We tend to forget that Hashem owns not only our houses, cars, and clothing, but our bodies as well. It is an absolute aveirah to destroy or injure our bodies in any way since they are only on loan from Hashem and do not really belong to us. Therefore, it is assur not only to use illegal drugs, but also to smoke cigarettes and to abuse alcohol.
See Shemot 19:5 as one of many examples that illustrate this idea.