^
This is what is unfortunate about the MH field. There is a still a stigma, and a lot of that is in this situation. I am not justifying what the pilot did; it was mass murder-suicide, or vise versa if that matters. But clearly as what has been said, people do not report because it can impact many jobs, getting one or keeping one. And I get that many disorders (schizophrenia, bipolar I, dissociative identity disorder etc) often disable people depending on where it is on a continuum. I would not want specific disorders doing certain jobs. But then where is the line drawn? Someone with well managed ADHD who takes low dosages of Intuitiv, and copes with it well but is then excluded from being a surgeon? A lawyer?
The other issue is the inherent self reporting of mental health. While certainly we can see differences in brains via MRIs and what not, it's not black and white that can be with other non MH conditions. It's not oh, this guy has Intermittent Explosive Disorder, this gal Major Depressive Disorder, that guy Bi-polar 2 disorder and etc. It is limited to stuff like Spectrum disorder and AOD use frequently from what I know.
So when I diagnosis someone, I go off what they say. A psychologist uses measures, and psychiatrists also use primarily what someone says. But if they under report, or over-report symptoms, the diagnosis will fit that. To me, it's not hard to gather questions are going. I'm guessing someone without my training would also be able to figure out where some questions are going, and such fake answers if they wanted.
Sure, always ways to improve measures. But with self reporting still a part of the process, and no way to black and white see conditions, mis diagnosing on the account of false reporting is inherent in the field.
Thinking of "curing" a MH disorder is not fully accurate. Especially from using medication, it's just the managements of triggers and symptoms. Certainly temporary things like grief related depression, adjustment disorders, and depression via a break up often resolve themselves. But schizophrenia, bipolar 1 & 2, Borderline, Anti-social personality, ADHD and so on have no true cures. People manage them with varying degrees of success.