This year has been a mixed bag for marijuana stocks.

After an initial rally at the start of this year, marijuana stocks have mostly been on a downward slide. The North American Marijuana Index, which is a basket of 41 tickers spanning the marijuana supply chain, is down by 19% since the start of this year, as of this writing. On balance, however, the industry’s prospects tilt towards the brighter side. According to research firm Veridian Associates, the industry raised $2 billion in funds, so far, this year. New Frontier Data, another research firm, estimates that the industry will surpass $9.5 billion in sales this year. (See also: 10 Canadian Marijuana Stocks For Your Portfolio).    

Two forces have recently determined movement of marijuana stocks, according to research firm IHS Markit. 

The first is positive news from legislative bodies in the United States and Canada, two of the industry’s largest markets. Regulatory uncertainty weighed on prices for marijuana stocks after Attorney General Jeff Sessions rescinded the Cole memo in January this year. The memo, which was crafted during the previous administration’s tenure, stops the federal government from interfering in legislation in states which have decriminalized marijuana. In April, however, President Trump indicated his support for Colorado Senator Cory Gardner (R-CO) proposed legislation that allows states to take the decision independently without federal interference. Due north, Canada is set to vote on June 7 on legislation that would bring recreational marijuana use on par with regulation for tobacco. In essence, this would amount to federal permission for the sale of marijuana.   

The second development is the proliferation of short sellers of cannabis stocks. According to IHS Markit, the short balances in marijuana-related stocks have increased by 102% since the fourth quarter of last year. At a combined short position of nearly $2 billion, the shorts in marijuana-related stocks are  “just below” the all-time high on January 24 earlier this year. Clarity in regulation could make or break short-seller fortunes. 

Here are the three most-shorted marijuana stocks, according to IHS Markit. 

Canopy Growth Corp (WEED) 

Canopy Growth’s fortunes have mirrored those of the broader industry. Its stock price is up by 12.2% this year but that figure does not tell the story of its decline in February and spike in early January. According to IHS Markit’s calculations, Canopy Growth has a total $471 million in shorts riding on it, a figure that represents an increase of $143 million since the start of this year. The Canada-based company announced the acquisition of Canopy Health Innovation, a firm that develops innovative cannabis products, earlier this year. (See also: This Is The First Fortune 500 Marijuana Stock). 

Scotts Miracle-Gro Co. (SMG)

Scotts Miracle-Gro is down by 21% year-to-date. Short sellers are feasting on its stock with short bets rising by $236 million since the start of this year. IHS Market has calculated that there is a total short value on the stock that amounts to $439 million. On the flip side, Moody’s Analytics reiterated its Ba2 rating for the company’s bonds in April after it announced the acquisition of a hydroponics company. 

GW Pharmaceuticals Plc. (GWPH) 

British company GW Pharmaceuticals is up by 15% this year. It reported a decline of 142% in its earnings last week. But short sellers are still bullish on the company. According to IHS Markit’s list, it is the only company to have witnessed a decline in short interest. That figure amounts to $20 million. GW Pharmaceuticals ranks a distant third in the list with $183 million in short bets.