Strong Weed Is No Reason for Prohibition

Weed has come a long way since Up in Smoke. While there are disagreements about the potency advertised by retailers, there is little dispute that cannabis products have higher THC content than ever before. Concerns about that development were recently heightened by a study challenging the idea that cannabis has low addictive potential.

The study, published in JAMA Psychiatry last week, is based on data for Americans 18 or older from the National Survey on Drug Use and Health (NSDUH). National Institute on Drug Abuse Director Nora Volkow and her three co-authors report that 9.3 percent of men and 5.6 percent of women reported at least two symptoms of cannabis use disorder (CUD) in 2024, up from about 7.3 percent and 4.5 percent, respectively, in 2021.

The American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders defines CUD based on 11 criteria, including a strong desire to use cannabis, consuming more than intended, devoting a lot of time to using cannabis or recovering from its effects, forgoing other activities, use in physically hazardous situations, unsuccessful attempts to cut back or quit, tolerance, withdrawal symptoms, cannabis-related problems at work or school, impairment of interpersonal relationships, and continued use despite negative effects. CUD is deemed “mild” when two or three symptoms are reported, “moderate” when four or five criteria are met, and “severe” in cases involving six or more symptoms. To measure CUD incidence, the NSDUH asked respondents whether they had experienced any of these symptoms.

Between 2021 and 2024, Volkow et al. report, the rate of “moderate-to-severe CUD” rose from 3.1 percent to 4.1 percent among men and from 1.7 percent to 2.5 percent among women. The increase was especially noticeable among men 35 or older and women 21 or older. Overall, moderate-to-severe CUD was most common among 18-to-20-year-olds. 

The study “suggests that cannabis products available today have significant addiction potential,” Volkow tells Reason. “The challenge is that we lack comprehensive data on the types of cannabis that people are using—including the concentrations of delta-9-THC and other cannabinoids—and how those relate to addiction potential.” Since the NSDUH data did not include information about potency, the study does not directly assess whether the increase in CUD rates was associated with an increase in THC levels.

According to the NSDUH, the share of Americans 12 or older who reported using marijuana during the previous year rose from 19 percent in 2021 to 21.2 percent in 2025, while past-month use rose from 13.2 percent to 15.1 percent. Although cannabis use declined among Americans 25 or younger, it increased in older groups. Overall, the widespread availability of THC in the form of flower, edibles, gummies, and vapes seems to have increased the drug’s popularity, leading to heated debates about the consequences of legalization.

Although addressing the hazards of cannabis use does not require prohibition, it does require careful consideration of the “principles and rules that we in a free society apply to restricting government interference in adult choices,” says Jonathan Caulkins, a drug policy expert at Carnegie Mellon University. “A total laissez faire, caveat emptor approach is going to mean that many millions of people have lives substantially damaged.”

That danger raises a “real question that we as a democratic society need to engage with,” Caulkins says. “To what degree can we ask the majority to sacrifice some of their fun and some of their freedom to protect the minority, who will badly harm themselves and their families and the people around them with their poor choices?”

Jeffrey A. Singer, a health policy expert at the Cato Institute and a practicing surgeon, has a different view. CUD shouldn’t “become the basis for a new moral panic,” he said in response to the JAMA study. Instead, he suggested, “we should educate people about cannabis’s risks” and “not assume that today’s trends represent the long-run effects of legalization—or that prohibition is the answer.”

Some politicians and activists see the commercialization of cannabis as a growing problem. This fall in Massachusetts, voters will decide whether to repeal the state’s legalization of recreational marijuana and home cultivation.

Smart Approaches to Marijuana, which supports that ballot initiative, is using research like the JAMA Psychiatry study to bolster the campaign. The organization’s action committee has contributed more than $1.5 million to the Coalition for a Healthy Massachusetts, the initiative’s main sponsor. If the measure passes, possessing one to two ounces of marijuana will be a civil offense punishable by a $100 fine and forfeiture of the weed.

Jodi Gilman, director of neuroscience at the Massachusetts General Hospital Center for Addiction Medicine, argues that the abuse potential highlighted by the JAMA Psychiatry study does not justify a revival of the war on weed. “It’s not surprising that there are more cannabis use disorders with this flooding of the marketplace with highly potent products,” she says. Gilman thinks people should “appreciate that this is a psychoactive substance that can be very strong,” which “carries risks like any other psychoactive substance.” Still, the best treatment for CUD isn’t jail, she says; it’s “motivational interviewing or cognitive behavioral therapy.”

If legalization means treating marijuana like alcohol, that includes fostering a culture of responsible use, which is hard to do under prohibition. “We don’t ban alcohol because some people use it unwisely or develop alcohol use disorder,” Singer notes. “Autonomous adults should remain free to make choices others consider unwise so long as they don’t violate the rights of others.”