A new study estimates that millions more Americans are using nicotine vapes and cannabis in states that have legalized recreational marijuana, worrying experts who warn that the drug is stronger and more dangerous than in the past.
Published Friday in JAMA Network Open, the analysis of 55,406 adults who participated in panels from 2013 to 2022 found that monthly marijuana use rose by 3.28% and tobacco e-cigarette use by 1.39% after legalization.
Both indicators increased faster after marijuana dispensaries opened in those states. The study also found “no differential change” in the share of people smoking conventional cigarettes.
Psychiatrist Andrew Hyatt, a Harvard Medical School instructor and lead author of the study, said that works out to an additional 7 million to 8 million people using cannabis and 2 million vaping.
“The rapidly rising potency of cannabis and its ease of use in vape form has the potential to increase substance use and dependence,” Dr. Hyatt said in an email. “While many people can use these substances without harm, we should be vigilant as to the effects on individuals predisposed to problematic substance use and mental illness.”
He cited an increase in marijuana retailers and advertising for the surge in cannabis use, but said it’s more difficult to prove a causal relationship between legalization and vaping.
The study comes as marijuana legalization efforts have stalled while the Trump administration and states ponder lagging tax revenues and growing health concerns.
Ohio, Maryland and Michigan officials have moved to hike taxes on dispensaries to plug state budget gaps. The Montana Legislature passed a bill in April to limit the psychoactive content of cannabis gummies that the state blamed for poisoning dozens of underage children.
A JAMA Health Forum study published in June linked state laws legalizing marijuana to increased opioid addiction in Veterans Health Administration patients over time, with the sharpest increases among middle-aged and older men in chronic pain.
Most Americans live in the 39 states that have legalized medical marijuana since 1996, including 24 that have also allowed recreational cannabis since Colorado and Washington became the first in 2012.
However, no states have legalized recreational marijuana since 2023, and President Trump has proved unwilling to lift a federal ban on the drug for any purpose.
Some experts not connected to Friday’s study warned that the growing potency of marijuana sold in states permitting recreational use could pose serious health risks.
“In the era when marijuana was a weak drug that most people used occasionally, there would not be much to worry about, but today the drug is much stronger and almost half of users consume it every day, so we should be more worried about increases,” said Keith Humphreys, a Stanford University psychologist and addiction researcher.
He said the study’s findings of increased nicotine vaping and no substantial change to cigarette smoking belied the claims of marijuana legalization advocates “that cannabis would replace other substance use.”
Marijuana use has also surged among older men in recent years and involves higher concentrations of tetrahydrocannabinol, or THC. THC is the psychoactive substance in cannabis that, in higher doses, can produce nausea and scream-vomiting.
The average potency of marijuana plant material has jumped from 1% to 3% THC content in the 1970s to 18% to 23% today, according to Smart Approaches to Marijuana, which warns about the potential harm of cannabis use.
Kevin Sabet, founder of Smart Approaches to Marijuana, said Friday’s study underlines the reality that marijuana and nicotine are “two inextricably linked addiction pathways.”
“Nicotine is itself a highly addictive chemical with well-documented harms, so any rise in vaping, even of ‘just’ nicotine, primes a new generation for broader substance use, including marijuana,” Mr. Sabet said in an email.
But Jerry Joyner, a Texas-based marijuana advocate who hosts the “Weed & Whiskey” podcast, said the study’s findings indicate an adjustment period rather than an epidemic.
“The smart move now is education, not panic,” Mr. Joyner said. “Let’s focus on harm reduction and responsible use, not scare tactics.”
He said the increase in nicotine vaping could reflect increased curiosity “among adults exploring alternatives to alcohol or cigarettes.”
“Some may experiment with vaping nicotine alongside cannabis, but the link could be more about overlapping social trends than cause and effect,” Mr. Joyner added. “We’d need deeper studies to say more.”
Coleman Drake, a University of Pittsburgh public health professor who studies the impact of recreational cannabis laws, said people will see whether the increase in cannabis use in marijuana-permitting states has a positive or negative effect on society.
“Whether or not this is good depends on many different factors, such as the health conditions for which a person is using cannabis and which drugs, legal or otherwise, they were using before legal recreational cannabis became available,” Mr. Drake said.
