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Substance abuse, largely driven by an increase in marijuana smoking, has increased nationally. Marijuana is the most commonly used “illicit” drug in the United States, used by about 12% of people 12 years of age or older [PDF]. Besides smoking, an array of cannabis products exists, such as edibles, transdermal formulations, and vaping, all reducing the need for inhaling a combustible smoke product and possibly improving its safety. While marijuana is not in the addictive class of illicit drugs such as cocaine or heroin, approximately 9% of those who experiment with marijuana become drug-dependent (Drug Alcohol Depend 2011;115:120-130), a percentage even higher among those starting as teenagers. Marijuana dependency in turn can lead to an increased risk of using other illicit drugs.
The legalization of marijuana in multiple states for medical and recreational use has led to an urgent need to better understand its impact on health.
Because the brain continues developing until approximately 21 years, adolescent exposure to marijuana can be particularly harmful. Adults who smoked marijuana regularly from adolescence to adulthood have impaired neural connectivity (fewer fibers) in specific brain regions, possibly accounting for significant declines in IQ, cognitive functioning, and memory. Marijuana exposure impairs thinking, psychomotor skills, and driving ability, making it the illicit drug most frequently reported in connection with impaired driving and car accidents, including fatalities.
Long-term marijuana smoking can inflame bronchial airways, leading to bronchitis, but its risks of causing lung cancer are unclear. While it is well established that cocaine can cause heart attacks, the adverse cardiovascular effects of marijuana are less certain, though marijuana use has been linked to strokes, heart attacks, heart rhythm problems, inflammation of the heart and blood vessels, and heart muscle damage. In general, however, evidence examining the effect of marijuana on cardiovascular risk factors and outcomes, including strokes and heart attacks, is meager. In a recent study of more than 2,000 patients 50 years old or younger admitted to a hospital with a heart attack, 10% admitted to using cocaine and/or marijuana and had higher all-cause and cardiovascular mortality. Marijuana users were more likely to be smokers, which may have played a role. The incidence of out-of-hospital cardiac arrest was higher in individuals using marijuana.
We need to improve our understanding of how to capture the potential medical benefits of marijuana use while avoiding its risks. Marijuana consumption has been reported to increase appetite in wasting diseases such as AIDS, combat nausea and vomiting from cancer-treating drugs, and be beneficial in treating some symptoms of glaucoma, multiple sclerosis, Parkinson’s disease, epilepsy, chronic pain syndromes, and a host of other illnesses. Acceptable medical documentation is skimpy for most of these, however. A just-published paper suggests that marijuana liberalization might help reduce the use and consequences of prescription opioids. This would be a major advance in health care.
It’s important to recognize the possible benefits of marijuana and, at this stage, continue to gather data about this drug before deciding its permanent place in society.