Several caveats should be considered, however, in the interpretation of these data. First, for the purpose of statistical analysis, the authors grouped the DRD4 7-repeat allele with the 8-repeat allele (because of the low frequency of the 8-repeat allele in this population). As we have commented elsewhere (2), this kind of arbitrary grouping reduces the degrees of freedom in the analysis and increases the potential for false positive results. An analysis of these data without the collapsing of these two alleles resulted in a marginally significant result (p=0.012). Moreover, the authors also conducted a "presence or absence" analysis despite the lack of data implicating a codominant mode of action for these alleles but did not correct for the other potential groupings—again inflating the potential for a false positive result.