Randomised controlled trials (RCTs) are universally considered as the gold standard for evaluating the efficacy of treatments. Their main strength is that, through randomisation, they avoid any major imbalance between compared groups: therefore, observed outcome differences between groups at the end of the trial are most likely related to treatment effects. Since they are inherently prospective by design, they also permit stability throughout the study to ensure that all conditions remain optimal to test the hypothesis of interest. These include high-quality follow-up, reinforced adherence, etc. Consequently, these studies can reach the highest level of internal validity, provided that all quality standards are followed, such as those defined by CONSORT guidelines.