Brain shrinkage from antipsychotic use is one of the reasons I decided to live with the symptoms of my illness instead of doping up to mask them. I'm not sure what the impact of anti-epileptic drugs is though.
The trouble with psychosis is it can be so debilitating when your brain feels electrically fried that you can become incapacitated to the point where taking antipsychotics may be the less destructive path (at least in the short term).
But for less severe cases, where moods give you an unpleasant ride, but are manageable without drugs, and where suicidality is not a significant component of the syndrome, it may be a feasible decision to stay off drugs which can impede your ability to function.