Negative Consequences of Marijuana Legalization Emerge

Sixty-four percent of Americans now live in states that permit medical marijuana use for a variety of conditions, including epilepsy, Parkinson's disease, multiple sclerosis and post-traumatic stress disorder. The latest state to join the club, West Virginia, approved a legalization plan in April. That means, two-thirds of Americans can now legally get a recommendation from a physician to use marijuana although the federal government continues to classify cannabis as a schedule I substance without accepted medical use and a high potential for abuse. Eight states and the District of Columbia have fully legalized marijuana for recreational use for adults who are 21 years of age and older.

Opponents of marijuana legalization have long feared significant negative consequences from legalizing cannabis for recreational purposes or medical use.

Two new reports appear to confirm those fears. A JAMA Psychiatry study found that states that have passed medical marijuana legislation have higher rates of illicit marijuana use and cannabis use disorder. And a report released by the Governors Highway Safety Association (GHSA) and the Foundation for Advancing Alcohol Responsibility suggests that for the first time in US history, driving under the influence of drugs is killing more motorists than drunken driving.

The JAMA study by Deborah Hasin and others concluded that medical marijuana laws have contributed to increasing US adult illicit cannabis use and cannabis disorders. “Policy and clinical professionals should recognize that cannabis disorders can be severe, treatment needs are increasing, and treatment can be effective. Medical marijuana laws may benefit some with medical problems. However, changing state laws (medical or recreational) may also have adverse public health consequences. A prudent interpretation of our results is that professionals and the public should be educated on risks of cannabis use and benefits of treatment, and prevention/intervention services for cannabis disorders should be provided.”

The researchers used data from three separate surveys that asked more than 100,000 US adults about their illicit cannabis use in the past year and whether they had been diagnosed with a cannabis use disorder. Both illicit cannabis use and cannabis use disorder diagnoses increased from 1991 to 2013 and the increases were higher in states that had passed medical marijuana laws.

The GHSA data suggest that one of the negative consequences of increased marijuana use is more traffic fatalities. Overall, 43 percent of drivers tested in fatal crashes in 2015 had used a legal or illegal drug, compared to 37 percent who tested above the legal limit for alcohol. Of the fatally-injured drivers tested, 35.6 percent had used marijuana before the accident.

Marijuana is known to impair psychomotor skills and cognitive functions associated with driving, including time and distance perception, lane tracking, divided attention tasks, and reaction time.

Unfortunately, testing vehicle operators for marijuana use is more complex than establishing blood alcohol content, which is often done at the scene of a crash. The effect of cannabis use can vary substantially among users but it can be deadly.

The GHSA report revealed that in Colorado, “marijuana-related traffic deaths increased 48% in the three-year average (2013-2015) since Colorado legalized recreational marijuana compared to the three-year average (2010-2012) prior to legalization.”

The GHSA report also quotes a survey of drivers in Colorado and Washington who reported any marijuana use in the past month. 43.6 percent reported driving under the influence of marijuana in the past year and almost 24 percent had driven within 1 hour of using marijuana at least 5 times in the past month.