No predictive power?
What is the most frequent cause of suicide? At least 90 percent of all people who died by suicide were suffering from a mental illness at the time, most often depression. Among people who are depressed, intense emotional states such as desperation, hopelessness, anxiety, or rage increase the risk of suicide. People who are impulsive, or who use alcohol and drugs, are also at higher risk.
There are VERY FEW people who "just snap" and decide to kill themselves - it's not a crime of passion. It's usually an act born of a LONG bout of depression, despair, and suicidal ideation, and if you're doing constant, frequent screening for mental illness, you may prevent these sorts of things. Don't fire the guy, but make him get treatment until a doctor clears him to resume flight status. In fact, if they're actively screening for suicidal tendencies and ideation, many factors are highly correlated with suicide attempts, and could easily help screen people who are not in a mental state to perform their flight duties.
I think that likely 90% of the people in car accidents ate carrots in the prior month. FYI: This does NOT mean carrots cause car accidents. Tim S.