Systematic reviews and meta-analyses are intended to give clarity by looking across studies, aggregating findings from the strongest, weeding out the weakest. Nonetheless, how different nations and organizations have evaluated this question of what counts as appropriate evidence has depended heavily on the context and the primary concerns of review bodies. In 2018, for instance, back-to-back systematic reviews from National Academics of Science, Engineering, and Medicine (NASEM) and Public Health England (PHE) took a very different view of what observational studies and randomized controlled trials offered. For NASEM, randomized controlled trials were the most conclusive evidence that could speak to pressing policy questions. Observational studies, whether cohort or cross-sectional, suffered from the messiness of real life. For PHE, although randomized controlled trials were important, observational studies were invaluable precisely because they captured the lived experience.2.
展开▼
