[jasallen]

This is a misunderstand intentionally propagated by the 'treatment' system. Sure there are plenty of factors that can play into a pre-disposition, but it is the act or the chemicals that begin a physical re-wiring of the brain. It is because of having new additional receptors, or having blocked receptors, or a number of other changes that we have what we call 'physical addiction', and that doesn't happen until "that first try".

It is also, in almost all cases, reversible. The receptors adapt, pathways change, hormonal sensitivities reset.