People say “punish”, but I prefer to say “heal”. A slap might just open the door to healing. Beyond drugs, there is mental health behind all of this. Mental health issues are at the root of many substance abuse problems. If we ignore that, blame everything on drugs and don't provide treatment, we'll just label the young person a drug user or a pot smoker, thinking that it will go away.
As Ms. Riendeau said, the earlier we intervene, the sooner we are able to identify the issue. Otherwise, parents are at a loss. Personally, I would have appreciated someone like her telling me exactly what we needed to do when David was 13 years old, as we didn't know what to do.
I think Justine wants to add something.