Fun fact: the federal government will not approve one dollar of funding for any cannabis research looking into the benefits of the plant. Bias is baked into the rules for the federal bureaucracy at the National Institute on Drug Abuse, which gets the sign-off on such research dollars. Cannabis research has to run a gauntlet that no other drug does, with both its arms tied behind its back. And yet more of its benefits leaked out again this year. Here are 10 of the top cannabis health studies from 2025 that defied the decades-old institutional bias.
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On adult-use consumption rates
Legalize weed, and more people smoke it, right? Wrong. Legalization did not create new potheads in California, a big study concluded in 2025.
Researchers at the Prevention Research Center in Berkeley, Calif., wrote up their findings in the journal Substance Use & Misuse.
“In summary, the overall trend for cannabis use in the past 30 days in California remained unchanged from 2018 to 2023, eight years after legalization and six years after cannabis retail became available,” the study’s authors concluded.
On teen consumption rates
Another year, another study showing legalization is not driving increases in teen use of weed.
This time, it comes from the International Journal of Mental Health and Addiction. Investigators concluded “No increases in past-month daily cannabis use” or problem use after adult-use laws passed. The study looked at people aged 12 to 20 from 2008 to 2017.
“We found post-[legalization] decreases in past-year and past-month cannabis use in males aged 12–20 and no prevalence changes among younger females, similar to previous research (Dills et al., 2021). There were no increases in past-month daily cannabis use among youth who used cannabis. These results may be expected in part because recreational cannabis is only legalized for adults ages 21+.”
On high driving
Folks who toked a few days before driving did as well as non-users in an important study with implications for DUI laws.
Many states will convict you for any residual THC in the blood. THC is the main active ingredient in weed. But leading researchers at the University of California at San Diego tested 190 people two days after they last smoked. Half still had trace amounts of THC in their blood, but they drove just fine.
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The study proved that so-called “per se” and zero-tolerance laws are ensnaring scientifically sober drivers.
On drinking
Fewer young people drank after legal weed shops opened, according to results published in the American Journal of Preventive Medicine.
Researchers looked at more than 400,000 respondents over 10 years. They found that college degree-holders and folks in their 30s, in particular, drank and smoked fewer cigarettes after legalization.
On head and neck cancer
Smoking pot is not giving people head and neck cancer, researchers reported in the Journal of Oral Pathology & Medicine.
Researchers pored over a huge hospital database to look for trends in head and neck cancer among weed users. They didn’t find any association. Alcohol and cigarettes drove head and neck cancers, not weed.
On weed and suicide
The famous movie Reefer Madness includes one character jumping out of a window. But results from a study of Canadian legalization proved once again that it’s fiction.
Researchers reporting on hospital data in Canada for the journal BJPsych Open studied the period of six months before legalization through two years after, and found “stable” rates of suicidality.
“Despite the rising potency and access to legal cannabis, suicide risk remains stable, although concerning,” researchers concluded.
On weed and unwanted pregnancy
Women who didn’t want to become pregnant were 50 percent more likely to end up pregnant if they drank heavily, as compared to those who drank little or no alcohol. Weed-smoking gals had no such unwanted pregnancy risk.
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Researchers at the University of California, San Francisco, tracked 936 women who did not want kids. The results published in the journal Addiction concluded:
“Heavy drinking, but not cannabis use or other drug use, appears to be associated with elevated pregnancy risk among those who most desire to avoid pregnancy.”
On heart attack and stroke
Old stoners don’t stroke out or have a heart attack more often than abstainers. That’s the conclusion from University of California, San Francisco researchers published in the journal Circulation.
Investigators looked at a cohort of 4,285 older veterans with a history of coronary artery disease. One quarter of them used weed. After 3.3 years of watching, cannabis use was not associated with heart attack, stroke, or all-cause death.
The results align with another 2025 study that looked at more than 729,000 people and found no evidence that smoking weed increased heart attack risk.
On high blood pressure
Smoking weed over your life is not associated with high blood pressure, a study published in the journal Hypertension found this year.
Investigators at the University of California at San Diego looked at over 2,800 participants over the course of 35 years.
Analyzing that same cohort failed to link decades of weed use to heart abnormalities, hardening of the arteries, or other heart disease.
On opioid abuse
Cannabis might be an exit drug, not a gateway drug. That’s the results from a Washington Post dive into federal opioid death statistics.
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Having a local dispensary is associated with a 30 percent lower death rate from opioids, and it starts right after the pot shop opens. The study results “strongly suggest that opioid users do shift to marijuana, at least enough to stop overdosing.”
And that’s the top 10 cannabis health studies of 2025. As long as NIDA bans looking for benefits as well as harms in herb, you can take federally funded studies with a grain of salt. Thankfully, state funding and international programs have stepped in to help sort the data from the noise.