"If all you have is a hammer, all your problems look like nails", I think is the one I've heard. But I agree that the nutritional angle doesn't seem likely in this case, because I eat pretty well.

How about coming to PC when they leave? Sort of an intermediary step between having lots of real-life people around, and being completely alone? That way, you can sort of "come down" slowly from the thrill of having chums nearby, to the general but still noticeable pleasantness of PC (chat, maybe).

(If you do this, PLEASE let us know how it goes. It might be the best idea I won't get a chance to test for a while! Good luck!)