One thing is certain: When you make a drug illegal you make it scarce. When you make it scarce you make it expensive. Addicts needing to finance their habit push the drug and create new addicts. That makes providing the drug very profitable. Good old free enterprise gets into the act to meet the demand, and the next thing you know the drug is still expensive, but abundant, there are many more addicts, and their numbers grow by leaps and bounds.
In the 1930s Britain started furnishing its junkies with heroin so they wouldn't create new junkies. It worked, and they got their addiction rate way down until they got an influx of opium-loving middle-easterners after WWII.