There’s probably definitions for what “high risk” is. Maybe for example “high risk” means 90% of people in that group overdose within 6 months. These definitions are obviously decided by the person creating the model, and so should be based on expert opinion. But predicting someone as “high risk” 86% of the time is pretty damn good, and it’s definitely a useful tool. However, it probably shouldn’t be the only tool. Doctors shouldn’t say “the ml model says you’re high risk, so no more drugs”, instead a discussion should be started with the patient at this point, and then the doctor can make a balanced decision based on the ml output, as well as the facts they’ve got from the patient.