This is in contrast to the findings of Moyer et al (2011), who found an odds ratio of 1.94 in their population of cocaine abusers. However, this may be an artifact of the small sample size used by Moyer et al (N=214), as random sampling can inflate odds ratios. An odds ratio of 1.3-1.4 is more consistent with the impact of risk variants reported in previous studies on polygenic diseases such as addiction. Furthermore, Moyer and colleagues used surrogate measures for defining chronic cocaine abuse such as hospital admission and arrest records. The participants used in this study were addicted to cocaine and diagnosed according to the DSM-IV. As Moyer et al analyzed cocaine abusers rather than cocaine addicts, the differences in the two samples may account for the lack of replication. It should also be noted that the samples genotyped as part of this study were not genotyped for ancestry informative markers. Given that population stratification can influence the results of association studies, it is a limitation of this study that these data were not available.
