PROVIDENCE, R.I. [Brown University] — Just like everyone else, people with panic disorder have real stress in their lives. They get laid off and they fight with their spouses. How such stresses affect their panic symptoms hasn’t been well understood, but a new study by researchers at Brown University presents the counterintuitive finding that certain kinds of stressful life events cause panic symptoms to increase gradually over succeeding months, rather than to spike immediately.

“We definitely expected the symptoms to get worse over time, but we also thought the symptoms would get worse right away,” said Ethan Moitra, a postdoctoral researcher in the Department of Psychiatry and Human Behavior at the Warren Alpert Medical School of Brown University.

But even if the events don’t seem to trigger an immediate panic attack, said Dr. Martin Keller, professor of psychiatry and human behavior and principal investigator of the research, patients, family members, or their psychiatrists need to keep their guard up.

“If they have the event and they are not feeling much different then maybe the vigilance on the individual’s part decreases somewhat,” Keller said. “With the knowledge we have, you may need to stay vigilant for three months or maybe longer. This is something you have to watch for.”

In their study, published in advance June 11 in the Journal of Affective Disorders, lead author Moitra, Keller, and their co-authors also found that panic symptoms did not seem to increase in advance of stressful life events, even if they were predictable, such as a divorce becoming official.

The study is based annual assessments of 418 adults with panic disorder or panic disorder with agoraphobia, who were enrolled in the Harvard/Brown Anxiety Research Project (HARP) between 1998 and 2004. Research staff asked the volunteers detailed, standardized questions about important events in their lives and their levels of anxiety.

A statistical analysis of the results found that for stressful life events in the categories of “work,” such as a demotion or layoff, or “friends/family/household,” such as a family argument, panic symptoms that had meandering severity before the event, increased steadily but gradually for at least 12 weeks afterward.

Stressful events in seven other categories, such as “crime/legal” or “deaths” did not seem to affect panic symptoms at all.

While the findings about the effect of some stressful life events on symptoms of people already diagnosed with panic disorder are new, other researchers have connected stress to panic attacks before. Stressful events are associated with the onset of panic disorder in the vast majority of cases, Moitra said.

Moitra said a possible biological explanation for the association is that stressful life events might exacerbate an underlying proclivity in people with panic disorder to perceive oncoming bouts of hyperventilation, which in turn lead to panic responses.

But while some stressful events have proven to be associated with changes in panic symptom levels, more research is needed to determine what kind of causal role stressful events may have.

“This may be one of those reasons why panic disorders can get worse,” Moitra said.

In addition to Moitra and Keller, other authors include Brown psychiatry and human behavior researchers Ingryd Dyck, Courtney Beard, Andri Bjornsson, and Nicholas Sibrava. Author Risa Weisberg is also affiliated with the Alpert Medical School’s Department of Family Medicine. The National Institutes of Health funded the research.