Rat park is highly illuminating in this conversation, and suggests that drug addiction is just a symptom. When people (or animals) are forced into a life of social and cultural isolation, drugs become the most appealing thing they have available. If we could find a way to give people a social/cultural support system that's more appealing than drugs, we might be able to reduce addiction without prohibition.

http://www.brucekalexander.com/articles-speeches/rat-park/14...