A few years back, a career foreign service officer was kept hostage for four months by South American terrorists and then released unharmed. At least, he came out of captivity physically unharmed and returned to the United States for a few months of well-earned leave.

His friends quickly noticed he wasn't the same. He was angry much of the time, irritable when he wasn't angry and tense and anxious when he wasn't irritable. He told his friends he was suffering from irregular heartbeats and that he thought he might be getting his first ulcer.

He said he couldn't sleep and was undergoing bouts of melancholy he found harder and harder to overcome. He fell into a depression he couldn't shake. He said he was depressed because he felt his four months in captivity had ruined his career in the State Department. He told his friends he thought they were shunning him, as if by having been a hostage he had picked up an insidious disease.

Oddly enough, he wasn't imagining things. He was right. His friends were shunning him, the way friends sometimes shun a victim of rape.

"It's like where friends and family don't want to associate with him because if they stay with the hostage they'll become a hostage," says Dr. Steven Peiczenick, a psychiatrist formerly at the State Department and an authority on hostage psychology. "It's magical thinking but it happens. Nobody wants to go in his car pool. It's like if lightning strikes once it will strike again.

The story is told to make a point: When the American hostages come back from Tehran, whenever and however that might be, their ordeal may not be over. It's possible that being kept hostage for as long as they already have may leave such deep scars that their lives will undergo long-time change, triggered by what they've gone through and even by what others perceive they've gone through.

It's also possible that few or even none of the 50 hostages in Iran will suffer post-captivity trauma. After all, hostages differ, their captors differ and hostage situations differ. But enough is already known about the rigors of their captivity to suggest that the Americans being kept hostage in Iran will not have an easy time when it is over.

There's a wrinkle in the Iranian incident that could make things worse for the hostages. A popular image of the incident is that it was spontaneous, ingited by unruly Iranian students whose demands for vengeance against the shah got out of hand. Not true, say psychiatrists who've studied the hostage business. They believe the taking of the hostages was an act long in the planning. They believe the treatment the hostages are getting is part of a plan to "depersonalize" them so they can be used for Iranian political aims.

"None of this is accidental. It's much too deliberate," says Harvard University's Dr. John Clark, who has studied cult, hostage and prisoner-of-war psychology and who believes they're remarkable similar. "It looks to me as if the hostages are being pressured into a fixed state of mind to suit the purposes of their captors."

State Department psychiatrists who've debriefed the black and women hostages Iran released two weeks ago paint this picture of how the hostages are being treated:

They've kept apart on separate floors and in separate rooms, all of them seated in armchairs. At least one was in solitary confinement for 10 days; others lived for days at a time in tiney cubicles.

They must ask to use the bathrooms and their only conversation is with their Iranian captors, who often wear masks to conceal their identities and facial expressions. They're kept in the dark alot. Their sleep is controlled and kept short. Their hands are tied, except when they're given a break to smoke. They're even forced to sleep with their hands tied.

"They're being badly mistreated," says one State Department psychiatrist. "It's not torture, but it's kind of hard to sleep with your hands tied."

Harvard's Dr. Clark points out that by isolating the hostages, by keeping them in the dark and making their sleep uncomfortable, the Iranians are following a practice perfeced on prisoners of war by North Veitnam. Clark says isolation and sleep control are so effective as manipulative tools that cults use the technique on their novice members to bring them quickly into line.

"We know now that these processes don't lead to the kind of overwhelming terror that might protect the mind," Dr. Clark said. "They lead to a narrowing of attention that leads to a trance state, where everything seems to ambiguous. Ambiguity is at the bottom of all this. It becomes impossible for the central nervous system to handle it."

Psychiatrists say the Iranians have already manipulated some hostages, who have been quoted publicly as saying their treatment is good and that the shah should face trial in Iran. These statements suggest to psychiatrists a form of brainwashing that might mean the hostages have already suffered some psychological harm.

Psychiatrists say there are three phases to most situations where people are kept captive or hostage. The Americans held in Iran have already passed through the first phase, which is such a strong disbelief in what is happening to them that they're struck with an overwhelming anxiety accompanied by fear of death.

"This fear of death doesn't come as the grim reaper. In fact, it often takes a very bizarre aspect," Dr. Pieczenik points out. "It comes with little obsessional thoughts like, 'Oh, my God, I forgot to turn off the stove.' It's a way of dispatching our anixieties but it's also telling us: 'Hey, we're in trouble.'"

Phase Two is a regression that can take anywhere from minutes to hours to days and is a fancy way of saying that the hostage quickly dependent on his captors for food, support, exercise, recreation, light, noise and even camaraderie. What this does is set up an unusual alliance between captive and captor.

The captive ends up losing his own personality and identifying with his captor, seeing in him parent, brother and even lover. This act of reidentification's called the Stockholm Syndrome, taking its name from an incident where a woman held hostage in a Stockholm bank vault had sex with her captor and eventually married him.

The Stockholm Syndrome may account for the statements of some of the hostages. They've said things aren't all that bad inside the the embassy, that their captors are in fact pretty nice people and that things could have been much worse.

In previous incidents, said one State Department psychiatrist who asked not to be identified, "We've had hostages who've been beaten up and tortured, and they've come out and shaken hands with their captors. It's very puzzling."

By placing maskes over their faces, the captors depersonalize their captives. The Iranians have also rotated the hostages' guards, heightening the depersonalizing process. Isolating the hostages from each other increases the fear, the tension and the sense of abondonment felt by the hostages, making them more and more dependent on their captors at the same time they're losing peices of their own personality.

Keeping the hostages in the dark deepens their anxiety. The screaming crowds outside the embassy, who shout in unison and on cue, serve the same purpose. Psychiatrists say that the hostages in Iran can expect to suffer visual and auditory hallucinations as a result of all this. When they do, they've entered Phase Three of the hostage process.

The third phase is the worst, since after hallucination comes psychosomatic pain and illness. Physchiatrists say that even after two weeks of being held hostage people begin to suffer frequent headaches. Ulcers flare up, nausea and vomiting come on, blood pressure rises and the heart begins to palpitate.Prisoners of war have been know to drop dead during this phase in their captivity.

What concerns psychiatrists most is what might happen to the hostages in the weeks ahead and the weeks, months and even years after their release. Hostages before these have survived months of captivity by toughening themselves mentally through their ordeal. Some have read poetry to themselves, others play word games with themselves or write long letters in their heads. It all depends on the hostage.

Yale's Dr. Robert J. Lifton thinks there's no way any of the hostages can come out of this unscathed. Liften believes they will suffer pain over what they've gone through and guilt over they could have done differently.

"They will be survivors of an ordeal," Dr. Lifton said, "and survivors have conflicts and suffer the psychological effects of what it was they survived. They will have indelible images of what they've been through." t