In case you haven't noticed, marijuana stocks have been nothing short of unstoppable over the past year. As of a few weeks prior, the average marijuana stock with a market cap in excess of $200 million had risen an average of more than 300% over the trailing-12-month period. And if we look at some of the macro catalysts behind these moves, it's not hard to understand why marijuana stocks have come into focus.

Two macro catalysts push pot stocks higher

For example, the percentage of respondents in surveys who favor the legalization of cannabis across the country has been on a pretty steady incline in recent years. Both the 2016 Gallup poll and April 2017 CBS News survey showed an all-time respective high of 60% and 61% of respondents who now want to see pot legalized nationally. A separate survey from Quinnipiac University in April found an overwhelming 94% of Americans want to see medical cannabis legalized. The thought here is that if consumers want marijuana legalized, elected officials will eventually have to listen or risk being voted out of office.

Cannabis buds in a jar lying atop a pile of investors' cash.

Image source: Getty Images.

The other catalyst has been legal weed sales. According to ArcView, a leading cannabis research firm, North American marijuana sales grew by 34% last year to $6.9 billion, and they're projected to grow by a compound annual rate of 26% through 2021. This implies a potential market value of up to $22 billion in North America. If legal sales are growing this rapidly, the thought is it should translate into superb sales growth and profitability for marijuana stocks.

These two volatile marijuana stocks went in opposite directions last week

However, with recreational marijuana still illegal in every country throughout the world, save for Uruguay, the only guarantee with pot stocks is volatility. Last week, investors witnessed this volatility in two particular marijuana stocks, which moved by a double-digit-percentage, but in completely opposite directions.

Canopy Growth Corp.

Leading the charge higher last week was Canadian medical cannabis producer and retailer Canopy Growth Corp. (NASDAQ:CGC), which rose by 11.4% and continued a recent string of market outperformance. Two catalysts appear to be behind the move.

First, we could have seen some carryover from the announcement on July 20 that Isodiol International had signed a licensing agreement with Canopy Growth that allows Canopy Growth to distribute Isodiol's Pot-O-Coffee and Pot-O-Tea single-serve K-Cup products throughout Canada and international markets. The press release does note that individual country laws will dictate what products are available for sale in Canada and elsewhere.

An indoor commercial cannabis grow farm.

Image source: Getty Images.

What's noteworthy about this licensing deal is that it signifies the success of Canopy Growth's ability to market its brands. In other words, Isodiol wouldn't have partnered up with Canopy Growth for international exposure opportunities if it didn't believe the company was doing things right beyond Canada. It's verification that other businesses may look to Canopy Growth for partnership opportunities.

The other catalyst appears to be the completion of a private placement financing with a single investor for about $20.1 million ($25 million Canadian). The company wound up selling a little over 3 million shares of its common stock to this investor, and it intends to use the proceeds from the placement to fund its growth initiatives.

The intriguing aspect of this financing is that it was from a single investor, implying that there's ample interest in the company from wealthy investors.

Of course, what investors should really have their eyes on is the debate ongoing in the Canadian parliament concerning Prime Minister Justin Trudeau's bill to legalize recreational cannabis by July 1, 2018. The resolution of this bill in parliament is likely to determine where Canopy Growth and other Canadian pot stocks head next.

Zynerba Pharmaceuticals

On the flipside, drug developer Zynerba Pharmaceuticals (NASDAQ:ZYNE) had a miserable week, with its shares tumbling 15.4%. However, we should point out that Zynerba's stock is up 72% over the trailing year through Friday, July 28, so it's not as if the drubbing it took last week has been all that terrible for long-term shareholders.

Cannabis buds lying atop a doctor's prescription pad.

Image source: Getty Images.

The only legitimate news story that jumps out from last week was the Friday announcement that director Cynthia Rask had passed away. Rask played a pivotal role in helping Zynerba get involved in developing therapies to treat epilepsy, which is a common target indication of cannabinoid-based therapies.

However, with this news coming out late in the week and Zynerba's share price taking a beating mostly early in the week, it appears that the company's drop in price is mostly pinned on investors' emotions and short-term trading rather than anything fundamental.

It's worth pointing out that shareholders are eagerly awaiting the release of phase 2 data from two key studies – Star 1, which is examining ZYN002 in adults with epilepsy, and Stop, which also involves ZYN002 as a treatment for patients with osteoarthritis.  Zynerba noted that it was to report data on both studies in either July or August, which essentially means a data release is imminent. Considering how little we have in the way of efficacy data on ZYN002, these two studies are expected to give us our first real look at what ZYN002 can do, and whether Zynerba's drug platform has merit.

Investors would be wise to stick to the sidelines and wait for this data release before betting on Zynerba's next move.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.