Marijuana, Genes, Medicines And Brain Scans Help Scientists Find Better Anxiety Treatments

ScienceDaily (Apr. 18, 2008 ) – Right now, about half of all people who take medicine for an anxiety disorder don’t get much help from it. And doctors have no definitive way to predict who will, and who won’t, benefit from each anti-anxiety prescription they write.
But a University of Michigan Medical School researcher and his team are working to bring more certainty to how doctors and patients choose anxiety treatments, by probing the connection between brain activity, genetics and medication.

K. Luan Phan, M.D., and his former University of Chicago colleagues recently reported intriguing findings from a brain imaging study in occasional, non-dependent, marijuana users in the Journal of Neuroscience.

In a placebo-controlled design, they made the findings after giving the volunteers delta-9-tetrahydrocannabinol (THC), the active ingredient in marijuana, and exposing them to photographs of emotional faces, which served as signals of social communication. The study results, which showed that THC reduces the response to threat in a brain region called the amygdala, allowed the researchers to zero in on an area of the brain that might serve as a good target for new anti-anxiety drugs.

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The cannabis study used THC, and a placebo caplet that looked exactly like the THC caplet. The researchers found that when the marijuana users received THC, their brain’s response to “threatening” faces was less than it was when they received a placebo.

The difference in response was seen in an area of the brain called the amygdala, which is a hub for the brain’s ability to process signs of danger or warning, and to decide how to respond. But there were no differences between THC and placebo in the areas of the brain that process non-emotional visual signals or govern body movement — suggesting that THC had a specific effect on a specific brain region and on a specific task of processing fear. Other researchers have shown this to be a region that’s rich in a receptor called CB1, part of the brain’s “cannabinoid” system.

The human brain produces compounds called endocannabinoids that act on these receptors, and are involved in anxiety and fear-learning, or the learning of which threats to be afraid of. But little has been known about the effect of THC, an exogenous cannabinoid, on the brain’s own system.

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The THC study links three key domains of human behavior: a specific region of the brain, the function of that area, and a neurochemical agent (THC) that appears to act on them.

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Journal reference: Journal of Neuroscience, March 5, 2008, Vol. 28, No. 10, 2313-2319

 

 

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