A major new study involving more than 50 million hospital records has found an association between recreational marijuana legalisation and rising hospital admissions for several serious cardiovascular conditions.
The research, published in BMJ Open, examined hospital discharge data from across the United States between 2012 and 2018.
Scientists found that admissions for certain heart conditions increased faster in the western United States following recreational cannabis legalisation than in regions where comparable laws had not yet been introduced.
The findings arrive as President Donald Trump's administration continues pursuing changes to federal marijuana regulations, with a fresh legal development affecting the timetable for reform.
What health conditions have been linked to marijuana legalisation?
Researchers found that recreational cannabis legalisation was associated with increased hospitalisation rates for atrial fibrillation, heart failure and heart attacks.
Atrial fibrillation is a condition involving an irregular heart rhythm, while heart failure occurs when the heart cannot pump blood as effectively as it should.
A heart attack happens when blood flow to part of the heart muscle becomes blocked.
According to the study, each additional year of legal recreational cannabis sales was associated with the following relative increases in hospitalisation rates:
These figures represent changes in population-level hospitalisation rates, not the percentage of cannabis users who experienced the conditions.
Researchers also examined other cardiovascular problems, including strokes, blood clots and ventricular tachycardia.
However, the associations for those additional conditions did not reach statistical significance in the adjusted analysis.
How was the marijuana study conducted?
Scientists analysed 50,042,564 hospital discharge records collected through the National Inpatient Sample between 2012 and 2018.
The study focused on 13 western states: Alaska, Arizona, California, Colorado, Hawaii, Idaho, Montana, Nevada, New Mexico, Oregon, Utah, Washington and Wyoming.
The researchers selected this region because recreational marijuana sales began becoming legal there in 2014, earlier than in much of the rest of the country.
They compared hospitalisation trends before and after legalisation with trends in other US regions.
This allowed them to examine whether rates changed differently following the introduction of recreational cannabis laws.
They also adjusted their analysis for several potentially influential factors.
What did researchers discover about patients' ages?
Another finding concerned the ages of patients admitted to hospital.
Patients in the western region had a median age of 51, compared with 55 in the other regions studied.
The researchers noted that recreational cannabis legalisation has previously been associated with increased use, including among older adults who may already have cardiovascular risk factors.
However, the difference in patient ages does not demonstrate that marijuana caused any individual hospitalisation.
Does the study prove marijuana causes heart attacks?
No. The researchers explicitly acknowledged that their observational study cannot establish a direct causal relationship.
Although hospitalisation rates increased more quickly in the western region after legalisation, other factors may have influenced those trends.
The researchers could not establish whether individual patients had consumed marijuana before being admitted.
They also could not distinguish between different methods of cannabis consumption, such as smoking or consuming edible products.
Another limitation was that the analysis grouped western states together rather than assessing the effects of each state's legislation separately.
Despite these limitations, the researchers argued that the findings warrant further investigation into the potential cardiovascular consequences of recreational cannabis policies.
What is Donald Trump's latest update on marijuana legalisation?
On October 22, 2026, a Drug Enforcement Administration judge issued a new ruling that will keep the broader federal marijuana rescheduling process on hold until at least November 5.
The development concerns the Trump administration's efforts to move marijuana from Schedule I to Schedule III under the federal Controlled Substances Act.
Chief Administrative Law Judge Derek C. Julius agreed to include a recently published Government Accountability Office report in the administrative record.
The report identified gaps in written policies and procedures used by federal agencies when making drug-scheduling decisions.
However, the judge rejected a request to reopen the hearing for additional testimony and evidence.
Instead, he allowed the parties to submit further written arguments about the significance of the report.
The deadline for those submissions is October 29, with replies permitted until November 5.
The judge must then continue towards a recommendation on the proposed reclassification.
No final date has been confirmed for completing the broader process.
What would moving marijuana to Schedule III mean?
Under federal law, Schedule I substances are classified as having no currently accepted medical use and a high potential for abuse.
Schedule III substances are recognised as having accepted medical uses and are subject to less restrictive controls.
Moving marijuana into Schedule III more broadly could make scientific research easier and potentially change the federal tax treatment of some cannabis businesses.
However, rescheduling is not the same as nationwide recreational legalisation.
Even if the broader proposal is approved, it would not automatically make recreational marijuana legal throughout the United States.
A narrower federal rule concerning certain medical marijuana products had already taken effect in April 2026, but the wider reclassification remains unresolved.
Could the new heart study affect Trump's marijuana reforms?
The research adds another dimension to the debate over cannabis policy, but there is no confirmation that it has influenced the DEA's current proceedings.
Importantly, the study's authors did not argue that marijuana should remain in Schedule I.
Instead, they suggested that moving cannabis to Schedule III could help researchers better understand its cardiovascular effects.
They also recommended that governments introducing recreational legalisation collect more detailed health data to monitor possible consequences.
The distinction is significant because changing marijuana's federal classification and allowing recreational sales are different policy decisions.
Research into potential health risks can inform both debates without necessarily supporting identical legal outcomes.
What happens next?
For researchers, the next priority is establishing whether the observed increases in hospitalisations are directly connected to cannabis use and whether particular products or consumption methods carry different risks.
For federal regulators, attention will turn to the remaining written arguments in the DEA rescheduling proceedings.
The latest ruling means the broader process cannot be expected to conclude before the November 5 briefing deadline.
Meanwhile, the BMJ Open study provides new population-level evidence of an association between recreational marijuana legalisation and increased admissions for three serious cardiovascular conditions.
Its findings raise important questions, but they do not establish that cannabis legalisation directly caused the additional hospitalisations.
Sources: BMJ Open, "Cannabis legalisation and cardiovascular hospitalisations in the United States: nationwide difference-in-differences analysis, 2012–2018"; BMJ Group, October 23, 2026; Cannabis Business Times, October 22, 2026; and previous Daily Struggles reporting on federal marijuana rescheduling.
