Air Force officials and independent experts have suggested several potential causes, among them witnessing combat violence on live video feeds, working in isolation or under inflexible shift hours, juggling the simultaneous demands of home life with combat operations and dealing with intense stress because of crew shortages.

“Remotely piloted aircraft pilots may stare at the same piece of ground for days,” said Jean Lin Otto, an epidemiologist who was a co-author of the study. “They witness the carnage. Manned aircraft pilots don’t do that. They get out of there as soon as possible.”

Dr. Otto said she had begun the study expecting that drone pilots would actually have a higher rate of mental health problems because of the unique pressures of their job…

The Air Force has also conducted research into the health issues of drone crew members. In a 2011 survey of nearly 840 drone operators, it found that 46 percent of Reaper and Predator pilots, and 48 percent of Global Hawk sensor operators, reported “high operational stress.” Those crews cited long hours and frequent shift changes as major causes.