The legal marijuana industry isn't just called the "green rush" because it sounds snazzier. The industry is growing at an incredible rate, and investors have certainly taken notice, with a majority of larger marijuana stocks having at least doubled in market cap this year.

Regardless of your source, growth estimates from the legal cannabis industry put nearly all other growth stories to shame. For instance, investment firm Cowen & Co. believes that U.S. pot sales could hit $50 billion by 2026, up from around $6 billion now. That type of consistent growth is nearly impossible for investors to ignore.

A person holding cannabis leaves in their cupped hands.

Image source: Getty Images.

Marijuana stock investors were also privy to a plethora of positive events in 2017, which may have helped budding pot stocks even more. For instance, Nevada began selling recreational marijuana on July 1, 2017, while West Virginia became the 29th state to have legalized medical cannabis. To the south, Mexican President Enrique Pena Nieto signed into law a bill legalizing medical cannabis throughout the country. And to our north, Prime Minister Justin Trudeau introduced legislation in April designed to legalize recreational marijuana in Canada by July 2018. With the details being hashed out, it's looking likely that adult-use weed will be legal in Canada by next year.

Public opinion has also played a role in lifting the cannabis industry in 2017. National pollster Gallup has been keeping tabs on the American public's perception on pot for nearly 50 years. In this year's survey, an all-time record 64% of respondents favored the idea of legalizing the drug, compared to just a quarter of all respondents as recently as 1995. A separate poll from the independent Quinnipiac University found even greater support for medicinal cannabis, which 94% of survey-takers want to see legalized. Conversely, just 4% opposed the idea of legalizing medical marijuana. 

The biggest marijuana news story of the year probably slipped under the radar

Yet, for all of these positives, there's perhaps an even bigger marijuana story out there this year -- and it amazingly didn't occur until mid-December.

A cannabis bud atop a doctor's prescription pad.

Image source: Getty Images.

This past week, the World Health Organization (WHO), which is a specialized agency within the United Nations whose central concern is international public health, declared that cannabidiol (CBD), the non-psychoactive component of the cannabis plant, should not be scheduled. Here's the full excerpt from WHO's press release:

There is increased interest from Member States in the use of cannabis for medical indications including palliative care. Responding to that interest and increase in use, WHO has in recent years gathered more robust scientific evidence on therapeutic use and side effects of cannabis and cannabis components.

To that end, the ECDD [Expert Committee on Drug Dependence] did an initial review of a cannabis compound called cannabidiol (CBD). Recent evidence from animal and human studies shows that its use could have some therapeutic value for seizures due to epilepsy and related conditions. Current evidence also shows that cannabidiol is not likely to be abused or create dependence as for other cannabinoids (such as Tetra Hydro Cannabinol (THC), for instance). The ECDD therefore concluded that current information does not justify scheduling of cannabidiol and postponed a fuller review of cannabidiol preparations to May 2018, when the committee will undertake a comprehensive review of cannabis and cannabis related substances. 

This is big news considering U.S. Attorney General Jeff Sessions has drawn a line in the sand with regard to medical cannabis' therapeutic effects. In the United States, marijuana is wholly illegal and on par with drugs like heroin and LSD.

However, WHO's data suggests that CBD may provide genuine benefits to patients without any risk of dependency or abuse. While it's unlikely to sway the opinion of the U.S. Drug Enforcement Agency or Food and Drug Administration, WHO's evidence-based opinion could open the door for significant medical use throughout Europe. As a reminder, we've already witnessed numerous European countries setting up import contracts with Canadian-based growers for medical patients with certain illnesses.

Cannabis leaves next to test tubes and other biotech lab equipment.

Image source: GW Pharmaceuticals.

CBD-based medicines have demonstrated positive clinical benefits in the U.S.

This news from WHO may not come as a surprise to many, as we've already witnessed a handful of clinical studies in which CBD-based drugs have demonstrated positive results in the United States. For example, GW Pharmaceuticals' (NASDAQ:GWPH) lead experimental drug, Epidiolex, is a cannabidiol-based medicine that delivered a statistically significant reduction in seizure frequency for patients with two rare types of childhood-onset epilepsy, Dravet Syndrome and Lennox-Gastaut syndrome. In fact, patients with Dravet syndrome demonstrated a three times greater reduction in seizure frequency from baseline (39%) than under the placebo (13%).

Similarly, in September Zynerba Pharmaceuticals (NASDAQ:ZYNE) announced positive top-line data involving its CBD-based gel, ZYN002, in pediatric and adolescent patients with Fragile X syndrome. The study met its primary endpoint, demonstrating a 46% improvement in the total score of Anxiety, Depression, and Mood Scale at the 12-week mark compared to baseline. 

A separate study released in August (the Stop trial) involving ZYN002 from Zynerba showed that the drug failed to meet its primary endpoint as a treatment for knee pain due to osteoarthritis. However, it hit a number of key secondary endpoints, including the complete responder analysis, which is defined as a greater than or equal to 30% reduction in worst average daily pain scores.

Taking into account that CBD doesn't cause the psychoactive effects as does THC, you should expect CBD to remain a key cannabinoid-based focus of numerous drugmakers in the U.S. and abroad.

Sean Williams has no position in any of the stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. The Motley Fool has a disclosure policy.