Big news for anyone who deals with anxiety: According to a new study, “anxiety cells” might exist in the brain — and there might actually be away to toggle them on or off. Researchers from UC San Francisco and Columbia University’s Irving Medical Center (CUIMC) located these cells in mice; what’s more, in a paper detailing their findings that was recently published in the journal Neuron, they also wrote about what their discovery might mean for the development of future anxiety treatments for humans. The news is pretty huge — and although there’s still much more research that needs to be done on the subject, the current study has some impressive and wide-reaching implications already.
In order to examine what was going on in mice’s brains during periods of anxiety, the researchers put tiny microscopes in the mice’s heads and exposed them to a situation that’s known to cause them anxiety: They put them in wide, open spaces and on elevated platforms. I’m not sure I’d go so far as to say that mice are agoraphobic —but to be fair, when you’re really tiny, huge, open spaces are disorienting and therefore a little bit terrifying. There’s a survival instinct at work here: As CUIMC psychiatry professor and senior study investigator Rene Hen, PhD put it in a press release, these kinds of areas are spaces “where they’re more exposed to predators.” When there’s nowhere to hide, you’re more likely to get caught and eaten — and that’s a terrifying prospect.
Anyway, when the mice were put into a maze that lead to these large spaces and elevated platforms, the researchers discovered that there was something interesting going on whenever they ended up in the open areas: In addition to the mice displaying anxious behaviors, particular cells started firing in their hippocampi. What’s more, these cells only fired when they were in “places that are innately frightening to them,” according to Hen. That’s why the researchers call them “anxiety cells” — whether or not they fire seems to be closely related to whether or not the mice are in situations that create anxiety for them.
(Note that the researchers didn’t prove that the anxiety cells were causing the anxious behaviors — just that the firing of the cells might be related to the behaviors. Correlation is not causation and all that.)
The researchers were able to trace the cells to the hypothalamus, an area of the brain that’s responsible for producing the hormones that regulate things like temperature, thirst, hunger, and mood — and which previous research found plays an important role in the triggering of anxiety. The results of a 2016 study suggests that anxiety behaviors are connected to one of the hormones produced by the hypothalamus.
And here’s the really interesting bit: Once the researchers had located those cells, they found that they can actually turn them on and off, so to speak — which, as you might imagine, has big potential implications for the future treatment of anxiety. The technique the researchers used to “flip the switch” in the anxiety cells is called optogenetics, which uses light to “control well-defined events within specific cells of living tissue,” according to Scientific American. When the cells were turned “off” with the right kind of light, the mice displayed fewer avoidance behaviors associated with anxiety — that is, they were less likely to cling to the walls of the maze and more likely to check out the elevated platforms in their maze — while when the cells were “on” and sort of dialed up via optogenetic stimulation, their anxiety behaviors not only came back, but also reared their little heads when the mice weren’t in the threatening parts of the maze.
According to the National Institute of Mental Health (NIMH), which provided funding for the current research, an estimated 19.1 percent of adults in the United States and 31.9 percent of teens between the ages of 13 and 18 have an anxiety disorder — although it’s possible that the actual numbers are much higher and skewed due to people either being misdiagnosed or going undiagnosed all together. The point is that anxiety disorders are incredibly common; however, as NIMH director Joshua Gordon told NPR, “Our treatments [for anxiety] are, at best, partially efficacious.” That's... not great.
Current treatments for anxiety might include Cognitive Behavioral Therapy, stress-management techniques, support groups, or medications, according to the NIMH — but if optogenetics are as effective in humans as the technique is in mice,then we might have another powerful tool added to our treatment roster in the future.
Of course, though, that’s all dependent on whether or not the research can be replicated in humans. Mice and other rodents are often used for research due to their brains’ similarities with human brains; according to cognitive scientist Andrea Chiba writing for the San Diego Union-Tribune in 2015, “Rodents can be a good model for humans because a lot of the structure and connective that exists in human brains also exists in rodents, especially rats.” But the fact remains that mice aren’t humans — and right now, we’re not sure if the anxiety cells that apparently exist in mouse brains also exist in human ones. Much more research is required before we can say with some certainty that optogenetics might be an effective treatment for anxiety in humans.
But the door is open to that right now, which is actually pretty exciting. As Joshua Gordon told NPR, “You can think of this paper as one brick in a big wall” — and the rate of research over recent years shows that lots of other bricks are being discovered and added to that wall all the time.The picture is becoming clearer — and as it does, better treatments emerge.
And that’s comforting, indeed.