Panic attacks that seem to strike out of the blue are not without warning after all, says SMU psychologist Alicia Meuret.
In a rare study in which patients were monitored around the clock as they conducted their daily activities, portable recorders captured changes in respiration, heart rate and other bodily functions. The researchers discovered that waves of significant physiological instability occurred for at least 60 minutes before patients became aware of an impending panic attack, says Meuret, associate professor of psychology and lead researcher on the study.
The new findings suggest sufferers of panic attacks may be highly sensitive to – but unaware of – an accumulating pattern of subtle physiological instabilities that occur before an attack, Meuret said. (By definition, the majority of the 13 symptoms of panic attack are physiological: shortness of breath, heart racing, dizziness, chest pain, sweating, hot flashes, trembling, choking, nausea and numbness.) Monitoring data also showed patients were hyperventilating on a chronic basis.
“Most patients obviously feel that there must be something going on physically,” Meuret says. “They worry they’re having a heart attack, suffocating or going to pass out. Our data doesn’t indicate there’s something inherently wrong with them physically, neither when they are at rest nor during panic. The fluctuations that we discovered are not extreme; they are subtle. But they seem to build up and may result in a notion that something catastrophic is going on.”
Notably, the researchers found that patients’ carbon dioxide (C02) levels were in an abnormally low range, indicating the patients were chronically hyperventilating. These levels rose significantly shortly before panic onset and correlated with reports of anxiety, fear of dying and chest pain.
“It has been speculated, but never verified with data recordings in daily life, that increases in CO2 cause feelings of suffocation and can be panic triggers,” Meuret says.
Meuret and her colleagues discovered these patterns using change-point analysis, a statistical method that searches for points when changes occur in a “process” over time.
“This analysis allowed us to search through patients’ physiological data recorded in the hour before the onset of their panic attacks to determine if there were points at which the signals changed significantly,” says SMU Associate Professor of Psychology David Rosenfield, lead statistician on the project.
The study is significant not only for panic disorder, but also for other medical problems where symptoms and events have seemingly “out-of-the blue” onsets, such as seizures, strokes and even manic episodes.
In a multidisciplinary collaboration, other authors on the study were psychologist Thomas Ritz, SMU Department of Psychology; psychologist Frank H. Wilhelm, University of Salzburg, Austria; electrical engineer Enlu Zhou, University of Illinois at Urbana-Champaign; and psychologist Ansgar Conrad and psychiatrist Walton T. Roth, both of Stanford University.
Meuret discusses their work in an SMU Research video. Click the YouTube screen at right to watch, or click this link to see the video on panic disorder research in a new window.
Written by Margaret Allen