Abstract

One of the cornerstones of critical analysis of clinical trials is the evidence on the associations between the quality of a study and its results. The following are likely scenarios. The lower the methodological soundness of a study, the more favorable results may be obtained for the studied interventions, thus overestimating their effectiveness. However, as many times occurs in epidemiology, the reported observation may not necessarily be reproduced when the phenomenon is studied again. One may also find evidence that points to the contrary - the better the methodological quality of the study, the greater the observed effect. This relationship can also be found in observational studies of a risk factor that compare cohort studies to case-controlled studies. The latter tend to overestimate the risk associated to the factor. There is also an association between better quality studies and high impact journals, but we cannot infer that all studies published in top journals are reliable, and viceversa.