However, contrary to Dong et al. (2011), who observed a main effect of PER1 genotype on risk for alcohol abuse in their second sample, consisting of 2184 Caucasian adults, we did not find any significant main-effects of PER1 rs3027172 after accounting for covariates (notably, this main effect was significant and in the direction reported by Dong et al. (2011) when covariates were not included; Supplemental Table 5). Here, PER1 is linked to alcohol abuse.