Anxiety Makes Our Brains Spot Threats Where No Threats Exist

Image credit: Jesse Orrico

Anxiety wouldn’t be so bad if it only cropped up in credibly dangerous moments. If it affected our ability to cope with a crisis, it might still be a problem–but at least it would feel like it made sense. Instead, it rears its head in otherwise innocuous moments. Knowing that no genuine threats are present isn’t the least bit helpful.

A study that has just been published in Current Biology explains the biological mechanism behind that frustrating facet of anxiety.

“We show that in patients with anxiety, emotional experience induces plasticity in brain circuits that lasts after the experience is over,” said Rony Paz of Isreal’s Weizmann Institute of Science in a press statement. That plasticity makes it so people diagnosed with anxiety respond to neutral, safe stimuli as though they are threats that were encountered in the past, even if a stimulus is merely similar to one encountered with a previous threat.

To work out this connection, researchers trained participants to associate three distinct tones with three different outcomes. One tone was associated with losing money. Another was associated with gaining money. The third had no consequence. Once those associations were firmly made, the participants were presented with one of fifteen tones and asked whether they’d heard it during training. If they were right, they were rewarded with money.

Participants with anxiety were more likely to believe a new tone was one of the tones associated with losing or gaining money. The emotional link to the earlier tones was so strong that they would find it in entirely new tones–over-generalization, as the researchers explain it.

“[These] plastic changes occur in primary circuits that later mediate the response to new stimuli, resulting in an inability to discriminate between the originally experienced stimulus and a new similar stimulus,” said Paz. “Therefore, anxiety patients respond emotionally to such new stimuli as well, resulting in anxiety even in apparently irrelevant new situations. Importantly, they cannot control this, as it is a perceptual inability to discriminate.”

Using functional magnetic resonance images (fMRIs) of the brains of people with anxiety and healthy controls, the researchers found brain activity differed under the study’s conditions. Differences were found mostly in the amygdala, the region most closely related to fear and anxiety, and in sensory regions of the brain.

But while this tendency to over-generalize might be hardwired into our brains, that’s not to say anxiety is impossible to overcome. While we can’t control which stimuli our brains identify as a threat, anxiety disorders are treatable through therapy, medication, and alternative treatments.

[Current Biology]
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