Weed is now America’s daily drug of choice. No one’s sure what that means.

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In the last few decades, marijuana’s had a major glow-up.

In 1992, less than 1 million people were using it daily or nearly every day — a low point, according to an analysis of data from the US National Survey on Drug Use and Health, which began surveying Americans in the 1970s. Ten times as many people, meanwhile, reported drinking alcohol daily or almost daily.

In the 1990s, weed was illegal nationally and in every state. But marijuana’s since had a major rebrand: Three decades later, it’s legal for recreational adult use in nearly half of the 50 states. Now, it’s even challenging alcohol for its status as America’s favorite daily intoxicant.

In 2022, for the first time, more Americans were using marijuana daily, or near daily, than consuming alcohol at the same rate, according to a study by Jonathan Caulkins, a professor at Carnegie Mellon University. The number of daily or near daily marijuana users has grown from less than 1 million in 1992 to 17.7 million in 2022; in terms of per capita rate, that’s a 15-fold increase.

Marijuana is having a moment just as Americans reconsider their relationship toward alcohol. As public awareness of the toxic effects of even moderate alcohol consumption grows, many people are turning to THC products as an alternative. The THC industry touts its wares as a more natural alternative to alcohol with myriad health benefits, including decreased nausea, pain, and sleeplessness.

The rise in daily smokers (and vapers, and edible enjoyers, if you will) is also driven by the explosion of the industry. Millions of Americans live in cities and counties with retail shops offering a range of products that make the dimebags of yesteryear seem quaint by comparison: vape cartridges, edibles, oils, and waxes, offering more highly concentrated THC doses. The rise of marijuana retail has opened new doors for people who might have once shied away because they didn’t like smoking or were worried about breaking the law.

For many people, the rapid shift toward liberalization of marijuana policy, and the swiftness with which Americans have taken up consumption, has been great. But it’s also caught researchers off guard. Society has moved more quickly than they’ve been able to keep up with. That means millions of daily users are essentially conducting a real-time experiment on their own bodies.

Marijuana isn’t benign for everyone, though. Some of the results of the real-time experiment are already becoming apparent, both to regular users and people working in health care.

“It is very desirable to believe that there is a drug that can make you feel good, that can relax you, and has absolutely no negative outcomes,” says Dr. Nora Volkow, director of the National Institute on Drug Abuse at the National Institutes of Health. “But in biology, there are no free lunches.”

Take the emergence of cannabinoid hyperemesis syndrome, a condition marked by intense and prolonged bouts of nausea and vomiting and brought on by regular, long-term marijuana use. While once extremely rare, some doctors are saying they now see patients with symptoms frequently. “It emerged because people were consuming marijuana regularly with high [THC] content,” Volkow says. “And similarly, there is now evidence that consumption in those patterns is associated with higher risk of stroke or cardiovascular disease.”

Maybe the most worrying studies about frequent, heavy marijuana use involve teens and young adults. (While experts say marijuana use appears to be less risky for middle-aged adults, there’s still a lot they don’t know that needs to be researched further. Some note that more research is needed on older adults in particular.) Studies show regular marijuana use among adolescents and teens can predict increased risk of the development of schizophrenia and other psychotic disorders. Others have shown an increased likelihood of depression and suicidal ideation, disrupted dopamine function, and disruptions in the anatomy of the brain.

And marijuana, contrary to popular belief, can be habit forming. It can also increase the risk of dependence on other substances. A recent analysis by Columbia University for the New York Times estimated that as many as 18 million people in the US may have some form of cannabis use disorder, or addiction.

Getting a handle on who might be harming their health is tricky. Even the findings that point to a major rise in daily users leave a lot of questions unanswered, especially around how often they’re smoking, vaping, or ingesting, and how potent the THC is.

Caulkins, the Carnegie Mellon professor who published the research showing that more Americans are using marijuana daily, says there are different categories of daily or near daily users. There are the people who use marijuana similar to the way someone might pop a melatonin before going to bed at night — a small, daily dose to help with sleep or pain. And then there are those who are more like heavy cigarette smokers, consuming marijuana multiple times a day, morning or night, before or after meals, on breaks from work, or out with friends.

His previous research has found that daily or near daily users are a small portion of overall users, but make up about three-quarters of all marijuana purchases.

But just how many of the 17.7 million daily or near daily marijuana users are truly heavy users remains a mystery, because the US National Survey on Drug Use and Health doesn’t ask about how many times a day someone is using, or what they’re taking.

“We can have people who are using near daily, but they’re taking a puff off their vape pen right before they go to sleep,” says Ziva Cooper, a researcher and director for the UCLA Center for Cannabis and Cannabinoids, “versus somebody who’s using daily or near daily and they’re using five to 10 one-gram pre-rolls every day. You can imagine that the health outcomes are going to be quite different.”

It’s not just that researchers are often unsure of how much people are taking. The consumers are also often not sure what they’re putting in their bodies. That’s partly because what’s being sold in stores is way stronger than the weed that millennials and previous generations grew up with. Over the last 25 years, government data shows, the percentage of THC in marijuana seized by the Drug Enforcement Agency (DEA) has more than tripled, from 5 percent to 16 percent. And a lot of the products for sale in dispensaries can be even more potent — with vendors selling concentrated products, some claiming 90 or close to 100 percent THC. Some teens who’ve used those products have struggled with vomiting and substance abuse.

Cooper says it’s not uncommon for her to end up on the phone with her patients as they read the label aloud to her and she searches the internet to try to find out what exactly they’re taking.

“As researchers,” Cooper says, “we are trying to catch up with what’s actually happening in the world of cannabis. And we are woefully behind.”

Though humans have been using cannabis for at least 10,000 years — it was widely used for medical purposes in the United States in the late 19th century — the demonization of marijuana under the Nixon administration in the 1970s pushed the plant into the shadows.

Nixon, according to secretly reported tapes, knew at the time that marijuana was “not particularly dangerous.” But his “war on drugs,” carried on by the administrations of Ronald Reagan, George H.W. Bush, and Bill Clinton forced consumers and their providers to stop or risk arrest.

The drug’s public image was less threatening — smoking pot was played for laughs in movies and TV shows — but the reality of its criminalization was much darker. Hundreds of thousands of people were arrested and incarcerated each year for selling and dispensing marijuana, with the harms falling disproportionately on Black people.

Public awareness of the harms caused by criminalizing marijuana grew, and so too did a movement to raise awareness about the medicinal benefits of its use, especially for chemotherapy and cancer parents, who found marijuana use helpful for combatting nausea. Meanwhile, advocates focused on reducing mass incarceration and addressing racial disparities in the judicial system pushed states to begin decriminalizing marijuana and revising the sentences for people serving time for it. After getting the states to approve marijuana for medicinal purposes, organizations began pushing for it to be legal for all adults.

Today, marijuana is legal for medical use in 38 states and for recreational use for adults in roughly half of the states, plus the District of Columbia.

But marijuana is still illegal on the national level, where it is classified as a Schedule I drug — meaning the government doesn’t recognize it for medical use. That’s made getting the safety approvals and government funding necessary to study the drug difficult. Researchers say it’s made it harder to study potential risks of long-term marijuana use. But it’s made it harder to study the potential benefits, too. Earlier this year, the Biden administration proposed changing marijuana to a Schedule III, which will put it in a lower-risk category with drugs like ketamine.

In 2022, President Joe Biden signed the Medical Marijuana and Cannabidiol Research Expansion Act, hoping to reduce some of the federal barriers that have stymied research in the past. The legislation required the DEA to register and approve more researchers, and more manufacturers who can provide them with marijuana or cannabidiol (CBD). In addition to creating more opportunities and resources for researchers, the bill asked the DEA to assess whether there is enough marijuana to meet researchers’ experimental needs, and allowed doctors to discuss the benefits and harms of marijuana with their patients.

The federal government’s approach to marijuana has also meant that each state is doing its own regulation of its markets, without a concrete set of federal safety guidelines. The piecemeal nature of legalization, absence of national regulation, and lack of public awareness has contributed to the uncertainty around marijuana use and its long-term consequences.

The market is also changing rapidly. The 2018 farm bill, for example, legalized hemp, which inadvertently popularized delta-8 THC. Delta-8 THC, which is similar to delta-9 THC, is less potent in its natural form, but producers have been able to extract and synthesize the delta-8 THC in hemp, converting it into more potent concentrates. Manufacturers are now selling products the FDA says have serious health risks.

But that isn’t the only thing that the government can and should be doing.

In September, the National Academies of Sciences, Engineering, and Medicine issued a report outlining what state and federal governments could do to establish better public policy around marijuana and minimize potential negative public health consequences over the next five years.

The report outlined specific actions, such as closing the loophole in the 2018 farm bill that legalized delta-8 THC and clarifying that all forms of THC are subject to regulation under the Controlled Substances Act. More broadly, the report calls for states that have legalized, public health officials, and government agencies like the CDC to come together and establish more unified guidelines for marijuana, working to develop a set of regulations around the production and sale. Marijuana, the report argues, should be regulated the same way as alcohol and tobacco.

The report also recommends that the federal government support more research into marijuana use, along with a public health campaign to educate people about individual risks for different populations, including teens and older people.

It’s a tall order, but even that doesn’t capture everything researchers want to know. Caulkins, for one, has other questions.

“Cannabis intoxication impairs short-term memory formation. When cannabis was only being used as a social drug on weekends, who cares if it reduced effective performance on intellectual tasks?” he says. “Now, roughly half of cannabis is consumed by people who use often enough that they spend perhaps 50 percent of their waking hours under the influence of the drug. A lot of those hours of cannabis intoxication are while people are on the job or in school. How does that impact your functioning, how much you’re learning in college? We underinvest in thinking about the consequences of so many billions of hours of work and school time being, in some form, under the influence.”

It’s a question that might be hard to answer empirically right now. But it matters — maybe most of all for the millions of people taking part in America’s real-time marijuana experiment. “Maybe it’s not a problem,” Caulkins says. “But possibly, it’s affecting people’s abilities to meet their life goals in some subtle ways.”