Post-traumatic stress disorder has been implicated in a very small percentage of fatal aviation accidents, according to new research published in the journal Aviation Psychology and Applied Human Factors.

“There is a practical need to understand the implications of pilots returning to work after experiencing potentially traumatic events (PTE)s. Currently there is very limited research available on aviation-related post-traumatic stress disorder (PTSD) among pilots and their long-term follow-up,” explained study author Alpo Vuorio of the University of Helsinki.

For their study, Vuorio and his colleagues analyzed data on fatal aviation accidents from the National Transportation Safety Board (NTSB). They found that PTSD was mentioned in eight fatal accident investigations in the United States from January 1, 2000, to December 31, 2015.

The eight PTSD-related accidents accounted for 0.16% of the 4,862 fatal accidents during that time period.

For example, a 65-year-old male pilot entered a stall and crashed shortly after takeoff. The NTSB concluded the fatal accident was related to his decision to fly an unfamiliar aircraft (a Loehle 5151 Mustang) and his psychiatric condition.

“[A] review of the pilot’s personal records indicated diagnoses of posttraumatic stress syndrome and bipolar disorder, both of which are associated with a variety of symptoms that tend to decrease and increase over time… it is likely that the pilot’s psychiatric condition(s) directly contributed to his decision to take off from an unauthorized grassy area in an airplane in which he likely had little or no experience,” the NTSB report said.

The pilot was also taking a number of medications, including clonazepam and quetiapine.

“There is an association between PTSD and fatal aircraft accidents as a potentially contributing factor,” Vuorio told PsyPost. “In incidents where potentially traumatic events occur, it is important to recognize them and to assess the need for treatment of the pilot.”

However, it is unclear just how many pilots have PTSD. The researchers also found some cases where pilots had concealed their psychiatric conditions from aeromedical examiners — who are responsible for issuing medical certificates.

“This study would be more representative if there was access to data that reflected the true number of pilots who have been diagnosed or presumed to have PTSD, but these data were not available. In the future, hopefully, systematic data collection following aviation and work-related traumatic events and incidents among pilots will result in more comprehensive PTSD analyses,” Vuorio said.

“There are certain protective factors that can be assessed after a PTE. These protective factors include social/psychosocial support — in other words, and support from the friends, family, and peers,” he added.

“Psychiatric comorbidity is common with PTSD. If a pilot presents with fear of flying, evaluation of traumatic events might reveal useful information in assessing comorbidity.”

The study, “Pilot Posttraumatic Stress Disorder and Fatal Aviation Accidents“, was authored by Tanja Laukkala,Robert Bor, Bruce Budowle, Pooshan Navathe, Antti Sajantila, Markku Sainio, and Alpo Vuorio.