What happened

Marijuana stocks slipped in Wednesday afternoon trading. Shares of Sundial Growers (SNDL -2.93%) are trading down 2.8% as of 2:35 p.m. EDT, followed by Aurora Cannabis (ACB -2.48%) with a 3.2% loss, Hexo (HEXO) down 3.8%, and Canopy Growth (CGC -1.71%) bringing up the rear with a 4.1% decline.

I blame CNN.

Marijuana plants,

Image source: Getty Images.

So what

Citing a report from the Canadian Medical Association Journal Tuesday, CNN warned that "whether you smoke it, vape it, or eat it as an edible, cannabis may be significantly increasing your risk of a heart attack" -- and that may have investors worried about investing in cannabis right now.  

How big of a risk are we talking about? According to a CMAJ analysis of a study involving 33,000 adults ages 18 to 44, says CNN, cannabis users under age 45 suffer heart attacks at nearly twice the rate of people who don't. Researchers theorized that the "extremely potent" strains of marijuana in use today may be affecting users' heart rates, adding to "increasing evidence that this could potentially be harmful to you."

Additionally, CNN cited research from the American Heart Association warning that "cannabis can have negative interactions with ... cardiovascular medications like blood thinners."

Now what

Could there be other reasons that cannabis stocks are down -- like the fact that the whole stock market seems to be in the red today, for example? Absolutely. But marijuana stocks are getting hit particularly hard -- harder than most other stocks. And I suspect it's largely these new reports of health risks from marijuana use, piled atop other warnings of risks to users' mental health that appeared in the news back in July, that are the primary cause of today's declines in marijuana stocks in particular.

What's more, so long as legislation to legalize marijuana remains under consideration in the U.S. House and Senate, I expect we'll see more stories along these lines as lobbyists for and against legalization try to catch the attention of legislators, and the media tries to capitalize on the story. So, even now that legalization seems inevitable -- with so many states having legalized already, and Congress likely to follow in time -- long-term investors in marijuana stocks will need to exercise patience.

Legalization will come, but that doesn't mean it will be a smooth ride getting there.