Leventhal and Cameron (52) provided a very useful overview of the history of adherence research. They outlined five general theoretical perspectives on adherence:
- biomedical perspective;
- behavioural perspective;
- communication perspective;
- cognitive perspective; and
- self-regulatory perspective.
The biomedical model of health and illness remains a dominant perspective in many health care settings and organizations. The biomedical approach to adherence assumes that patients are more-or-less passive followers of their doctor's orders, further to a diagnosis and prescribed therapy (52,53). Nonadherence is understood in terms of characteristics of the patient (personality traits, sociodemographic background), and patient factors are seen as the targets of efforts to improve adherence. This approach has helped to elucidate the relationships between disease and treatment characteristics on the one hand, and adherence on the other. Technological innovations (e.g. assessing levels of adherence using biochemical measures, developing new devices to administer medications) have had this as their impetus. However, other important factors, such as patients' views about their symptoms or their medications have been largely ignored.
Behavioural (learning) theory emphasizes the importance of positive and negative reinforcement as a mechanism for influencing behaviour, and this has immediate relevance for adherence.
- The most basic, but powerful, principle is that of antecedents and consequences and their influence on behaviour (i.e. operant learning) (54,55).
- Antecedents, or preceding events, are internal (thoughts) or external (environmental cues) circumstances that elicit a behaviour.
- Consequences, or expected consequences, that can be conceptualized as rewards or punishments, also influence behaviour.
- The probability of a patient, provider, or health care system initiating or continuing a behaviour partially depends on what happens before and after the behaviour occurs.
- From a theoretical standpoint it would be possible to "control" the behaviour of patients, providers and health care systems if one could control the events preceding and following a specific behaviour. From a practical standpoint, behavioural principles can be used to design interventions that have the potential to incrementally shape behaviour at each level of influence (i.e. patient, provider and system) to address adherence problems.
Communication perspectives that emerged in the 1970s encouraged health care providers to try to improve their skills in communicating with their patients. This led to emphasis being placed on the importance of developing rapport, educating patients, employing good communication skills and stressing the desirability of a more equal relationship between patient and health professional. Although this approach has been shown to influence satisfaction with medical care, convincing data about its positive effects on compliance are scarce (56). Adopting a warm and kind style of interaction with a patient is necessary, but is insufficient in itself to effect changes in the adherence behaviours of patients.
Various models emphasizing cognitive variables and processes have been applied to adherence behaviour (53). Examples of these include the health belief model (57), social-cognitive theory (58), the theory of planned behaviour (and its precursor, the theory of reasoned action) (59), and the protection - motivation theory (60). Although these approaches have directed attention to the ways in which patients conceptualize health threats and appraise factors that may be barriers to, or facilitate, adherence they do not always address behavioural coping skills well.
Self-regulation perspectives attempt to integrate environmental variables and the cognitive responses of individuals to health threats into the self-regulatory model (61,62). The essence of the model pertains to the central importance of the cognitive conceptualization of a patient (or a patient-to-be (63) of a health threat or an illness. Illness representations (the ideas patients have about the diseases they suffer) and coping are seen as mediating between the health threat and the action taken. Recent empirical studies seem to lend support to the importance of illness cognitions in predicting adherence (64 - 66). Patients create personal representations of health threats and models of the illness and its treatment, and it is these that guide their decision-making and behaviour. Thus, adherence requires an appropriate model and the belief that one can manage one's own environment and behaviour, specific coping skills, and a belief that the issue requires one's attention and the modification of one's behaviour.
Although these theories and models provide a conceptual framework for organizing thoughts about adherence and other health behaviours, each has its advantages and disadvantages and no single approach may be readily translated into a comprehensive understanding of, and intervention for, adherence. More recent approaches that are more specific to health behaviours and the demands of following recommended health practices may provide more helpful frameworks.
Meichenbaum and Turk (42) suggested that four interdependent factors operate on adherence behaviour and that a deficit in any one contributes to risk of nonadherence.
- knowledge and skills: about the health problem and self-regulation behaviours required, their mechanisms of action, and the importance of adherence;
- beliefs: perceived severity and susceptibility (relevance), self-efficacy, outcome expectations, and response costs;
- motivation: value and reinforcement, internal attribution of success (positive outcomes are reinforcing, negative results seen not as failure, but rather as an indication to reflect on and modify behaviour);
- action: stimulated by relevant cues, driven by information recall, evaluation and selection of behavioural options and available resources.
The recently developed information-motivation-behavioural skills model (IMB model) (67,68), borrowed elements from earlier work to construct a conceptually based, generalizable, and simple model to guide thinking about complex health behaviours. The IMB constructs, and how they pertain to patient adherence, are outlined below.
- Information is the basic knowledge about a medical condition that might include how the disease develops, its expected course and effective strategies for its management.
- Motivation encompasses personal attitudes towards the adherence behaviour, perceived social support for such behaviour, and the patients' subjective norm or perception of how others with this medical condition might behave.
- Behavioural skills include ensuring that the patient has the specific behavioural tools or strategies necessary to perform the adherence behaviour such as enlisting social support and other self-regulation strategies.
Note that information, motivation and behavioural skills must directly pertain to the desired behavioural outcome; they have to be specific.
Interventions based on this model have been effective in influencing behavioural change across a variety of clinical applications (67 - 69). In both prospective and correlational studies, the information, motivation and behavioural skills constructs have accounted for an average of 33% of the variance in behaviour change (68).
Figure 1 Information-motivation-behavioural skills model
The IMB model demonstrates that information is a prerequisite for changing behaviour, but in itself is insufficient to achieve this change (70).Motivation and behavioural skills are critical determinants and are independent of behaviour change (67,68). Information and motivation work largely through behavioural skills to affect behaviour; however, when the behavioural skills are familiar or uncomplicated, information and motivation can have direct effects on behaviour (see diagram). In this case, a patient might fill a prescription (a simple, familiar behaviour) based on information given by the provider. The relationship between the information and motivation constructs is weak. In practical terms, a highly motivated person may have little information, or a highly informed person may have low motivation. However, in the IMB model, the presence of both information and motivation increase the likelihood of adherence.
The stages-of-change model (SOC - also referred to as the transtheoretical model) identifies five stages through which individuals progress as they change behaviours, and stage-matched strategies that predict progress to each subsequent stage of change (71,72). The stages of change are: precontemplation (not considering changing behaviour in the next 6 months), contemplation (considering changing behaviour in the next 6 months), preparation (planning to change behaviour during the next 30 days), action (currently changing behaviour) and maintenance (successful behaviour change for at least 6 months). Stages of change describe an individual's motivational readiness to change.
The SOC model is useful for understanding and predicting intentional behaviour change. Most patients at one time or another make unintentional errors in taking their medication because of forgetfulness or misunderstanding of instructions. However, intentional non-adherence is a significant problem, particularly among patients with conditions requiring long-term therapy such as asthma, hypertension and diabetes.
Stage of change is an indicator of an individual's motivation to change, and is a powerful predictor of behaviour (73 - 75), but variables that explain behavioural change are needed to develop actionable, effective strategies to help people change. The SOC model has proven useful in this regard because it utilizes key psychological constructs to characterize individuals at different levels of readiness for change. Some of these constructs are: decisional balance, temptation to relapse, and processes or strategies for change (76). These constructs are briefly summarized below.
Decisional balance. Decisional balance consists of the pros and cons of behaviour change. Longitudinal research has established a characteristic relationship between stage of change and the pros and cons (77,78). The pros of healthy behaviour are low in the early stages of change and increase as stage of change increases. Conversely, the cons of the healthy behaviour are high in the early stages of change and decrease as stage of change increases. The positive aspects of changing behaviour begin to outweigh the negative aspects of change late in the contemplation stage or early in the preparation stage. Scales measuring pros and cons are particularly useful when intervening with individuals in early stages of change (precontemplation, contemplation and preparation) because decisional balance is an excellent indicator of an individual's readiness to move out of the precontemplation stage (74,78,79).
Temptation to relapse. The degree of temptation associated with situations that present a challenge for maintaining behavioural change is a concept based upon the coping models of relapse and maintenance. Situational temptation to engage in unhealthy behaviour is often viewed as an important companion construct to measures of confidence or self-efficacy. Confidence and temptation function inversely across stages of change (80), and temptation predicts relapse better (81). Scores on temptation are generally highest in the precontemplation stage, decreasing linearly from the precontemplation to maintenance stages (81).
Strategies for change. The SOC model identifies specific strategies or processes of change that are associated with successful movement from one stage to the next. The strategies for change outlined in the SOC theory are based upon components of several theoretical models in behavioural science. Each of the strategies for change is categorized as either experiential or behavioural in nature (82). Experiential strategies reflect cognitive, evaluative and affective planning for change whereas behavioural strategies reflect observable change strategies such as using reminders or rewards (73).
Specific strategies for change are useful for intervening with individuals in particular stages of change; individuals who are thinking about change need different strategies from those who are actively involved in change.
Tailored interventions provide individualized information based upon a specific theoretical framework, demographic characteristics or a combination of variables. There is evidence that tailored communications are more effective for influencing health behaviours than non-tailored materials (83), and comparisons of stage-tailored versus non-tailored interventions have shown that tailoring resulted in increased efficacy in influencing health behaviours (84).
A recent review found that interventions to improve adherence to medication were more effective when they included multiple components such as more convenient care, information, counselling, reminders, self-monitoring, reinforcement or family therapy (43). SOC tailoring may be a useful strategy for implementing complex, multi-component interventions in a cost-effective manner. Identification of stage of change can help determine the most relevant intervention components for each person, thus eliminating the need to deliver all intervention components to all patients. The availability of valid measures to assess stage of change provides a foundation for the development of stage-matched interventions for the promotion of adherence to medication. Stage-tailored communication has been shown to be an effective method for changing health behaviour, but has yet to be applied to the problem of nonadherence with medication.