1.)I would talk to them
2.) let them know the risks
Explanation:
I've known people who were doing drug and the main reason they told me they did them was because it was a way for them to relieve stress and it was a way for them to just let them forget about there problems for a while,I would talk to them ask them whats bothering them what's problems they have that I am able to help them with or create another outlet for them to relive that stress that doesn't involve drugs , Ive never did drugs or have had been addicted to any types of drugs so this is how i would help from someone looking thru the outside,Maybe for someone who was on drugs and stopped doing them have different views on what i'm saying.