Sounds a little like what I went through. I don't know if I'm MENSA smart, but I'm smart. I got depressed in high school, tried a lot of meds but still dropped out of college once, bummed around for a few years before trying again and nearly dropped out a second time. Then I tried cannabis, and it worked. It brought me out of my fog, I was able to finish school, and I function pretty well at my job right now despite my husband being very ill. If your brother hasn't tried it, I recommend it.

But if that's not his thing (or even if it is), I've been having good luck with The Feeling Good Handbook by David Burns. I've tried a few self-help books that were junk, but this one's based on cognitive behavioral therapy. It's got a chapter on perfectionism (something which probably afflicts your brother).

Also, make sure he knows -- from you and your parents -- that you do not judge him any more than if he had a chronic physical illness, and that whatever he wants to do with himself the family will support him and help him achieve his (realistic) goals. Bullying and type I diabetes played a role in my own depression, but my parents didn't help by putting pressure on my about my future career path.