Although we found evidence of an association between SNPs in CHRNA4 and ND symptoms in the CADD sample our results with non-Hispanic EA were stronger than when Hispanics were also included in the analysis. We may have observed this pattern because in our samples the non-Hispanic EA show more severe ND compared to the Hispanics (see Table 1). In our samples, the EA have a greater number of DSM-IV ND criteria as well as a greater number of substance use disorders compared to the corresponding Hispanic sample.
