At the end of 1985, sociological studies showed that young adults in increasing numbers were continuing to live with their parents beyond age 18, the chronological marker of adulthood. After that age, we have come to expect young adults to be out on their own, "making it" in the adult world.

The Washington Post hypothesized an association between the proliferation of earphones and the ability of young adults and their parents to continue to share living space. Others proposed economic factors or a lack of independence in this generation.

It has been well established that the period of life from about age 18 to about age 30 is probably the most stressful because of rapid change as a young person becomes "adult."

For most adolescents, 18 is the age at which they complete their high school education. Their lives are no longer structured by required daily school, and the question of "what next?" looms large.

Over the next decade, most 18-year-olds, gradually and stressfully rather than instantly and smoothly, become adults. They begin to make decisions about adult occupations. Many young people have worked in marginal capacities as adolescents, but have trouble thinking about themselves as functional adults who can hold down full-time jobs.

Eighteen-year-olds also must begin to make decisions about an adult life style. How do I want to live and with whom? How will I take care of my cleaning, laundry, transportation? What will I eat and when and with whom?

Most people think of stress as intense emotional or physical reaction to change. With all the changes that occur between 18 and 30, it is not surprising that this period is so stressful.

In a recent survey of young adults by Group Health Association (GHA), the sources of stress most frequently mentioned by this age group were: changing work situation, changing residence, changing social activities, changing recreational activities, changing financial status, changes in family closeness, beginning or ending a relationship, making major decisions about life goals, and concerns about the world situation.

Many young adults also mentioned the pressure they feel to meet high expectations in their work and private lives.

Good coping skills come from within the individual -- calm, thoughtful, confident people usually do better with stress than anxious people. They know how to put stressful experiences into perspective so that they don't feel overwhelmed. Good coping also comes from prior success in managing stress.

Stress is also less devastating when you have people around who care about you and can help you get through. Caring friends and family can be good listeners, ask the right questions, offer an arm around the shoulder, and contribute suggestions for effective decision-making.

Poor coping, however, often leads to increased stress and becomes part of a vicious circle, in which the individual may feel trapped and hopeless. It can cause stress-related illness. The body gets tired of responding to the continual pressures of stressful events, and symptoms appear, including headaches, weight gain or loss, excessive fatigue, sleep difficulties, back pain, nervousness, excessive worry, depression and stomach cramps.

One moderating factor identified in the GHA study was the quality of their relationships with their parents. The young adults who felt warmly connected to their parents had far fewer stress-related symptoms than those who were emotionally cut off from their parents.

What does this say about the young adult "stay-at-home" trend? One might speculate that this group will be healthier and have fewer stress-related illnesses than their more "independent" contemporaries. Not necessarily.

The fact that young adults are in the same household with their parents doesn't mean they are close and sharing thoughts and feelings. It is certainly possible to maintain emotional distance from those with whom one is physically close. It is also possible to maintain emotional closeness (and dependency) and avoid solving problems by fighting about who is in charge, what the rules are, and whose music gets listened to.

Parents, of course, have no legal obligation to care for offspring who are older than 18. But few parents wish to push their confrontations into this legal arena, and many live with an easy tolerance for their adult children's life-style experiments.

It seems that a few general conclusions can be drawn from the stay-at-home phenomenon:

Maybe young adults and their parents in our society are getting more relaxed about the magic of age 18.

*If staying at home for a few extra years becomes a viable option for young adults, then they can optimally grow up at their own pace and can meet the stresses and expectations of adulthood as they are ready for them.

*But whether or not this works well depends on the quality of the parent-child relationship that has evolved over the previous 18 years, the young person's sense of responsibility for self, and the parents' ability to gradually disengage from their children's lives.

Earphones for all and a good sense of humor may help in the meantime.