The opioid-user group (OUG) reported greater negative affect than the healthy control group (F(1,57) = 14.79, p < .001, d = .98; OUG M = 18.25 ±1.21, Control = 10.98 ±1.24). The greater reported negative affect by the OUG was partially mediated by weaker frontostriatal resting-state functional connectivity (rsFC) between the left nucleus accumbens (NAc) and the left ventromedial prefrontal cortex (vmPFC) (β = 1.26, SE = .92, CI [.04 – 3.92]). Level of confidence intervals was 95% and error bars represent ± standard error (SE).