[Anonymous]

no.
First I would say that knowledge is subjective.
I know a man with down's syndrome who suffers from great depression. Most people would not say he was highly 'intelligent'. You could say he has a simple life from a non-personal objective standpoint.
Also, I myself am an idiot and I'm just about as depressed as a person can get. I know people who are far more intelligent than I am who think life is good.
I had a german teacher a long time ago when I was in school who seemed to be the most happy/peaceful person I have ever known in my life. I always thought he must have some great knowledge. He reminded me of Buddha.