There is extremely scant evidence to support this claim, and conversely, an enormous amount of evidence to disprove it.
The first part is questionable in its very premise. Mental disabilities as an adaptation? By what metric do you measure this? And having huge upsides? There aren't many upsides to someone being born severely mentally retarded. There aren't really even many upsides to severe autism.
For every "House, M.D." you're thinking of, there's another totally non-functional person who requires an enormous amount of caretaking.
My God, this is so well said. Thank you for this comment.
I could not agree with you more.
This was really not my intent. Would you care letting me know where I implicitly said that so I cannot make the same error in the future?
So one explanation is that natural selection has found a balance that yields benefits for the group.