QDMQDMQDM, thanks for you post. I had to work with a psychotic chap for some years. Exactly what you say and for me it looks like it may be very relevant here. Depression itself is not really the issue here, it is the psychotic side of human nature.
What I remember from Germany: there is a bit lack of understanding of mental illness, or psychiatric injuries, or psychotic behavior. Its all put in just one big bowl by the psychiatrists and they probably just prescribe drugs: fatal if you get the wrong stuff! Makes some mentally ill people really crazy and a lot worse - they change from depressive to psychotic because of the wrong drug. Then the psychologists only see the family background and childhood and they have no idea of endocrine disorders. Even worse, in Germany all needs to be absolutely perfect. The cars , the houses, the streets and of course your profession and career. That must be big pressure on people with understandable little problems. With that pressure the problems get bigger. Some people just have a psychotic predisposition, it depends on the stress and pressure from the outside if this time bomb is triggered at some stage in their life - usually between the age of 15 and 35. Often this predisposition never comes out and never will be discovered. This week it looks like the hole World became aware of one persons very tragic mental rush hour.
Let's hope all friends and relatives of the victims, including the co-pilot family, all witnesses and rescue staff on site, get the help they need in the next days, months and years to come.