Must have mental illness/phobia, Ideas?

[Nifft]

Essentially, in our upcoming campaign (3.5e) every player must have a mental illness or phobia of some sort. Most player really like the idea but I am not confident in my ability to roleplay something like that at all and unlike most I barely know any applicable mental illnesses. Has anyone got any ideas for how to roleplay things like this?

For reference, I'm playing a Rogue Tiefling with the stats str 13, dex 17, con 14, int 16, wis 13, cha 14

Put yourself in the role of Director rather than Actor, then act out what you (as Director) decide the character should do.

Do some google work and read up on mental illnesses so you can pick one to portray.