Binding potentials for amygdala (adjusted for session, OPRM1 genotype, sex, FTND, and hemisphere) are plotted for each participant for both sessions. In the multiple regression models, NAR scores were significantly associated with MOR BPND in the amygdala (β = 0.06, p = 0.007). MOR BPND = µ-opioid receptor binding potential; NAR = Negative Affect Reduction score