He's never been diagnosed with any such mental disorder as far as we can tell.
It's a pet-theory with many Kiwis that he's :autism: but I think he's just a manchild with an inflated ego, absolutely no coping mechanisms due to being mollycuddled all his life and a massive entitlement complex.
In terms of relationships, I think Dobson is a weird kind of emotional leech and abuser. Not in that he'd ever intentionally harm, let alone hit, his significant other, but seeing how petty and miserable this dunce is, I assume that he drags down the people around him merely by being in their presence too long.
From the few things we know about Dobby and his gf, we know that his gf had to constantly make sure to accomodate Dobson's wishes. For instance, he dislikes being out after dark, it seems, so his gf just kind of dealt with that by not going out with him after dark, even when they were visiting her family at Hanukkah. She had to support him when he was home "working on his comics by playing vidya" while she was out earning money.
So, in short, the kind of guy that passively reduces the quality of life of his mate due to his inconsiderate and egoistic behaviour.