I'm not supposed to be here lurking - so I'll make this quick. Drugs and chemicals are not the only thing that affect brain chemistry. Thought, mood, environment, exercise, sex and many other things also influence the way neurotransmitters are transmitted and how new pathways and connections are formed in our brain. We notice the influence of chemicals introduced into our system because the reaction time is quick - but I would hazard to say that the other "slow reaction" changes are more important in the long run - which is why it is imperative to be mindful of these things not just from a spiritual stand point, but from a biological standpoint as well. In our society we tend to separate the mind, body and spirit instead of seeing them as part of a larger whole. Okay - crap - I gotta get some work done!