Advancing Evidence-Based Public Health Policy: How Core Component Thinking Can Illuminate the Multilevel Nature of Public Health Policy.

A growing body of literature uses the concept of core components to better understand small-scale programmatic interventions. Instead of interventions being viewed as unitary "black boxes," interventions are viewed as configurations of core components, which are the parts of interventions that carry their causal potential and therefore need to be reproduced with fidelity to produce the intended effect. To date, the concept of core components has not been as widely applied to public health policy interventions as it has to programmatic interventions. The purpose of this topical review is to familiarize public health practitioners and policy makers with the concept of core components as applied to public health policy interventions. Raising the profile of core component thinking can foster mindful adaptation and implementation of public health policy interventions while encouraging further research to enhance the supporting evidence base. We present 3 types of multilevel interactions in which the core components of a public health policy intervention produce effects at the population level by (1) seeking to directly affect individual behavior, (2) facilitating adoption of programmatic interventions by intermediaries, and (3) encouraging intermediaries to take action that can shape changes in upstream drivers of population health. Changing the unit of analysis from whole policies to core components can provide a basis for understanding how policies work and for facilitating novel evidence-generating strategies and rapid evidence reviews that can inform future adaptation efforts.