variant allele might be more sensitive to early life stress and subsequent vulnerability to cocaine addiction. However, one caveat should be discussed. Due to the limited sample size and loss of power stemming from categorization of variables we did not expect strong effects of G×E interactions and indeed the RSquare values (reflecting the proportion of the total uncertainty that is attributed to the model fit) of the whole model tests for rs111503014 (0.13 for cocaine dependence only, 0.06 for all cocaine dependence) are modest indicating that, if there were no a priori biological hypothesis, the likelihood of expected cross validation in other samples on a statistical basis alone might be low.
