McGrath, regarding those who can partake in the use of tobacco, at will, and have no problem putting it aside. There was some research done, within the last year or so, that determined that about 15% of all people genetically lack a certain receptor in their brain, that the the chemical in nicotine "plugs" into. As a result they do not become "addicted" to the nicotine.

The other 85% of the population has the receptor and hence are genetically predisposed to addiction to the chemical.