What are the components of complex interventions in healthcare? Theorizing approaches to parts, powers and the whole intervention

► Outlines that components of complex interventions are often addressed in health services research but are poorly defined and theorized. ► Argues that for theory, method, transparency and wider usage of complexity approaches, components need to be better understood. ► Conceptualizes components using three key concepts: the intervention's parts and its powers, and the whole of intervention. ► Views components in at least seven different ways in terms of their parts, powers and the whole of intervention. ► States that complex interventions are formed of parts, which may be stratified, that exercise power individually, in combination or as emergent properties.