THC Model May Lead to More Effective Anti-Anxiety Treatments
> 4/21/2008 3:04:38 PM

Millions of individuals take specific medications for chronic anxiety problems, but fewer than half report any real degree of satisfaction with the effects of these drugs. Researchers in two converging studies at the University of Michigan look to develop more effective personalized anxiety disorder treatments with the ultimate goal of designing more specific medications and developing genetic tests to determine which treatments work best for individual subjects. The newest ongoing study focuses on the mechanisms of popular SSRIs. The first attempted to zero in on the biochemical stress response system with the help of a surprising chemical aide: marijuana. While habitual use eventually prompts paranoia and withdrawal-like anxiety, the primary appeal of marijuana lies in its ability to regulate mood and induce states of physical and emotional relaxation. Many chronic users name the drug's supposed anti-anxiety properties as the main reason for their continued usage. By focusing on the brain regions touched by marijuana's active ingredient THC, researchers hope to be able to fill that need with controlled medications.

Their concept is not a new one as previous studies have considered THC as an important guide for creating models of chemical reactivity. Marijuana works by acting on elements of the endocannabinoid system, a group of protein receptors known to play a central role role in shaping moods and regulating our stress and pleasure response systems. It is, according to researchers, "a key neurochemical mediator of anxiety and fear learning." The most crucial cannabinoid receptors are those of the CB1 variety. Located in the amygdala, a known center of fear and other threat responses, the CB1 receptors are those most directly affected by marijuana.

In order to more carefully analyze the relationship between CB1, THC and anxiety, researchers gathered several casual marijuana users and provided them with either pill-form doses of THC or physically identical placebos. They then performed fMRI (magnetic resonance imaging) scans on the subjects' brains as they viewed a series of images of hostile faces meant to evoke fear and anxiety responses. These photos obviously posed no real threat to the subjects, but chemical activity in the monitored brain clearly demonstrates a subject's chemical response to even slightly ominous stimuli, and researchers noted that the THC dulled the subjects' stress responses. Activity in the amygdala was subdued, but other brain regions were unaffected, again confirming the unique relationship between THC and the anxiety-response system.

In no way does this research validate the recreational use of marijuana, but a drug that so dramatically affects the human brain can obviously add to our still-tenuous knowledge of the central nervous system. Future medications may well be able to mimic the endocannabinoid interactions. And, of course, they will not carry any of marijuana's major side effects: cardiovascular complication, memory loss, and chemical dependence. Related studies may also play into the drug addiction equation as many individuals use drugs and alcohol in order to self-medicate severe anxiety and this research could further illustrate the compulsive nature of that biochemical relationship.

The second study by the same group will focus on the ability of genetics to determine the efficiency of SSRI antidepressants. With brain scans and genetic tests, researchers aim to discover how inherited variations in certain receptors like CB1 can help to determine how successful certain antidpressants will be with certain individuals. If these factors align as closely as they suspect, researchers will be able to create a more accurate system of diagnosis and medication. Observing the way the brain responds to various stimuli is by far the best way to design treatments focused on the central nervous system. Even as we discourage the use of marijuana, we should be open to its potential as a tool for learning more about the human brain and designing more effective medications. Some of those who feel the need to use marijuana in response to their own anxieties should seek the care of a professional who can help them address those feelings. It may be soon that they will also have a safe, legal alternative to the drug because of this research.

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