Harms in Systematic Reviews Paper 1: An introduction to research on harms

•Data on harms come from different sources including randomized controlled trials, observational studies, surveillance systems, and other sources (e.g., pre-clinical studies)•Harms differ from benefit outcomes in methods for study planning, data collection, analysis, and reporting•Most harms in both clinical trials and observational studies are assessed non-systematically and incompletely reported, which limits causal inferences•Systematic assessment and standardized terminology improve causal inference concerning harms•Primary studies and systematic reviews often fail to capture multiple dimensions of harms such as rate, severity, and timing Most systematic reviews of interventions focus on potential benefits. Common methods and assumptions that are appropriate for assessing benefits can be inappropriate for harms. This paper provides a primer on researching harms, particularly in systematic reviews. Commentary describing challenges with assessing harm. Investigators should be familiar with various terminologies used to describe, classify, and group harms. Published reports of clinical trials include limited information about harms, so systematic reviewers should not depend on these studies and journal articles to reach conclusions about harms. Visualizations might improve communication of multiple dimensions of harms such as severity, relatedness, and timing. The terminology, classification, detection, collection, and reporting of harms create unique challenges that take time, expertise, and resources to navigate in both primary studies and evidence syntheses. Systematic reviewers might reach incorrect conclusions if they focus on evidence about harms found in published reports of randomized trials of a particular health problem. Systematic reviews could be improved through better identification and reporting of harms in primary studies and through better training and uptake of appropriate methods for synthesizing evidence about harms.