@Wasywasydoodah post is very good one to consirder and reflect too,
@Westsussex also is insightful good post too,
May take on this that it's a good sign that he is being honest straight with you, it shows emotional maturity,
following on from these two posts points they have brought up,
would be what healthier alternatives for escapism to replace the drug addiction does he actively do now or would seriously consirder nowadays instead?
Such as creative Arts, or could be something else could be participating in a,game of chess and other retro board games sessions as this is,quite popular interest in certain pubs night out,
He could have obviously other hobbies interests such as Geeks 🤓 dungeons and dragons game or dressing up historical re ancient reenactment ect
Whatever it is hobbies interests wise ,
My no fear would if he was going through stressful time depending the severity of this and how long it went on for he could relapse into taking up drugs, again like before, or just take less hardcore drug, such as smoking "joints or equally just swapping drug addiction for another type of addiction alternatives".