Wednesday, May. 23, 2001
20th-century disease linked to panic disorder, researchers say

By HELEN BRANSWELL -- The Canadian Press

TORONTO (CP) -- Environmental intolerance, a condition sometimes known as 20th-century disease, appears to be genetically linked to panic disorder, University of Toronto researchers have discovered.

That revelation may help medicine unlock the mysteries of the ailment and aid doctors treating those suffering from the disabling condition.

"The symptoms are very real and these people are suffering," lead author Dr. Karen Binkley said about people with idiopathic -- meaning its origin is spontaneous and unknown -- environmental intolerance, or IEI.

"They need help and we have to be open to anything that can improve the quality of their lives."

The article was published in the May issue of the Journal of Allergy and Clinical Immunology, a peer-reviewed publication of the American Academy of Allergy, Asthma and Immunology.

People with IEI suffer a wide variety of symptoms when exposed to an array of products, chemicals and pollutants that are hard to avoid in modern life. Items commonly blamed for reactions include perfume, carpets, scented products and household cleaners, although some sufferers also finger certain foods and electromagnetic radiation.

Contact with these items can induce reactions such as breathlessness, chest tightness, lightheadedness, weakness, nausea or trouble concentrating.

There are no good estimates of how many people suffer from IEI, though Binkley said it would be incorrect to call the condition rare.

The ailment is often likened to allergies -- it is sometimes called total allergy syndrome -- but differs from allergies in one important way.

Tests have shown that when IEI sufferers are in close contact with one of their trigger items, but are unaware of its presence because researchers have managed to mask its scent, they do not consistently experience symptoms.

People who suffer from pollen allergies or who are allergic to nuts, for instance, will have an allergic reaction when exposed to their trigger, regardless of whether they are aware of its presence or not.

"This is a condition clearly distinct from hay fever, clearly distinct from asthma, clearly distinct from food allergies such as peanuts," said Binkley, who added that research "suggests that there may be a cognitive component to it."

Because IEI symptoms are so similar to those of panic disorder, researchers had questioned whether the two were linked.

A discovery made two years ago about panic disorder prompted Binkley and her colleagues to look for genetic similarities between people with panic disorder and people with IEI.

Researchers elsewhere reported that patients with panic disorder had more receptors for a chemical called cholecystokinin than other people do.

Cholecystokinin is a natural substance made in the human gut and brain. In the gut, it plays a role in digestion; in the brain, it is believed to be related to anxiety and fear behaviours.

It is recognized to be a panicogenic agent, meaning it will induce attacks in patients who suffer from panic disorder. It will not provoke an attack in those who do not, however.

"It's a kind of a test for panic disorder," Binkley said.

Given that IEI looked so much like panic disorder in so many ways, the University of Toronto researchers asked themselves whether the two shared genetic characteristics was well. 

All humans have two types of cholecystokinin receptors, A and B. Type B comes in 15 different variations, called alleles. Our genetic code -- the interaction of our parents' genes -- determines which alleles we carry.

Allele 7 has been found to be more prevalent in patients with panic disorder than in the population at large.

So Binkley and her team studied a group of 11 patients with IEI, comparing them with 11 people who do not have the condition. Of those with IEI, 41 per cent carried allele 7. Only nine per cent of the controls had that allele.

Binkley admitted the sample size was small and the results need to be replicated in a larger study. But she is confident she and her colleagues are on to something.

"It does fit with all of the studies looking at other aspects of the problem that suggest that patients with IEI have an underlying condition very much like panic disorder."

Will patients with IEI feel relieved at the prospect of proof that there is a physiological basis to their condition? Or will the tie to panic disorder seem like just another attempt to dismiss their ailment as a form of mental illness?

"I think that the distinction between mind and body is really an artificial one," Binkley said. "They function as a whole. You can't view one without the other."

While the research continues, Binkley said the findings to date suggest the multidisciplinary approach used to treat panic disorder -- the combination of relaxation therapy and stress management with anti-depressants -- may prove beneficial for sufferers of environmental intolerance. 

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