Know any good mental illnesses?

I'm writing a novel and i have a character. He is a vampire slayer, and i want him to be insane. i dont feel like making up an illness or disease so....
he's about 25 and is intimidating. he laughs a lot.
I don't know wat mental illness he should hav, so if u know one that would or could fit, and could describe it a bit, that would b great.
 
Back
Top