Marijuana as a "pain distracter"

To determine exactly how cannabis relieves pain, a group of Oxford researchers used healthy volunteers, an MRI machine and doses of THC, the active ingredient in marijuana. Their findings, published today in the journal Pain, suggest something counterintuitive: that the drug doesn’t so much reduce pain as make the same level of pain more bearable.

“Cannabis does not seem to act like a conventional pain medicine,” Michael Lee, an Oxford neuroscientist and lead author of the paper, said in a statement. “Brain imaging shows little reduction in the brain regions that code for the sensation of pain, which is what we tend to see with drugs like opiates. Instead, cannabis appears to mainly affect the emotional reaction to pain in a highly variable way.” 

This indicates that marijuana doesn’t function as a pain killer as much as a pain distracter: Objectively, levels of pain remain the same for someone under the influence of THC, but it simply bothers the person less. It’s difficult to draw especially broad conclusions from a study with a sample size of just 12 participants, but the results were still surprising. 

From at the Smithsonian's Surprising Science blog.