes, Winters said research indicates that THC is a “possible trigger,” or “aggravating factor,” for psychosis because until about age 25, the brain is undergoing significant development in terms of structure, and how well it will function.

“We have a lot of neurochemical receptors in the brain that are called endocannabinoids. And these endocannabinoids are activated when you ingest THC, so you’re lighting the Christmas tree in your brain, if you will,” he said.

“This abnormal excitation of your endocannabinoids triggers all kinds of other negative neurotransmitter phenomena that impacts mood, decision making, and risk for psychosis and other mental health problems.”

Winters isn’t alone in his concern regarding THC’s impact on the undeveloped brain.

In January, Molecular Psychiatry published a study that looked at the effects of high-potency cannabis use on DNA methylation (a biological process where methyl groups—a small molecule made of one carbon and three hydrogen atoms—are added to DNA).

They concluded that high-potency cannabis (THC concentration greater than 10 percent) impacted genes linked to immune and mitochondrial function and left a marker on the DNA of users who later developed psychosis.

Greybeard Cannabis Co. Live Resin Terp Slush (L) and an activated live resin vape pen, both produced at Thrive Cannabis's plant in Simcoe, Ont., on April 13, 2021. The Canadian Press/Tara Walton

In 2023, the National Institute of Health (NIH) published a study that looked at data from the National Comorbidity Survey Adolescent Supplement, a nationally representative survey of 10,123 adolescents aged 13 to 18 to see if cannabis use impacted depression or suicidal behavior.

The study concluded, “Cannabis use is associated with higher odds of depression and depression severity in adolescence. Furthermore, depression and cannabis use are independently associated with higher odds of suicide attempt.”

In 2021, the NIH published a longitudinal brain imaging study that looked at 799 teens before cannabis use and five years later found that cannabis use was negatively associated with thickness in the left prefrontal and right prefrontal cortices.

The study further found that the higher the THC level, the greater the thinning of the prefrontal cortical regions.

Also, in 2021, Sage Journals published a systematic review and meta-analysis of 81 studies that examined the effects of adolescent cannabis use on the risk for psychosis.

The review concluded that “adolescent cannabis use is associated with an increased risk for psychosis later in life.”

THC and Overall Life Satisfaction

Winters said studies also indicate adolescents who use THC have lower IQs and less satisfaction in life.

For example, in the Dunedin New Zealand Longitudinal Health Study, which tracked 1,100 New Zealanders from birth to 45 years old, researchers compared people who began using cannabis before age 18 to those who abstained and found that cannabis users had an average IQ decline of seven points from childhood to 38 years old. By 45, the average IQ decline was 5.5 points.

“Cognitive deficits among long-term cannabis users could not be explained by persistent tobacco, alcohol, or other illicit drug use, childhood socioeconomic status, low childhood self-control, or family history of substance dependence,” the study stated.

The study also found that daily cannabis users had downward socioeconomic mobility, more workplace problems, decreased economic prosperity, and more conflicts in their relationships.

“It’s hard to get the public’s attention when we’re talking about these kinds of less dramatic outcomes, or insidious trajectories that take a long time to happen,” Winters said.

“It’s a bit like the challenge back in the ‘50s to get people to realize smoking cigarettes was harmful. That was slow-acting, long-term outcomes for people. Most people didn’t get any illness that could lead to death until they had 30 or 40 years’ worth of smoking.

“We’ve got the same problem with cannabis. THC is insidious and slow acting, so it’s really hard to make a public health warning case.”

Legalization Proponents

Based on his research, Winters says that legalizing marijuana, especially for those under 25, is problematic. But some see benefits.

The Marijuana Policy Project, an organization dedicated to legalizing cannabis in the United States, found that in Washington state, taxes from cannabis sales resulted in $600 million in “much needed revenue.”

It further states that in 2019, the FBI reported 663,367 cannabis arrests and citations and argued that if the U.S. legalized marijuana, the FBI would be free to focus on “real crime” instead of “ruining countless lives” by putting Americans “through the criminal justice system.”

Similarly, Johannes Thrul, an associate professor at Johns Hopkins Bloomberg School of Public Health, said that there are legitimate concerns about the effect of THC on the developing brain but argues that one of the benefits of legalization is removing cannabis from the black market.

“When we look at the public health landscape and the effect of legislation, in this case, legalization, one of the big benefits is taking cannabis out of the underground illegal market. Taking cannabis out of that particular space is a great idea,” he said.

A man holds up a marijuana cigarette during a rally on Capitol Hill on April 24, 2017. Mandel Ngan/AFP/Getty Images

“You’re taking it out of the illegal market and giving it to legitimate businesses where there is going to be oversight and testing of products, so you know what you’re getting.”

He said that “in general,” drug laws have targeted and criminalized minority communities, and making cannabis legal will reduce “over-policing” these populations.

Like Thrul, Wayne Hall, emeritus professor of the National Centre for Youth Substance Use Research at the University of Queensland in Brisbane, Australia, acknowledges the risks associated with youth cannabis use but agrees that minority communities have felt the brunt of cannabis regulations, and believes that is problematic.

“In some countries, in some periods, cannabis users have been imprisoned or more often, suffered the stigma and adverse effects of having a criminal conviction or an arrest record. These burdens have disproportionately affected socially disadvantaged ethnic minorities,” he stated in his study on the costs and benefits of cannabis control policies.

Still, he believes that if a country wants to legalize cannabis, it first needs to fund more research into the pros and cons of legalization.

Need for Education

“Legalizing cannabis has changed the perception of harm,” Winters said. “A greater percent of students, and we’re talking about middle and high school aged, report or say that it’s not as harmful to use cannabis as they did in the past.”

List agreed, and added as an increasing point of concern, “It’s not unusual for kids to be at school, high [on THC]. And I mean, every age group and generation has seen that, but now it’s much more likely to happen.”

Winters said that what he hopes parents understand is that they need to talk to their kids about the possible harms of THC.

“The bottom line is, it’s just not healthy for a young person, and high potency products are really quite dangerous,” he said.