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Frightening people about a health risk does not reliably change what they do, and knowing that a behaviour is harmful is famously no guarantee that a person will stop. To understand why — and to design interventions that actually shift behaviour — health psychology draws on formal models of health behaviour: theories that specify the beliefs, attitudes and processes that lie between a health threat and a person's decision to act. This lesson develops three of the most influential, all directly applicable to reducing substance misuse. The Health Belief Model (HBM) explains health action in terms of a cost–benefit weighing of perceived susceptibility, severity, benefits and barriers, triggered by cues to action. The Theory of Planned Behaviour (TPB) treats behaviour as the product of an intention shaped by attitudes, subjective norms and perceived behavioural control. The Transtheoretical Model (TTM), or stages of change, reframes change not as a single event but as movement through a sequence of stages, each needing a different kind of support. Throughout, the models are used to explain and improve attempts to reduce smoking, drinking and gambling, and substance misuse is treated objectively, in the standard academic register expected at A-Level.
Key Definition: A model of health behaviour is a theoretical framework that specifies the beliefs, attitudes and decision processes that determine whether a person adopts, changes or maintains a health-related behaviour. Such models are used both to explain why people do or do not act on health information and to design interventions that make healthy behaviour more likely.
This lesson addresses the Edexcel 9PS0 — Paper 2, Topic 8: Health Psychology content on attitudes to health and changing health-related behaviour: models of health behaviour and behaviour change — the Health Belief Model (perceived susceptibility, severity, benefits and barriers, and cues to action), the Theory of Planned Behaviour (attitudes, subjective norms and perceived behavioural control determining intention), and the Transtheoretical / stages of change model — applied to reducing substance misuse. In assessment-objective terms, you should be able to describe the components of each model (AO1), apply them to a described individual or scenario — for example, using the HBM or TPB to explain why a particular smoker has or has not quit, or locating someone on the stages of change (AO2), and evaluate the models, including the attitude–behaviour gap, the neglect of habit and emotion, and their practical value for intervention design (AO3).
Connects to…
The Health Belief Model (HBM), developed by social psychologists including Rosenstock (1966) and colleagues such as Hochbaum, Becker and Kegels, was originally devised to explain why people did or did not take up preventive health services. Its core idea is that health behaviour results from a rational, if often implicit, cost–benefit analysis: a person weighs the perceived threat of a health problem against the perceived pros and cons of taking action. Whether they act depends on several interacting beliefs.
| Component | Meaning | Applied to quitting smoking |
|---|---|---|
| Perceived susceptibility | Belief about one's own personal risk of the health problem | "I could realistically develop lung cancer or heart disease" |
| Perceived severity | Belief about how serious the consequences would be | "Lung cancer would be devastating and possibly fatal" |
| Perceived benefits | Belief that the recommended action reduces the threat | "Quitting would greatly cut my risk and improve my health" |
| Perceived barriers | Belief about the costs, obstacles and unpleasantness of acting | "Quitting means withdrawal, stress, weight gain and losing a coping tool" |
| Cues to action | Triggers that prompt the decision to act | A doctor's warning, a health scare, a friend's diagnosis, a graphic advert |
| Self-efficacy | Confidence that one can perform the action (a later addition) | "I believe I can actually manage to stop and stay stopped" |
The model proposes that action is most likely when perceived threat (susceptibility × severity) is high and the perceived benefits of acting clearly outweigh the perceived barriers, with cues to action tipping the person into actually doing something. The later addition of self-efficacy recognised that even someone convinced of the threat and the benefits will not act unless they believe they are capable of succeeding — a belief especially important in addiction, where previous failed attempts can erode confidence.
graph LR
A[Perceived susceptibility] --> T[Perceived threat]
B[Perceived severity] --> T
C[Perceived benefits] --> W[Benefits vs barriers weighing]
D[Perceived barriers] --> W
T --> L[Likelihood of action]
W --> L
E[Cues to action] --> L
F[Self-efficacy] --> L
L --> G[Health behaviour e.g. quit attempt]
Applied to substance misuse, the HBM immediately explains a familiar pattern. A smoker who does not feel personally at risk (low susceptibility — "my grandfather smoked and lived to ninety"), or who is fatalistic ("the damage is already done"), or for whom the barriers loom large (withdrawal, stress, the social cost of quitting) relative to the benefits, is unlikely to attempt to stop even if they fully accept that smoking is dangerous in general. The practical value of the model is that it identifies the specific beliefs an intervention must change: to increase quit attempts, a programme might personalise the risk (raising susceptibility), stress concrete near-term benefits (fitness, money, smell) rather than only distant ones, actively reduce barriers (offering nicotine replacement and support to blunt withdrawal), build self-efficacy, and provide clear cues to action. Because the model pinpoints which belief is the obstacle for a given person, it turns "change your behaviour" into a set of targeted, modifiable levers.
Key Definition: The Health Belief Model proposes that the likelihood of a health behaviour depends on perceived susceptibility and severity (which together form perceived threat), the balance of perceived benefits against perceived barriers, and cues to action, with self-efficacy added later as the belief that one can carry out the action.
Where the HBM focuses on threat and cost–benefit beliefs, the Theory of Planned Behaviour (TPB) — developed by Ajzen (1991) as an extension of the earlier Theory of Reasoned Action (Fishbein & Ajzen) — places intention at the centre. Its central claim is that the best single predictor of a behaviour is a person's behavioural intention, and that intention is itself determined by three components.
| Component | Meaning | Applied to cutting down drinking |
|---|---|---|
| Attitude toward the behaviour | The person's overall positive/negative evaluation of doing it, based on beliefs about its likely outcomes | "Cutting down would improve my health and sleep" (positive) vs "drinking is how I relax and socialise" (negative) |
| Subjective norm | Perceived social pressure — whether important others approve of the behaviour, and the motivation to comply | "My partner and my doctor want me to cut down, and I care what they think" |
| Perceived behavioural control (PBC) | Belief about how easy or difficult the behaviour is, and how much it is under one's control | "I could realistically cut down if I avoided the pub on weeknights" |
| Intention | The motivational readiness to perform the behaviour (the immediate antecedent of action) | "I intend to cut my drinking to weekends only" |
The three determinants combine to shape intention, and intention (given adequate control) drives behaviour. Crucially, perceived behavioural control has a dual role: it feeds into intention and, because it partly reflects genuine ability and resources, it can predict behaviour directly — someone may intend to quit but fail because the behaviour is not, in fact, fully within their control (a central issue for addiction, where craving and dependence undermine control). PBC is conceptually close to Bandura's self-efficacy, which is one reason it is such an important addition.
graph LR
A[Attitude toward the behaviour] --> I[Behavioural intention]
B[Subjective norm] --> I
C[Perceived behavioural control] --> I
C -->|direct path| BEH[Behaviour]
I --> BEH
Applied to substance misuse, the TPB explains why simply improving attitudes is often not enough. A gambler might develop a genuinely negative attitude toward gambling (recognising the harm) yet still not form a strong intention to stop if the subjective norm pulls the other way — for instance, if gambling is normalised within their social group — or if their perceived behavioural control is low because they doubt they can resist the urge. The model therefore directs an intervention to work on all three routes: reshaping outcome beliefs (attitude), shifting the perceived norm (for example, by making clear that most people disapprove of, or do not engage in, the behaviour), and — often most importantly for addiction — building perceived control through skills, planning and support. It also highlights the intention–behaviour gap: because intentions do not automatically become actions, techniques such as forming specific implementation intentions ("if I feel the urge after work, then I will phone a friend") are used to help translate a good intention into behaviour.
A further strength of the TPB, and part of why it has been so widely used in health research, is that each component is defined precisely enough to be operationalised and measured. In a typical study, researchers construct belief-based questionnaire items: attitude is assessed from the person's evaluation of the likely outcomes of the behaviour (each weighted by how much they value that outcome); subjective norm from beliefs about what specific important others think, weighted by the motivation to comply with each; and perceived behavioural control from beliefs about the specific facilitators and obstacles the person expects to encounter. This gives the model a clear, testable structure — one can measure the three predictors, measure intention, and later measure behaviour, then test how well each link holds. It also makes the model diagnostically useful: for a given individual or group, an intervention designer can identify which belief is weakest (say, a low sense of control among smokers who have failed before) and target it directly, rather than treating attitude, norms and control as an undifferentiated whole.
Key Definition: The Theory of Planned Behaviour proposes that behaviour is driven by behavioural intention, which is determined by attitude toward the behaviour, subjective norms (perceived social pressure) and perceived behavioural control; perceived behavioural control can also influence behaviour directly.
Both the HBM and the TPB treat the decision to act largely as a single weighing-up. The Transtheoretical Model (TTM), developed by Prochaska and DiClemente (1983), takes a different and complementary view: behaviour change is a process that unfolds over time through a series of stages, and — crucially — the kind of help a person needs depends on which stage they are in. The model was developed partly from studying how smokers quit, so it is especially well suited to substance misuse.
| Stage | Characterised by | What the person needs |
|---|---|---|
| Precontemplation | Not intending to change; may not see a problem ("I don't need to quit") | Raise awareness; personalise the risk; plant doubt — not an action plan |
| Contemplation | Aware of the problem and considering change, but ambivalent ("I know I should, but…") | Help weigh pros and cons; tip the decisional balance; build confidence |
| Preparation | Intending to act soon; may have taken small steps | Concrete planning; set a quit date; arrange support and resources |
| Action | Actively changing the behaviour (recently stopped or cut down) | Practical coping strategies; manage withdrawal and cues; reinforce success |
| Maintenance | Sustaining the change over the longer term | Relapse-prevention skills; consolidate the new behaviour and identity |
| (Relapse) | Returning to the old behaviour — treated as a normal part of the cycle, not failure | Support to re-enter the cycle without demoralisation; learn from the lapse |
Two features make the model distinctive. First, change is cyclical, not linear: relapse is built into the model as a common, expected event, and a person who lapses typically re-enters at contemplation or preparation rather than starting from scratch — a realistic and non-judgemental view that matches how most people actually quit smoking (often over several attempts). Second, and most usefully for intervention, the model implies that help must be stage-matched: giving a precontemplator a detailed quit plan is likely to fail because they are not yet ready to act, whereas the same plan is exactly right for someone in preparation. Trying to move a person to action before they are ready is one of the commonest reasons interventions and well-meant advice fail.
graph LR
A[Precontemplation] --> B[Contemplation]
B --> C[Preparation]
C --> D[Action]
D --> E[Maintenance]
E -.relapse.-> B
D -.relapse.-> B
The stages of change also connect naturally to the concepts within the other two models. Movement from precontemplation to contemplation often depends on a cue to action and a rise in perceived susceptibility (HBM); movement from contemplation to preparation and action depends heavily on self-efficacy and perceived behavioural control (TPB); and maintenance depends on the relapse-prevention skills examined in the behavioural-treatment lesson. Seeing the models as complementary — the HBM and TPB specifying which beliefs matter, the TTM specifying when to target them — is more sophisticated than treating them as rivals.
Key Definition: The Transtheoretical (Stages of Change) Model describes behaviour change as movement through the stages of precontemplation, contemplation, preparation, action and maintenance, with relapse treated as a normal, expected part of a cyclical process; effective help is matched to the person's current stage.
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