Yes. If you give two sets of people sugar pills and tell one set they are sugar pills, and the other that they’re eg painkillers, the latter group will report (on average) a reduction in pain related issues while taking them.

This is why alternative treatments that don’t medicinally do anything, like homeopathy, can appear to be effective - people believe they work and so they do, but if they just believed a cheap sugar pill they would help them, it would do for much cheaper. Even better get real meds that you believe in, and you get actual medicinal effect with a placebo boost.

Good Pharmaceutical trials are generally “blind” for this reason, ie there will be a control group getting a placebo to compare the effect of the medicine to that, rather than to nothing as comparing to nothing would make most things appear effective. Even better is “double blind” where the researcher doesn’t know until after either, so that their interactions or behaviour don’t give anything away, and that they don’t bias their analysis.