One of the most unsettling facts to emerge from the trial of John W. Hinckley Jr., 27, is how few ripples he made in his frightening descent from quiet youngster to deluded would-be assassin. Acquaintances hardly remembered him. His family realized the extent of his problem only when it was too late. The question that will linger long after his trial is how other disturbed young people can be identified and treated before their actions erupt into violence. For Dr. Douglas H. Powell, a psychologist trained at Harvard and since 1962 a member of the university's Mental Health Service, the answers to that and related questions have been a life's work. He recently completed Understanding Human Adjustment, a text outlining warning signs of mental illness, to be published by Little, Brown in December. Powell also heads a private group practice in Cambridge that specializes in the psychological evaluation of young people. A native of Grand Rapids, Mich., Powell, 48, now lives in Concord, Mass. with his wife, Virginia, who helps run the group practice. They have two children, Carolyn, a Harvard senior, and Douglas Jr., a freshman at the University of Pennsylvania. Powell discussed some of the warning signs of psychosis, particularly in adolescents (an age group he broadly defines as 15 to 25), with Eric Levin of PEOPLE.

Isn't it remarkable that the therapist who treated Hinckley before the Reagan shooting didn't seem to pick up on the youth's serious delusions?

All I can say is that hindsight is almost always 20/20 and that any clinician who's been in the field very long is going to miss something. One depends on what comes from the patient. If a child or adolescent is sent in against his will, that person may not feel like telling you everything that's going on inside his head. And that makes it very difficult to treat that person.

Is it odd that so many people who encountered Hinckley found him rather blandly genial and normal?

No. I have not met Hinckley nor intensively studied his case, but the thing about psychotic people that intrigues me is that they are not psychotic all the time. A colleague of mine once spent two weeks observing at a mental hospital to find out what the day-to-day difference is between schizophrenics and the rest of us. He found out there was surprisingly little difference. They all had some systematic delusion ranging from the bizarre to the innocuous. But most people who are crazy do not run around doing crazy things all the time.

What are the signs that someone is not coping well?

The first casualty when someone begins to have significant psychological problems is his or her sense of humor. There are experts who view that as the cardinal feature of mental health. Humor allows a person to objectively face a distasteful reality and still handle very strong emotions in socially appropriate ways. The second casualty is zest. The enthusiasm most of us feel for life goes by the boards.

At what point does normal fantasizing tip over into disturbance?

When fantasy begins to supplant satisfaction from work, love and play. Normal fantasies are provoked and stimulated by reality. If your car is stolen, it's natural to entertain extremely violent fantasies of what you would do if you caught the crook. But eventually it passes. A psychotic's fantasies aren't governed by reality but by inner urges, and they recur intensely again and again with little alteration. With a person who fits Hinckley's description, an unattractive reality is increasingly compensated for by a delusional fantasy that will make it all right: "I'm going to become a happy, powerful, beloved person if I marry the right woman" or win the lottery or whatever.

How else can you tell if someone is becoming seriously disturbed?

Most people who are out of it in a delusional way don't have a good grasp of data. They'll read books and listen to music, but if you were to ask them this week where the Falkland Islands are they may not know. It's selective inattention. They miss whole aspects of things.

Defense doctors have called Hinckley a "process" schizophrenic. What does that mean?

Basically, schizophrenia is characterized by distortions of reality, inappropriate emotions, hallucinations and delusions. Process schizophrenia involves a slow onset of symptoms not tied to a single event. Recovery is also slow. There's also "reactive" schizophrenia, which involves a sudden onset of symptoms after a traumatic event. You flunk out of school. Your boyfriend is killed in a car crash. Most people recover from that quickly, and if you follow up three years later, 90 percent of them are doing fine. Quick recovery doesn't happen for process schizophrenia. But schizophrenia of either type is usually a young person's disorder. People who are paranoid or depressed tend to get those conditions later in life.

What warning signs might parents look for in their adolescent children?

One of the things you look at is the quality of the person's relationships. Does the kid have friends? Friends are good litmus paper for us; they can tell us when we're acting crazily. They give a psychotic a wide berth. You would also expect the normal adolescent, no matter how much in turmoil, to be involved in some kind of productive activity. I'm forever hearing from parents that their kid is not motivated. It turns out the kid has a paper route, he's working at McDonald's, and he made $2,000 last summer mowing lawns. Now, tell me that kid isn't motivated. What those parents are looking at is schoolwork. The kid is perfectly well motivated, just not academically. You have to look at the whole picture.

What if parents and their teenagers are always fighting?

Adolescents need some kind of emotional contact with parents, whether warmly affectionate or relentlessly adversarial. Even an acrimonious relationship with an adult is beneficial. They need somebody with another opinion, so they can push up against it as a springboard to finding their own way. It's very helpful if parents will state their values directly. If we can't be in contact with our kids as much as we'd like, we have the responsibility to make sure some other adult is—a coach, teacher, religious leader, camp counselor, scout leader, somebody.

Is it a mistake to throw a troublesome kid out of the house?

Yes. When you do that you deprive the child of the single factor which has been shown over and over to be associated with recovery from mental diseases: the love of other people. There are alternatives, including halfway houses run by mental hospitals, special boarding schools, and relatives with whom the kid can live for a while.

If there hasn't been much contact, is it unrealistic to sit down with one's kid and suddenly have a heart-to-heart talk?

Yes. This business that it's the quality and not the quantity is way off base. Anybody with a teenage kid will tell you that when you're ready to talk, he's going out or is just not ready. And when he is ready, you're exhausted from working all day. You might spend a whole weekend with your son fishing and have only a half hour of useful conversation. With teenagers, you have to invest an enormous amount of time to get any quality at all.

Is this just the nature of the age?

Yes, you can't blame the poor parents. Nobody ever talks about what having a teenager does to a parent. The kid asks provocative questions you'd rather not deal with. "You say you hate your work. Why do you do it?" "How can you stay married to the same person for 20 years?" Teenagers are deadeyes at picking up on rationalizations and hypocrisies. Like any minority group, it's in their interest to know the people in superior positions to them. Kids know their parents much better than parents know their kids.

If you think your child needs help, how do you delicately broach the subject?

You don't say, "We're taking you in for a psychiatric evaluation to determine what your problems are." You can say, "We're concerned. This problem doesn't seem to be getting any better, it keeps coming back and it doesn't seem to be under your control. We think it might help to get a consultation just to find out if it's really something to be concerned about and, if so, what can be done to help."

Won't this be met with resistance?

Of course. I tell people to say, "Yes, I know you don't want to go. We all like to feel we're normal. Most of the time you are functioning pretty normally." Usually there are three things that prevent us from seeking help when we need it: a sense that the trouble really isn't so bad; a feeling that something simple is going to help, like willpower or just saying our prayers every night; and the fact that the craziness isn't there all the time.

Once treatment is under way, what more can parents do?

Try to put some pleasure in the kid's life. Help him find a hobby he can enjoy. Help him select courses in school in which his disorder can work for him. If he has an active fantasy life, a course in creative writing may not be too bad. Work your tail off to find groups of kids he can relate to and be a part of. Teach him skills that will enable him to go and get into a game of basketball or tennis at the playground. If he is depressed a lot, you might encourage him to get regular exercise. If he is always exploding and out of control, you might want to get him into some competitive sport or martial art. It will help vent pent-up aggression, but in a controlled and disciplined way.

One of the Hinckleys' neighbors said, "There but for the grace of God goes anyone's kid." Is that a valid statement?

Yes and no. We all have the repertoire of madness within us. The question is what do we do with it and what do we have to cushion us from those terrifying feelings and bizarre thoughts we all share?