There was a significant cannabis-dependence group effect (F = 6.2, p = 0.02) and SNP x cannabis-dependence interaction (F = 4.7, p = 0.03) for the PENK SNP rs2609997, as this SNP was significantly associated with Neuroticism in cannabis-dependent subjects (p<0.05), but not in control subjects (p = 0.8; Fig. 2). Here, PENK is linked to cannabis dependence.