Over 40 million Americans are affected each year by anxiety disorders such as panic disorder and PTSD. The exact cause of anxiety isn't known, which makes it difficult to find effective treatments for the disorders. And it also leaves doctors without a specific target on which to focus their search.
Recently, however, one promising target has emerged — a specific connection between two areas of the brain that can lower or even eliminate anxiety when it is turned off.
Working with mice, a team of MIT researchers took a set of nerve cells that run from the amygdala to the ventral hippocampus, connecting these two regions of the brain, and modified them so they could turn on the electrical signals these cells send by shining light on them and stop the signaling by turning the light off.
The researchers think that because anxiety is such an important trait for survival, multiple circuits, some redundant backups, are needed just in case one avenue gets blocked.
Mice are particularly anxious in open spaces, where they're most exposed, so they tend to stay near the edges of an open area when they happen to be in one.
When the researchers placed the mice in an open area and activated the connection between the amygdala and the hippocampus, the mice spent more time at the edges, suggesting that they felt anxious. When they shut off the connection between the amygdala and hippocampus, the mice were less anxious — they became more adventurous and willing to explore the open space around them. When the connection was turned back on again, the mice scurried back to the security of the edges.
Find a food, drug or lifestyle change that dampens this connection and you have a potential anxiety treatment. And since anxiety disorders collectively are the most common mental health disorder in the U.S., a new treatment would be very welcome.
In 2011 the same researchers found that a different set of nerve cells — a connection between two different parts of the mice amygdala — when turned on decreased anxiety. This suggests that there are multiple circuits involved in anxiety.
You could say that there's more than one way to scare a mouse. Hopefully that also means that there's more than one way to cure anxiety disorders.
An article on the study appears in Neuron.