Randomized trials and public health interventions: time to end the scientific double standard

Randomized controlled trials have become the accepted standard for testing the efficacy and safety of clinical treatments but are rarely used in evaluating public health interventions. This article reviews the types of interventions and outcomes for which randomized trials are necessary to provide a scientifically rigorous evaluation. It also presents the results from two trials analyzed both experimentally and observationally to illustrate why observational studies can yield highly biased findings. This article provides a brief historical account of controlled human experiments, which reveals a surprising earlier tradition of rigorous experimental studies in the social sciences. After contrasting that tradition with the status quo, this article concludes with a plea to reject the double scientific standard of what constitutes acceptable evidence of efficacy for clinical versus public health interventions.