A new study shows that people with generalized anxiety disorder unconsciously label harmless things as threats, which may serve to further their anxiety. These findings were published last week in the journal Current Biology.

Psychologists recognize several forms of clinical anxiety. The most common is generalized anxiety disorder, or GAD, in which people frequently feel very worried or anxious even when it seems like there’s nothing to worry about. Some studies have suggested that anxiety disorders may stem from a process called overgeneralization.

In overgeneralization, the brain lumps both safe and unsafe things together and labels them all unsafe. For this reason, the researchers also call this the “better safe than sorry” approach. Our brains naturally pay more attention to negative or threatening information in our environments. If anxious people perceive more threats in the world around them, it would make a lot of sense for them to be worried.

To find out if overgeneralization was involved, researchers recruited 28 people diagnosed with GAD and 16 people without anxiety and brought them into the lab. The experiment had two parts: training and testing. In the training section, study participants learned to differentiate between three different sounds. Each sound was tied to a different outcome; pressing a key could lead to winning money (the “positive” tone), losing money (the “negative” tone), or nothing (the “neutral” tone).

In the second phase of the experiment, researchers played 15 different sounds for the participants and asked them to press a key when they heard a sound they recognized from the training phase. If they guessed right, they’d win money, but if they guessed wrong, the researchers would take some of their money back.

Because of the risk of losing money, the best strategy for everyone would be a conservative one—not pressing the button much at all based on the assumption that most of the tones were new. But anxious participants were trigger-happy, believing they’d heard many of the unfamiliar tones before. The experience of winning and losing money in training had made a strong emotional impression on them, which led them to overgeneralize new information as relevant.

The researchers also administered brain scans during the testing phase. They found notable differences between anxious and non-anxious brains. While they were focused on parsing new information, anxious people showed more activation in several parts of the brain, including the amygdala, a region associated with fear and worry.

"We show that in patients with anxiety, emotional experience induces plasticity in brain circuits that lasts after the experience is over," senior co-author Rony Paz said in a press release. "Such 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. 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."

Paz noted that in dangerous circumstances, the hyper-vigilance associated with anxiety might be a good thing. The problem is that most circumstances aren’t dangerous. "Anxiety traits can be completely normal, and even beneficial evolutionarily," he says. "Yet an emotional event, even minor sometimes, can induce brain changes that might lead to full-blown anxiety."