I am not sure about this. I think sometimes it might. However it depends what you mean by placebo effect. If you consider it only a psychological reaction, for which there is at best dubious evidence, then yes. However the problem on review is these studies tend to be seriously flawed. Its not clear what the effect actually is. Its entirely possible its merely an amalgam of errors and bias, as already mentioned. It might be mostly myth.If you don't have positive expectations, I don't think the placebo effect can occur.