Guidance for systematic reviews of interventions recommends both benefits and harms be included. Systematic reviews may reach conclusions about harms (or lack of harms) that are not true when reviews include only some relevant studies, rely on incomplete data from eligible studies, use inappropriate methods for synthesizing data, and report results selectively. Separate reviews about harms could address some of these problems, and we argue that conducting separate reviews of harms is a feasible alternative to current standards and practices. Systematic reviews of potential benefits could be organized around the use of interventions for specific health problems. Systematic reviews of potential harms could be broader, including more diverse study designs and including all people at risk of harms (who might use the same intervention to treat different health problems). Multiple reviews about benefits could refer to a single review of harms. This approach could improve the reliability, completeness, and efficiency of systematic reviews.
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