Ignoring the problem, many health care facilities have failed to provide a safe working environment for their employees, workplace violence experts said.
"Hospitals don't want to have a reputation as being the wild, wild West," so they "try to minimize it and keep it quiet," said Dr. William Dubin, chairman of the psychiatry department at Temple University School of Medicine, who has written about violence against mental health professionals.
The great majority of people with mental illness are not violent, noted Gabriel Nathan, spokesman for Montgomery County Emergency Service, a private psychiatric hospital outside Philadelphia.
"Unfortunately, as in all populations, there are outliers," he said, "which is why it is important to be aware and alert."
A Department of Justice survey found 55,882 workplace violent crimes against psychiatrists, social workers and other mental health professionals from 2005 to 2009, making them four times as likely to be assaulted on the job as workers generally, according to statistics compiled by the U.S. Department of Justice.
Independent experts said the number of assaults is almost certainly far higher because violent incidents are grossly underreported.
That reluctance often stems from a belief among mental health providers that violent outbursts come with the territory, or a fear they'll be blamed for provoking the attack or an unwillingness to turn in someone they're trying to help. And health care administrators often discourage reporting, experts said.
"No one wants bad publicity that potentially comes from workers reporting that they suffered" an assault, said University of Maryland professor Jane Lipscomb, who researches occupational injuries in health care. "That's a huge barrier."
In the latest case of violence, authorities said Richard Plotts, 49, shot and killed his caseworker, 53-year-old Theresa Hunt, and wounded Silverman during a July 24 appointment at Mercy Fitzgerald Hospital outside Philadelphia.
Silverman, who was grazed in the temple and thumb, crouched behind a chair, pulled out his own gun and fired several shots at Plotts, authorities said. Plotts has been charged with murder.
The psychiatrist has not spoken publicly about the shooting, but prosecutors have said he regularly carried a weapon for protection.
No one answered the door at Silverman's home Friday. A picture evidently drawn by his child and posted on the front door depicted him with a bandaged head and thumb.
"My dad is a hero," it said.
The exchange of gunfire occurred on the third floor of the hospital's Wellness Center. Authorities have said there were no surveillance cameras in the doctor's office or the waiting area outside nor does the center have metal detectors.
A Mercy spokeswoman said the hospital, which has a policy prohibiting employees from carrying guns, is reviewing its security procedures.
Mental health workers typically receive training on how to recognize when a patient might be about to become violent, and on verbal de-escalation techniques aimed at preventing it. Some hospitals also train staff in self-defense.
Mental health professionals are often especially vulnerable to injury because their first impulse is to help, said Dr. Michael Privitera, a psychiatrist at the University of Rochester Medical Center in New York state.
"There is this conflict in your thinking right away," said Privitera, editor of a book on workplace violence in mental health facilities. "What you're trained to do is to try to help the person. To make it click in your mind — that you are under threat now — it takes a while."
In rare cases, attacks are fatal. Twenty people in health care support occupations, a category that includes psychiatric workers, were killed on the job from 2005 to 2009, according to the Bureau of Labor Statistics.
The Occupational Safety and Health Administration has published safety guidelines for psychiatric staff and other health care workers, recommending metal detectors, enclosed nurses' stations, multiple exits, furniture bolted to the floor in crisis treatment rooms, curved mirrors at hallway intersections and a variety of other steps.
But the guidelines are voluntary, and congressional investigators are looking into whether they have been widely implemented and whether they should become mandatory.