Theories and Models

Core Concepts

What theories and models do

Theories and models explain (why does this behavior exist?), predict (who is likely to change, and when?), and guide (what should the intervention do?). A good model also tells the team what to measure: if the theory says perceived barriers drive behavior, evaluation should measure whether barriers decreased. No single theory explains everything, so nurses often combine theories or use an ecological model that holds all levels in view.

Individual-level theories: beliefs and readiness

The Health Belief Model (HBM) explains behavior through perceptions: perceived susceptibility ("could this happen to me?"), perceived severity ("how bad would it be?"), perceived benefits ("will this help?"), and perceived barriers ("what will it cost me?"), plus cues to action (reminders, advice) and self-efficacy (confidence in one's ability to act). HBM is strongest for one-time preventive decisions such as screenings. Note the trap: perceived susceptibility is not actual risk — a high-risk person can feel invulnerable, and a low-risk person can feel terrified.

The Transtheoretical Model (TTM), or Stages of Change, describes change as movement through precontemplation (no intention to change), contemplation (thinking about it), preparation (getting ready), action (making the change), and maintenance (sustaining it). Relapse is common and expected — people recycle through stages rather than marching once. The key teaching point: match the intervention to the stage — a precontemplator needs awareness and reasons, not technique.

The Theory of Planned Behavior (TPB) proposes that intention drives behavior, shaped by attitude toward the behavior, the subjective norm (what the person believes important others expect), and perceived behavioral control (how easy or hard the behavior seems). It explains why social pressure matters: a teen may personally want to avoid vaping yet feel peer norms push the other way.

The Social Cognitive Theory (SCT) emphasizes learning from observing others (role models) and reciprocal determinism: behavior, personal factors, and environment constantly influence each other. Self-efficacy is central — people who believe they can perform a behavior are far more likely to attempt and sustain it, which is why community programs use peer leaders.

Community- and policy-level frameworks

Individual theories cannot explain neighborhood-level patterns. The Social Ecological Model (SEM) places the person inside nested layers — individual, interpersonal, organizational/community, policy/environmental — and insists that real change often needs action at several layers at once. Teaching healthy eating does little if the neighborhood has no grocery store; both layers need attention.

Diffusion of Innovations describes how a new idea spreads over time: innovators and early adopters try it first, then the early majority, late majority, and finally laggards. The lesson: do not expect everyone to adopt at once — find and support opinion leaders early, because their endorsement carries the majority.

The PRECEDE-PROCEED model is a planning framework: start from the end (the health outcome a community wants), then work backward through behavioral, environmental, and educational assessments to design, implement, and evaluate an intervention. The Ottawa Charter for Health Promotion (WHO, 1986) frames promotion as five actions — build healthy public policy, create supportive environments, strengthen community action, develop personal skills, reorient health services — promotion is social and political, not only clinical.

Choosing and combining models

Select a model by asking: what level is the problem at, and what does the population say matters? Individual beliefs? Use HBM, TTM, or TPB. Peer influence? Use SCT or TPB's subjective norm. Environment and policy? Use SEM. Many programs combine a stage model (to segment the population) with an ecological model (to act at several levels).

Common Confusions