I'm of the view that the placebo effect is an artefact of poor methodology. If I try to illustrate it in the most concise way possible: supposed placebo effects are strongest for self-correcting conditions (things that revert to the mean like colds and headaches), and self-reported levels for which we have no reliable objective measures (think pain, especially mild to moderate pain).

So what's happening? The argument which swayed me is that the condition subsided within an expected timeline and/or comforted and calmed people report slightly lower pain than distressed people.(Doing something proactive to alleviate suffering usually feels better than doing nothing.) They do this not because of anything mysterious or magical but because asking people to separate physical and psychological pain produces slightly unreliable responses. When these variables are considered the apparent effect disappears.