High anxiety?

The idea is to see whether variations in the genes for certain brain receptors and transporters are linked with variations in how a person’s brain reacts to pictures of emotional faces, and variations in how they respond to the anti-anxiety drug. This information could lead to an individualized or personalized approach to medical care.

“These two studies are trying to get to the same goal: to find better treatments for anxiety disorders that affect millions of Americans and seriously interfere with their functioning,” says Phan, an assistant professor of psychiatry at U-M and the VA Ann Arbor Healthcare System. “The cannabis study highlights a new avenue that we need to explore further as we try to develop novel medications, while the sertraline study will try to find out if we can tell which patients might or might not respond well, and by what mechanism, to an already existing medication known to have some efficacy in treating anxiety disorders.”

Phan led the cannabis study at the University of Chicago, collaborating with Harriet deWit, Ph.D., the director of the Human Behavioral Pharmacology Laboratory in the Department of Psychiatry there. Their results are based on brain scans of 16 recreational marijuana users who agreed to undergo functional magnetic resonance imaging, or fMRI.

The researchers chose fMRI because it allows them to see in real time which areas of the brain are most active while a volunteer is performing a certain task – for example, viewing a picture of a human face that is expressing anger or fear, or performing a decision-making exercise.

That same approach will be used in the new sertraline study, with two different scans before and after anxiety patients are prescribed the medication. The healthy volunteers in the study will also have fMRI scans, though they will not receive the drug. All study participants must between 18 and 55 years old, and those with anxiety disorders must not be taking any other medication that could be affecting the brain in order to qualify to enter the study.

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.