I am not licensed to practice law in Indiana so the following should not be taken as legal advice, but simply as information based on general principles of law which is intended to educate. If you need legal advice, please consult a lawyer who holds Indiana licensure.
I am hearing that your son or daughter is 19 years old. The age of majority is 18 everywhere in the United States, so far as I know. At 18, the law considers an individual to be an adult capable of making his or her own decisions.
In terms of preventing the child from moving out, you have no rights. The legal age of majority in Indiana is 18 and as such a 19 year old does not need your permission to leave home. School and health probelms have no bearing on the issue.
As far as keeping them at home, once a child hits the age of majority, one of if not the only tool available is financial. By that I mean inisiting that if a child (and at 19 they are still children) wants to live independently, they actually live independently - generating their own income and paying all of their own expenses. This trick usually works pretty well - at least until they are old enough and well educated enough to get a decent job. Hopefully by then they will have matured and be in less of a hurry to start paying their own expenses.