Image source: Cannabis Culture, Flickr.

Last year was, unquestionably, marijuana's breakout year if there ever was one.

You could certainly argue that 1996, the first year that California approved medical cannabis, or 2012, the first year that Colorado and Washington approved recreational weed, were marijuana's breakout years. But 2016 saw five states approve medical cannabis (two of which did so by entirely legislative means), while four additional states legalized recreational pot, doubling the number of adult-use states to eight. Furthermore, Gallup's poll showed that nationwide approval for pot is now at an all-time high of 60%, and sales of legal weed continue to grow by a double-digit annual percentage.

Marijuana also enters 2017 with a lot of momentum. President-elect Donald Trump placed his support behind the legalization of medical cannabis during his campaign, and he's maintained that the federal "hands-off" approach to regulating pot is probably the best method for now. In other words, marijuana would appear to be on track to grow sales and add more legal states to the medical cannabis and recreational pot columns in the years to come.

Nationwide legalization remains elusive

However, a rescheduling of marijuana at the federal level remains elusive. Republicans in charge of Congress have demonstrated little desire to change its current illicit status, and the U.S. Drug Enforcement Agency passed on its opportunity to reschedule the substance this past August. The DEA suggested in its ruling that marijuana has a high potential for abuse, currently has no accepted medical use, and that it lacks accepted safety measures of use, even under medical supervision.

Image source:, Flickr.

Pro-legalization advocates, especially those who support the legalization of medical cannabis, have been particularly critical of the stance the DEA has taken with regard to labeling marijuana as having no medical benefits and not being safe. Various clinical studies run by universities and researchers have demonstrated clinical benefits for marijuana and/or its cannabinoids in treating diseases such as glaucoma, epilepsy, type 2 diabetes, chronic pain, and even cancer. What's more, pro-legalization advocates will point to the fact that no one has died from an overdose of marijuana as proof of its safety compared to prescription opioids, which claimed about 15,000 lives in 2015 from overdoses.

Is long-term marijuana use actually dangerous?

But marijuana's safety profile isn't perfect. In fact, according to recent data in the post-legalization environment in select states, marijuana could prove dangerous to some users.

As reported by CBS News last week, the number of incidences of a somewhat rare and mysterious illness characterized by nausea, vomiting, and abdominal pain in long-term marijuana users has been on the rise. The disease, known as cannabinoid hyperemesis syndrome, or CHS, tends to go largely undiagnosed by physicians, especially emergency room physicians, because a patient often has to present with similar symptoms on numerous occasions, and have standard imaging tests done, to rule out other possible causes of their symptoms. It's known to cause dehydration and kidney failure in patients, but resolve with IV fluids and the termination of marijuana use within a few days. Users also note that taking hot showers or baths tended to resolve the symptoms.

Image source: Getty Images.

According to a study co-authored by Dr. Kennon Heard, an emergency room physician at the University of Colorado Hospital in Aurora, Co., emergency room visits with a CHS diagnosis nearly doubled in two Colorado hospitals since 2009, when medical cannabis became widely available within the state. "It is certainly something that, before legalization, we almost never saw. Now we are seeing it quite frequently," said Dr. Heard in his interview with CBS News.

However, Forbes contributor Robert Glatter, MD, also brings up an excellent point. Dr. Heard's study suggests that the propensity of long-term marijuana users to admit their use to a physician in a post-legalization environment may have led to an increase in diagnoses compared to the pre-legalization setting where admitting marijuana use to a physician was viewed as taboo. In other words, the near-doubling in CHS incidences since medical cannabis became widely available may be overstated.

What's also not well understood is what's caused a complete bifurcation from the norm when it comes to marijuana use. Normally, cannabis acts as an antiemetic that keeps people from being nauseous. In this instance, cannabis became the source of nausea in select long-term users. One theory, as pointed out by Glatter, is that a buildup of cannabidiol (CBD), the non-psychoactive component of pot, could be the cause. In animal models, low doses of CBD led to an antiemetic effect, whereas large CBD doses had the opposite effect.

Image source: Getty Images.

Only time will tell

This recently released data suggests that there are still quite a lot of unknowns with regard to long-term marijuana use. It doesn't necessarily suggest that marijuana is dangerous; but it's not exactly a glowing endorsement for safety, either.

The only way the pot industry is going to sway Congress or the DEA is if there's clear-cut evidence from a Food and Drug Administration-approved clinical trial that the benefits of cannabis outweigh the apparent risks. Of course, getting the FDA's approval to run well-designed and controlled trials has been essentially nonexistent. This is one of the many Catch-22 loops pot is stuck in. Researchers can't offer acceptable evidence to the FDA that marijuana may have medically beneficial properties because of its schedule 1 status, but the DEA won't reschedule marijuana until it has this evidence in hand.

The other Catch-22 for pot is that even if Trump and Congress do wind up legalizing medical marijuana at the federal level, things aren't necessarily going to get easier for the industry. Rescheduling cannabis to schedule 2, the most logical step if it were legalized, would admit that the substance has medically beneficial properties, but it would also place medical cannabis under the strict regulation of the FDA. The FDA could dictate how pot businesses market and package their product, it would likely oversee the manufacturing and processing of pot, and it could require medical marijuana companies to run FDA-approved clinical studies to demonstrate the effectiveness of pot in treating certain ailments. In other words, we're talking about a wave of new regulations that could wind up bankrupting a number of smaller industry players.

2016 was unmistakably a great year for marijuana, but the future for pot isn't nearly as clear.