Smoking Weed. Is it a sin?

To give some context, I personally think as a Christian that smoking weed is indeed a sin to an extent. However, my husband has been smoking since he was 16 years old. Even after we have came to Jesus and have pretty close relationships with Him, he still smokes. He has told me that he doesn’t smoke to get high but to help his depression/bad thoughts. I’m not sure what to do, or if I can even do anything. But I’m just curious to others opinions!