To the Editor Clinical trials can contribute knowledge about both efficacy and mechanisms of action. Efficacy concerns whether the intervention is “better” than a control, such as standard of care; mechanisms concern how the intervention produces desired outcomes—its hypothesized causal pathways. For pharmacotherapies, after years of bench research, a new drug’s action pathways are typically understood well enough that a clinical trial can both test efficacy and generate evidence about causal mechanisms.
Klasnja P, Hekler EB. Wearable Technology and Long-term Weight Loss. JAMA. 2017;317(3):317-318. doi:10.1001/jama.2016.19268