Medical and psychological topics are not inappropriate. The question is if they are being used primarily as an excuse to try to explain away deficiencies in academics (not a good essay). If your disorder led to your “growing” as a person as you confronted this disease and led you down paths that make you unique in a good way, it could make for a very good, maybe even compelling essay. If this is a condition that still plagues you, you might want to avoid the topic. Then it is a question for you and your medical professional whether going to college at this time is going to make your condition even more challenging.