New research shows that 911 operators are at increased risk of developing post-traumatic stress disorder. Dispatchers may not be in physical danger when they encounter a crisis over the phone or radio, but they still experience trauma, according to Heather Pierce, a former 911 dispatcher and a research associate at Northern Illinois University.

Pierce and NIU psychology professor Michelle Lilly surveyed 171 emergency dispatchers. Pierce says the study shows the worst calls are those involving children, or suicides.

“If someone is saying that they want to commit suicide you’re trying to develop a rapport with them,” she says. “Some of the telecommunicators talked about developing that rapport and then the person goes ahead and hangs up and commits suicide, and how difficult that was.”

Researchers found that the dispatchers face a moderate increase in the risk for PTSD. Pierce says that puts them in the same league as the police and firefighters who respond in person to a crisis.

The group sampled was mostly white and female. The findings are published in the Journal of Traumatic Stress.