A study of the athletic effects of Growth Hormone show the athletes on the fake drug got better performance results than the athletes on the real drug. Placebo is a very real part of effects from treatment. Depending on the attitude of the people administering the treatment a person can be either effected in a positive way, placebo, or have the opposite response called nocebo.
“The study told us that athletes who were on the dummy drug, but who believed they were on growth hormone, thought their performance had improved and actually showed some improvement in all measures of performance. One test in particular, jump height or power, showed a significantly greater improvement among these incorrect guessers.”
“There were some men who were 110% sure they were on active treatment, and their cards said they were on placebo. They almost refused to believe it. It was as if some felt they’d been cheated.”