Paphits you pilots are already going through medical tests to retain your license. What's wrong with one more test regarding one's mental health?
Notice that the examples you provided -lets take that of a person going through divorce , may well classify one as going through bad mood, but this psychological reaction is totally healthy. Specialists know when such conditions become a disease, usually it's when the person can't cope for a prolonged time , the symptoms don't ease with time, and or the person becomes totally irresponsive .
When a person suffers from severe depression for no reason, that's a actually a serious disease , and most clinical psychologists can diagnose it very easily.
btw a person who is about to commit suicide exposes well recognized patterns of behavior one of them been it starts getting rid of everything with which he has an emotional attachment. Photographs, wedding rings, sports equipment, etc. When a psychologically ill person gets diagnosed as having suicidal tendencies on top of everything, usually the doctor advices the relatives of what "signs" they should watch out.It's not something that can go unnoticed.