In a genuine medical trial, the medicinal product is supposed to be tested against a completely harmless substance, such as water or a sugar pill, however, in most trials a harmful placebo is given so that both sides have side-effects and it looks as if the medicine is safe. For instance, the placebo in Gardasil trials was aluminium and this has many side-effects.
Now a review of medical studies has found that most of them are scientifically invalid:
No regulations govern placebo composition. The composition of placebos can influence trial outcomes and merits reporting.
Most studies did not disclose the composition of the study placebo. Disclosure was less common for pills than for injections and other treatments (8.2% vs. 26.7%; P = 0.002).
Limitation: Journals with high impact factors may not be representative.
Conclusion: Placebos were seldom described in randomized, controlled trials of pills or capsules. Because the nature of the placebo can influence trial outcomes, placebo formulation should be disclosed in reports of placebo-controlled trials.
Source: Annals of Internal Medicine –
http://www.annals.org/content/153/8/532.abstract
