There’s Been Over 20,000 Studies On Marijuana; What Is It That Scientists ‘Do Not Yet Know?’

US News & World Report recently probed the subject of cannabis science, publishing a pair of stories on the subject here and here.

Neither story particularly breaks any new ground, though the author (who I spoke with extensively prior to the stories publication) does note that investigators are now assessing the use of cannabis for a wide range of disease conditions, including Alzheimer’s disease and the so-called ‘superbug’ MRSA (multi-drug resistant bacterial infections).

Quoted in the story is Columbia University researcher Margaret Haney. I’ve written about Haney’s clinical work with cannabis before. In particular, Haney was the lead author of a 2007 clinical trial concluding that inhaled cannabis increased daily caloric intake and body weight in HIV-positive patients in a manner that was far superior to the effects of oral THC (Marinol aka Dronabinol). The study further reported that subjects’ use of marijuana was well tolerated, and did not impair their cognitive performance.

Yet Haney’s comments in US News and World Report ring tepid at best.

“I am not anti-marijuana, I’m not pro-marijuana. I want to understand it.” Haney expresses frustration at what she considers wrongheaded efforts by states to legalize medical marijuana. There is too much, she says, that scientists do not know.

Haney’s refrain is a common one, and at first glance it appears to make sense. After all, who among us doesn’t want to better understand the interactions between the marijuana plant and the human body? Yet placed in proper context this sentiment appears to be little more than a red herring. Here’s why.

Marijuana is already the most studied plant on Earth, and is arguably one of the most investigated therapeutically active substances known to man. To date, there are now over 20,000 published studies or reviews in the scientific literature pertaining to marijuana and its active compounds. That total includes over 2,700 separate papers published on cannabis in 2009 and another 900 published just this year alone (according to a key word search on the search engine PubMed).

And what have we learned from these 20,000+ studies? Not surprisingly, quite a lot. For starters, we know that cannabis and its active constituents are uniquely safe and effective as therapeutic compounds. Unlike most prescription or over-the-counter medications, cannabinoids are virtually non-toxic to health cells or organs, and they are incapable of causing the user to experience a fatal overdose. Unlike opiates, cannabinoids do not depress the central nervous system, and as a result they possess a virtually unparalleled safety profile. In fact, a 2008 meta-analysis published in the Journal of the Canadian Medical Association (CMAJ) reported that cannabis-based drugs were associated with virtually no serious adverse side effects in over 30 years of investigative use.

We also know that the cannabis plant contains in excess of 60 active compounds that likely possess distinctive therapeutic properties. These include THC, THCV, CBD, THCA, CBC, and CBG, among others. In fact, a recent review by Raphael Mechoulam and colleagues identifies nearly 30 separate therapeutic effects — including anti-cancer properties, anti-diabetic properties, neuroprotection, and anti-stroke properties — in cannabinoids other than THC. Most recently, a review by researchers in Germany reported that since 2005 there have been 37 controlled studies assessing the safety and efficacy of cannabinoids, involved a total of 2,563 subjects. By contrast, most FDA-approved drugs go through far fewer trials involving far fewer subjects.

Finally, we know that Western civilization has been using cannabis as a therapeutic agent or recreational intoxicant for thousands of years with relatively few adverse consequences — either to the individual user or to society. In fact, no less than the World Health Organization commissioned a team of experts to compare the health and societal consequences of marijuana use compared to other drugs, including alcohol, nicotine, and opiates. After quantifying the harms associated with both drugs, the researchers concluded: “Overall, most of these risks (associated with marijuana) are small to moderate in size. In aggregate they are unlikely to produce public health problems comparable in scale to those currently produced by alcohol and tobacco. On existing patterns of use, cannabis poses a much less serious public health problem than is currently posed by alcohol and tobacco in Western societies.”

That, in a nutshell, is what we ‘know’ about cannabis. I’d say that it’s ample enough information to, at the very least, cease the practice arresting people who possess it.  As for what else Dr. Haney and others of a similar mindset would still like to know — and how many additional studies would it take to provide them with that information — well, that’s anybody’s guess.