Figure 1.

Mean (and standard error) drug craving response (averaged across all time points) during each of the neutral (N), stress (S) and drug cue (T) conditions for the two OPRK1 rs6989250 genotypes is shown. The genotype-by-condition two-way interaction was significant (P=0.0056, Cohen's d=0.79). Carriers of the CG genotype showed markedly stronger craving when exposed to the stress condition compared with individuals with the CC genotype (P=0.0191, Cohen's d=0.82). There was no significant difference detected between the two genotype groups in either the neutral (P=0.0823) or drug cue conditions (P=0.678).