Blog | Monday, August 18, 2014

Why I'm skeptical about marijuana's medical benefits

There’s a little place up the street from me with a great beer list. My favorite is a Trappist ale that I order maybe once or twice a year (an ale whose name I never remember but simply refer to as “my medicine”). It’s great after a particularly stressful day, not because of the serenity of the monks who brew it, but because of its ridiculously high alcohol content. A glass of this medicine takes the edge off of just about anything.

As of July 5, the state of New York has a medical marijuana program. Medical cannabis laws have become the “gateway” law toward full legalization. Legalized medicinal use of marijuana has become less and less controversial, the main exceptions being anti-drug zealots and doctors and scientists who look at the evidence objectively.

Decriminalization and medical use of pot are (or should be) separate questions. The decision to legalize pot should be based on a risk-benefit analysis: are we better off tossing people in jail for using a relatively mild drug, and supporting an illegal trade, or should we make it legal, regulate it, and tax it?

The medical use of marijuana is a different question, not one of social policy but of science: are there specific medical benefits to cannabis? If so, what are they? Should we look at pot as another legal drug like alcohol and tobacco, or should we treat it as medicine?

If we are going to treat pot as medicine, it will have to do a better job at proving itself worthy of that title. There are plenty of prescription medicines of questionable benefit and with the potential to harm. Some are worse than useless, despite being legal, and some are nearly miraculous. Where does cannabis fit in?

The science so far doesn’t look good. At this point, despite thousands of studies, there is very little evidence that cannabis is good for any specific medical condition. If you choose to cherry-pick the data a bit, you can find some evidence for benefit in some sorts of painful nerve disorders. And that’s about it. Pot, when tested alone or compared to currently available treatments doesn’t seem to carry any of the advantages touted by its supporters.

This isn’t to say marijuana has no benefits. Many people report it helps them with the symptoms of a wide variety of medical conditions. But is this any different from my Trappist medicine?

Maybe. As research continues into the various chemicals that marijuana carries into your body, our understanding (which is already impressive) will grow. We probably will find some use for marijuana, but I doubt it will be a stand-out in our pharmacopoeia. Like any scientist, my mind is open to new data, to altering my hypothesis as the evidence changes. But one thing we’ve learned in medicine in the last century is that it can be dangerous to leap too far out ahead of the evidence. The line between excitement about a potential new medication and hucksterism is a narrow one.

The Wall Street Journal (disclosure: not my favorite editorial page) just published an opinion piece in support of medical marijuana, one that should be viewed with skepticism. The author, Steven Patierno, explains how non-smoked cannabis, in carefully documented doses, can bring great benefit. His industry disclosure shows him to chair the medical board of a company called PalliaTech that—surprise, surprise—works on developing carefully dosed, non-smoked cannabis medications. This doesn’t invalidate everything he writes, but it makes it suspect, especially if he doesn’t give us hard data (he doesn’t).

Last night I watched a CNN piece on medical marijuana (“Weed2″). It followed the sad case of a young girl with a horrible seizure disorder and her parents’ struggle to get her help. According to Sanjay Gupta, they finally found some help with cannabis, and the piece documents their struggle to get their daughter the medicine that they believe is helping her.

It makes for a great story, but it gives us no help in deciding if marijuana has any legitimate medical uses. A thorough search of the medical literature finds no good studies that support the use of cannabis or any of its constituents in seizure disorders. This doesn’t invalidate this family’s experiences: perhaps this is worthy of further study. What alarms me is the implication that a good parent is the one who gets an unproven medication for their child, no matter the evidence.

If I were the parent of a child with a rare disease, I would probably do as the family on CNN. I’d try anything. But as a doctor, I’d recommend against using what is clearly a powerful drug/medication in a way that may do no good and may even cause harm, especially in a child.

The active chemicals in marijuana have many effects on the brain, and likely elsewhere in the body. These effects are worthy of continued study, and I wouldn’t be surprised if marijuana or drugs derived from it find a legitimate place in the pharmacy. At this point, though, it’s mostly hope, fantasy, and guesswork.

The question of legalization is an important one, but distinct from pot’s potential as medicine. One is a decision based on our values. The other on cold, hard, dispassionate science. We should keep this distinction clear and stop using medical marijuana as a stepping stone to legalization.

Peter A. Lipson, ACP Member, is a practicing internist and teaching physician in Southeast Michigan. After graduating from Rush Medical College in Chicago, he completed his internal medicine residency at Northwestern Memorial Hospital. This post first appeared at his blog at Forbes. His blog, which has been around in various forms since 2007, offers "musings on the intersection of science, medicine, and culture." His writing focuses on the difference between science-based medicine and "everything else," but also speaks to the day-to-day practice of medicine, fatherhood, and whatever else migrates from his head to his keyboard.