I was in a similar situation with my parents in my early 20s (although their motivations and characteristics were probably very different). Looking back I think they were not ready to deal with my independence (I was the oldest) and tried to deal with things in the same way they did when I was a child. Your mention of medical appointments really rang a bell with me - my parents did the same and this made me perhaps the most uncomfortable of all.

In my case, severely limiting contact was a highly successful approach. I didn't do this explicitly; we had no conversation "I am limiting my contact with you". I took a job in a different place, got my own (tiny, horrible) room in a shared flat and just started being more independent in my life. I must admit I used the workload of my new job as a convenient excuse to limit contact - just the occasional phone call to let them know how things were going (back in those days my parents didn't have email). I also didn't visit nearly as often as before --- I found myself reverting back to a teenage mentality, they would treat me like a child, I would get very angry/upset.

Now many years later (I'm approaching 50) I have a somewhat positive relationship with both parents - perhaps in large part because I live in a different country. After a lot of time had passed we were able to discuss the earlier issues more dispassionately (although not entirely) & get a better understanding of each other's motivations.