The reasoning behind adherence-enhancing interventions within theoretical models of medication adherence – a narrative review

Introduction

Although randomized clinical trials demonstrate significant drug efficacy, these outcomes are not always replicated in nonexperimental, real-world settings. One reason is the poor adherence to treatment. Medication adherence is the degree to which individuals follow their prescribed medication regimen, while nonadherence occurs when people don’t use their medication as agreed with their healthcare providers⁽¹⁾. It is estimated that approximately 30-50% of patients do not comply with their medication prescriptions⁽²⁾.

Various theoretical models, mainly advanced by psychologists, aim to describe, predict and improve medication adherence as part of treatment adherence. These models are widely applicable in explaining individuals’ healthcare behaviors and in devising strategies to improve them.

Up to now, efforts to enhance medication adherence through interventions have shown only moderate effectiveness. In a meta-analysis published in 2012, aggregating 771 studies investigating interventions to increase medication adherence, the patients from the intervention group took roughly 7% more of prescribed doses compared to the control group⁽³⁾.

There is a pressing need for more adherence interventions that are firmly grounded in robust theoretical foundations. For example, in the realm of adherence interventions for older adults with polypharmacy, adherence interventions are seldom developed based on theory, according to a review done by Patton et al.⁽⁴⁾ Often, there is a lack of explicit information on how theory informs the development of these interventions.

Methodology

We conducted a search on PubMed and Google Scholar using various terms related to medication adherence and theory-based interventions. The chosen terms included: “medication adherence”, “adherence to medication”, “drug adherence”, “treatment adherence”, “theory of adherence”, and “theory-based intervention”. After selecting the most pertinent results, we structured the present paper to link adherence interventions to theoretical models of medication adherence.

Results and discussion

We introduce the primary theories that characterize medication adherence. Adherence to medication encompasses various aspects, including cognitive, behavioral, physical and economic dimensions.

The fundamental assumptions are that individuals possess forethought, planning abilities and rational decision-making skills. All these theories acknowledge that decision-making and self-regulation are social learning processes experienced by individuals.

1. Social learning theories or cognitive theories

These theories, which integrate elements of cognitive psychology with behavioral psychology, propose that behavior is influenced by external stimuli that can be understood in terms of reward and punishment. Behaviors are shaped by mental processes like thinking, decision-making and problem-solving. These approaches suggest that the establishment of these behaviors is significantly influenced by social factors, particularly attitudes of acceptance and encouragement. Learning behaviors involves observational learning, where individuals may increase their medication adherence by observing others who are already adherent to medication⁽⁵⁾.

Social learning’s cognitive aspect stems from the recognition that behavior is influenced by outcome expectations, which are an individual’s beliefs about positive consequences resulting from their actions⁽⁶⁾. To explain how this belief is established, two theoretical proposals compete: the locus of control theory and the theory of self-efficacy.

1.1. Locus of control theory

The locus of control theory pertains to an individual’s perception of their ability to influence events. According to it, people may have either an internal locus of control, when they believe it is within their power to influence the outcome, or an external locus of control, when they believe the outcome is determined by chance, luck or fate⁽⁷⁾. In the context of health-related behaviors, Wallston et al. (1978) expanded the locus of control theory, advocating that individuals with a strong internal locus of control consider that their healthy behaviors have as outcomes a good health. On the contrary, individuals having a locus of control located predominantly externally rely more on external factors, seeking explanations and positive health outcomes from others, particularly health professionals whom they perceive as having authority in their relationship⁽³⁾.

Several studies indicate that higher internal locus of control is associated with higher levels of medication adherence^(8,9), while other studies have not found any significant association⁽¹⁰⁾. The interaction between locus of control and factors like social support or motivation could be better predictors of medication adherence⁽¹¹⁾.

1.2. Self-efficacy theory

 Self-efficacy pertains to beliefs that individuals develop about their ability to mobilize the cognitive and motivational resources they need to appropriate a behavior. The theory of self-efficacy proposed by Bandura^(12,13) revolves around the notion that an individual’s involvement in a specific behavior relies not only on their knowledge of what to do, but also on their belief in their ability to perform that behavior. Self-efficacy predicts the behavior to be adherent to medication⁽¹⁴⁾.

Practical approaches for enhancing medication adherence using social learning theory concepts involve:

• Demonstrating desired behaviors through examples, where patients are shown how to properly use medication and monitor treatment’s safety and effectiveness.

• Engaging in discussions about past successes and failures in adhering to medication regimens.

• Exploring the individual and environmental factors that influenced those outcomes.

• Encouraging patients to persist in their efforts to boost self-efficacy and shift the locus of control towards internal empowerment⁽¹⁵⁾.

2. Continuum theories

Continuum theories, like stage theories, are contemporary theoretical frameworks that extend the principles of social learning theory. These theories propose that all factors influencing behavior can be unitarily integrated into a predictive equation that consistently affects the actions of individuals⁽⁶⁾.

2.1. Theory of reasoned action and theory of planned behavior

The intention to perform a particular behavior is the most important predictor of the occurrence of that behavior. The intention depends on the attitude towards the behavior and on subjective norms. Attitude represents the individual’s global assessment of enacting the behavior, which is influenced by their beliefs about the consequences of that behavior. Subjective norms pertain to the individual’s perceptions of how others will view their behavior, particularly influenced by expectations from significant individuals and the individual’s motivations to meet these expectations⁽¹⁶⁾.

To account for behaviors that are not solely governed by willpower, the theory of planned behavior proposes a third determinant of intention, the perceived behavioral control. It refers to the level to which the individuals consider they have control over accomplishing the behavior⁽¹⁷⁾.

By adopting implementation intentions rather than general intentions, individuals could strengthen the weak association between intention and behavior, being more likely to perform desirable behavior⁽¹⁸⁾. Such implementation intentions create reminder cues, specifying the when, where and how of a behavior (e.g., if a patient links taking medication to brushing their teeth in the morning, brushing teeth serves as a reminder to take the medication)⁽¹⁹⁾.

Patients having a positive attitude towards the intended behavior appear to have a better adherence to medication; therefore, doctors and pharmacists may begin by assessing patients’ attitude towards following the recommendations. To alter negative attitudes, persuasion techniques can be employed, such as presenting compelling arguments for the recommended behavior (e.g., highlighting increased life expectancy due to reduced cardiovascular disease risk), providing knowledge to reinforce one’s attitude, or addressing fears. Social norms also play a significant role. Health professionals can explore whether patients perceive support from their loved ones in adopting the desired behavior. Positive social pressure should be sought and applied appropriately. Following the recommended behaviors is more likely when health professionals themselves exhibit social norms by adhering to the behaviors they recommend.

Some studies indicate that patients place less trust in health advice given by obese doctors compared to those given by normal body weight doctors⁽²⁰⁾. Perceived behavioral control can be increased using strategies to increase self-efficacy. Open discussions between healthcare providers and patients should focus on addressing barriers perceived by the patient, such as concerns about medication costs or access to medicines. Supporting the patient in developing implementation intentions, which are more specific and effective than general intentions, is crucial. Offering concrete examples of behavior implementation can assist the patient in this process⁽¹⁾.

2.2. Protection motivation theory

The protection motivation theory is based on the concept that fear-appealing messages can prompt shifts in attitude, subsequently leading to changes in behavior⁽²¹⁾. As per this theory, the decision to adopt healthy behavior arises from the desire to avoid unfavorable outcomes. It is the fear of illness that influences the adoption of healthy behavior. Behavioral intentions are shaped by two main factors: threat assessment (determined by perceived vulnerability, severity of the perceived threat, and the fear generated) and evaluation of coping strategies (based on self-efficacy, perceived effectiveness of responses to the threat, and assessment of the costs involved in responding). Both threat and coping assessment rely on personal factors (personality type, prior experiences) and environmental factors (how risk is communicated, observing others’ responses to similar threats, and observational learning)⁽³²⁾.

Evaluating potential threats and response strategies can sometimes result in maladaptive reactions, including denial, avoidance, fatalism, wishful thinking or losing hope. For instance, if an individual assesses a threat as irrelevant to his situation, he might adopt a coping strategy based on denial, leading to a lack of motivation to take protective measures⁽²²⁾.

Healthcare providers should evaluate how patients are affected by the health threat and perceive its severity, tailoring health recommendations accordingly. Pharmacists can engage patients in discussions about the advantages and disadvantages of adopting desirable behaviors, identifying barriers to change and finding solutions. To increase the perceived threat, healthcare professionals can emphasize the potential negative consequences of problematic behaviors and highlight the patient’s vulnerability based on their medical history. However, negative information should be balanced with coping strategies and helpful information. Pharmacists and healthcare providers can assess the perceived benefits of adopting positive behaviors and use these as reinforcing factors. Providing factual evidence on the efficacy of specific responses can be helpful, such as illustrating how quitting smoking can reverse lung damage. Additionally, strategies to boost self-efficacy and strengthen the link between intentions and behavior can be employed⁽²⁰⁾.

2.3. Health belief model

The health belief model is one of the most extensively used models in studies of health-related behaviors and studies of adherence to healthy behaviors. This model considers an individual’s likelihood of engaging in healthy behaviors as depending on how the individual perceives his susceptibility to the disease and its severity, namely the perceived risk of contracting a disease and the views about the potential consequences of leaving the disease untreated. When it comes to acting, individuals weigh the benefits of adopting a desirable behavior against the costs of engaging in that behavior. Various incentives can influence the decision to act and adopt the behavior⁽²⁴⁾.

In essence, this model suggests that the likelihood of taking action is higher if there is a strong perceived threat of the disease, with the benefits of the behavior outweighing any barriers, and if certain incentives are in place. The components of this model help in understanding the nature of the health threat and its various impacts. They also propose potential protective actions that can be taken and assess their value, as well as evaluate the resources and skills required for such actions.

Additionally, how information about the disease is communicated can be influenced by existing beliefs about the health problem, and an individual’s attention can be influenced by the way a health threat is presented and emphasized⁽⁶⁾.

Motivational interviewing based on health belief model guides the health professional in detecting obstacles to medication adherence using concepts like perceived susceptibility and perceived severity of the disease. Based on the identified obstacle triggers, counselors use the motivational interviewing approach to communicate and motivate patients, helping them create plans to change these triggers, thus promoting behavioral changes that support drug adherence and treatment success⁽²⁵⁾.

2.4. Self-regulatory model of illness

In contrast to social cognitive models, this model presents distinct characteristics of the connections between cognition, motivation and behavior⁽²⁶⁾. The self-regulatory model of illness is based on reducing the existing discrepancy between the current state (e.g., illness) and a desired future state (e.g., health status or disease attenuation). The concept of self-regulation comprises three components:

• Disease representation, which can be triggered by internal cues (e.g., symptoms) or external information about the disease and its risks.

• Development and implementation of a disease management plan.

• Evaluation of the outcomes resulting from actions taken according to the plan.

These components influence each other through feedback, so the individuals enter a process in which they move from one phase to another.

The limitations of the process in terms of increasing adherence to treatment come from the fact that it is too complex and difficult to operationalize. The empirical support of the model comes mostly from studies which have shown that representations of disease quite accurately predict rehabilitation after acute events such as acute myocardial infarction⁽²⁷⁾ or adherence to various antihypertensive drug treatments⁽²⁸⁾ or antiasthmatics⁽²⁹⁾.

The model is particularly effective in elucidating behavioral changes required in response to an immediate threat, such as an acute illness or a worsening of a chronic disease. However, it is less applicable in indicating behavioral changes needed for managing situations where the threat is not imminent or is low, such as when receiving treatment for an asymptomatic chronic disease⁽⁶⁾.

According to this model, several approaches can be suggested to improve medication adherence. Healthcare professionals can help the patient to create more precise disease representations, using appropriate strategies to highlight threats based on protection motivation theory. Patients should be informed about the potential long-term consequences of not adhering to treatment plans. Additionally, doctors, pharmacists and other healthcare providers can offer adjustment strategies and help patients evaluate the effectiveness of their coping behaviors, thus allowing for a review and potential improvement of these strategies⁽⁶⁾.

3. Stage theories

Other theories view change as a step-by-step process that occurs in clearly defined stages. For instance, when it comes to adhering to pharmacotherapy, the process involves adopting the behavior of taking medication and then maintaining this behavior over time. Each stage presents distinct challenges and obstacles that individuals must overcome. Therefore, interventions aimed at enhancing adherence are more successful when they consider the specific stages of the process and address the unique difficulties associated with each phase⁽³⁰⁾.

Transtheoretical model, originally designed to comprehend the process of smoking cessation, can be extended to encompass various other health-influencing behaviors⁽³¹⁾.

The transtheoretical model proposes that behavioral change occurs in specific stages, influenced by factors like the pros and cons of change (the decisional balance), self-efficacy, temptation to return to unhealthy habits (relapse), and coping strategies⁽³¹⁾.

The transtheoretical model outlines six stages of change:

Precontemplation – the individual is not willing to change or denies the existence of a problem, not intending to change his behavior in the following six months.

Contemplation – the individual considers change in the next six months, weighing the pros and cons of continuing the current behavior versus undertaking change.

Preparation – the individual plans to take action in the next month.

Action – the individual actively adopts the changed behavior for at least a few months.

Maintenance – the individual persists in the desired behavior for at least six months, integrating it into his lifestyle and avoiding relapses.

Completion – this stage occurs when the problematic behavior is no longer a challenge, but it may not apply to behaviors recommended for lifelong adherence, such as taking antihypertensive medication indefinitely^(31,32).

Change processes encompass actions carried out throughout the process of transformation, shaped by the individual’s emotions, thoughts and values. Five cognitive or experiential processes exist: realization, accumulation and release of tension, assessment of surroundings, self-evaluation, and self-empowerment (where the individual believes in his capability to change). Additionally, five behavioral processes encompass counter conditioning (seeking alternatives to undesired actions), nurturing relationships (relying on trust, acceptance and assistance), reinforcement of favorable conduct (providing motivation, positive incentives and establishing tangible objectives), environmental control (reorganizing the surroundings to minimize triggers), and societal empowerment (society presenting alternatives to undesirable actions)⁽³³⁾.

The levels of change consider the simultaneous presence and interconnected impact of multiple undesirable behaviors. Approaching these behaviors collectively, as opposed to separately, increases the prospects of achieving successful transformation. For instance, a patient struggling with both high blood pressure and nonadherence might also be grappling with smoking, excessive alcohol intake and a sedentary routine. Attaining the best results necessitates an examination of changes across different dimensions, including environmental adjustments, unhelpful thought patterns and interpersonal concerns like familial relationships⁽³³⁾.

Drawing from the transtheoretical model, motivational interviewing aids individuals in traversing various phases of transformation. Employing patient-centered counseling methods, reflective listening and open-ended inquiries, this approach empowers patients to uncover resolutions for change-related hurdles and diminishes their resistance to change. Significantly, motivational interviewing has demonstrated its efficacy in enhancing patients’ adherence to medication⁽³⁴⁾.

4. Recent developments

4.1. The Theoretical Domains framework

The Theoretical Domains framework combine multiple theories of behavior and behavior change, allowing for cognitive, mood, social and environmental dimensions^(35,36).

Mapping specific aspects conducive to nonadherence in domains such as “Knowledge”, “Skills”, “Social/professional role and identity”, “Beliefs about capabilities”, “Beliefs about consequences”, “Motivation and goals”, “Memory, attention and decision processes”, “Environmental context and resources”, “Social influences”, “Emotion”, “Behavioral regulation” and “Nature of the behaviors” creates opportunities for designing targeted interventions to enhance medication adherence⁽³⁵⁾.

4.2. The Medication Adherence Context and Outcomes framework

An organizational framework could organize the multitude of adherence determinants.

An ecological perspective on medication adherence was proposed by Berben et al. in 2012⁽³⁷⁾. Patients’ behavior is influenced by various factors at different levels, including patient-level factors, micro-level factors (provider and social support), meso-level factors (healthcare organization), and macro-level factors (health policy)⁽³⁸⁾. To comprehensively understand medication adherence and effectively implement interventions to improve it, it is essential to consider the impact of these factors at all levels⁽³⁷⁾.

The MACO (Medication Adherence Context and Outcomes) framework redefines medication adherence as a result that appears from a sequence of processes unfolding in diverse, yet interconnected contexts. In doing so, the MACO framework addresses an existing gap by providing an organized structure that reflects the patient’s experience as they interact with the healthcare system and manage prescribed medications, something not explicitly outlined in other models⁽³⁸⁾.

The MACO framework encompasses a range of settings (such as clinics, pharmacies and patient residences) and situation-specific procedures (like medication choices, prescription approaches, and home medication organization) that impact the adherence behaviors towards medications. It underscores approaches centered on the patient’s needs and aimed at achieving tangible results, customizing them to ensure optimal management of medications for better adherence. The framework primarily hones in on the processes related to medication usage and quantifiable outcomes tied to adherence, encompassing initiation, execution, discontinuation and persistence of drug therapy. By providing a comprehensive structure, it serves as a valuable roadmap for designing interventions to enhance adherence and choosing suitable measurements of adherence metrics based on the specific processes and context under examination⁽³⁸⁾.

Conclusions

Various theoretical perspectives strive to elucidate, explain and predict medication adherence. Given the intricate nature of human behavior, none of these theoretical frameworks stand as a comprehensive solution. Consequently, devising dependable and impactful interventions to enhance long-term and consistent medication adherence, particularly for chronic therapies, presents a challenge. While multifaceted interventions tend to yield the most favorable outcomes, even these strategies, within the constraints of limited resources, must be judiciously selected and applied to individuals who can derive the greatest advantages from them. 
 

Conflict of interest: none declared

Financial support: This article was published with the support granted by the project entitled “Net4SCIENCE: Applied doctoral and postdoctoral research network in the fields of smart specialization Health and Bioeconomy”, project code POCU/993/6/13/154722.

This work is permanently accessible online free of charge and published under the CC-BY.