US States that legalised recreational marijuana saw a subsequent increase in traffic crashes and fatalities, researchers reported in the Journal of Studies on Alcohol and Drugs.
“The legalisation of marijuana doesn’t come without cost,” stated lead researcher Charles M. Farmer, PhD, of the Insurance Institute for Highway Safety.
Dr Farmer and colleagues’ analysis of five states that allow the recreational use of marijuana for adults age 21 and older revealed a 5.8% increase in the rate of traffic crash injuries and a 4.1% increase in fatal crash rates after legalisation and the onset of retail sales. At the same time, there was no increase in a comparison group of states which did not legalise marijuana.
The injury crash rate jumped after legalisation but before retail sales began. Traffic crash injuries rose 6.5% after legalisation but decreased slightly (-0.7%) after retail sales commenced. However, fatal crash rates increased both after legalisation (+2.3%) and after retail sales were authorised (+1.8%).
“Legalisation removes the stigma of marijuana use, while the onset of retail sales merely increases access,” explained Dr Farmer. “But access to marijuana isn’t difficult, even in places without retail sales. Users who previously avoided driving high may feel that it’s okay after legalisation.”
Marijuana legalisation’s stronger relationship with traffic crash injuries, rather than fatalities, may be due to how some drivers compensate when impaired by marijuana. Often, drivers under the influence of marijuana slow down and maintain a larger distance between themselves and other vehicles. A crash may be harder to avoid while impaired, but the lower-speed crashes that occur may be less likely to be fatal.
The authors note that earlier studies involving driving simulators have shown marijuana use to affect reaction time, road tracking, lane keeping and attention. However, Farmer notes that the current study is correlational, and increased marijuana use itself is likely not the sole cause of the increases seen.
“Studies looking for a direct causal link between marijuana use and crash risk have been inconclusive,” he says. “Unlike alcohol, there is no good objective measure of just how impaired a marijuana user has become. Until we can accurately measure marijuana impairment, we won’t be able to link it to crash risk.”
The researchers collected data on traffic crashes and traffic volume for 2009–2019 from 11 states and from the Federal Highway Administration. During the study period, five states had legalised recreational marijuana while a comparison group of six states did not. The authors statistically adjusted for factors known to contribute to crashes and fatalities, including seat belt use and unemployment rate.
In the states that legalised cannabis, changes in injury crash rates varied: Colorado had the biggest jump (+17.8%) and California the smallest (+5.7%) after both legalisation and the onset of retail sales. Nevada’s rate decreased (-6.7%). For fatal crashes, increases occurred in Colorado (+1.4%) and Oregon (3.8%), but decreases were found in Washington (-1.9%), California (-7.6%) and Nevada (-9.8%).
Farmer points out that states considering marijuana legalisation should consider a few steps to help forestall a potential increase in crashes. “First, convince everyone that driving under the influence of marijuana is not okay,” he says. “Then, enact laws and sanctions penalising those who ignore the message. Finally, make sure you have the resources (ie, staffing and training) to enforce these laws and sanctions.”
Source: EurekAlert!
