The placebo effect is honestly pretty wild. There’s a common false understanding that placebo = scam, but if you can achieve a therapeutic effect via thinking that you’re going to achieve a therapeutic effect, then… cool!!
The opposite is also true, called the “nocebo” effect. I’ve noticed this in the OR a lot depending on our anesthesiologist, specifically when they’re administering the propofol (the IV drug that knocks you out). Unfortunately it’s an irritant, so I’ve seen a few different approaches to try to get ahead of the sensation of pain, including warnings like “This can hurt initially - that’s normal!” but I think tends to backfire, cuz you’ve just set the expectation of pain, and those patients seem to have a much heightened experience of pain. This is opposed to saying things like “You might feel a warm sensation in your IV” which seem to reduce the nocebo effect.
It’d be cool to do a study on this action specifically.