The gold standard for assessing the efficacy of a therapy is the controlled clinical trial. The Declaration of Helsinki mandates that clinical trials should only be performed with volunteers, and therefore the progress of medicine is absolutely dependent on the immense generosity of subjects willing to be part of a clinical trial. They do this in return for the greater good for society, yet this beneficence is not always returned. We know that many clinical trials are not reported, leading to difficulties in assessing the true efficacy of a therapy. Underreporting of clinical trials also can obscure the adverse effect profile of an intervention, as witnessed by the recent COX-2 inhibitor debacle.
Levin LA, Gottlieb JL, Beck RW, Albert DM, Liesegang TJ, Hoyt CS, Dick A, Bhisitkul R, Schachat AP. Registration of Clinical Trials. Arch Ophthalmol. 2005;123(9):1263-1264. doi:10.1001/archopht.123.9.1263