One minute you are feeling fine. Then suddenly you are trembling, nauseated and short of breath; your heart is racing, and your chest hurts. You fear you are about to die. A panic attack is a terrifying experience—and one that can strike anyone at any moment. Although the cause of panic attacks remains uncertain, new research suggests too much carbon dioxide might be to blame.

Experimental psychiatrist Eric Griez and his colleagues at the University of Maastricht in the Netherlands asked healthy volunteers to inhale air with varying levels of carbon dioxide. The higher the dose of carbon dioxide, the more the participants reported feeling fear and discomfort, as well as a fear of losing control and dying. “Metabolic distress is unconditionally translated into a dramatic emotional distress,” Griez says.

The research builds on Columbia University psychiatrist Donald Klein’s “false suffocation alarm” theory, which suggests that people have an evolved suffocation monitor sensitive to carbon dioxide and sodium lactate levels, both of which rise in the brain during suffocation. More than a decade ago Klein found that air enriched with carbon dioxide induced attacks in patients with panic disorders. These individuals have an overly sensitive monitor, he proposed, which fires false biological alarms in the form of panic attacks. Griez’s work adds to the theory by showing that even healthy people exhibit signs of panic in the midst of high levels of carbon dioxide.

This new work may yield clues about what causes panic attacks, which until now has largely been a mystery. Genes may play a role, according to family and twin studies. “It’s clear that there is a genetic component to vulnerability,” says biological psychiatrist Jordan Smoller of Harvard University. “It’s also clear that genes don’t explain all of it.” For people with certain phobias or post-traumatic stress disorder, objects that elicit fear or reminders of traumatic events can trigger attacks. In those with other anxiety disor­ders, episodes can happen without obvious cues, which makes them difficult to prevent. To add to the puzzle, panic attacks in healthy people occur out of the blue.

Griez’s research on carbon dioxide could be a step toward relief. Experts agree that the work may lead to the development of new ways to test anxiety medications and treatments.

This article was originally published with the title A False Alarm.

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