<unk>  occurs when the administration of<unk> s leads to pain relief. Because<unk> s by definition lack active ingredients, the effect of<unk>  is considered to result from the patient's belief that they are receiving an analgesic drug or other medical intervention. It has been shown that, in some cases, the endogenous opioid system is critical for mediating<unk> , as evidenced by the ability of such analgesia to be reduced by the opioid antagonist naloxone. However, it is also possible for<unk>  to be mediated by non-opioid mechanisms, in which case it would not be affected by naloxone. Other research has indicated that the human spinal cord, prefrontal cortex, and rostral anterior cingulate cortex also play a role in<unk> .
Placebo analgesia
Electroanalgesia
Nerve block
Preemptive analgesia
Paracervical block
Spinal manipulation
Patient-controlled analgesia
Analgesic adjuvant