Efforts to assess marijuana-impaired driving in Massachusetts have been hindered by federal restrictions and a lack of comprehensive data, complicating attempts to draw clear conclusions about public safety risks. The Massachusetts Cannabis Control Commission, along with industry representatives, supports expanding research on impaired driving and related health concerns but faces legal barriers because cannabis remains illegal under federal law.
For decades, federal regulations have limited marijuana research to the use of cannabis grown at a single University of Mississippi farm, producing strains that differ significantly from those currently available in legal markets. As a result, experts say scientific understanding of the effects of contemporary marijuana consumption, particularly in relation to driving impairment, remains limited.
Opponents of cannabis legalization have cited a 2025 study from Ohio analyzing autopsy reports in a Midwestern county, which indicated that the rate of THC-positive drivers had not increased following legalization. However, this study has not undergone peer review and explicitly notes a lack of a clear connection between blood THC levels and impairment—unlike alcohol, THC can remain detectable in the body for weeks after use, complicating assessments of driver impairment.
In Massachusetts, the Cannabis Control Commission and the marijuana industry advise against driving after cannabis use, especially on high-consumption days such as April 20 and Thanksgiving. Advocates for a marijuana ballot initiative focused on public health risks, including impaired driving, have raised nearly $3.8 million, chiefly funding advertisements that highlight marijuana as the most common drug found in fatal vehicle crashes.
State crime data show a decline in operating under the influence (OUI) arrests involving alcohol or drugs in 2025 compared to previous years, a finding that contrasts with some claims of rising drugged driving incidents. Industry representatives acknowledge the risks linked to cannabis use and driving but emphasize the need for further research to inform policy and public guidance.
Critics have accused opponents of using selective studies to support their arguments while overlooking other research that does not align with their narrative. Without a dedicated Massachusetts cannabis research center, investigations into the specific effects of marijuana on driving impairment remain limited.
The issue continues to be politically sensitive, with calls from various stakeholders for clearer scientific understanding and more informed policy measures to address cannabis-impaired driving.