STACY IS A CHURCHGOING MIDWESTERNER, a 25-year-old secretary who wears cardigan sweaters and wire-rimmed glasses. She's the blond, blue-eyed girl next door--seemingly about as wholesome as they come. But for more than 10 years, Stacy secretly indulged in a passion fit for B-grade horror movies: she scratched at her skin, burned it with hot knives and sliced it repeatedly with razor blades and shards of glass. Today Stacy's arms are a jumbled mess of thin white lines from elbow to wrist. They are not just physical wounds, but emotional battle scars. The cutting wasn't gruesome or even painful, Stacy says. It was soothing, a release for inner turmoil she could not articulate. ""Once I did it,'' she says, ""I felt better.''

Self-mutilation--also called self-injury and, in its most basic incarnation, cutting--is alarming and unfathomable even to many therapists. For decades, patients like Stacy have been mental health's untouchables, bounced from emergency rooms to institutions. ""They've been ignored, they've been shunned,'' says Dr. Armando Favazza, a psychiatrist at the University of Missouri-Columbia medical school who has written extensively on self-mutilation. But three years ago, Princess Diana outed cutting on a global scale when she admitted in a television interview that she had intentionally injured her arms and legs. ""You have so much pain inside yourself that you try to hurt yourself on the outside because you want help,'' she said. There are two new books out on the topic, ""Bodily Harm'' and ""A Bright Red Scream.'' And though research is still in its infancy, therapists say there are now promising treatments--from medications to intensive psychotherapy--for the estimated 2 million self-mutilators in this country.

The vast majority are women who started cutting as teenagers. Stacy recalls picking up a piece of broken glass in a parking lot when she was 13, but she can't remember why or how she decided to slash herself. Some self-mutilators are suicidal as well; most cut themselves not to die, but to cope with the pressures of staying alive. Experts say that at least half were sexually abused as children. Many learned to shield themselves from horror in their lives by dissociating from their emotions. They say cutting snaps them back into consciousness. ""It proves "I'm alive, I'm human, I have blood coursing through my veins','' says Marilee Strong, author of ""A Bright Red Scream.'' Others, many of whom also suffer from anorexia or bulimia, self-mutilate to gain control over their bodies or to express their feelings about being abused. ""They're wearing a visible symbol of the violation imposed on them,'' says Dr. Joseph Shrand, director of the Child and Adolescent Outpatient Clinic at McLean Hospital in Belmont, Mass.

Cutters come from less tormented backgrounds, too. As children, some endured their parents' bitter divorces or may have been verbally abused--demeaned as too fat or lazy. Others were told never to cry. Whatever the trauma, experts say almost all grew up in homes with poor communication between parent and child. They suffer not just low self-esteem, but absolute self-loathing. ""Cutting is literally like letting out bad blood,'' says Strong. Many are high achievers, even perfectionists, but they are failures when it comes to emotions. ""They have no language for their own feelings,'' says Steven Levenkron, a psychotherapist and author of the book ""Cutting,'' published earlier this year. ""Cutting is the replacement for the absent language.''

Experts say they can help. Self-mutilators often suffer from related conditions like depression, anxiety, eating disorders and post-traumatic stress syndrome. Treatment varies accordingly. Some patients benefit from antidepressants. In certain cases, the cutting impulse can be quelled by the drug Naltrexone, commonly used to treat heroin addicts. Medication alone, though, is unlikely to be enough. Cutters are often unreceptive to traditional talk therapy, but some psychologists are finding success with dialectical behavior therapy, devised in the 1980s by University of Washington psychologist Marsha Linehan. The treatment teaches patients skills for tolerating distress and controlling behavior.

Intensive inpatient therapy can work, too. Karen Conterio and Wendy Lader, authors of ""Bodily Harm,'' run a 30-day clinic for self-mutilators outside Chicago. Stacy is one of their successes. A year after entering the program, she's stopped cutting. ""It just seems so absurd,'' she says. Experts hope that through compassionate counseling, other cutters will one day be able to say the very same thing.

KAREN SPRINGEN