The legalization of marijuana for recreational purposes is associated with an increase in its abuse, overdose injuries and car accidents, but does not significantly alter the use of health care, according to a study conducted by researchers from the University of San Francisco.

As part of a study of more than 28 million hospital records dating back two years before and after cannabis legalization in Colorado, UCSF researchers found that admissions to a Colorado hospital for cannabis abuse increased after legalization compared to other states. However, taking into account all hospital admissions and time spent in hospitals, there was no appreciable increase after the legalization of recreational cannabis.

The study, published online May 15, 2019, in BMJ Open also found fewer chronic pain diagnoses after legalization, which is consistent with a report published in 2017 by the National Academy of Sciences that concludes that cannabis can reduce chronic pain.

Gregory Marcus, MD, MAS, lead author of the study.

"We need to think carefully about the potential health effects of a substantial improvement in the accessibility of cannabis, as has been done in the majority of states," said lead author Gregory Marcus, MD, MAS, Cardiologist and Deputy Chief of Cardiology at UCSF Health. for research in the division of cardiology of the UCSF.

"This unique transition to legalization offers an extraordinary opportunity to investigate the hospitalizations of millions of people with improved access," said Marcus. "Our results demonstrate several potential detrimental effects that are relevant for physicians and policy makers, as well as for people considering using cannabis."

According to the National Survey on Drug Use and Health conducted in 2014, more than 117 million Americans, or 44.2% of all Americans, have used cannabis during their lifetime and more 22 million Americans said they have done so in the past 30 days. Although its use is a federal crime as a controlled substance, 28 states and the District of Columbia now allow it to treat health problems. Nine of these states have legalized it for recreational purposes.

To understand the potential evolution of health care utilization resulting from extensive policy changes, Marcus and his colleagues examined the records of over 28 million people living in Colorado, New York and the United States. Oklahoma as part of the 2010-2014 Health Care Costs and Utilization Project, which included 16 million people. hospitalizations. They compared health care utilization rates and diagnoses in Colorado two years ago and two years after the legalization of marijuana for recreational purposes in December 2012 in New York as a state geographically urban and remote, and in Oklahoma, as a geographically close and predominantly rural state. .

The researchers found that after legalization, Colorado had experienced a 10% increase in road accidents, as well as 5% of alcohol abuse and overdoses resulting in injuries , or even death. At the same time, the state has recorded a 5% decrease in hospital admissions for chronic pain, Marcus said.

"There has been little rigorous research on the actual health effects of cannabis use, particularly on the level of public health," said Marcus, Chair of Research in Atrial Fibrillation at the Faculty of Medicine. UCSF medicine. "These data demonstrate the need to strongly warn against driving under the influence of psychotropic substances, such as cannabis, and may suggest that efforts to combat substance abuse and abuse". other recreational drugs become even more important once cannabis has been legalized. "

The results of the study could be useful for guiding future decisions regarding cannabis policy, said the researchers.

"While it is practical and often more convincing to simply conclude that a public policy is" good "or" bad ", an honest assessment of the actual effects is much more complex," Marcus said. "These effects are most likely variable, depending on the needs, trends and needs of each individual. Using recreational cannabis revenues to fund this type of research would probably be a wise investment, both financially and for public health in general. "

The researchers were unable to explain why the overall use of health care remained essentially neutral, but said the adverse effects might simply have been diluted among the much larger number of total hospitalizations. They added that there may also be some positive effects, whether at the individual level or at the societal level, such as violent crime, that counterbalanced the negative aspects.

Co-Authors: Lead author Francesca Nesta Delling, Eric Vittinghoff, Mark Pletcher, Jeffrey Olgin, Gregory Nah, Kirstin Aschbacher, Christina Fang, Emily Lee, Shannon Fan and Dhruv Kazi, UCSF; and Thomas Dewland, of Oregon Health & Science University

Funding: The study was funded by the Health Research and Quality Information and Health Care Division of the Oklahoma Department of Health.

Disclosures: The authors do not report any conflict of interest.

The UC San Francisco (UCSF) is a leading university dedicated to promoting health worldwide through advanced biomedical research, advanced-level training in life sciences and related topics. health professions and excellence of care provided to patients. It includes leading graduate schools in dentistry, medicine, nursing and pharmacy; a graduate-level division with nationally-recognized programs in the basic, biomedical, translational and demographic sciences; and a leading biomedical research company. It also includes UCSF Health, which includes three leading hospitals – the UCSF Medical Center and UCSF Benioff Children's Hospitals in San Francisco and Oakland – as well as Langley Porter Hospital and Psychiatric Clinics, UCSF Benioff Children's Physicians and the faculty practice of UCSF. UCSF Health has affiliations with hospitals and health organizations throughout the Bay Area. UCSF faculty also provides all medical care to the public at Zuckerberg San Francisco General Hospital, Trauma Center and SF VA Medical Center. The UCSF Fresno Medical Education Program is a major branch of the University of California, San Francisco School of Medicine.