New study shows that anxiety can be created by the body

Anxiety is described as a feeling of fear, worry or unease and its cause is often difficult to determine. A new American study on animals recently revealed that increased heart rate can create anxiety. The results could shed some light on the treatment of chronic anxiety disorders.

Emotions, such as fear and anxiety, can make the heart beat faster. A study conducted on mice by researchers at Stanford University in California found that the reverse was also possible.

The results, published in the journal Nature, show that a faster heart rate generates anxiety in the body.

This study addresses a question that has puzzled the medical profession for more than a century: do physical sensations follow emotion or vice versa? To test the phenomenon, the team of American researchers turned to optogenetics, a method that uses light to control cellular activity. The scientists created a tiny vest that incorporated a red light directed at the chest of the mice. When a mouse’s vest emits a pulse of light, the animal’s heart muscles fired, making the heart beat.

The team trained the animals to expect to receive a shock when they pressed a lever for a water reward. Using optogenetics, the scientists artificially accelerated the mice’s heart rate from 660 beats per minute to 900. At this point, the rodents no longer have the reflex to press the lever or find other alternatives, which results in them exhibiting signs of anxious behaviour.

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On the other hand, when the mice did not perceive any danger in the context, the increased heart rate had no influence on them. The researchers theorized that the brain and heart actually work together to produce anxiety.

By measuring the brain activity of the mice, the researchers found that the insula, a part of the brain associated with emotions and body signals, became more active when the heart rate increased, particularly in a state of anxiety. The researchers deduce that the insula becomes an intermediary between the heart and the brain in moments of anxiety. It puts together signals from the heart reacting with environmental threats before transmitting the information to the areas involved in higher cognition.

The insular cortex “is known to be involved in interoception — the ability to perceive the body’s internal states, including heart rate, hunger, temperature and pain,” the study authors explain.

“The insular cortex receives all kinds of information from all across the body, so it could be playing a general role across a broad range of emotional states,” outlined Dr Karl Deisseroth, professor of bioengineering and of psychiatry and behavioural sciences and senior author of the study.

This discovery could contribute to a rethinking of treatment methods for chronic anxiety disorders. The team of researchers now intends to retest the system in order to analyze the links between the human brain and other organs, such as the intestines and facial muscles.

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