But in the vast majority of other illnesses, placebo is exclusively a confounding factor. People's bones don't fuse from sham surgery. Sugar pills don't cure malaria or TB. Placebo chemotherapy doesn't kill cancer cells. The placebo effect does exist in these cases as well if not using double-blind trials, or if conducting patient subjective assessments, but it disappears if lab techs and objectively measurable data are investigated (things like viral load, not patient perception of their symptoms).
Before a placebo treatment, you pick something at the higher end. After the treatment, you think maybe it helped, so you pick something on the lower end despite feeling the same.
Maybe you even feel worse than you did at the start of the study but you've gotten used to a higher baseline amount of pain and you're having a relatively good morning compared to that so you report a low number.
This is about how your self-reports change, not necessarily about how your state of mind changes.
If you report a different number, that means some things in your mind changed. Those things may or may not include the level of pain you're experiencing.
Let's take an example with a bit more objectivity. If you ask me to rate how long a tv show is on a scale of 1-10 and I know the show is 30 minutes, how do I turn that into a 1-10 scale? Suppose I mostly watch shows with 12-minute episodes. This is relatively long, so I give it an 8.
Later I start watching hour-long shows. You ask me again how long this show is on a 1-10 scale. Now I put it at a 5. I don't think the show got shorter, and I don't experience it as being shorter. I just changed how I contextualize the length of shows for a 1-10 scale.
It would be silly to say that watching hour-long shows is a good way to shorten the mental experience of watching a 30-minute show.
It's not a stretch to understand that if you consistently imagine such issues the stress hormones and other biochemical changes caused by such sensations will create actual damage in the organs.
Why shouldn't thoughts influence the body? If the body can cause thoughts, then surely it could go both ways such that thoughts effect changes in the body. Because of course thoughts are a bodily process.
It seems to me that dualism is in error and consequently has done marked damaged to our understanding of ourselves. Thoughts are not non-physical and neither are the mind & body distinct or separable.
https://www.smithsonianmag.com/science-nature/science-explai...
It makes sense that triggering different systems in the body could result in medical benefit. The science of placebo effect is very active, but runs into fundamental issues of neuroscience pretty quickly. Science needs to figure out how brains work before we unlock the secrets of the placebo effect.
AFAICT there's quite a lot of study on the phenomenon, and it's a lot more complex than just expectation bringing about physiological change. Some portion of it is likely action of the immune system, general "regression to the mean" effects, and some of it is that patients who are receiving treatment are likely to report milder symtoms and less pain (so there may not always be a physiological change, just a psychological one).
Either way, I don't think you can count the placebo effect as a medical miracle waiting to be exploited, or as something that medical science just ignores.
IIRC there are different kinds of placebo effects. One of the most robust is pain relief. I think Sapolsky makes the case that endorphins (“endogenous morphines”) do some of the leg work here, but that’s probably not the whole story.