As recently as the end of March, cannabis stocks were chugging along and handily outpacing the returns of the broader market. At one point, there were more than one dozen marijuana stocks sporting a market cap of at least $1 billion. But times have definitely changed.

Since the first quarter ended, the Horizons Marijuana Life Sciences ETF, the first-ever cannabis-focused exchange-traded fund, has lost about 56% of its value, inclusive of dividends paid, and aggregate market value losses for the entire industry look to be well in excess of $40 billion. As of the end of November, just nine pot stocks remain as billion-dollar companies, and this figure may continue to decline.

A tipped over clear jar packed with dried cannabis buds that's lying atop a small pile of cash.

Image source: Getty Images.

1. Canopy Growth: $6.48 billion

Although Canopy Growth (NASDAQ:CGC) easily remains the largest marijuana stock by a mile, the company has shed more than $10 billion in market cap in just a seven-month time frame. Over that span, we've witnessed Canopy Growth's share-based compensation and goodwill soar, leading to bigger losses and an ugly balance sheet. To top things off, Canopy's board fired its visionary co-CEO Bruce Linton in early July and has still yet to name a permanent successor, which sort of puts the company's long-term plans into flux. Suffice it to say that there's very real downside possibility still left in the world's largest pot stock.

2. GW Pharmaceuticals: $3.19 billion

Even though management prefers that it not be lumped in with "marijuana stocks," GW Pharmaceuticals (NASDAQ:GWPH) now finds itself as the second-largest pot stock. GW Pharmaceuticals, which has benefited from the rapid uptake of Epidiolex and the company's ability to secure insurance coverage for its lead drug, is liable to be profitable much earlier than Wall Street had initially anticipated. Although this hasn't saved the company's share price from being beaten up in recent months, a possible label expansion for Epidiolex, or positive clinical data for any of the other cannabinoid-based drugs in GW Pharma's pipeline, should do the trick.

3. Curaleaf Holdings: $2.8 billion

The largest U.S. pot stock in the world is Curaleaf (OTC:CURLF), which chimes in with a valuation of $2.8 billion after leading all cannabis stocks to the upside in November. Curaleaf currently has more open locations (50) than any other multistate operator, and on a pro forma basis is pushing for the lead in total retail licenses held. The company has also benefited of late from the passage of the Marijuana Opportunity, Reinvestment, and Expungement (MORE) Act by the House Judiciary Committee, which could signal that the tide is turning on Capitol Hill when it comes to cannabis reform.

A dried cannabis bud and small vial of cannabinoid-rich oil next to a small Canadian flag.

Image source: Getty Images.

4. Aurora Cannabis: $2.64 billion

Maybe the biggest surprise on the entire list is how far Aurora Cannabis (NASDAQ:ACB) has fallen. Once a nearly $10 billion company that was pushing Canopy Growth for the top spot, Aurora has face-planted since mid-March, losing about three-quarters of its value. Over the past five years, Aurora has drowned its shareholders by issuing over 1 billion shares of its common stock, and it's currently lugging around an unsightly $2.4 billion in goodwill on its balance sheet. After overpaying for more than a dozen acquisitions, and with losses mounting, the most popular pot stock among millennials is finding little love of late.

5. Cronos Group: $2.36 billion

Having a lot of cash on hand isn't necessarily saving pot stocks anymore, as evidenced by Cronos Group's (NASDAQ:CRON) fall from grace. Despite sporting close to $1.5 billion in cash and short-term investments -- pretty much all of which came from a $1.8 billion equity investment from Altria Group that was completed in March -- Cronos Group continues to lose money on an operating basis, once one-time benefits are stripped from the equation. This is also a company whose outlook has taken a hit due to the vaping health scare in the United States. Cronos is no longer a sure thing to "kick bud" when derivatives hit Canadian dispensary shelves in about two weeks.

6. Tilray: $1.99 billion

Speaking of how the mighty have fallen, need I remind everyone that Tilray (NASDAQ:TLRY) moon-shot to a valuation of $26 billion just two months following its initial public offering, only to give up most of that market cap over the past year. Tilray's management team has looked lost at times, with the company de-emphasizing investments in Canada in favor of Europe and the U.S., and continuing to lose quite a bit of money on an operating basis. Tilray's purchase of hemp foods company Manitoba Harvest has added some predictability to its bottom line, but it's also been a drag on margins.

A large cannabis dispensary sign in front of a retail store.

Image source: Getty Images.

7. Green Thumb Industries: $1.92 billion

Other than Curaleaf, the only other billion-dollar pot stocks in the U.S. are vertically integrated multistate operator Green Thumb Industries (OTC:GTBIF) and the next company on this list. Green Thumb has been making acquisitions to move into potentially lucrative marijuana markets, such as Nevada, and is nearing 100 retail licenses owned. Further, the company has received a bit of a boost of late from discussion on the MORE Act. Even with Senate Majority Leader Mitch McConnell (R-Ky.) unlikely to bring the MORE Act to the Senate floor for vote, assuming it's passed by the House, momentum continues to push cannabis into the political spectrum.

8. Trulieve Cannabis: $1.42 billion

That "next company" is none other than Florida's Trulieve Cannabis (OTC:TCNNF). Trulieve is among the few pot stocks that's actually having a good year. The company's laser focus on the Florida market has led to the opening of 40 stores in the Sunshine State, while at the same time allowing Trulieve to keep its costs down and effectively build its brand. No pot stock is more profitable at the moment. 

9. Aphria: $1.2 billion

Last, but not least, Aphria (NASDAQ:APHA) continues to cling to its billion-dollar market cap, despite losing it very briefly in November. Aphria has benefited in recent quarters from steady results in its pharmaceutical distribution business, as well as positive fair-value adjustments from its cannabis operations. But when looking strictly at its pot business, Aphria is still losing money on an operating basis. Further, it's yet to fully regain the trust of investors following two notable transactions. It would not be a surprise if Aphria loses its billion-dollar valuation.

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.