While marijuana may provide a stepping stone to other more dangerous drugs, we must always consider the will and constitution of an individual. If a person is a susceptible and weak they are then always likely to further dangerous behaviors no matter how much intervention. There's no working around that. Those toxic behaviors are about as innate as breathing. I worked in psych and I learned that alcohol use is at the top of the list in substance abuse. Alcohol is legal, celebrated and ruins lives.