A Little Marijuana Helps, but Lots May Hurt

October 23, 2007

Brandon Keim, Wired

A moderate dose of medical marijuana can soothe your hurts, both mental and physical -- but getting flat-out toasted may actually make the pain worse.

So conclude two recently-published studies, one published in The Journal of Neuroscience by McGill University researchers and the other published in Anesthesiology by researchers from the University of California. But just how strong are these findings?

In the University of California study, doctors shot capsaicin -- the pepper spray compound -- under the skin of 15 healthy volunteers, then got them high. After 45 minutes, those who smoked only a moderate dose said their pain was much better. Those who smoked a lot said their pain was worse (though, as the BBC so dutifully reports, "They did, however, feel "higher" than counterparts who had taken moderate doses.")

At McGill University, low doses of marijuana increased levels of serotonin -- a mood-regulating neurotransmitter -- in rats, but high doses made their serotonin levels plummet.

The verdict? Both studies are limited but intriguing. The University of California study needs to be conducted on a far larger group of subjects suffering from the sort of pain -- back pain, migraines -- that marijuana is used to treat in real life. However, serotonin and pain thresholds have been linked. If too much marijuana actually decreases serotonin, as shown in McGill's rats, it makes sense that pain, both physical and mental, would worsen.

Cannabinoids Elicit Antidepressant-Like Behavior and Activate Serotonergic Neurons through the Medial Prefrontal Cortex [The Journal of Neuroscience]

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