In the medical world, the placebo effect looms. It's acknowledged as very real and powerful. But it's regarded by healthcare practitioners (with the exception, IME, of cognitive psychologists), with some trepidation. This is because it's ethically questionable to study on real patients, and appears to be widely variable and unpredictable between subjects. In other words, it's kind of the opposite of concrete medical therapies backed up by robust controlled studies. But at the same time it works. That's a bit of a distant but ever present threat to an industry that thrives on predictability, and has lawyers waiting in the depths to pounce when predictions go wrong.
As I mentioned, cognitive psychologists are the only healthcare professionals I've encountered who seem to tread on the territory of the placebo effect with no fear whatsoever. But these folks really have little in common with other healthcare practitioners, IME, in terms of their professional motivations. Namely, I see an offputting institutionalized comfortability with treating people as specimens, rather than recipients of compassion, which the rest of the health professions have really done their best to rid themselves of. For this reason, I'd say cognitive psychologists ("rats and birds people", as opposed to clinical psychologists) really skirt the definition of healthcare practitioners. I digress.
I believe in clinically utilizing the placebo effect with a safety net. Let me give you an example. Just the other day, I saw a patient with the gynecologist I was working with. She was bipolar, and quite likely in a hypo-manic state when we saw her. She was convinced she had vaginal odor. We examined her, and found some abraded areas in her genitals, but no odor or strange fluids. So we diagnosed it as a yeast infection and gave her a topical antifungal. We also asked her when she last saw her psychiatrist, reminded her to follow up with regular appointments with him, and documented this. Did she have a yeast infection? Maybe. Yeast infections are sometimes only minimally symptomatic. More likely, though, she was delusional. Giving her an antifungal cream, which topically is pretty safe, killed two birds with one stone. If she had an infection, it treated it. If she had an olfactory hallucination, it harnessed the placebo effect to quell it. Plus, we covered our asses by making sure she saw her shrink. And a good time was had by all.
I don't think I'd ever rely on the placebo effect alone, i.e. trick a patient, even if I felt certain it would work. The medico-legal framework is just not in place to support such a move, especially if it didn't end up working, and the consequences were disastrous.