The investigation into the deadly Germanwings crash revealed Friday that co-pilot Andreas Lubitz hid a psychiatric condition from his employer.

While prosecutors have yet to specify the exact nature of that illness, there is speculation that mental illness may have affected his performance and perhaps the final decisions he made in the plane's cockpit.

Lubitz is accused of purposefully crashing Flight 9525 into the French Alps on Tuesday, killing all 150 people on board.

Dr. David Ballard, director of the American Psychological Association's Center for Organizational Excellence and Psychologically Healthy Workplace Program, tells Mashable that it would be misguided to draw any conclusions about why Lubitz steered the plane onto a fatal course.

"Even if we had more information, without having a detailed case history or hearing from a psychologist who examined him, we can’t make any assumptions about what happened or what was going on with this individual," Ballard says.

Mental illness is common. (For instance, more than 350 million people worldwide experience depression.) But there is no evidence linking it to homicidal actions or tendencies. Only 3% to 5% of "violent acts" are committed by those with mental illness.

In fact, people with severe mental illness are more than 10 times more likely to be victims of violent crime than the general population.

Ballard says accidents or issues related to pilot mental illness are "exceptionally rare."

Police carry a computer out of the residence of the parents of Andreas Lubitz, co-pilot on Germanwings flight 4U9525, on March 26, 2015 in Montabaur, Germany.

During a search of Lubitz's flat in Dusseldorf and the home he shared with his parents in Montabaur late Thursday, German police removed several boxes and a computer. Among the items seized were medical documents that prosecutors said indicate "an existing illness and appropriate medical treatment."

Prosecutor Ralf Herrenbrueck said in a statement Friday that torn-up sick notes for the day of the crash "support the current preliminary assessment that the deceased hid his illness from his employer and colleagues." Lubitz did not leave a suicide note.

Dusseldorf University Hospital confirmed in a statement on Friday that Lubitz had been treated at their facility in February and again on March 10. He came for a "diagnostic evaluation" and his medical records are being kept private.

The records have been handed over to the investigating prosecutor in Dusseldorf according to the hospital. The hospital says reports that he had been treated for depression in the facility were "incorrect."

Lubitz reportedly did not provide Germanwings and its parent company Lufthansa with his complete medical records.

A police car waits in front of the house of the family of Andreas Lubitz in Montabaur, Germany, Friday, March 27, 2015. Image: AP Photo Frank Augstein/Associated Press

We don't know, and may never know, why Lubitz hid his condition or whether that played a role in the crash. Yet, we do know that stigma surrounding mental illness is pervasive and may have kept Lubitz from reporting his struggles.

"Work is still an area where people are concerned about repercussions," Ballard says. They may fear being seen as incompetent, becoming the subject of gossip, or being passed over for a promotion. "For pilots, there's that added risk that disclosing a mental illness might prevent them from being cleared to work."

Pilots, like other employees whose jobs are intricately tied to public safety, must navigate a complicated relationship between their personal and professional lives.

While most mental health conditions are unlikely to affect a pilot's performance, the Federal Aviation Administration takes the precaution of temporarily grounding pilots who are being treated for depression. They can return to work after a clinician evaluates their condition as "stable" over a period of six months.

The FAA also tries to balance privacy with safety, requiring medical exams every six months or a year depending on age, but the evaluating physician is not required to perform a psychiatric assessment. Instead, they are asked to "form a general impression of the emotional stability and mental state of the applicant," according to the guide for aviation medical examiners. This includes looking for signs like physical symptoms of anxiety, a record of traffic violations, and a disheveled appearance. Pilots are expected to report if they are diagnosed with a psychiatric condition and prescribed medication.

Some conditions that can impair judgment disqualify a pilot, including an established medical history of severe personality disorder; psychosis involving delusions, hallucinations or disorganized behavior; or bipolar disorder.

The use of medications like antipsychotics and antidepressants also disqualify a pilot from flying, though pilots can apply for an exception to that rule if they take one of four approved prescription drugs. Ballard says newer anti-depressants have fewer side effects that could interfere with a pilot's wakefulness or judgment.

While these policies might seem like they create a chilling effect, Ballard says they should help decrease the stigma often attached to reporting a mental health condition at work. The goal is to make pilots feel comfortable seeking treatment; though doing so may come with a timeout from flying, there is promise of getting back to work in a reasonable timeframe. Lubitz received flight training in Arizona several years ago, according to the Associated Press It is unclear which regulations Lubitz would have been subject to and how FAA policies compare to those Lubitz encountered as a pilot for Germanwings.

Unfortunately, the speculation about the role of Lubitz's condition may now put intense pressure on pilots worldwide to conceal their experiences with a mental disorder.

No doubt many who experience mental illness are familiar with this feeling. Each time a mass murder takes place, public judgment quickly focuses on disorders like schizophrenia, bipolar disorder and severe depression.

The reaction is so immediate and so intense that it leaves no room for a more nuanced or complicated understanding of how mental illness actually affects a person. Nor does it recognize that most people are successfully treated for their conditions. Instead, Ballard says, the "disease, disorder, dysfunction" of mental illness appear to offer a plausible explanation for an unthinkable tragedy.

Plus, the focus omits other considerations, like chronic physical health conditions and health choices, and how those relate to a person's mental wellbeing.

No matter what investigators discover about Lubitz's psychiatric condition, this solemn occasion is an opportunity to rethink the way we talk about tragedy and mental illness so that it reflects more than just an obsession with a diagnosis.

"We need to create an environment," says Ballard, "where we can have conversations about health that include the whole person — mental and physical."

Additional reporting by Tim Chester and Megan Specia.