Could This Recent Study on Casual Marijuana Use Crush Marijuana's Momentum?

Source: Flickr user Moran Rijavec

If you polled Americans a decade ago for their opinion on marijuana, there's a good chance you would have received an overwhelming number of responses against the idea of legalization. In fact, Gallup polls suggest that just one-in-four respondents were in favor of legalizing marijuana 10 years ago.

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Marijuana's perception evolution Nowadays things are far different. A Gallup poll in 2013 showed that nearly three in five people are in favor of marijuana's legalization. Furthermore, growing public acceptance of marijuana for its medical benefits and the tax revenue it can generate have led to 23 states approving marijuana for medical purposes and four legalizing it for recreational, adult use.

Source: Flickr user Cannabis Culture

But just because marijuana's momentum is increasing doesn't mean that the slate of studies highlighting its potential dangers have decreased in any meaningful way. Of course I'd be remiss if I didn't mention that a majority of studies to date (and when I say majority I mean more than nine out of 10) have examined marijuana's negative effects rather than any benefits it might present, so the sheer number of negative studies could very well be due to this research imbalance.

Still, studies like the one presented in the Journal of Neuroscience by nine authors last year, including those from Harvard Medical School, Northwestern University, and Massachusetts General Hospital, concerning cannabis use in young adults, could remain a deterrent toward a rapid expansion of marijuana's potential uses in the medical field.

Will this study limit marijuana's momentum?For the study, researchers used magnetic resonance imaging, or MRIs, to compare the brains of low-to-moderate marijuana users between the ages of 18 and 25 to a control group that didn't use marijuana of the same age range. There were 40 people chosen for the study: 20 low-to-moderate marijuana users and 20 control group participants. In spite of running psychiatric evaluations to ensure that none of the 20 marijuana users were dependent on the drug, a discernible difference became apparent on the MRIs of young adult marijuana users relative to the control group.

Specifically, researchers compared the size, shape and density of the nucleus accumbens (the portion of the brain that controls motivation, pleasure and addiction) and the amygdala (which plays a central role in emotions), discovering that marijuana users had greater gray matter density and shape differences than nonusers. The study was consistent with what researchers had witnessed in animal models, and higher marijuana use resulted in greater shape and volume abnormalities in the MRIs.

Source: Flickr user Torben Hansen

As National Institute on Drug Abuse researcher Carl Lupica noted in an interview with Science Daily, "This study suggests that even light to moderate recreational marijuana use can cause changes in brain anatomy. These observations are particularly interesting because previous studies have focused primarily on the brains of heavy marijuana smokers, and have largely ignored the brains of casual users."

On the flipside, it should also be noted that a 40-person study probably isn't representative of the entire population. In fact, the study points out that "causation cannot be determined, although marijuana exposure parametrically correlated with structural differences." Furthermore, no quantifiable marijuana metabolite levels were measured in patients, leaving researchers in the dark as to what amount of marijuana exposure the participants in its study were actually dealing with. In short, more studies than just this one would be needed to definitively say that marijuana has negative effects on the brains of casual young users.

Still a negative for medical marijuana Despite needing additional research to be proven accurate, this and a number of other small studies that have delved into the mind-altering effects of marijuana on our nation's adolescents and young adults add enough doubt about its long term safety that the federal government is unlikely to change its stance on marijuana as a schedule 1 drug anytime soon.

Even more than that, these studies could make drug development difficult for pharmaceutical companies looking to fight tough-to-treat diseases with cannabinoids derived from the cannabis plant. For example, GW Pharmaceuticals is currently developing a promising adult and pediatric drug known as Epidiolex, which uses CBD extract.

Source: GW Pharmaceuticals

In early clinical studies for Epidiolex, Dravet syndrome patients saw their convulsive seizure frequency fall by 56%, while patients with Lennox-Gastaut syndrome had a nearly similar 52% reduction in seizure frequency. These are rare epileptic diseases that often manifest in childhood; thus any drug derived from the cannabis plant that may need to be administered over the long run in adolescents could be a concern if marijuana in fact does have serious long-term effects on the brain.

The story here remains the same: We need more studies that look into the potential benefits and drawbacks of marijuana. We are beginning to see studies like this undertaken, but it takes time to develop a big picture view on the benefits and risks of marijuana when the studies were so far skewed in one direction for decades. It's possible we could discover a world of benefits for marijuana. We've already seen studies speak to its potential to help aggressive brain cancer patients as well as diabetes and Alzheimer's patients. Then again, there is a mountain of negative data to contend with as well.

Caveat emptor From an investing perspective, marijuana still looks far too hit and miss for even long-minded investors. GW Pharmaceuticals is the go-to stock here if you are planning to dabble in the marijuana trade, but a recent failure from Sativex in the first of a three-part late-stage trial could take the wind out of its sails for the time being. Plus, with profitability still at least five years out, I'd suspect there are far better investment opportunities available.

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Sean Williamshas no material interest in any companies mentioned in this article. You can follow him on CAPS under the screen nameTMFUltraLong, track every pick he makes under the screen nameTrackUltraLong, and check him out on Twitter, where he goes by the handle@TMFUltraLong.The Motley Fool has no position in any of the stocks mentioned. Try any of our Foolish newsletter servicesfree for 30 days. We Fools don't all hold the same opinions, but we all believe thatconsidering a diverse range of insightsmakes us better investors. The Motley Fool has adisclosure policy.

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