It's not a new disease, Sigmund Freud referred to it. Some of our great-greats may well have talked about our "having the vapours."

Women, espesially young women, and a few men, have been having panic attacks for generations.

Doctors still don't know why, although current studies are shedding some light. And some new therapies are helping victims cope.

A panic attack, anxiety attack or, at it is possibly misnamed, agoraphobia -- from the Greek, literally, fear of the market place -- is, without question, one of life's more terrifying experiences.

You can be standing in a roomful of people -- anywhere -- and suddendly, for no apparent reason, you feel, well, alienated. Apart.

You may feel dizzy, or you may feel a wave of nausea. But it's more than just feeling sick. You have a sense that reality is slipping away from you.

I can still remember the time (more than 20 years ago) in Bloomingdale's, New York City, feeling that the tiled floor was moving out from under my feet . . .

The overriding sense is that something is terribly, terribly wrong, The feeling that you're going to die. That you're going to love your mind. Certainly, that you're going to faint. Your heart is beating out of your chest. You can't catch your breath. You've got to get out of there so you can breathe.

In fact -- and this is important to remember -- you're not going to die.

You're not even going crazy. In all probability you're not even going to faint.

You're just having a panic attack.

But often, that's just the beginning.

"Think of it as being like a layer cake," says Dr. Donald F. Klein, who has been treating and testing agoraphobics for some years at the New York State Psychiatric Insitute and is one of this country's half-dozen top specialists in the illness.

The first layer is the attack itself, which seems to "come out of the blue." Doctors usually find nothing wrong and the patient is reassured. For a time.

Because the attacks usually come in clusters, there will be another, and then another, and then another. Because they come with no warning, the victim begins to feel deep apprehension and fear of another attack. That's the layer, which Doctor Klein and colleagues call Anticipatory anxiety."

This can lead to the third layer -- avoidance -- in which victims begin to keep out of situations in which they have had attacks, or where they fear they could have one. The may refuse to go out alone or, in the most severe cases, at all.They may refuse to drive over bridges or through tunnels.

"The anxiety of anticipating a panic attack," Kein says, "produces a phobia."

As the syndrome has become better publicized, and as behavioral therapies have increased in popularity, some agrophobics are getting varied degrees of help from groups and therapies often devised by ex-patients.

But even though Dr. Klein says that anything the patient accepts -- be it guru, therapist, or family member -- may also help overcome the final phobia, a recurrence of the panic attacks "will make the whole thing topple like a pack of cards."

It is a syndrome, says Dr. David Sheehan, another top specialist, "notorious for spontaneously remitting and going away for months or years, sometimes forever. In 20 percent of the patients they never come back. In 40 or 50 percent they go away for a period of time and, of course, if (patients) are treated with anything during that time, even if it's just orange juice, they would think that was effective."

Klein and Sheehan and an increasing number of colleagues specializing in agoraphobia -- an treating it as something different from, and more complex than other phobias -- have found that two families of anti-depressant drugs (trycyclics and some MAO inhibitors) can block the attacks. (Tranquilizers, major and minor -- like Valium -- often have been prescribed for the syndrome, but are rarely useful.)

Studies have indicated that patients treated with both anti-depressants and behavorial theraphy do better than patients receiving placebo or therapy alone. b

"The problem with desensitization (behavorial therapy) alone," says Dr. Sheehan, "is that it's been credited with the entire cure. And while it works for this small percentage of people who have it in a mild form, it just doesn't work for the majority of the people with agoraphobia."

On the other hand there is, Dr. Sheehan concedes, a political problem within the medical community.

"Traditionally, psychologists -- not psychiatrists -- have treated phobias, because they do behavorial therapy in which psychologists are usually better trained. So as a result, psychologists are rather unhappy about the whole posture of their practice (regarding agoraphobis) suddenly not being effective anymore and having that disorder pulled back into the domain of psychopharmacology."

"Another dilemma," says Sheehan, "is that the family of drugs we are talking about is very, very tricky to manage. It takes a quite a lot of skill, not only to regulate the dose, but to get the optimal effect."

Sheehan has just co-authored an article in the current Journal of Psychiatry and Medicine which gives, he says (for doctors, of course) "explicit, cookbook sort of instructions on how to prescribe MAO inhibitors, explicit instructions about all the ins and outs and ups and downs . . ."

Once the attacks have been supressed, however, psychologists' behavorial therapies are effective, even essential, to the agoraphobic.

Because the attacks do respond to drugs, and because attacks can actually be precipitated by infusions of a chemical called sodium lactate, research is now seeking a biochemical cause for the initial attacks, a metabolic imbalance which may be inherited."

It is, Sheehan feels certain, "an inherited vulnerability."

It strikes a small percentage of the population, with around three-quarters of the victims women, and usually emerges in the late teens or early 20s.

"In my view," says Sheehan, "it cuts across all personality types, intelligence levels, racial barriers and socio-economic levels."

Premilimary indications about its biochemical makeup are "rather surprising," says Dr. Klein. For example, although it has been generally accepted that adrenalin flows during panic attacks, tests are not showing high levels of adrenalin during the attacks.

Dr. Sheehan says he hopes that "not too far off" are a diagnostic blood test and new safer and more effective drugs. At the moment, he says, the most effective drug is the hardest to regulate.

Agoraphobic is not considered a do-it-yourself illness. It probably requires professional -- probably psychiatric -- treatment at the outset and possibly long-term therapy from then on.

"We're still at the early stages," says Sheehan, "but it's only a matter of time before the big breakthrough."