As a physicist, I was surprised by coming to realization that placebo can actually affect physical illnesses. I searched on the internet, but explanations for mechanism of placebo were either unclear (I am a layman in medical science after all) or not convincing enough. So I would appreciate any clarification (or even some references) on this subject. I am asking for a widely accepted theory (or at least a hypothesis) behind physical mechanism of it.

For example from this study:

Several research studies have demonstrated the placebo effect's role as a powerful determinant of health in certain disease conditions. Migraines, joint pain, arthritis, asthma, high blood pressure, and depression are some disease conditions that are more sensitive to the placebo effect.

Identifying a physiological basis for the placebo effect may open doors to modulating processes that can improve mental and physical health.

Or from here:

The results suggest that placebo interventions can improve physical disease processes of peripheral organs more easily and effectively than biochemical processes

Am I misunderstanding something and placebo doesn't affect physical health?

  • Welcome to the site! Maybe you could tell us where you found that a placebo can affect physical illness, so there's something more specific that can be answered. Also you can look into the terms psychophysiological and psychosomatic which can be related, but not a complete answer to your question. Jan 28 at 15:32
  • @user1271772 Thank you. I am afraid I don't have any credible source to refer to; for the most part I just read blogs. However, I can cite this article europepmc.org/article/NBK/nbk513296 which mentions arthritis, asthma, high blood pressure as examples of positive effect of placebo. If I am wrong in concluding that placebo affect physical health, please let me know.
    – Paradoxy
    Jan 28 at 16:18
  • 1
    See also, this Q&A: medicalsciences.stackexchange.com/q/28825/22190
    – Ian Campbell
    Jan 28 at 16:25
  • Have you read the discussion section of the second link in your question?
    – Bryan Krause
    Jan 28 at 16:56
  • 5
    @Paradoxy Probably also worth looking at figure 2 to see their summary of placebo effects in the literature; you'll see from their examples that a) they are small, b) variable (and you'll see the same sort of symptom has some studies with a "positive" and some with a "negative" effect; this is expected to happen by chance and especially when the actual real effect is either very small or zero), and c) the effects are limited to some factors that have a likely psychological component. They discuss this especially in the 6th & 7th paragraphs of the discussion, but you should read it all.
    – Bryan Krause
    Jan 28 at 17:31


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