Context-mechanism-outcome (CMO) configuration. The CMO configurations were informed by three different theories: Yerkes-Dodson Law, health beliefs model, and the stage of change model. It is argued that aspects of each theory should be used to explain how and under what circumstances BIs work. Specifically, engagement, resolving ambivalence, insight, and self-efficacy were found to be mechanisms leading to desirable BI outcomes, including increased motivation to change, decreased alcohol use, and decreased alcohol-related consequences. Mechanisms are impacted by the following contexts: emotional state upon admission (moderate is best), injury upon ED admission (moderate is best), alcohol use severity (moderate is best), and stage of change at baseline (contemplation is best). See text for more detail.