individuals differ widely in their experience and report of pain-related process, exhibiting profound variability in their sensitivity to noxious stimuli, susceptibility to acute and chronic pain, and responses to analgesics. Furthermore, genetic association studies
lend themselves to the study of occasionally perplexing but nearly universal observation that apparently identical structural injury or pathology leads to no report of pain in some individuals, rapidly resolving pain in others, and severe, persisting pain in still others