To most Americans, the threat of nuclear war seems remote. Yet its impact may be more significant than previously thought, as researchers examine more closely the psychological fallout of living with the prospect of mass extinction.

"It's a pervasive context in which we all live, and it affects us in ways we don't even know," said Dr. John E. Mack, academic director of the Center for Psychological Studies in the Nuclear Age, which was founded in 1983 as an affiliate of Harvard Medical School.

A 1982 Task Force Report of the American Psychiatric Association on the "Psychosocial Aspects of Nuclear Developments" concluded that "the threat of nuclear destruction through enemy attack, terrorism, human accident, computer error or power plant disaster creates an environment of fear and imposes stresses upon the human psyche which are without precedent."

Since then, there has been an outpouring of research on the emotional stresses of the nuclear arms race, and many leaders in this new medical field are activists in the anti-nuclear movement. To them, the summit between Ronald Reagan and Mikhail Gorbachev represents an opportunity to put the psycho-social aspects of the nuclear arms race on the political agenda.

That the public has deep-seated fears of a nuclear holocaust is clear. A recent Gallup poll found that almost two out of three Americans worry "often" about the chances of a nuclear war. A Washington Post poll of adults and teen-agers in 1984 found that both age groups rank the buildup of nuclear arms as among the most important problems facing the United States. In fact, nearly two out of three teen-agers saw it as the nation's biggest problem; one out four said the fear of nuclear war causes them to "worry frequently about death."

A University of Michigan study found that high-school seniors' fear of nuclear war increased fourfold between 1975 and 1982. Another survey on children's views of the future showed that compared to the early 1960s, children in the 1980s are generally more pessimistic.

All this, say mental health experts, is fueling a sense of futurelessness and live-for-now impulsiveness in America's youth. Professor Robert J. Lifton of City University of New York, who studied the aftermath of Hiroshima, calls it "psychic numbing" -- a diminished capacity to feel.

Generally, most Americans deal with fears of nuclear war by denial. "The main way we cope with it is not to think about it," said Dr. Jerome Frank of Johns Hopkins University. "With the summit, we are forced to think about it." To get a better understanding of the psychological mechanisms that allow people to live with the bomb, researchers have recently turned their attention to the physicists, engineers and military strategists who work with nuclear weapons. In general, their coping strategies involve: Using language that obscures the catastrophic consequences of nuclear war. Mass human death is "collateral damage." The MX missile, named "the Peacekeeper," is referred to as a "damage limitation weapon." Some nuclear devices are "clean bombs." Carol Cohn, a senior research fellow at the Center for Psychological Studies, wrote in her article on nuclear language published in the Bulletin of the Atomic Scientists: "Language reveals the mechanisms of distancing and denial . . . learning the language gives a sense of control, a feeling of mastery over technology that is finally not controllable." Focusing on the technology. As Cohn noted, this way a person doesn't have to consider the broader issues of nuclear war. As an engineer who designed a missile guidance device told one researcher: "But this thing I make doesn't blow up." Fragmenting responsibility. Even in interviews with high-ranking military strategists, such as the director of a nuclear weapons laboratory, "each person sees himself as a small cog," observed Harvard researcher Mack. "Nobody is really responsible." As Sam Gardiner, a retired Air Force colonel, said: "You can separate yourself from what you do an awful lot." The thinking is: That's not my responsibility -- my job is to see that when the button is pushed, the light goes off. "You have to be that way in combat, no matter what you do," said Gardiner. Belonging to an elite group. The public may have a Dr. Strangelove image of people who design nuclear weapons, but the vast majority, said Mack, are committed scientists and officials who "feel they are doing something helpful." They belong to a "nuclear priesthood" -- almost like a secret society where outsiders cannot understand their work. The issues are technical, not political, and satisfaction comes from doing the best possible job. :: "Doubling." Psychiatrists use this term to describe how people are able to create a functioning second self that is totally separate from the on-the-job self. The term was originally applied to Nazi doctors who could perform unspeakable horrors in concentration camps during the day and come home at night to be fine, functioning husbands and fathers. The phenomenon of doubling and the ability to have totally separate job and non-job selves is a powerful -- and common -- protector against unwanted emotions. There is some evidence based on interviews, said Lifton, that this doubling effect is also present in nuclear strategists and weapons designers.

Many of these same coping mechanisms -- denial, embrace of technology, avoidance of personal responsibility -- are seen in the general public. With the summit, many mental health experts hope that these psychological defenses will be addressed and that the superpowers will move toward what Lifton calls "a sense of shared fate."

But psychological analysis can only go so far in explaining the underlying dynamics of the nuclear arms race. While psychiatrists and psychologists, so accustomed to dealing with "conflict resolution" in their medical practice, are eager to apply their therapeutic techniques to superpower negotiations, there are major differences between politicians and patients. As Mack explained: "In psychotherapy, I try to get people to recognize and take responsibility for contributing to tensions in the family. But political leaders are reluctant to acknowledge their country's contribution to international tensions."