Marijuana Legalization Decreases Chronic Pain, Increases Car Accidents

MAY 15, 2019
Patrick Campbell
Recreational cannabis legalization in Colorado has led to decreases in hospital admissions for chronic pain, but increases in car accidents, injuries and overdose injury, according to a recent study.

Investigators from the University of California, San Francisco found that while rates for chronic pain and car accidents may have changed, overall hospitalization rates remained the same in the 2 years following legalization in Colorado.

"This unique transition to legalization provides an extraordinary opportunity to investigate hospitalizations among millions of individuals in the presence of enhanced access," said senior author Gregory Marcus, MD, MAS, a UCSF Health cardiologist and associate chief of cardiology for research in the UCSF Division of Cardiology. "Our findings demonstrate several potential harmful effects that are relevant for physicians and policymakers, as well as for individuals considering cannabis use."

Investigators used the Healthcare Cost and Utilization Project (HCUP) database, funded by the agency for Healthcare Research and Quality, to examine inpatient healthcare utilization and diagnoses in CO between 2010 and 2014. Investigators also used data from New York (NY), the most populous state with inpatient HCUP data available, and Oklahoma (OK), a predominately rural state adjacent to CO with HCUP data. Investigators examined records for more than 28 million people and 16 million hospitalizations and compared rates of health care utilization and diagnoses in CO and the 2 control states. Investigators used guidelines established by a National Academy of the Sciences summary created to assess the changes brought on by cannabis legalization.

After analyses, investigators found that the legalization of recreational cannabis was associated with greater cannabis abuse, but minimal effects on overall healthcare utilization. It was noted that legalization of recreational cannabis resulted in a decrease of chronic pain admissions but increases in motor vehicle accidents, alcohol abuse, and overdose injury.

Between 2010 and 2014, the rates of cannabis abuse admission after versus before legalization in 2012 was grater in CO than in NY and OK (RR 1.27, 95% CI 1.26 to 1.28 and RR 1.16, 95%CI 1.15 to 1.17; both p<0.0005, respectively). Authors noted that there were no significant changes comparing the two control states over the same time period (RR 0.93, 95%CI 0.87 to 1.00, p=0.05). Investigators found a reduction in total overall admissions after legalization, but only when comparing CO to OK (RR 0.97, 95%CI 0.96 to 0.98, p<0.0005).

The results of the study correlate to a 10% increase in motor vehicle accidents and a 5% increase in alcohol abuses and overdoses that resulted in injury and death post-legalization of recreational marijuana in CO. Despite this, the number of chronic pain admission across the state dropped by 5%

In their conclusion, authors highlighted the benefit these findings may have on guiding future decisions regarding cannabis policy. Researchers also noted that they were unable to explain why overall utilization remained neutral. They stated the harmful effects may simply have been diluted among the large number of hospitalizations or that some societal impacts, such as violent crime, could have counterbalanced the negatives.


"While it's convenient and often most compelling to simplistically conclude a particular public policy is 'good' or 'bad,' an honest assessment of actual effects is much more complex," Marcus said. "Those effects are very likely variable, depending on each individual's idiosyncratic needs, propensities and circumstances. Using the revenues from recreational cannabis to support this sort of research likely would be a wise investment, both financially and for overall public health."

This study, titled “Does cannabis legalisation change healthcare utilisation? A population-based study using the healthcare cost and utilisation project in Colorado, USA,” is published in BMJ Open.

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