Researchers are a little closer to explaining the placebo affect.
According to a report in The Journal of Neuroscience, placebo appears to activate certain chemical receptors in the brain called mu-opioid receptors.
'Placebo effects probably form part of brain mechanisms involved in the resiliency of the organism to respond to environmental events such as injury and not biases in reporting,' Dr. Jon-Kar Zubieta from The University of Michigan, Ann Arbor, Michigan told Reuters Health. 'Further understanding of these mechanisms would help harness them for innovative treatment strategies.'
Zubieta and colleagues examined the effect of deep sustained pain with or without a placebo in young male volunteers. (The pain was produced, the sadistic among you might like to know, by a prolonged infusion of 5% hypertonic saline into the cheek muscle.)
Introducing the placebo was effective in reducing the sensation of pain, the team reports, as evidenced by higher ratings of pain relief and by an increase in the rate of painful stimulus required to maintain the same level of pain.
Using positron emission tomography (PET scans) and molecular imaging, the researchers observed that the expectation of pain relief activates the brain to produce opiate-like substances. The changes in the sensation of pain intensity correlated with mu-opioid system activation in several different regions of the brain.
The study provides evidence that the administration of a placebo with presumed analgesic properties activates pain and stress inhibitory systems in the brain.
The investogators told Reuters: 'the results...are consistent with the notion that placebo-responding regions and neurochemical systems are an intrinsic part of neuronal processes that mediate the interaction between positive environmental conditions (in the present case the suggestion of analgesia) and the corresponding physical and emotional responses of the individual.' In other words, the brain reacts to what it expects, a potential that could have enormous implications for healing.
'We are now looking at individual differences in the placebo response -- why some individuals have a more profound response than others -- for example, the effects of gender, hormones and genes,' Zubieta said.
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