Table 1.

Four theoretical approaches for understanding the population health interventional system (ISy)

Terms	Definition	Constructs	Purpose	Specificities	Examples in the public health field	Value in understanding intervention systems
Determinant framework	An overview of determinants and categories presumed to account for a phenomenon by acting as barriers and enablers	Environmental determinants Sociological determinants Psychological determinants Organizational determinants	Providing clues as to how the micro–meso–macro context could influence a health phenomenon	Multilevel With multiple influences Provides no explanation, only clues Derived from empirical studies of barriers and enablers	Social determinant frameworks [22]	Identifying all of the elements to be considered in understanding the system from multilevel points of view
Classical theory	An explanatory definition of relationships between variables and the specific results of their combinations	Psychosocial constructs Structural constructs Relationships among all constructs and specific predictions, especially those formulated as mechanisms	Explaining how and why specific relationships among a set of constructs lead to specific events	Focused on the mechanisms of effects Provides some explanations Derived from fundamental work in various disciplines (psychology, sociology, political sciences, etc.)	Behavioural: social cognitive theory [26] Organizational/social: social capital theories [27]	Identifying the mechanisms of effects and the factors potentially involved in their triggering
Process model	A deliberate simplification of a process describing how different resources could be combined to produce a change within a specific context	Variables relating to implementation (training, communication, decision, revision, etc.) May include some contextual elements influencing the delivery	Describing and/or guiding a process	Recognizing a temporal sequence and conditions of the progression of implementation endeavours More or less emphasis on the context and its influence on delivery Derived from field expertise and experimentation	The PRECEDE–PROCEED model [28]	Identifying the combination of resources and activities, as well as their sequence, needed to produce a change
Implementation theories	A combination of classical theories and activities, with or without a temporal sequence	Implementation Constructs involved in mechanisms triggering effects Mechanisms of effects	Explaining how and why specific relationships between a set of constructs and interventional elements lead to specific events	Derived from field expertise and experimentation Derived from fundamental work in various disciplines (psychology, sociology, political sciences, etc.)	The behaviour change wheel [29]	Linking mechanistic hypotheses and the resources and activities potentially influencing them to design or understand how interventional inputs could work