Last updated: Tue, Mar 11, 2025
Stress can cause analgesia, the lessening of pain. Threatening situations such as the presence of a predator or unavoidable electric shock trigger this effect, which is called stress-induced analgesia. This effect depends on the PAG-RVM descending modulatory system. Stress-induced analgesia has been shown in humans. (Although this phenomenon has been labeled "stress-induced," it hasn't apparently been established that it is triggered by "stress" as opposed to fear.)
Fear can be conditioned. If the fear experience is consistently associated with a neutral event such as a light or a bell, the subject can be conditioned to experience analgesia in response to the associated neutral event. Conditioned stress-induced analgesia involves the amygdala in addition to the PAG-RVM system.