This study generated numerous remarkable findings, including those at or near GWS. Several design factors may have contributed to the results. First, we studied two distinct populations of reasonable sample size. Second, one of the analytic models that we employed defined cocaine-related effects as an ordinal trait. This approach increased the average phenotypic information for subjects and increased power; similar approaches have been used successfully in previous SD GWAS, e.g., for alcohol dependence.30 This was especially important in light of our case-control design, which used exposed controls, reducing sample size for those analyses (but excluding from the control group individuals who were unexposed to cocaine and who therefore can reasonably be considered diagnosis-unknown in this context).
