It’s unethical to prescribe a patient a placebo in a way that suggests that what they are receiving is scientifically proven.

In a clinical trial setting, you can prescribe a placebo, because the patient is fully aware and clearly consenting to the fact that they may receive a placebo. Lying to a patient, in a clinical setting, from a position of authority, is a completely different matter. The informed consent would be completely absent, the patient’s ability to make informed choices about their own healthcare would be undermined and withheld, and the provider would be deriving financial benefit from the patient and / or through insurance claims for what amounts to a scam.

The patient, who would be seeking a treatment from a trusted expert, would believe that they are receiving proven treatments in exchange for their time, patience, money, reduced quality of life due to side effects, and opportunity costs in terms of not going to a different provider or trying something else, but in reality their provider would be misleading them. Some patients would even die as a result of taking a particular placebo and depending on it—either because of side effects or due to the lack of effectiveness—when they tragically would have been better off trying a different approach or medication. How could a patient possibly give informed consent in such a scenario, for one thing? How could they meaningfully compare treatment options and make their own informed choices when the advice they receive includes lies?

Alas, some providers believe in placebo effects so much more strongly than their patients’ right to autonomy that when faced with complaints of side effects, they will just lie more and more to their patients in hopes that the side effects will go away, but that’s really just more gaslighting to people who are already in difficult situations.