Rape is a significant health problem for American women.

Based on national surveys, it is estimated that 11.8 million women have been raped sometime in their lives. Of those women, about 3.9 million suffer from what is known as post-traumatic stress disorder, a debilitating and often long-lasting psychiatric problem traditionally associated with combat veterans.

Among the classic symptoms, mental health workers say, are flashbacks, guilt, nightmares, a numbed attitude, insomnia and pronounced "startle" responses to sudden movements or loud noises.

Other side effects commonly experienced by rape victims include depression, avoidance of sex and generalized fear and anxiety that result in physical reactions, such as elevated heart rate and rapid breathing.

Dean G. Kilpatrick, director of the Crime Victims Research and Treatment Center at the Medical University of South Carolina, studied 101 rape victims in a sample in Charleston, S.C. Kilpatrick found that neither the relationship with the perpetrator nor the circumstances of the attack affected the degree of subsequent trauma.

"Women raped by strangers, by their husbands or boyfriends or by former boyfriends viewed their rapes equally as violent," Kilpatrick said. "The victims were equally likely to have feared serious injury or think they might die" during the rape.

"There's an abundance of evidence that rape causes very serious mental health effects on women," he said. That trauma, he said, can last a lifetime.

Sexual abuse, particularly incest, is strongly correlated with eating disorders, alcohol and drug use and depression, according to mental health workers.

Patricia Resick, a professor of clinical psychology at the University of Missouri-St. Louis who heads the school's rape trauma team, said that a variety of long-term studies have shown that as many as half of rape victims never fully recover and suffer lifelong chronic depression or post-traumatic stress disorder.

"We have women here who are just now dealing with the fact they were raped 30 or 40 years ago," she said. "Because it was an act of sex, they felt shame and guilt and never dealt with it." Studies have shown about 75 to 80 percent of women blame themselves for the rape. The average rape victim, Resick said, does not seek help until five years after the attack.

The majority of victims, Kilpatrick said, do not report rape or seek help afterward. "They don't realize how many people are out there with the same problem. And they blame themselves as a way to gain control over the situation.

"It's a very chilling prospect to think: maybe I didn't have control, and maybe it could happen again," he said. "But women have to remember that no matter what they do, that doesn't give somebody the right to rape them."