New research discovers that panic attacks do not strike without warning – a finding contrary to common beliefs – but start subtly as much as an hour beforehand or more.

Southern Methodist University researchers monitored participants wearing portable recorders for 24-hour periods. Investigators discovered changes in respiration, heart rate and other bodily functions that occurred for at least 60 minutes before patients’ awareness of the panic attacks, said psychologist Dr. Alicia E. Meuret.

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.

Monitoring data also showed patients were hyperventilating on a chronic basis.

“The results were just amazing,” Meuret said. “We found that in this hour preceding naturally occurring panic attacks, there was a lot of physiological instability. These significant physiological instabilities were not present during other times when the patient wasn’t about to have a panic attack.”

An interesting finding was that patients were unaware of their changing physiology and reported the attacks as unexpected.

“The changes don’t seem to enter the patient’s awareness,” Meuret said. “What they report is what happens at the end of the 60 minutes — that they’re having an out-of-the blue panic attack with a lot of intense physical sensations. We had expected the majority of the physiological activation would occur during and following the onset of the panic attack. But what we actually found was very little additional physiological change at that time.”

Meuret’s findings are published in the journal Biological Psychiatry.

The diagnostic standard for psychological disorders, the DSM-IV, defines panic attacks as either expected or unexpected. Those that are expected, or cued, occur when a patient feels an attack is likely, such as in closed spaces, while driving or in a crowded place.

“But in an unexpected panic attack, the patient reports the attack to occur out-of-the-blue,” Meuret said. “They would say they were sitting watching TV when they were suddenly hit by a rush of symptoms, and there wasn’t anything that made it predictable.”

To sufferers and researchers alike, the attacks are a mystery.

A key characteristic of the study was use of a methodology called 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,” said psychologist Dr. David Rosenfield of SMU, 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.

“I think this method and study will ultimately help detect what’s going on before these unexpected events and help determine how to prevent them,” Meuret said. “If we know what’s happening before the event, it’s easier to treat it.”

Although individuals were not aware of an impending attack, subtle physical changes appear to impact panic sufferers more severely. People with panic disorder probably won’t be surprised by the results, 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. Only three are psychological: feeling of unreality, fear of losing control and fear of dying.

“Most patients obviously feel that there must be something going on physically,” Meuret said.

“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, or 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. We found 15 subtle but significant changes an hour before the onset of the panic attacks that followed a logical physiological pattern. These weren’t present during the non-panic period,” Meuret said.

“Why they occurred, we don’t know. We also can’t say necessarily they were causal for the panic attacks. But the changes were strikingly and significantly different to what was observed in the non-panic control period,” she said.

The study’s results invite a reconsideration of the DSM diagnostic definition that separates “expected” from “unexpected” attacks, Meuret said.

Also, the study might explain why medication or interventions aimed at normalizing respiration for treating panic are effective, she said. Medication generally buffers arousal, keeping it low and regular, thereby preventing unexpected panic attacks.

For psychological treatments such as Cognitive Behavior Therapy (CBT), the results are more challenging. CBT requires a patient to focus on examining thoughts to prevent an attack.

“But a patient can’t work on something they don’t know is going to happen,” Meuret said.

“This study is a step toward more understanding and hopefully opening more doors for research on medical events that are difficult to predict. The hope is that we can then translate these findings into new therapies,” she said.

Source: Southern Methodist University