The first model to include cognitive factors in the determination of behavior was the Health Belief Model , developed in the early 1950s by Godfrey Hochbaum, Stephen Kegels and Irwin Rosenstock (Becker and Maiman 1975).

This model superimposes the perception of threats and expectations onto a socio-demographic background, which includes, for example, age, gender, ethnicity, profession, etc. To make the decision to adopt a new health behavior the agent must feel personally vulnerable, regardless of what the “objective” situation might be. Threats include the perception of the individual’s own vulnerability in the face of a health problem and her perception of the problem’s severity. The model considers severity not only in terms of health, (including pain , discomfort, and the risk of death ), but also as regards its professional, social and family consequences. The expectations are the benefits that the individual anticipates from the health behavior, the individual’s perception of her capacity to perform the action (self-efficacy ), and her perception of the obstacles to performing it. Once the individual, having weighed the pros and the cons, has decided to submit to treatment, a cue might be necessary to trigger its implementation. This might be an internal event (the appearance of the first symptom, for example) or an external one (a media campaign or the loss of a relative to the same illness ) (Fig. 2.2).

The Theory of Reasoned Action was developed in 1967 by Martin Fishbein and Icek Ajzen (Fishbein and Ajzen 1975). Its title implies that individuals are rational beings who use the information at their disposal and consider the consequences of their actions before performing them. This theory maintains that the behavior depends essentially on the intention of the subject to perform it. Here intention is described as the indication of the strength of the subject’s desire to perform the behavior and the efforts that she plans to invest in order to reach this goal.

The intention of the individual to perform a particular behavior depends on two types of factors. The first factor is the individual’s attitude towards the behavior, consisting of the positive or negative evaluation of the behavior. The attitude in turn depends on different beliefs of the patient concerning the consequences, positive or negative, of adopting the behavior. The second type of factor are the subjective norms , or the beliefs concerning the way the behavior is perceived by the people important to the patient (for instance, family, friends, the physician, the police) and her more or less intense desire to follow their advice. Ajzen later modified this model by another factor, how the patient perceives her own capacity to control her behavior, leading to a new conceptual framework, the Theory of Planned Behavior (Ajzen 1985). According to this theory, the triggering of the behavior depends on the presence of particular circumstances or on the possession of resources (for example, time , money, a certain skill, cooperation of other people).

These theories have been applied to behavioral changes such as quitting smoking, beginning a physical activity, a diet , safe sex practices or adherence to a treatment for hypertension, bipolar disorder or urinary infection.

In the Theory of Interpersonal Behavior (Fig. 2.3), developed in the late 1970s by Harry Triandis , three factors participate in the genesis of a behavior: The strength of habit in performing a certain behavior, the intention to perform it, and the presence of conditions that make performing the behavior easy or difficult.

This theory’s major contribution is the importance accorded to the strength of habit : The degree of a behavior ’s automaticity (Triandis 1979). Later in this book, I will discuss in detail the crucial role that habit plays in patient adherence.

Leventhal ’s theory (Leventhal et al. 1997) maintains that there is a regulatory cycle originating with the patient ’s representation of her illness , and proceeding to the measures that she takes. For the patient, it is a question of solving the problem posed by her illness or any other threat to her health . The patient responds in three stages: an interpretation of her illness, which can be triggered by internal signals (symptoms) or external signals (a doctor ’s diagnosis); the choice of adjustment measures or coping ; and finally the evaluation of the results of her action —which, in turn, may modify her initial interpretation.

Adherence or nonadherence can be interpreted as one strategy among many of coping , each used to deal with the disease as perceived by the individual. For example, one may take an aspirin as a strategy to relieve a headache, and this strategy may be chosen thanks to the individual’s belief that aspirin is usually a quick cure for headaches. If during the stage of evaluation the patient notices that the pain persists, she may change her strategy of coping (take a stronger pain medication ) or reevaluate her representation of the illness (if the aspirin didn’t work, maybe it’s something more serious). According to this theory, the interpretation of the illness is based on a holistic picture that takes into account the problem’s identity (what illness do I have?), its causes (how did this happen?), its consequences (what might happen?), and its curability (will this treatment work?).

This theory, developed by Howard Leventhal in the 1970s, is unique for explicitly introducing two parallel paths for the three stages, one cognitive and one emotional (Fig. 2.4).

The Transtheoretical Model of Change (Fig. 2.5) (Prochaska and DiClemente 1983; Prochaska and Norcross 1994) describes the different stages leading up to the adoption of a behavior . Developed by James Prochaska in the beginning of the 1980s, this model has been used to understand various behaviors: Smoking , alcoholism, drug addiction , routine exercise , weight loss, condom use, sun-screen use, mammography screening, and others. The model has also been called transtheoretical because it is a synthesis of the different psychological theories that were used at the time .

While other theories describe the adoption of a behavior as an event (stopping drinking , quitting smoking , beginning a diet ), this model gives a progressive description and identifies five stages in the process leading up to the adoption of a behavior. Change is seen as the endpoint of an evolving process.

In the precontemplation stage, the individual is not conscious of having a problem, and so she has no intention to modify her behavior in the foreseeable future . A patient may be unaware of her problem thanks, for example, to a lack of information, or because she refuses to believe that there is a problem, or because she has already tried to resolve it, has failed and has given up. During this period, the individual avoids talking, thinking, and obtaining information about the problem, and is deaf to the words of others on the subject—it couldn’t be otherwise, she knows nothing of it! In the pre-contemplation stage, the person either never heard about the problem, or, through a process of denial , refuses to see that there is a problem.

In the contemplation stage, the individual has begun to realize that there is a problem and considers doing something about it. For instance: She has weighed the benefits and drawbacks of taking action , but has not yet reached a decision ; she puts off the decision to another day. Unfortunately, this state of procrastination can last a very long time .

During the preparation stage, the individual intends to act in the near future , and studies the ways of resolving the problem: She talks to her doctor , buys books on the subject, picks a start date for her diet or exercise plan, etc. The action stage is when the individual actually changes her behavior ; and while the change in behavior may be quite dramatic—the alcoholic who puts down the bottle after years of steady drinking , for example—this model suggests that it is preceded by a long, and sometimes painful, germination.

Finally, the maintenance stage is the more or less prolonged period of time when an effort is required to avoid relapse.

Progression is seldom linear. There are frequent steps back, for instance with brief relapses . Usually the regression does not go all the way back to the pre–contemplation stage, but stops at the preparation or contemplation stages.