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NIDA. (2014, September 8). What’s Wrong With “Medical Marijuana”?. Retrieved from

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The NIDA Blog Team
September 8 2014
Jars of marijuana in a dispensary

This is the first post of a 3-part series on the science of medical marijuana.  Check out Part 2: Making Medicine From Marijuana, and Part 3: Medicines or Poisons?—Why Cannabinoids Can Both Help and Hurt You.

Before modern medical science, most medicines were raw herbs or herbal concoctions of one sort or another. They sometimes helped patients, but those benefits weren’t very powerful by today’s standards, and they often had a lot of unpredictable or even dangerous side effects.

That’s because all plants contain hundreds or thousands of different chemicals. If you eat or smoke the leaves of any plant, you are putting all those chemicals in your body, and the results can be unpredictable.

Marijuana is no different.

Still, there is growing public support for “medical marijuana,” based on anecdotal evidence (that is, from individual people’s personal experience) that the drug might be useful in treating various diseases, including PTSD (post-traumatic stress disorder), pain, and epilepsy.

Voters in 23 states have now passed laws allowing marijuana to be dispensed to patients, as long as they receive permission from a doctor.

Why doesn’t the Food and Drug Administration (FDA) approve “medical marijuana”?

Turns out, there’s very little scientific evidence that smoking or eating marijuana is effective and safe for treating any medical issues. Scientific evidence would have to come from carefully controlled research studies.

Since there’s no science to back it up, the FDA has not approved smoked or vaporized marijuana for the treatment of any medical condition.

The FDA only approves medicines when large studies examining lots of patients (called clinical trials) show that the medicines work safely. Without these studies, the FDA can’t promise people that the medications will help them and not harm them. 

So why haven’t there been clinical trials on marijuana? 

Because marijuana is a raw herb. There are over 500 different chemicals in marijuana, in combinations that vary widely between different strains and even from plant to plant. This causes serious problems trying to use the whole marijuana leaf, or crude extracts like hash oil, as medicine:

  1. It’s hard to deliver precise, accurate doses of the right chemicals;
  2. It can harm the lungs if users smoke it; and
  3. It causes additional effects—like the “high”—that may interfere with the quality of life of patients taking the drug for serious medical conditions.

Plus, when used by teens or children, it could even harm their brains as they develop.

Today, there are almost no approved medicines that are whole herbs. Although it’s not impossible, it would be very unusual if marijuana became an exception.

How can we discover and use marijuana’s medical benefits without the harms?

In Part 2, you'll learn how scientists are busy trying to create actual medicines from the chemical ingredients in marijuana.