Read what you've said again; do you realize how completely ridiculous this sounds?
A "strong dose" of heroin, to a 9-year-old who is opiate naive, will obviously not cause them to "chill out." It will cause them to horribly itch, turn green in the face, violently vomit, alternate between pouring sweat and feeling freezing cold, moan and cry, and finally lose consciousness and quite plausibly their life.
Cannabis, even at a very "strong dose," will cause none of this.
As plant medicines go, cannabis is something like a wonder drug at least in the limited sense that it is therapeutically active for a wide array of conditions at very, very safe doses.
There may be no other drug which is a candidate for relief for the symptoms described in the article and for which a trial regiment has such a low cost in terms of risk.
Heroin most certainly isn't one.