To makesher,
Mentally ill people will not be successful in therapy until they realize they have a problem. That is the first goal of the therapist. Medications work no matter what you tell yourself. Smoking comes under the mental health catergory due to classification as an addiction -not all of them have underlying issues or like you say “mentally unstable”.
The yeshivos can hire school psychologists and evaluate everyone. That would be the first step. This program would evaluate everyone for mental illness -maybe we should include the Rebbeyim. This would not be limited to smoking, but any mental issue should be evaluated.