Interpersonal violence is a leading cause of death in adolescents and young adults worldwide.1 For every death caused by violence, scores of people have injuries that require urgent medical care, and in 2004 an estimated 16 million such cases received medical attention.2 In the linked study (doi:10.1136/bmj.d3313), Florence and colleagues evaluate whether sharing anonymised information obtained during the clinical care of victims with police and local government partners can help prevent violence.3 Their programme typifies the public health approach to violence prevention,4 which the programme leader, Jonathan Shepherd of Cardiff University, has pioneered in the United Kingdom.5

The study found that sharing of information was associated with a significant reduction in violence related hospital admissions (adjusted incidence rate ratio 0.58, 95% confidence interval 0.49 to 0.69) and in woundings recorded by the police (0.68, 0.61 to 0.75) in Cardiff relative to comparison cities. The study also showed that less serious assaults recorded by the police increased significantly (1.38, 1.13 to 1.70).3

The study makes several assumptions. Firstly, that at a population level the “who, what, when, where, and why” of violence can …