Study Links Legal Marijuana to Rise in Heart Attacks

WHO:

Gizmodo - Researchers based in Boston conducted the study; the article does not name them.

Gizmodo - The research team analyzed hospitalized patients’ data from the National Inpatient Sample, described as the largest publicly available database of hospitalized patients collected from medical centers across the country.

Gizmodo - The study’s authors wrote: “Our findings point to potential adverse effects of recreational legalization on population health.”

NY Post - The article describes the research as a “first-of-its-kind study” and says it found a rise in hospital admissions for several deadly diseases.

WHAT:

Gizmodo - The study found a statistically significant association between recreational cannabis legalization in the western U.S. and rising hospitalization rates for atrial fibrillation, heart failure, and heart attacks.

Gizmodo - For each year of legal cannabis, rates of atrial fibrillation rose roughly 2%, heart failure nearly 4%, and heart attacks around 3%.

Gizmodo - After legalization, cannabis-related diagnoses increased in the West, while urinary-stone rates remained stable.

Gizmodo - The study was observational and showed correlation, not proof that legalization or cannabis caused cardiovascular problems. Its data could not compare individual states.

Gizmodo - The authors did not call for cannabis to be outlawed. They supported “a cautious approach” to future legalization, including detailed collection of cardiovascular-outcome data, and said their findings supported efforts to reclassify cannabis from Schedule I to Schedule III.

NY Post - The headline says marijuana legalization was linked to a troubling health trend; the article’s supplied text provides no additional study findings or figures.

WHERE:

Gizmodo - The study focused on the western U.S. census region: Alaska, Arizona, California, Colorado, Hawaii, Idaho, Montana, Nevada, New Mexico, Oregon, Utah, Washington, and Wyoming.

Gizmodo - Researchers compared western hospitalization rates with rates in other U.S. regions.

WHEN:

Gizmodo - The analysis examined cardiovascular-disease hospital diagnoses from 2012 to 2018 and compared rates before and after legalization began taking hold in 2014.

Gizmodo - Colorado became the first U.S. state to legalize recreational cannabis after voters approved a ballot initiative in 2012; legalization took effect in 2014.

Gizmodo - Massachusetts became the first eastern state to open legal dispensaries in late 2018.

Gizmodo - The study was published in BMJ Open.

WHY:

Gizmodo - The researchers used legalization as a “natural experiment” to study population-level health effects, which could avoid differences between cannabis users and nonusers that may affect individual-level studies.

HOW:

Gizmodo - The team compared western-region hospitalization rates before and after legalization and against other U.S. regions, adjusting for possible factors.

Gizmodo - The article says Schedule III classification would make it easier for scientists to study cannabis in laboratories. It reports that the federal government reclassified medical cannabis as Schedule III in April, while recreational cannabis remained under evaluation.

(UPDATED October 23, 2026 02:19 UTC)

A study of hospitalized patients found that recreational cannabis legalization in the western United States was associated with rising rates of several cardiovascular conditions. Researchers in Boston analyzed national hospital data, comparing western states with other regions and examining trends before and after legalization began taking hold. For each year of legal cannabis, atrial fibrillation rates rose about 2%, heart failure rates nearly 4%, and heart attack rates around 3%. Cannabis-related diagnoses also increased after legalization, while urinary-stone rates remained stable. The study was observational, so it shows an association, not proof that cannabis or legalization caused the health problems. Its data also could not distinguish between individual states. The authors urged a cautious approach to future legalization and more detailed tracking of cardiovascular outcomes, but did not call for cannabis to be outlawed. They said the findings supported reclassifying cannabis to make research easier.