EDINBURGH, Scotland (AP) - Preliminary research suggests an unusual genetic abnormality may be linked to panic attacks and phobias.

A Spanish scientist reported Sunday at a meeting of the Human Genome Organization that among a random sample of people with anxiety disorders, 97 percent had a duplication of genetic material on chromosome 15 - compared with 7 percent in a comparison group of healthy people.

Experts say the finding could lead to better drugs for the condition, which afflicts about 10 to 20 percent of the population.

Researchers also say Dr. Xavier Estevill, head of medical and molecular genetics at the Duran i Rynals Hospital in Barcelona, appears to have uncovered a new genetic mechanism for causing disease.

His study suggested that a gene on some other chromosome, or some environmental factor early in development, may cause in some people an abnormality in chromosome 15. The defect may in turn make people more susceptible to panic attacks and anxiety.

The idea of a mutation in one gene triggering a mutation in another gene has been noted before in plants, but not in humans, experts said.

``This is provocative,'' said Dr. Lap-Chee Tsui, geneticist-in-chief at the Hospital for Sick Children in Toronto, Canada. ``He's come up with a new genetic mechanism and that's why it's exciting.''

Estevill said it does not seem the abnormality is inherited because it wasn't found in all the cells of those people affected.

``You're probably born with this mutation, but it probably arises during development,'' he speculated. Estevill found the mutation in half of 25 samples of sperm, but it is unclear whether those defective sperm would be able to create a successful pregnancy.

``We are very excited about it,'' Estevill said. ``But we need to identify, of course, the genes that may be involved in this and the mutations that these genes may have.''

Estevill first studied 140 people from various families in a Spanish village who suffered from either social phobia, fear of open spaces or recurrent panic attacks.

He then examined 70 unconnected people with the psychiatric problem and a comparison group of 189 people with no anxiety disorders.

He found that almost 100 percent of those with panic or phobias in the family group had the duplication of genetic material on chromosome 15.

Sixty-eight of the 70 in the non-family category, or 97 percent, had the abnormality, compared with only 14 of the 189 healthy people, or 7 percent.

``This is a susceptibility factor. It doesn't mean that because you have this variant (of chromosome 15) you will get panic disorder,'' Estevill said. ``Not everybody that had the mutation developed the disorder - 40 percent of the people in the family group that had the duplication had panic disorder.''

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