Correlates of Engagement and Associations With Outcomes in a Cannabis Harm-Reduction Mobile App for Youth With First-Episode Psychosis: Exploratory Analysis of the CHAMPS Pilot Randomized Controlled T

Collective movement under emergency conditions has long been a critical topic in safety science. In large gatherings, uncoordinated escape behavior can lead to congestion, clogging, and even fatal stampedes. Recent disasters, such as the 2021 Meron festival in Israel, the 2022 Kanjuruhan stadium incident in Indonesia, and the Itaewon tragedy in South Korea, tragically demonstrate how uncontrolled or high-pressure crowd flow can result in severe casualties [–]. These events underscore the urgent need to understand the mechanisms that govern collective escape under high-stress conditions. Despite extensive research efforts, reproducing and analyzing crowd-crush phenomena remains highly challenging in both empirical and computational studies. In controlled experiments, the primary difficulty lies in replicating high-stress evacuation interactions without compromising participant safety. In numerical simulations, the challenge arises from the multifactorial nature of human movement. It is affected by psychological responses under emergency evacuation, physical contact forces, frictional interactions, and body deformation under compression. Moreover, when individuals traverse bottleneck regions, even minute variations in personal velocity or intent can amplify nonlinearly, leading to abrupt slowdowns of the collective flow. Previous experimental investigations on collective escape behavior have been conducted using both human participants and animal models. Experiments involving humans provide direct observations of evacuation behavior [–]. However, conducting such experiments requires rigorous ethical review and strict safety protocols, which significantly limit the number and scale of human studies. As a result, empirical data on human crowd behavior under high-stress evacuation conditions remain scarce, making it difficult to fully capture the complex mechanisms governing collective escape.