Whether you realize it or not, legal marijuana is really beginning to turn heads. In North America, cannabis research firm ArcView estimates that growth in legal weed sales could average 28% per year through 2021, pushing it to nearly $25 billion annually. A big reason for this dramatic rise in sales is the expected legalization of recreational cannabis in Canada by this coming summer, marking the first time in history a developed country has green-lighted adult-use pot.

Additionally, at least within the United States, we've witnessed a marked shift in how the public views marijuana. What was once a drug that just a quarter of respondents wanted to see legalized (according to a 1995 Gallup survey) is now a drug that almost two-thirds of respondents would prefer to see legalized. Support for medicinal marijuana is even higher, with the independent Quinnipiac University finding 94% support for such an idea in an August 2017 poll. As a result, 30 states have legalized cannabis in some capacity since 1996.

But in spite of this progress, marijuana remains a Schedule I drug at the federal level in the United States. It's deemed to be wholly illegal, highly prone to abuse, and has no recognized medical benefits.

Is marijuana the key to fighting the opioid epidemic?

Yet, according to two newly published studies in JAMA Internal Medicine, medical and recreational pot may indeed offer a big benefit to the American public: a reduction in opioid use.

For those unfamiliar, prescription opioid misuse and addiction is a growing problem. Roughly 21% to 29% of patients prescribed opioids for chronic pain misuse them, some 8% to 12% develop an opioid disorder, and approximately 115 Americans die each day as a result of opioid-related overdoses, according to the National Institute on Drug Abuse. And despite being a front-and-center issue, it's not getting any better. In fact, opioid overdoses have been increasing by a double-digit percentage in recent years. Though remedies have been discussed to combat this rising rate of overdoses and abuse of prescription opioids, nothing seems to have worked.

However, when referencing prescription opioid data in states that have legalized cannabis in some capacity, researchers in two separate studies (who just so happened to have their findings published in JAMA Internal Medicine on the same day) discovered that access to legal marijuana reduced the number of opioid prescriptions.

Two studies, one similar result

The first study -- conducted by a father-daughter team, David and Ashley Bradford, along with two other researchers -- examined opioid prescription data from Medicare Part D between 2010 and 2015. According to their findings, 23.08 million daily doses of any opioid were dispensed per year in the average state under Medicare Part D. However, in states that had legalized cannabis in some capacity, opioid prescriptions written dropped by 14%. This includes a 3.7-million-dose decline in states with dispensaries of any form, and a 1.8-million-dose drop in states that allowed homegrown cannabis for medical use.

However, the authors are also quick to point out that marijuana use in select states hasn't caused opioid use to go in reverse. The study suggests it's been merely slowing the rise in the rate at which opioid prescriptions have been written and used.

The other study, conducted by Hefei Wen, Ph.D., and Jason Hockenberry, Ph.D., took a similar path. It examined opioid prescription data for Medicaid between 2011 and 2016. Medicaid generally covers working-age Americans, whereas Medicare is primary for folks aged 65 and up. The results of this second study showed a 5.88% reduction in opioid prescribing rates for states that had medical marijuana laws, and a slightly higher 6.38% reduction in prescribing rates for states with recreational cannabis laws on their books.

However, both studies are very clear that this is a correlation and not a concrete finding, which means that it'll merit more research. Running additional studies could take years, meaning we may not know for certain if cannabis offers a means to lessen the opioid crisis for some time to come.

Furthermore, there are concerns that legalizing weed across the U.S. could lead to unforeseen consequences of its own. For example, it could coerce users to try other dangerous (and illicit) drugs. It also raises concerns about driver safety, with cannabis use being shown to negatively impact users behind the wheel.

Sessions digs in his heels

In the interim, the cannabis industry probably isn't going to get very far in the U.S. with Attorney General Jeff Sessions at the helm, and that's bad news for investors.

Sessions has been very clear about his feelings on all forms of cannabis, and he's been trying hard to roll back or slow the expansion of pot in the United States. In May 2017, he sent a letter to a few of his former congressional colleagues requesting the repeal of the Rohrabacher-Farr amendment, which protects medical marijuana businesses from federal prosecution. Though unsuccessful, Sessions did succeed in rescinding the Cole memo in early January 2018, which opens the door for state-level prosecutors to use their discretion in bringing charges against individuals and businesses in violation of the Controlled Substances Act, even in states that have legalized pot.

For what it's worth, Sessions has said that he believes medical marijuana isn't an adequate substitute to fight the opioid crisis. Instead, he suggests that it's a cause (one of many) that's led to the current crisis. While speaking before the National Association of Attorneys General in March 2017, Sessions said:

Marijuana is a cure for opiate abuse? Give me a break! This is the kind of argument that's been made out there to just -- almost a desperate attempt to defend the harmlessness of marijuana of even its benefits. I doubt that's true. Maybe science will prove I'm wrong. But at this point in time you and I have a responsibility to use our best judgment, that which we've learned over a period of years, and speak truth as best we can. My best view is that we don't need to be legalizing marijuana.

In other words, cannabis remains an extremely risky investment for U.S. investors. We're potentially years away from knowing if marijuana offers any real hope of lessening the opioid epidemic, and investing on hope isn't exactly a good idea. The fact is that the federal government still holds pot to be illegal, and at any time we could see a step-up in enforcement with Sessions in charge. That's a game of chicken that this investor wouldn't recommend you play.