The episode I'm describing was one of his post-9/11 speaking appearances -- this time at Georgetown University sometime in November of 2001. He looked terrible, his speech was slurred and he looked so gosh-awful deranged that C-SPAN wouldn't even show the video of the event when they replayed it a few days later (they played the audio of the speech over a still photo of some kind, if I recall correctly).
By my count, it was at least 6-8 weeks before he made another public appearance after that. I've long speculated that he was being treated for some kind of psychiatric breakdown and/or substance abuse problem in that intervening time.
Actually, that interview was likely one of Clinton's more honest moments in that he showed his anti-American self.
I don't think he is being treated for a psychiatric illness. I do think he is a sociopath and I think his whole interview with Chris was a show.