The placebo effect tends to only work for certain values of 'work'. Lately there have been a lot of studies finding that while placebos are great at improving

The placebo effect tends to only work for certain values of 'work'. Lately there have been a lot of studies finding that while placebos are great at improving subjective factors, they don't show the same ability to elicit objective improvements. So if you come down with a respiratory infection, a placebo might have you saying you feel better a bit sooner, but you'll still be hacking up phlegm for just as long.