Of course I can't claim that my personal experience is representative of all people. But you're the first person I hear say that did not feel any psychological effects of doing a PhD.

Every single person I know that did a PhD (including myself) has mentioned feeling frustrated/isolated/depressed/etc at different stages in their PhDs. It is interesting to see that some people are actually not affected that much.

I guess I'll just chime in and say that, going into my fourth year, I've never felt frustrated/isolated/depressed more than I thought was normal. (I mean, does getting frustrated with GHC count? :P)

I'd actually say it's the opposite: the process of getting my PhD has been one of the more wonderful experiences of my life thus far. Although, I tend to believe that at least part of this is due in large part to one particularly awesome professor that I've worked closely with (and isn't my advisor).

I would say that 1 is a very likely outcome for many students, though of course certainly not universal. So it's something to consider.