5: Intervention Theory

Intervention Theory

The importance of developing the theory of the problem, the theory of implementation, and the theory of change is well recognized and emphasized in recent guidance for the design, delivery, and evaluation of health interventions (Bartholomew et al., 2016; Medical Research Guidance, 2019). The theory of the problem makes explicit the aspects of the health problem amenable to change and addressed by the intervention. The theory of implementation describes and justifies the active ingredients, operationalized into specific components that characterize the intervention. The theory of change delineates the mechanism through which the intervention produces beneficial outcomes related to the prevention, management, or resolution of the health problem and the mitigation of its consequences. Whereas each of these theories is important and useful for designing an intervention, their integration into the intervention theory is critical for a comprehensive understanding of the intervention, the context of its delivery, and its mechanism of action. This understanding forms the foundation for the development of materials and the mobilization of resources needed to deliver the intervention; the actual delivery of the intervention with fidelity, which is necessary to initiate its mechanism of action; and the design and conduct of a study to evaluate the intervention. In this chapter, the elements of the intervention theory are described. The importance of the theory in guiding the actual delivery of the intervention, and the design and conduct of an evaluation study is discussed.


The intervention theory integrates elements of the theory of the problem, the theory of implementation, and the theory of change into a unified comprehensive conceptualization of a health intervention. In general, the elements of the theory provide answers to these questions: What specifically does an intervention address, in what target client population and in what context? What comprises the intervention? How is the intervention to be delivered? How does the intervention work in improving what outcomes? What could influence the implementation, mechanism of action, and outcomes of the intervention?

TABLE 5.1 Configurations of intervention theory.

Configuration 1 Configuration 2 Configuration 3
Field Program evaluation Healthcare organization Realist evaluation
Sources Chen et al. (2018)
US General Accountability office (2012)
Sidani and Sechrest (1999) Dalkin et al. (2015)
De Souza (2013)
Greenhalgh et al. (2015)
Pawson and Manzano‐Santaella (2012)
Wong et al. (2012)
Elements and definitions Situation = problem that intervention attempts to address and context in which intervention is delivered
Input = resources required for intervention delivery
Activities = actions, therapies, or processes comprising intervention
Outcomes = changes in clients’ condition, including intended and unintended immediate, intermediate, and ultimate outcomes
Structure = characteristics of clients receiving intervention, characteristics of health professionals delivering intervention, characteristics of context in which intervention is delivered
Process = intervention components
Outcomes = series of changes leading to ultimate outcomes
Context = conditions or circumstances in which intervention is introduced, encompassing resources and contextual factors that may moderate (enable or prevent) mechanisms and outcomes
Mechanism = processes through which intervention components produce outcomes
Outcome = intended and unintended changes in clients’ condition

The intervention theory describes the health problem, the intervention, and the outcomes; explains the associations among them; specifies the conditions that may influence the associations; and offers directions for implementing the intervention (Dalkin et al., 2015; Davidoff et al., 2015; Slater & Kothari, 2014).

Three configurations are proposed to organize the elements of the intervention theory. The terms used in these configurations are presented in Table 5.1. Despite differences in terminology, the following specific elements are commonly identified.

5.1.1 Experience of the Health Problem

The intervention theory: (1) identifies and defines, at the conceptual and operational levels, the health problem addressed by the intervention; (2) clarifies and defines, at the conceptual and operational levels, the aspects (indicators, determinants) of the problem that are potentially modifiable and targeted by the intervention; and (3) explains the reasons for focusing on the selected aspects of the problem. For tailored and adaptive interventions, the theory describes variability in clients’ characteristics and/or experience of the problem (i.e. tailoring variables) that should be attended and accounted for in the process of customizing the intervention.

5.1.2 Client Factors

The intervention theory identifies client factors that influence their: experience of the health problem, perception of the intervention, capacity to engage in the planned intervention activities, ability to enact the treatment recommendations, and experience of the immediate and intermediate (i.e. mediators) outcomes, as well as the ultimate outcomes. The theory explains why and how the factors exert their influence.

Influential client factors can be categorized into personal and health or clinical characteristics, and accessibility of resources, as mentioned and illustrated in Chapter 3. Personal characteristics encompass sociodemographic profile, and personal or cultural beliefs about health in general and the health problem and its treatment. Health or clinical characteristics represent individuals’ physical, cognitive, and psychosocial functioning, presence of concurrent comorbid physical or mental conditions, and receipt of pharmacological and non‐pharmacological therapies to manage the health problem and the comorbid conditions. Accessibility reflects the availability and clients’ ability to access or use resources required to engage in the intervention (e.g. transportation to attend the group sessions in‐person) and to enact treatment recommendations (e.g. physical, social, financial resources). For tailored and adaptive interventions, the theory identifies, in addition to these characteristics, client factors that form the basis for tailoring and explains the rationale for selecting them to inform the customization process.

5.1.3 Resources

The intervention theory specifies the material and human resources needed to enable the delivery of the intervention (Ball et al., 2017; Chen et al., 2018). Material resources are inferred from the description of the intervention’s components (including content and activities) and mode of delivery (see Chapter 4 for examples). Material resources include the equipment (e.g. projector, models for demonstration of a skill like location of pressure points); infrastructure (e.g. room, access to computer or telephone); supplies (e.g. USB keys, folders) and written documents such as intervention manual that guides health professionals in implementing the intervention, and pamphlets, booklets, or modules that clients refer to when carrying out the treatment recommendations.

Human resources refer to all personnel involved in the delivery of the intervention. The specification of human resources should be consistent with local professional regulations; these indicate the qualifications of health professionals who can be entrusted the delivery of the intervention. The personnel involved in the delivery of the intervention may include: (1) support staff responsible for screening clients; (2) IT personnel responsible for developing technology‐based interventions, and for supporting clients in the use of the respective technology; and (3) health professionals responsible for providing the intervention (face‐to‐face or distance) to clients. The characteristics of health professionals in direct contact with clients are of particular importance because they play a role in the implementation, and consequently the effectiveness of the intervention (see Chapter 8). Accordingly, the intervention theory specifies the salient personal attributes (e.g. communication skills) and professional qualifications (e.g. educational background) of health professionals that enable or limit the adequate implementation and subsequently, the mechanism of action, of the intervention (Dalkin et al., 2015; De Souza 2013; Greenhalgh et al., 2015).

5.1.4 Contextual Factors

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Nov 28, 2021 | Posted by in NURSING | Comments Off on 5: Intervention Theory
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