This happened to my buddy. He got in a car accident or something. This was shortly after he graduated from high school, and his father had just died. He ended up on pain meds, ended up getting addicted after a couple of months. When his prescription ran out, he called up our mutual friend who was in to drugs and got more. This went on for about 18 months before he decided he wanted to become a veterinarian, somehow his friends and family weaned him off pills, and after two years was accepted in to vet school. Through no small miracle he made it through grad school and graduated, he's now pretty successful.
I grew up in a pretty rich suburb, we had time to help him and his family through the addiction, and he had a strong goal to strive for. Many people don't have the opportunities or strong safety net that he did.