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Is anyone familiar with a possible evolutionary explanation of the placebo effect? It seems strange to me that the body would have a limit to the degree it heals itself, and that this limit gets bypassed by the belief that one is receiving treatment.
The only explanation I could string together is that the body limits how much it heals itself because it's conserving energy/resources/whatever it might need for other things (periods of scarcity, danger, etc.) Receiving medicine sends the signal that the person is being taken care of and thus at a much lower risk of needing to use it's 'reserves', so the body goes ahead and diverts them to repairing whatever is wrong with it.
However, this would suggest that a self-administered placebo would be ineffective, whereas treatment but no medicine by a doctor/caregiver would be effective. As far as I know, this isn't how the placebo effect works, but I'm not exactly up to date on the subject.
Has anyone seen a better explanation?
Yes, that the original papers advocating the placebo effect were misleading in their reports and the popularisations thereof grossly exageratted.
Placeobo's can be shown to reliably have an effect on: