In the popular 1999 movie 'Girl, Interrupted,' Winona Ryder portrays a young woman who tries to commit suicide, then spends nearly a year in a psychiatric hospital with a diagnosis of borderline personality disorder. The film, based on a 1993 memoir by Susanna Kaysen, was gripping. But experts say it oversimplified this common yet poorly understood mood disorder. Georges Han, a recovered patient now studying at the University of Minnesota for a Ph.D. in psychology, describes borderline personality disorder as 'a serious psychiatric disorder involving a pervasive sense of emptiness, impulsivity, difficulty with emotions, transient stress-induced psychosis and frequent suicidal thoughts or attempts.' Moods can change quickly and unpredictably, behaviors can be impulsive (including abuse of alcohol or drugs, reckless driving, overspending or disordered eating), and relationships with others are often unstable. Many patients injure themselves and threaten or attempt suicide to relieve their emotional pain. People with the disorder are said to have a thin emotional skin and often behave like 2-year-olds, throwing tantrums when some innocent word, gesture, facial expression or action by others sets off an emotional storm they cannot control. The attacks can be brutal, pushing away those they care most about. Then, when the storm subsides, they typically revert to being 'sweet and wonderful,' as one family member put it. In an effort to maintain calm, families often struggle to avoid situations that can set off another outburst. They walk on eggshells, a doomed effort because it is not possible to predict what will prompt an outburst. Living with a borderline person is like traversing a minefield; you never know when an explosion will occur. MISLEADING LABEL The name of the disorder was coined in the 1930s, in a misleading reference to the border between neurosis and psychosis. Experts say it has nothing to do with either condition. Rather, affected individuals seem to be born with a quick and unduly sensitive emotional trigger. The condition appears to have both genetic and environmental underpinnings. Brain studies have indicated that the emotional center of the nervous system -- the amygdala -- may be overly reactive, while the part that reins in emotional reactions may be underactive. As children, people who will develop the disorder are often 'hyperreactive, hypervigilant and supersensitive,' Valerie Porr, a therapist in New York, said in an interview. Typically they receive a host of misdiagnoses and treatments that are inappropriate and ineffective. 'Some children need more than others in learning to regulate their emotions,' said Marsha M. Linehan, a psychologist at the University of Washington who devised the leading treatment for borderline disorder. 'These kids require a lot of effort to keep themselves emotionally regulated,' Linehan said in an interview. 'They do best with stability. If the family situation is chaotic or the family is very uptight, teaching children to grin and bear it, that tough kids don't cry, these children will have a lot of trouble.' Even in a normal family, such children need extra help. Linehan told of one mother who said: 'I was an ordinary mother, and my child needed a special mother. I took training and became the special mother he needed.' Borderline personality disorder afflicts about 2 percent of the general population, according to the Diagnostic and Statistical Manual, and it is twice as common as a much better-known disorder, schizophrenia. (Other studies suggest the prevalence is as high as 6 percent.) Many borderline patients hurt themselves, and 10 percent die by suicide. Yet as common and serious a problem as it is, Linehan said that patients often have difficulty getting the help they need -- partly because therapists tend to regard borderline patients as manipulative and demanding of an inordinate amount of time and attention. Porr, a social worker who specializes in helping families of borderline patients, said therapists with traditional analytic training often provide ineffective treatment, then experience feelings of failure and frustration. Psychotherapeutic drugs have not been effective in controlling the disorder. As a result, 70 percent of these patients drop out of traditional treatments, Porr said. Porr tries to help families learn to handle the problem and not make it worse. She said in an interview that families need to understand why borderline patients act and react the way they do, then respond in ways that validate the patients' feelings and help them regain and maintain emotional control. TREATMENTS THAT CAN HELP Experts say that even suicidal patients are unlikely to benefit from the kind of extended hospitalization depicted in 'Girl, Interrupted.' More often, a few days in the hospital should be followed by psychotherapy directed at helping them learn to live more effectively with their cognitive misinterpretations and emotional instability. Linehan practices dialectical behavior therapy, the only therapy that has been demonstrated to be effective in a number of randomized clinical trials. She said two other approaches, called mentalization and Stepp, were also likely to be helpful. Dialectical behavior therapy, a derivative of cognitive behavior therapy, helps patients identify thoughts, beliefs and assumptions that make their lives challenging and then learn different ways of thinking and reacting. In effect, Linehan tells patients, 'Your problem is that you don't know how to regulate yourself, and I can teach you how.' She said thousands of therapists have been trained in dialectical behavior therapy, and many others practice it without special training. But the value of the therapy can be thwarted if patients return to an environment that misunderstands them. Thus, Linehan said, it is important for others to recognize that people with borderline personality disorder are genuinely suffering. 'They are in excruciating pain that is almost always discounted by others and attributed to bad motives,' she said. The idea is 'to validate the person's emotional reactions, to say, 'I understand how you feel,' to pay attention, not to the situation, but to the emotion behind it,' Linehan said. Alan E. Fruzzetti, a psychologist at the University of Nevada, said that families have to learn how to 'soothe themselves, to realize that though the situation is awful, not to blame or be judgmental of the person but to see the person as also suffering.' Reacting in a nonloving way magnifies the trauma tenfold, he said in an interview, adding: 'You may have to leave a bad situation, but you must come back in a loving way, maybe say something like, 'That blowout yesterday, I really want to understand your experience.'' Therapists trained in dialectical behavior therapy can be located through the Web site www.behavioraltech.org. 