The second cohort was recruited at the University of Florida at Gainesville. Subjects included 133 healthy European American volunteers (80 females, 53 males) recruited by posted advertisements from the local community. In a subset of this cohort (n = 68, 40 females, 28 males), the analgesic effect of morphine on experimental pain sensitivity was also assessed. The experimental pain procedures were similar to those described for the UNC cohort and can be found in the Supplementary Material.
