Wider availability of medical marijuana in Colorado starting in 2009 coincided with an increase in calls to poison control centers and hospital discharges, according to a study published in the American Journal of Preventive Medicine.1

Researchers led by Jonathan M. Davis, PhD, from the University of Denver, found that the public health effects were significant — a 57% increase (95% CI, 43.4 – 72.0%, P<.001) in marijuana-coded hospital discharges from 2007 to 2013, and a 56% increase (95% CI, 49.0 – 62.8%, P<.001) in calls to poison control centers after 2009.

Colorado voters chose to legalize marijuana for recreational use in 2012, and the findings represent a cautionary tale for states that have voted or will be voting on this issue.

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“In 2009 there was a big change. In that year, the Department of Justice instructed federal prosecutors not to focus on individuals who were in compliance with state marijuana laws. People no longer had to worry about getting in trouble with the [Drug Enforcement Administration],” Dr Davis told Clinical Pain Advisor.

A Change in Public Perception

Analysis of Colorado records showed that poison control calls for marijuana increased by 0.8% per month after 2009 (95% CI, 0.2 – 1.4%; P<.01, and hospital discharges coded as marijuana dependence increased 1% each month from 2007 to 2013 (95% CI, 0.8 – 1.1%, P<.001).

The monthly number of applications for medical marijuana increased more than 20-fold in 2009 alone, from 495 in January to over 10,000 by December. Significantly, there was 1 dependency-related hospital discharge for every 3.159 (95% CI, 2.465 – 3853; P<.001) medical marijuana applications.

Admissions for marijuana dependence treatment showed the opposite trend, decreasing by 0.7% (95% CI, 0.9 – 0.5%, P<.001) per month after 2009, accompanied by a 26% decrease in marijuana arrests (95% CI, 31.1 – 20.3%, P<.001).

“The decrease in treatment probably reflects the decrease in arrests [and] mandatory treatment sentencing. It was probably not a personal choice to avoid treatment,” Dr Davis explained.

“When taken with changes suggesting a decrease in the perceived risk of marijuana, these factors may mark increased use and increased acceptance of marijuana,” the authors noted.

Moving Towards Full Legalization

Massachusetts legalized medical marijuana in 2013, and the issue of recreational marijuana use will go before voters in 2016.

“If medical marijuana was the midterm exam, we have failed miserably. If full legalization is the final exam, we are definitely not ready,” Kevin P. Hill, MD, director of substance abuse service at McLean Hospital and assistant professor of psychiatry at Harvard Medical School in Boston, told Clinical Pain Advisor.  

Massachusetts law allows quantities of marijuana that are much too high, for indications that are not specific, Dr. Hill noted.

As of March 2016, the District of Columbia and 23 other states have legalized medical marijuana. Policies differ by state, and can best be described as extremely varied; possession limits range from 1 to 24 ounces.

Moreover, questions remain as to whether botanically-derived medical marijuana offers clinical benefit over pharmaceutical-grade THC, its active ingredient. Also known as cannabinoids, prescription THC products — dronabinol and nabilone — have been legally available since 1985.

“Many doctors see the whole medical marijuana movement as a scam. They don’t see enough evidence to support it. On the other hand, we only have 2 cannabinoids — and there are over 80 cannabinoids in marijuana smoke,” Dr Hill pointed out.

According to the National Cancer Institute, several controlled trials support the use of cannabinoids for nausea and vomiting, but there is insufficient evidence to support the use of cannabis.3 In a recent randomized controlled study (N=30), dronabinol provided a longer analgesic effect than smoked marijuana, with lower abuse-related subjective effects.4

This article originally appeared on Clinical Pain Advisor