Editors’ note: This story will appear in the October/November 2008 issue of Scientific American Mind.

Many athletes credit drugs with improving their performance, but some of them may want to thank their brain instead. Mounting evidence suggests that the boost from human growth hormone (HGH), an increasingly popular doping drug, might be caused by the placebo effect.

In a new double-blind trial funded by the World Anti-Doping Agency, in which neither researchers nor participants knew who was receiving HGH and who was taking a placebo, the researchers asked participants to guess whether or not they were on the real drug. Then they examined the results of the group who guessed that they were getting HGH when, in fact, they had received a placebo. That group improved at four fitness tests measuring strength, endurance, power and sprint capacity. The study participants who guessed correctly that they were taking a placebo showed much less improvement, according to preliminary results presented at the Society for Endocrinology meeting in June. The researchers are currently analyzing the results of the other participants for future publication.

“This finding really shows the power of the mind,” said Ken Ho, an endocrinologist at the Garvan Institute in Sydney, Australia, who led the study. “Many athletes are reaping the benefits of the placebo effect, without knowing whether what they’re taking is beneficial or not.”

And in fact, HGH may not be helpful at all, reveals a recent review published May 20 in the Annals of Internal Medicine. Endocrinologist Hau Liu of Stanford University and his colleagues looked at 44 studies and found that although HGH did increase athletes’ lean body mass, it did not lead to improvements in athletic performance in double-blind trials.

The implications for athletes are serious, according to Ho. Many athletes take a cocktail of supplements, vitamins and drugs, believing that they are enhancing their game. “But it’s really the belief in the mind that improves performance” in most cases, Ho says. “Athletes need to be cautious about ‘snake oil’ merchants.”

4 Comments

1. 1. larswp 05:44 AM 7/24/08

   of the people being on plecebo it would be logical to see that the people with the most progess in the fitness tests also are the people most likely to guess that they where getting HGH. and there can be drawn no conclusion on that basis.
   tell a group that they are getting HGH but give them plecebo and then see if they get better result than a group getting nothing

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2. 2. Chuck Darwin 02:01 PM 7/24/08

   ... if they guessed incorrectly they were getting HGH, they improved more than the people who guessed correctly that they were getting the placebo. This study shows the power of the placebo effect, nothing more. The claim that it shows HGH may not improve performance is pure propaganda, probably intended to discourage use of HGH.

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3. 3. Chuck Darwin 03:34 PM 7/24/08

   I just noticed that this article is going to appear in Scientific American Mind, so I am motivated to state my view more strongly. A finding that people who (incorrectly) think they're getting a reputed performance enhancer, HGH, show improved performance over people who (correctly) think they are getting a placebo shows NOTHING WHATSOEVER about the performance-enhancing effects of HGH. Stating that this study is part of "mounting evidence" that HGH does not improve performance is false and is a disservice to your readers. I call on Sci Am's Human Mind editor to correct the error prior to publication.

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4. 4. John_Toradze 04:00 PM 7/27/08

   This is an utterly ridiculous article by an overly credulous journalist who exhibits no analytical abilities. Look, athletes who take HGH over too long a period have certain bones grow right through their skin. Every behemoth on the cover of the muscle mags is juicing.
   
   Regarding the study itself, first, it takes time for HGH to show it's effects. It is impossible for a long-term study to show the effect described. The effect of HGH has been far too well documented. Therefore, this study must have taken place over a short period. This invalidates the study relative to any claims it makes.
   
   Second, there is no discussion of dosage, route of administration, source, etcetera in this article. Since the study is not published and peer reviewed yet, it is impossible to know the methods, etcetera, if the journalist doesn't ask the questions.
   
   Third, there is no discussion of age of the athletes. Growth hormone levels peak in late teens and decline at varying rates thereafter. Giving amounts of HGH to a young adult will be proportionally less than giving HGH to an older adult. the most dramatic gains occur for adults over 70 years of age.
   
   All in all, a truly dumb article that I would expect to come out of a local paper, not "Scientific American".

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