Better psychological & physiological testing for pilots?

[Dizzy1]

I don't know how apparent it would be, people can be good at hiding such problems.
I think most of the time I can detect someone who's been drinking, drugs I don't know.

That's the thing, psychological disorders such as depression or suicidal tendencies can be easy to hide where as a psychiatrist/psychologist could also make a mountain out of a mole hill like if you had a tendency to bite your nails or something. As for drug use, might be more difficult to hide ... don't know though.