When someone you care about is struggling with addiction, it can be difficult to know what to say. It's important to be clear about your feelings and express them in a calm manner. Let your loved one know how much it hurts and worries you to see them addicted to drugs and how much you fear for their safety. Avoid putting pressure on them and instead be a trusted friend with whom they feel safe.
Don't say things like, “If you loved me, you'd stop smoking” as this is harmful behavior that almost never works. Instead, share your concerns with your loved one and ask how you can help them recover. Remind them often that you are willing to be their support for recovery and that they are valued, that they can do it, and that they are not alone. If your loved one has relapsed, it's important to ask without judgment what they need from you. You can also encourage them to discuss this issue with their therapist or addiction counselor.
It's never a bad idea to shift the focus to their past successes and the potential for success again. Be specific about what you see and frame the conversation with phrases with I, such as “I've noticed” or “I'm worried”.