The legalization of recreational marijuana is associated with an increase in its abuse, injury due to overdoses, and car accidents, but does not significantly change health care use overall, according to a study by researchers at UC San Francisco.

In a review of more than 28 million hospital records from the two years before and after cannabis was legalized in Colorado, UCSF researchers found that Colorado hospital admissions for cannabis abuse increased after legalization, in comparison to other states. But taking the totality of all hospital admissions and time spent in hospitals into account, there was not an appreciable increase after recreational cannabis was legalized.

The study, appearing online May 15, 2019, in BMJ Open, also found fewer diagnoses of chronic pain after legalization, consistent with a 2017 National Academy of Sciences report that concluded substantial evidence exists that cannabis can reduce chronic pain.

"We need to think carefully about the potential health effects of substantially enhancing the accessibility of cannabis, as has been done now in the majority of states," said senior author Gregory Marcus, MD, MAS, a UCSF Health cardiologist and associate chief of cardiology for research in the UCSF Division of Cardiology.

"This unique transition to legalization provides an extraordinary opportunity to investigate hospitalizations among millions of individuals in the presence of enhanced access," Marcus continued. "Our findings demonstrate several potential harmful effects that are relevant for physicians and policymakers, as well as for individuals considering cannabis use."

According to the 2014 National Survey on Drug Use and Health, more than 117 million Americans, or 44.2 percent of all Americans, have used cannabis in their lifetime, and more than 22 million Americans report having used it within the past 30 days. While its use is a federal crime as a controlled substance, 28 states and the District of Columbia now allow it for treating medical conditions. Nine of those states have legalized it for recreational use.

To understand the potential shifts in health care use resulting from widespread policy changes, Marcus and his colleagues reviewed the records of more than 28 million individuals in Colorado, New York and Oklahoma from the 2010-2014 Healthcare Cost and Utilization Project, which included 16 million hospitalizations. They compared the rates of health care utilization and diagnoses in Colorado two years before and two years after recreational marijuana was legalized in December 2012 to New York, as a geographically distant and urban state, and to Oklahoma, as a geographically close and mainly rural state.

The researchers found that after legalization, Colorado experienced a 10 percent increase in motor vehicle accidents, as well as a 5 percent increase in alcohol abuse and overdoses that resulted in injury or death. At the same time, the state saw a 5 percent decrease in hospital admissions for chronic pain, Marcus said.

"There has been a dearth of rigorous research regarding the actual health effects of cannabis consumption, particularly on the level of public health," said Marcus, holder of the Endowed Professorship of Atrial Fibrillation Research in the UCSF School of Medicine. "These data demonstrate the need to caution strongly against driving while under the influence of any mind-altering substance, such as cannabis, and may suggest that efforts to combat addiction and abuse of other recreational drugs become even more important once cannabis has been legalized."

The study findings may be beneficial in guiding future decisions regarding cannabis policy, the researchers said.

"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."

The researchers could not explain why overall health care utilization remained essentially neutral, but said the harmful effects simply may have been diluted among the much larger number of total hospitalizations. They said it also may be that some beneficial effects, either at the individual or societal level, such as violent crime, counterbalanced the negatives.

Interesting post as I've been studying up on this for a while since my wife's cancer diagnosis. I bought her some good cbd oil and tbh it's helped with pain quite alot. More do than the morphine and other pain meds the dr's have prescribed her. The state I live in just passed the medical marijuana law so I'll be trying to get her a prescription to see if it helps. I would imagine that there are are always going to have people abusing the stuff just because they can since it's legalized in their state. Curious to see stats from other states that passed the same law.

Great job on the story, I'm not sure how much stock I put into marijuana causing a raise in car accidents or overdose deaths only because there are too many factors left out of the equation. For example what percentage of those people had a history of reckless driving and speeding tickets to begin with? What percentage had experimented with heavy drugs before they overdosed and before they began tracking? How sure are we that they were intoxicated when they had the wrecks? What actually is intoxicated in regards to THC in the blood stream. The government suppressed research for so many years there are PLENTY of things we don't know. My doctor is actually opening the first studies in my state for the state government that will be fed into a federal database and he said the data on many of these things is vague and disembodied from prohibition. More things to consider: What strains actually do what people say they do and to what degree, we know THC impairs motor skills but here's the X factor, there are a bunch of more chemicals like CBD and THC that have impact on it's effects (over 100 I believe) and it's the interaction between these chemicals that changes the "buzz" and also what it may treat. How much of a dose are you supposed to take to treat what and exactly what amount is too much to drive? Here's my point: I think it would be better served if people railed against the elephant in the room. Everyone is talking about the benefits of marijuana to health but what is detrimental? I can tell you this as a long time on and off user, inhaling anything whether it be vape, smoke, or whatever is bad for you, common sense tells you that, but no one ever talks about the fact that even inhaling vape may negate the cancer killing properties marijuana has and what amount of use makes it cause cancer? From a medical standpoint is where I would have taken the argument because we know inhaling anything is bad, or at least we should, and we know it causes a higher rate of schizophrenia and psychosis in those with that genetic predisposition which is another fact people seem to glaze over, driving stoned is bad, for one thing you are only doing fifteen miles an hour. That's a joke. Driving impaired in any manner is a terrible choice when we know life and death hang in the balance. To me though, the dangers medically far outweigh anyone who fights through apathy and paranoia to get behind the wheel. We need studies and all encompassing data that doesn't cherry pick statistics with good control groups in place IMHO. The article is fascinating, great job.

It's worth noting, it has been verified that marijuana increases the driving impairment effects of alcohol, so many of these accidents might have been from people who were under the influence of both. The study you posted is correlational, which doesn't necessarily determine a direct effect, and I strongly believe that the drug interactions are the likely cause.

People should be educated that smoking marijuana increases the drunk driving risk considerably, but the other major study that was done on driving deaths did not find that marijuana alone significantly increased accident risk.

Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2722956/

Originally Posted by geetarman513

....we know it causes a higher rate of schizophrenia and psychosis in those with that genetic predisposition which is another fact people seem to glaze over

Studies like This One do establish a strong relationship between psychosis and inhalant use, but can't conclude that it is causational - if teenagers prone to psychosis are more interested in trying inhalants, it would establish the same statistical relationship. This means that it is possible that people prone to psychosis might be seeking escape/self-medication to reduce symptoms.

I do think there are clearly cognitive effects on developing brains, but the science is really early here, there is for example a statistical relationship between people who used inhalants 2-4 times and psychosis, and I find it very hard to believe that there are strong pharmacology-induced brain changes from that few uses of inhalants. The behavior and socialization are clearly major factors in the findings of these studies.

Touche my friend, nice source listing, although I would submit ONE major study in the history of mankind is nowhere near enough to determine anything and it sounds like to me that we agree, there just isn't enough data yet to determine a whole lot, so in that I shouldn't have said we KNOW that it causes psychosis but only that so far that's where the evidence may be headed, there just isn't enough information, that being said you made a couple of good points there, and nice talking to you.