Last year, an investigation into a deliberate plane crash in the French Alps that killed 150 made the startling revelation that the aircraft’s pilot suffered from depression and unnoticed suicide attempts. The tragedy prompted researchers to reexamine mental health issues among commercial airline pilots, and, sadly, what they found was that the case was not a one-off.

In an anonymous survey given to nearly 3,500 pilots by Harvard researchers, only 1,848 were willing to answer mental health questions. But of those that did, 233 pilots, or 12.6 percent, met the criteria for clinical depression and 75, or four percent, reported having suicidal thoughts, that is "having thoughts of being better off dead or self-harm," within the past two weeks. Of the 1,430 pilots that filled out mental health questions and flew a plane in the last seven days, 193, or 13.5 percent, met the criteria for depression.

The findings appear Thursday in the journal Environmental Health.

In some ways, the pilots' responses shouldn’t be surprising: About 21 percent of Americans suffer from a mood disorder at some point in their lives. And the work of a pilot, which is often stressful and requires long shifts, can increase the risk of developing mental health problems. But with pilots being responsible for an enormous number of lives every day, the researchers argue that airlines should do more to prevent and treat depression and other mental health problems among their pilots—including breaking down stigmas.

Such high-pressure professions emphasize being “resilient and independent,” the researchers say, which makes admitting problems with depression difficult. And although airlines may periodically screen and monitor employees, “fear among pilots of being “grounded” or not fit for duty” likely encourages pilots to conceal any mental health problems.

“Although current policies aim to improve mental health screening, evaluation, and record keeping, airlines and aviation organizations should increase support for preventative treatment,” the authors, led by exposure assessment expert Joseph Allen at Harvard, concluded.

To do that, Allen and colleagues suggest that airlines normalize getting mental healthcare (such as having bosses endorse the practice), emphasize preventative mental health care, and try to tailor that care to pilots’ unique challenges and stressors.

In a statement to Ars, the Air Line Pilots Association said:

It is important to remember that airline travel is the safest mode of transportation in the world…The airline pilot profession in North America is one of the most highly vetted careers today… US pilots are continuously evaluated throughout their careers through training, medical exams, crew resource management, and programs such as the Line Operations Safety Audit, as well as by the airline and during random flight checks by the Federal Aviation Administration. Flight and cabin crewmembers also monitor and evaluate each other while on duty, and procedures, processes, and programs exist to respond should a concern arise.

Environmental Health, 2016. DOI: 10.1186/s12940-016-0200-6 (About DOIs).