Alcohol and tobacco cause far more harms to people who consume them, and to society overall, than marijuana does, according to a new government-funded study.
A panel of 20 experts with professional experience with substance use issues from across Canada were asked to evaluate 16 different drugs on 10 dimensions of harm to consumers, as well as six dimensions of harm to others, scoring each on a scale of 0 to 100.
“Alcohol causes the most harm overall, with a cumulative weighted score of 79,” the study, published in the Journal of Psychopharmacology, found. “It was followed by tobacco (45), nonprescription opioids (33), cocaine (19), methamphetamine (19), and cannabis (15).”
The analysis, which was supported with Canadian Institutes for Health Research grant funds, concluded that marijuana’s biggest harm comes not from its effect on consumers but instead is related to the illegal market.
“Cannabis’s highest weighted score was for organized criminal activity,” the paper, authored by a large team of academics affiliated with various research institutions throughout Canada, the United Kingdom and New Zealand, says. “Though more than 70 percent of Canadians who purchase cannabis now do so through legal sources, organized criminal groups are heavily involved in the remaining illegal cannabis market, from production to distribution.”
Marijuana—which was legalized nationally in Canada in 2018 but remains federally prohibited in the U.S.—is not completely without harms to consumers, however, with the study finding that it “also scored relatively high for mental harms to users (dependence, withdrawal, short- and long-term impairment of mental functioning), ranking third in that combined category.”
When it comes to alcohol, which is federally legal in the U.S., it “ranked first in 9 of the 16 harm categories: drug-related damage to physical health, withdrawal, short-term impairment of mental functioning, long-term impairment of mental functioning, loss of tangibles, loss of relationships, injury, family and social adversity, and economic cost,” the study found.
“This analysis of drug harms in Canada found that alcohol causes the most harm overall… Alcohol was followed by tobacco, nonprescription opioids (like fentanyl), cocaine, methamphetamine, and cannabis.”
Tobacco “ranked first in 4 of the 16 harm categories: drug-related mortality, drug-specific damage to physical health, dependence, and environmental damage,” the researchers wrote.
The paper concludes by urging governments to “consider the harm—both individual and societal—caused by drugs and by the laws and regulations that govern them” when developing drug policies.
The findings about relative harms of different substances may help explain why alcohol consumption—and particularly tobacco use—have been gradually declining over recent years, and why multiple surveys and studies have indicated that more adults are opting for marijuana.
For example, recent polling shows that younger Americans are increasingly using cannabis-infused beverages as a substitute for alcohol—with one in three millennials and Gen Z workers choosing THC drinks over booze for after-work activities like happy hours.
Another survey released last October found that a majority of Americans believe marijuana represents a “healthier option” than alcohol. And most also expect cannabis to be legal in all 50 states within the next five years.
Smoking marijuana is also associated with “significantly” reduced rates of alcohol consumption, according to a recent federally funded study that involved adults smoking joints in a makeshift bar.
A study published in 2024 that looked at adults who drink cannabis-infused beverages found more evidence of a “substitution effect,” with a significant majority of participants reporting reduced alcohol use after incorporating cannabinoid drinks into their routines.
In September, an international study identified a a “strong negative association” between tobacco use and legal medical marijuana sales, indicating a “strong potential substitution effect” where people choose to use cannabis where it is allowed instead of smoking cigarettes.
Meanwhile, as the Trump administration considers moving marijuana out of Schedule I, the most restrictive category under U.S. federal law, another recent study concluded that cannabis isn’t as dangerous as its current classification would suggest.
