We just don't understand everything of what is natural, but there is nothing in the universe that is not natural or supernatural. And if there would be something, than we can't understand what it is.
If drug abuse wasn't a health problem , what would be the point of criminalizing it ? No point right ? So it's definitely a health problem, the question is if the criminalization helps solving the problem. Simply thinking of the story about the forbidden fruit makes me already doubt that. Any sane person can come to the conclusion that the forbidding of drugs is the only real criminal act but as it is done by governments, people are just too afraid to admit it's a wrong law and stand up against it.
