Hello Melanie Adkins,
If the young man isn't taking his meds and refuses treatment, he could possibly have anosognosia, the lack of insight that he has an illness.
Try to develop a relationship of trust with him, and ask about his goals and hopes for the future, and suggest that if he were in treatment, he would be able to achieve his goals.
The book, I Am Not Sick, I Don't Need Help by Xavier Amador, Ph.D., may be helpful to read as it talks about such techniques as LEAP and motivational interviewing, shown to aid in getting someone to accept treatment.
Regards,
Chris