NEJM weighs in on pros and cons of medical marijuana use

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Editor’s note: The following is cross-posted from Politics of

The New England Journal of Medicine, among the most respected journals read by physicians worldwide, has weighed in on the risks and benefits of medical marijuana in what seems to be a rarely neutral expose on the topic.

As Florida begins to implement legal access to Charlotte’s Web — the low-TCH marijuana strain that can alleviate symptoms of epilepsy, pain, and cancer — articles such as this one will be at the top of your doctor’s reading list and will likely inform how he or she decides to approach prescribing.

Here is what they may see:

First, we can eliminate lung cancer as a likely consequence for most. In terms of the strength of current evidence, even for heavy or long-term use, the authors have low confidence in the association between marijuana and lung cancer.

That said, the authors feel evidence is quite strong for related issues such as chronic bronchitis. Further, strong connections exist between marijuana use, particularly when it begins young in life, and issues of addiction to the drug and other substances, diminished lifetime achievement, and motor vehicle accidents.

The latter issue may be among the most important in terms of both health care and public policy. Marijuana is the most common illicit drug found in connection with impaired driving and accidents, including fatal crashes. Blood THC concentrations are strongly correlated with performance in simulated driving studies, which appear to be good predictors of real world driving abilities; and recent marijuana use is associated with substantial driving impairment. In fact, looking at a meta-analysis of multiple studies on the topic, the risk of auto accidents increases by a factor of about 2 when a person drives soon after using marijuana. This represents a lower probability of vehicular accidents when using marijuana than drinking alcohol.

Here is something that you may not have known: marijuana has become more potent over the past many decades. The THC content in confiscated marijuana samples has increased from about 3% in the 1980s to 12% in 2012 — meaning that the marijuana used in previous generations is not quite the marijuana of today. To the authors, these changes may account for increases in emergency department visits by marijuana users and greater frequency of marijuana-related fatal motor vehicle accidents.

Further concerns raised by the NEJM authors include somewhat increased risks of abnormal brain development, greater depression or anxiety, and increased risk of developing schizophrenia. For each of these, however, the authors are careful to explain that while these conditions are correlated with marijuana use, it is difficult to establish causality.

In the case of anxiety, depression, and schizophrenia, people with preexisting genetic vulnerability may find these symptoms exacerbated by regular marijuana use. According to at least one study, marijuana exposure at a younger age can negatively affect the disease trajectory by advancing the time of a first psychotic episode by 2 to 6 years. Further, for younger people, marijuana has been associated with significant declines in IQ, and may impact synapse formation during brain development.

All of this considered, the authors acknowledge the clinically demonstrated benefits of marijuana for conditions including epilepsy, MS, inflammation, chronic pain, AIDS-associated anorexia and wasting syndrome, and nausea.

Their conclusion is a balanced one: when it comes to the medicinal use of marijuana, just as with any drug, the potential benefits need to be weighed individually against the potential for adverse reactions.

They end with a careful admonition:

“As policy shifts toward legalization of marijuana, it is reasonable and probably prudent to hypothesize that its use will increase and that, by extension, so will the number of persons for whom there will be negative health consequences.”

Peter Schorsch is the President of Extensive Enterprises and is the publisher of some of Florida’s most influential new media websites, including,,, and Sunburn, the morning read of what’s hot in Florida politics. SaintPetersBlog has for three years running been ranked by the Washington Post as the best state-based blog in Florida. In addition to his publishing efforts, Peter is a political consultant to several of the state’s largest governmental affairs and public relations firms. Peter lives in St. Petersburg with his wife, Michelle, and their daughter, Ella.