However, University of Michigan Medical School researchers are working to help doctors and patients choose anxiety treatments, by probing the connection between brain activity, genetics and medication.

In a placebo-controlled design, Dr. K. Luan Phan and his former University of Chicago colleagues, used brain imaging on volunteers given delta-9-tetrahydrocannabinol, or THC, the active ingredient in marijuana, and exposing them to photographs of emotional faces, which served as signals of social communication.

The study, published in the Journal of Neuroscience, showed that THC reduces the response to threat in a brain region called the amygdala, allowing the researchers to zero in on an area of the brain that might serve as a good target for new anti-anxiety drugs.

In a new clinical trial, Phan is searching for more clues as to how anxiety treatment could be tailored to the individual patient, to give the best chance that a treatment will work for him or her.