In the past decade in which countless young patients have been diagnosed with new psychotic disorders, one striking result has stood out for New York psychiatrist Dr. Ryan Sultan.
“Of all the people I’ve diagnosed with a psychotic disorder,” he said, “I can’t think of one who wasn’t also positive about cannabis.”
Sultan, an assistant professor of clinical psychiatry at Columbia Irving Medical Center, is one of many experts expressing serious concerns about increasing marijuana use among adolescents and young adults.
And evidence is growing of marijuana’s association with psychiatric disorders such as depression, bipolar disorder and schizophrenia, especially in young men.
New research published this month, involving millions of people around the world over decades, raises fears that heavy use of potent cannabis and legalization of recreational weed in many U.S. states could exacerbate the country’s mental health crisis among young adults. worsen.
“There’s a great sense of urgency, not only because more people are smoking marijuana, but also because more people are using it in ways that are harmful, with increasing concentrations of THC,” Dr. Nora Volkow, director of the National Institute on Drug Abuse (NIDA), said in an interview.
One of the studies, conducted by researchers in Denmark in collaboration with the US National Institutes of Health, found evidence of a link between cannabis use disorder and schizophrenia. The finding was most striking in young men aged 21-30, but was also seen in women of the same age.
The paper, published in the journal Psychological Medicine, looked at data from nearly 7 million men and women in Denmark over the course of a few decades to look for a link between schizophrenia and cannabis use disorder.
The magnitude of the link between cannabis and schizophrenia for young men surprised study author Volkow, who expected the number to be closer to 10%.
“This is worrisome,” she said.
There are now 22 states that allow recreational use of marijuana, including Minnesota probably become the next state to legalize it.
Whether recreational cannabis laws contribute to underage consumption is unclear, but Volkow has made tackling cannabis use among teens one of NIDA’s top priorities. Daily use of marijuana among young adults has risen to record highs, with more than 1 in 10 young adults ages 19-30 now reporting daily use, and nearly half reporting use in the past year, according to the agency’s most recent data.
Another study, led by researchers at Sultan and Columbia, published earlier this month, found that teens who only use cannabis recreationally are two to four times more likely than teens to develop psychiatric disorders, including depression and suicidality who do not use cannabis at all.
Because research to date has been observational and does not directly prove cause and effect, the link between marijuana and psychiatric disorders is controversial. It is unclear whether people who already have or develop a psychiatric condition are more likely to use cannabis as a means of self-medication or whether cannabis use causes mental problems.
Volkow is optimistic that a large ongoing study on adolescent brain development at the National Institutes of Health may help answer this question.
Sultan acknowledged the limitations of the evidence. “It’s kind of a circular feedback where they just feed off each other,” he said.
Dr. Deepak D’Souza, a psychiatrist at Yale University who has studied cannabis for 20 years, insists there is too much evidence to ignore.
“We may be grossly underestimating the potential risks of cannabis,” he said.
With increasing legalization and increasing potency in cannabis products, D’Souza has never been more concerned about the mental health implications of cannabis use among young people.
“This is a huge concern,” he said. “We have been woefully inept at educating the public and influencing policy.”
Does legalization affect marijuana use?
According to an analysis published earlier this month in the journal Substance Abuse, early data shows that legalization is leading to increased cannabis use among young adults ages 18 to 25, particularly in Oregon and Washington.
The study, led by researchers from McMaster University in Canada, found the evidence a little less clear in other age groups, and more research is needed to understand how legalization affects rates of cannabis use.
In areas where marijuana is becoming legal and more easily accessible, Volkow is concerned about the ease with which products can be mixed, leading to a high total dose of marijuana consumed.
One of the biggest problems, she says, is the lack of regulation on the concentration of THC in products.
Marijuana consumed decades ago had THC concentrations, the main psychoactive ingredient, of 2 to 3%, but cannabis products today can have THC levels as high as 90%.
“That doesn’t even apply to alcohol, because you can’t put more than a certain percentage of alcohol in liquor,” she said. “Same with tobacco cigarettes, you control how much nicotine they have. We have no regulations here.”
The potency of THC is significant, Volkow said, because cannabis is more likely to be associated with psychosis when higher doses are consumed.
What age is most vulnerable?
Research has shown that the human brain is the last organ to fully develop and is not ready until the mid to late 20s. This makes adolescents and young adults particularly vulnerable to the effects of cannabis as their brains mature.
“Really, the ideal time to consider weed — if you’re going to use it — is 26 or later,” Sultan said.
People who wait until at least age 26 are much less likely to become addicted or develop mental disorders, said Dr. Sharon Levy, a pediatrician and addiction specialist at Boston Children’s Hospital.
“The greatest risks are clearly in the adolescent and young adult age range,” she said.
However, people with a family history of a psychotic disorder should not use cannabis at all, Sultan warned
What does cannabis do to the brain?
While scientists are still learning about the effects of marijuana on developing brains, studies to date suggest that marijuana use in teens may affect functions such as attention, memory and learning, multiple studies have found.
“It somehow disrupts the connections we use in our brains to differentiate between what’s happening in our heads and what’s happening outside our heads,” Levy said of the psychotic symptoms that can occur.
D’Souza added that cannabis use can have serious consequences for the developing brain because of its effects on the endocannabinoid system, a complex signaling system in the brain that marijuana targets.
“Endocannabinoid systems play an important role in shaping the brain during adolescence, when schizophrenia usually manifests itself,” he said.
Disrupting that system with cannabis use could have “far-reaching complex implications for brain development.”