Depends on what it is.
To my knowledge, the Church of Satan
does not welcome those with severe behavioral disorder.
Physical disorders do not affect competency and are irrelevant to membership.
Stephen Hawking, for example, would most likely be welcomed should he ever apply for membership. A person who's spent a lot of time in halfway houses for pyromania might find it more difficult.
Again, however, it depends. If a person had audio hallucinations but recognized them as such and had it under control, it might present no particular obstacle.
I think you can see the realistic implications of this.