Despite their seemingly sudden onset, panic attacks are preceded by physiological changes, according to findings from a new small study.

Most people with panic attacks describe their episodes as occurring 'out of the blue', or without any physical warnings or cues. According to sufferers, they suddenly experience an event marked by extreme fear that something terrible, yet, unstoppable is about to occur. The alarming sensation is accompanied by such physical symptoms as increased heart rate, sweating, shaking, shortness of breath, nausea and dizziness.

While the physical reactions involved in a panic attack are not dangerous, their presence is nonetheless terrifying and overwhelming. When people experience repeated attacks, they may develop ongoing and persistent worries of new episodes. In such cases, panic disorder may be diagnosed.

Certain Biological Changes Occur

Many experts have speculated that panic attacks are triggered by biological changes, similar to those preceding seizures, strokes and manic episodes. Until now, however, little research has been available to determine the physical underpinnings of panic attacks.

In this research conducted by scientists at Southern Methodist University, researchers hypothesized that physiological changes and instability markers should occur at the beginning or during panic attacks, but not preceding them.

To test their theory, researchers monitored the respiration, heart rates, skin conductance levels and other physiological measurements of forty-three panic disorder patients during repeated 24-hour cycles. The skin tests determined the moisture levels produced by sweat glands in response to psychological triggers.

Signs Appear As Early As An Hour Before

During the nearly 2,000 hours of monitoring, thirteen spontaneous panic episodes were recorded, with detailed biological indications also captured. Specifically, researchers were able to track physiological changes 60 minutes before the attacks and continuing through until 10 minutes after the beginning of the individual attacks. Controls for physical activity were in place, and periods of stability within the same person were also obtained.

Results showed significant patterns of instability within various physiological areas as early as 47 minutes before the attacks began. The last minutes before the beginning of the attacks were marked by changes in respiration, significant decreases in tidal volume and a sudden rise in carbon dioxide partial pressure; the inverse occurred at the actual onset as seen by a drop in the same pressure and a rise in tidal volume and heart rate. Tidal volume refers to the amount of air held in the lung during a natural inhalation, with carbon dioxide partial pressure referring to the relationship between that gas and oxygen during breathing. Skin conductance levels were elevated in the hour before and throughout the attacks, while no consistent changes were noted during the matching control periods.

The fact that most patients report the attacks as wholly unexpected indicates they do not feel the preceding instabilities, noted lead researcher Alicia E. Meuret, Ph.D. While such information may be disheartening to patients because they cannot control symptoms that they do not sense, Meuret noted that future treatments may enable healthcare professionals to train patients to be aware of them, much as epileptics or migraine sufferers recognize warning signs of oncoming attacks.

The study was published in the July issue of Biol Psychiatry.

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Date of original publication:

Updated: November 21, 2016