The bodies of mammals, including humans, respond to injury by releasing endogenous opioids -- compounds that mitigate acute pain. A team of researchers has uncovered groundbreaking new information about how the body responds to traumatic injury with the development of a surprisingly long-lasting opioid mechanism of natural chronic pain control. Remarkably, the body develops both physical and physiological dependence on this opioid system, just as it does to opiate narcotic drugs.