Like terminalfrost said, Roger Keith "Syd" Barrett did suffer mentally because of a combination of underlying problems and heavy doses of acid. As far as anyone knows, he currently lives a low-key lifestyle and does not wish to associate in any way with his Pink Floyd past, as that is very traumatic.

As for Roger Waters, some would argue that he suffered from megalomania and paranoia earlier in his career (Animals, The Wall, and perhaps into his solo career). He behaved with cruelty towards his bandmates, particularly Mr. Wright, which I believe was a way of turning his internal frustrations with himself outward--I think he picked Mr. Wright for "symbolic" value, because the man was his complete opposite.

While he may have been unstable at that time (emphasis on MAY--this is only a possibility), he did not have a complete breakdown that we know of, and was certainly never hospitalised. He speaks of having been in therapy, but that is certainly not the same thing; many people have been in therapy who are not "stark raving mad", or anything like that. Currently, he seems to be doing well in starting to make amends for his past mistakes...though he still has a long way to go, IMHO.

__________________
"And with these words I can see
Clear through the clouds that covered me
Just give it time then speak my name
Now we can hear ourselves again..."

WrightSatellite #1