Clinical Research: Small Studies Often Yield Large Outcomes

Remember this.

Proceed cautiously when you come across a clinical study declaring a large treatment effect. Such findings most often emerge from small studies, and if replicated, the strength of the finding generally drops significantly. In addition, only very rarely do these reports show a significant survival benefit for patients, according to a study published in...JAMA.

"Nominally significant very large effects arose mostly from small trials with few events," write the authors, Tiago V. Pereira, PhD, from the Health Technology Assessment Unit, Institute of Education and Sciences, German Hospital Oswaldo Cruz, Sao Paulo, Brazil; Ralph I. Horwitz, MD, from GlaxoSmithKline and the Yale University School of Medicine, New Haven, Connecticut; and John P.A. Ioannidis, MD, DSc, from the Stanford University School of Medicine in California. Dr. Ioannidis is known for a 2005 study published in PLOS Medicine entitled "Why Most Published Research Findings Are False."

Because it it true.