just thinking that a medicine will relieve pain is enough to prompt the brain to release its own natural painkillers, and soothe painful sensations, a new university of michigan study finds.

　　the study provides the first direct evidence that the brain's own pain-fighting chemicals, called endorphins (内啡肽), play a role in the phenomenon known as the placebo effect (安慰剂效应) —— and that this response corresponds with a reduction in feelings of pain.

　　previous studies at u-m and elsewhere have shown that the brain reacts physically when a person is given a sham (假的) pain treatment, which they believe will help them.

　　but the new study is the first to pinpoint (正确指认) a specific brain chemistry mechanism for a pain-related placebo effect. it may help explain why so many people say they get relief from therapies and remedies with no actual physical benefit. and, it may lead to better use of cognitive (认知的), or psychological, therapy for people with chronic pain.

　　"this deals another serious blow to the idea that the placebo effect is a purely psychological, not physical, phenomenon," says lead author jon-kar zubieta, m.d., ph.d., associate professor of psychiatry and radiology at the u-m medical school and associate research scientist at mbni. "we were able to see that the endorphin system was activated in pain-related areas of the brain, and that activity increased when someone was told they were receiving a medicine to ease their pain. they then reported feeling less pain. the mind-body connection is quite clear."