A long-awaited change in drug policy could bring scientists one step closer to understanding the harms and benefits of marijuana, the most commonly used federally illegal substance.
On Thursday, President Donald Trump signed an executive order that moved to reclassify cannabis from a Schedule I to a Schedule III substance, following through on a regulatory shift first pushed during the Biden administration.
“Decades of federal drug control policy have neglected marijuana’s medical uses,” the order says. “That oversight has limited the ability of scientists and manufacturers to complete the necessary research on safety and efficacy to inform doctors and patients.”
While the reclassification is intended to bolster medical marijuana research and won’t legalize cannabis at the federal level, the move comes at a time when use in the United States is at a high. Gallup data from 2023 and 2024 estimates that 15% of adults smoke marijuana, up from 7% in 2013.
The poll, which didn’t differentiate between medical and recreational consumption, showed the highest use (19%) among young adults 18 to 34, a group for whom studies have found cannabis to have damaging psychiatric effects. For example, a study published Tuesday in the journal Pediatrics found that using marijuana as little as once or twice a month was linked to emotional distress and worse school performance among teens.
Medical marijuana is typically prescribed to ease chronic pain; control nausea and vomiting, often in people receiving chemotherapy for cancer; and bring about an appetite in people with certain medical conditions. It’s unclear whether rescheduling cannabis will affect funding for recreational marijuana research.
Scientists like Ziva Cooper are hopeful the reclassification could revolutionize public health through more comprehensive marijuana research.
“It is extremely difficult to study cannabis, aka marijuana, for both the potential adverse effects as well as therapeutic effects,” said Cooper, director of the Center for Cannabis and Cannabinoids at the University of California, Los Angeles. “The industry is developing at a very fast pace, and so consumer behavior is developing along with that industry.
“It’s very hard for us, as scientists, as people who are interested in public health, to be able to keep up with the changes, in part because the research is difficult.”
Schedule I is the strictest of the five controlled substance categories recognized by the Drug Enforcement Administration, reserved for drugs “with no currently accepted medical use and a high potential for abuse,” including ecstasy, heroin, LSD and peyote. Schedule III drugs, which include ketamine, testosterone and anabolic steroids, have “a moderate to low potential for physical and psychological dependence,” according to the agency.
Despite working in a cannabis-friendly state, Cooper said she faces the same research hurdles as her peers in states such as Idaho, where no marijuana use is permitted whatsoever.
“Researchers cannot test what is readily available to the market, just basic questions about what is in those products that are available in the dispensary I can see outside of my laboratory window, for example,” Cooper said. “It also means that there are certain restrictions with respect to where we can get our cannabis that we do research on.”
Harms and benefits of marijuana need further study
Last year, the National Institutes of Health awarded $75 million to therapeutic cannabinoid research, up from $70 million in 2023. Additionally, $217 million went to cannabinoids, or cannabis compounds, and $53 million went to cannabidiol, or CBD, a nonpsychoactive cannabinoid.
However, administrative red tape means cannabis studies are often observational, compared with the rigorous clinical trials required of pharmaceutical research, said Dr. Brooke Worster, medical director of the M.S. in medical cannabis science and business program at Thomas Jefferson University in Philadelphia. Their findings have been mixed.
For example, a 2024 study published in the journal Current Alzheimer Research found that recreational cannabis use among adults 45 and older was associated with a 96% lower risk of subjective cognitive decline, compared with nonusers. Yet a 2025 study published in JAMA Network Open found that among adults 22 to 36, heavy cannabis users showed impaired working memory.
Research published this year in the journal Biomedicines suggested cannabinoids are a “promising” alternative to opioids for chronic pain management but cited an urgent need for large-scale, randomized controlled trials. Meanwhile, a study published last year in JAMA Network Open found that older, Medicare-insured adults showed increased rates of health care visits involving cannabis-related disorders from 2017 through 2022.
The reclassification will allow researchers to dispense and study specific formulations of marijuana, Worster said. Now, even in states with medical marijuana programs, the quality and potency of cannabis products can vary greatly between dispensaries.
“We can actively track immediate symptoms or blood levels of things, longer-term effects,” she said. “All the things you’d want to do when you’re studying a medication, all the things that the federal government otherwise requires us to do to study a medication.”
While marijuana may have some medical benefits for some people, Jonathan Caulkins, the H. Guyford Stever university professor of operations research and public policy at Carnegie Mellon University in Pittsburgh, denied that administrative roadblocks have prevented cannabis from curing ailments such as cancer or Alzheimer’s disease.
“They do not restrict research in Canada or France or Israel,” Caulkins said. “I don’t think that we should imagine that the only reason cannabis hasn’t become the wonder drug is because of anything about U.S. law, because we’re not the only country in the world that has a pharmaceutical industry and a research base.”
Still, the change brings new responsibility to the medical community, Worster said, as smoked and inhaled products of any concentration or formulation aren’t safe for everyone.
“What still needs to be figured out is, how do we get the right patient the right medication and the right guidance?” she said. “The products out there are, a lot of times, not regulated. There are real risks with mental health, with youth who use it too regularly, certainly some cardiovascular effects that we need to pay more attention to.”
Cannabis policy to be revised after 55 years
The regulatory hurdles researchers face date back more than half a century. During the Nixon administration, the Controlled Substances Act of 1970 established cannabis as a Schedule I drug.
Nearly 60 years later, much of marijuana’s medical potential, or lack thereof, remains unknown. In the eyes of the law, Worster said, “it is simply a drug of abuse.”
Susan Ferguson, director of the Addictions, Drug and Alcohol Institute at the University of Washington School of Medicine, anticipates scientists will soon have an easier time acquiring cannabis research licenses. Currently, she said, researchers may obtain a broad license to study any Schedule II through V drug. Those who wish to study a Schedule I drug must get a separate license for each substance.
“It involves extensive writing of protocols,” she said. “It involves DEA agents coming out and inspecting the lab and talking to me about the research and the plans for the experiments. It gets very, very complicated.”
Rescheduling marijuana, Ferguson said, would “open the floodgates” for clinical research. For starters, people may be more inclined to enroll in studies of Schedule III rather than Schedule I drugs.
Ferguson likened cannabis to alcohol and tobacco — products that are commonplace but not harmless. Medical research is the reason their harms are well known.
“We haven’t done that research on cannabis,” Ferguson said. “It’ll be able to ultimately tell people what are the risks, what are the benefits, and just give people more information.”
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