Before these data and results are discussed, a few caveats are in order. First, though epidemiologically sound [12], the IAS is a high risk adoption, largely white, population. Therefore, extrapolation to non-white populations should be done with caution. Second, the average age of the participants is in the forties. Since the phenomenology of many forms of substance use varies with age, extension of these findings to younger or older cohorts should also be done with caution. In particular, the effects on initiation of use on haplotype risk should be examined in younger cohorts who are entering the age of risk for first use. Finally, the number of subjects in the current study is relatively limited.
