Not a professional pilot, but had worked with a with a colleague who had mental health problems, until he got early retirement for health issues. He was never suicidal. He was sometimes awkward. As a pax I wouldn't worry too much about many mental health issues.
But suicidal (or having a grudge against humanity) as an adult is different for flightdeck. I'd prefer not.
I wouldn't be so bothered about an actual suicide attempt in early teens.