Models and determinants language

The World Health Organization identifies five dimensions that influence medication adherence: social and economic, healthcare system and team, condition-related, therapy-related, and patient-related factors, providing a comprehensive framework for healthcare professionals to systematically assess and address non-adherence in their patients.¹ Poor medication adherence contributes to suboptimal clinical outcomes globally, with studies suggesting that approximately 50% of patients with chronic conditions do not take medicines as prescribed.¹Understanding the multidimensional nature of adherence barriers, the conceptual difference between barriers and determinants, and the growing recognition of treatment burden empowers clinicians to design more effective, patient-centred interventions that respect the complexity of medication-taking behaviour in real-world settings.^1,2

What is the WHO “Five dimensions” model of adherence barriers?

The WHO five dimensions model categorises adherence influences into five interrelated domains: social and economic factors, healthcare team and system-related factors, condition-related factors, therapy-related factors, and patient-related factors.¹ This model recognises that non-adherence is rarely caused by a single issue but emerges from complex interactions across multiple levels of influence.¹

Social and economic factors include poverty, unemployment, low health literacy, lack of social support, unstable housing, and cultural or language barriers that affect a patient’s capacity to obtain, understand, and follow treatment recommendations.¹ A patient may fully understand the importance of a medication but lack financial resources to purchase it consistently, or may face cultural beliefs that conflict with treatment approaches.^1,2

Healthcare team and system-related factors encompass accessibility of care, quality of patient-provider relationships, consultation time constraints, continuity of care, inadequate health insurance reimbursements, and the complexity of navigating health systems.^1,2 Short consultation times, poor communication, or lack of follow-up can leave patients confused about treatment plans or feeling unsupported.^1,2

Condition-related factors refer to characteristics of the disease, including symptom severity, rate of progression, comorbidities, disability, and psychological consequences such as depression or anxiety.¹ Asymptomatic conditions present challenges because patients may not perceive the consequences of non-adherence and be less motivated to continue prescribed treatment.²

Therapy-related factors involve aspects of the treatment regimen: complexity, dosing frequency, duration, side effects, and the immediacy of beneficial effects.^1,2 Regimens requiring multiple daily doses or causing bothersome side effects create practical and psychological barriers to consistent adherence.^3,4

Patient-related factors include knowledge, beliefs, attitudes, expectations, motivation, self-efficacy, cognitive function, and mental health status.¹ The WHO framework explicitly positions patient-related factors within the broader context of the other four dimensions, recognising that patient beliefs and behaviours are shaped by social, economic, system, condition, and therapy factors—not by personal failing alone.¹

The five dimensions framework guides systematic assessment in clinical encounters, prompting healthcare professionals to explore barriers across all domains rather than assuming non-adherence reflects only patient motivation or forgetfulness.^1,2

Once clinicians are working with a multi-dimensional framework, a related conceptual question arises: are all of these factors “barriers,” or do some operate differently? This distinction between barriers and determinants has important implications for both research design and clinical reasoning.

What is the difference between “barrier” and “determinant” in adherence research?

In adherence research and clinical practice, “barrier” and “determinant” are related but conceptually distinct terms.⁵determinant is any factor—positive or negative—that influences adherence behaviour, including enablers, facilitators, and obstacles. Determinants can increase adherence (facilitators) or decrease it (barriers), and exist across all levels of influence identified in frameworks like the WHO five dimensions model.⁵

A barrier specifically refers to an obstacle or hindrance that impedes adherence, making it more difficult for patients to take medications as prescribed.⁵Common examples include high medication costs, complex dosing schedules, side effects, forgetfulness, lack of social support, or poor health literacy,^3,4

This distinction matters clinically because focusing only on “barriers” can lead to a deficit-based approach that overlooks patient strengths, resources, and facilitators that can be leveraged to support adherence.³ A determinants-focused approach encourages healthcare professionals to assess both obstacles and enablers: asking not only “What is preventing this patient from taking their medication?” but also “What resources, motivations, or supports does this patient have that we can build upon?”^3,6

From a behaviour change perspective, the Theoretical Domains Framework (TDF) and the Capability, Opportunity and Motivation (COM-B) model conceptualise determinants across capability, opportunity, and motivation domains, recognising that behaviour change requires addressing multiple interacting factors.^3,6 For example, a patient may have adequate knowledge (capability) and access to medication (opportunity) but lack confidence in managing side effects (motivation)—or conversely may be highly motivated but face structural barriers such as pharmacy access (opportunity).⁵

In clinical conversations, using determinants language can feel less judgmental and more collaborative than barrier-focused language, particularly when discussing patient-related factors. Asking “What factors influence your medication-taking?” invites broader reflection than “What barriers do you face?”, opening space for patients to share both challenges and resources.

What is “treatment burden” and how does it relate to adherence?

Treatment burden refers to the workload imposed by healthcare on patients, and the impact this workload has on patient functioning and wellbeing.^7,9 It not only encompasses medication intake but also attending appointments, undergoing tests, monitoring symptoms, navigating healthcare systems, managing side effects, coordinating care across multiple providers, and making lifestyle modifications.^7,9

Treatment burden operates as a key determinant of adherence because excessive burden can overwhelm patients’ capacity to follow treatment plans, even when they are motivated and understand the importance of therapy.⁸ The concept emerged from recognition that contemporary healthcare—particularly for chronic and multimorbid conditions—often demands substantial patient work that may exceed individual capacity, creating a mismatch between treatment demands and capacity of the patient.⁸

Components of treatment burden

Treatment burden encompasses multiple domain:^7,9

Practical demands: appointment scheduling, travel to clinics, pharmacy visits, insurance paperwork, medication administration logistics
Cognitive demands: understanding treatment plans, monitoring symptoms, making treatment decisions
Financial demands: medication costs, transportation, time away from work, expenses not covered by insurance
Social and emotional demands: impact on relationships, worry, anxiety about health and treatment

The cumulative complexity model

The cumulative complexity model proposes that when treatment demands exceed a patient’s capacity to respond, non-adherence, clinical deterioration, and poorer quality of life may result.⁸ Capacity is influenced by factors including health literacy, cognitive function, social support, financial resources, physical functioning, and emotional resilience. The model suggests that as the number of conditions and treatments increases, burden may rise while capacity simultaneously declines; however, direct empirical evidence quantifying this interaction in individual patients remains limited, and no claim is made about its universality.⁸

The minimally disruptive medicine framework

Reducing treatment burden is increasingly recognised as essential to minimising non-adherence. The Minimally Disruptive Medicine (MDM) framework proposes that clinical care should be designed to achieve treatment goals while imposing the smallest possible burden on patients’ lives.¹⁰Applied to adherence, MDM encourages clinicians to ask not only “Is the patient taking their medication?” but “Is the treatment we have prescribed proportionate to this patient’s capacity to manage it?” This reframes non-adherence as a shared responsibility between patient and health system, rather than a patient-level failure.¹⁰

Healthcare professionals can assess treatment burden through brief conversational prompts: “How are you managing all the demands of your treatment?” or “What parts of your treatment plan feel most difficult or time-consuming?”^4,7,15When burden is high, appropriate responses include reviewing the necessity of each treatment component, simplifying regimens where clinically appropriate, addressing financial barriers, and engaging in shared decision-making about treatment goals and trade-offs.^11,15

What you can do

The following steps are evidence-informed and should be adapted to your clinical context, patient population, and local guidelines:

Conduct systematic adherence assessment using the WHO five dimensions framework to explore social/economic, system, condition, therapy, and patient-related determinants.^{1, 2}
Use open-ended, non-judgmental questions such as “How has it been going with your medications?” to elicit honest disclosure ^4,10
Assess treatment burden explicitly by asking about the practical, financial, cognitive, and emotional demands of the treatment plan^4,9,13
Apply the COM-B and TDF to map barriers and facilitators before selecting a behaviour change technique^3,6
Engage in shared decision-making to align treatment plans with patient values, preferences, and capacity, particularly when burden is high¹¹
Simplify regimens where clinically appropriate by reducing dosing frequency or minimising pill burden¹⁵
Enhance health literacy using plain language, teach-back methods, and visual aids⁴
Address practical barriers by discussing medication costs, linking patients to financial assistance programmes, or adjusting appointment schedules^4,15
Build self-efficacy through action planning, problem-solving specific anticipated obstacles, and reinforcing small successes^4,11,12
Arrange structured follow-up to monitor adherence, address emerging barriers, and adjust plans as needed^2,4,12
Strategies should be tailored to individual patients, local contexts, and healthcare system resources. No single approach works universally; effective adherence support requires ongoing collaboration, flexibility, and clinical judgment.

Conclusion

The WHO five dimensions model provides a comprehensive, non-judgmental framework for understanding the complex interplay of factors influencing medication adherence, extending far beyond patient motivation or memory.¹Distinguishing between barriers and determinants encourages healthcare professionals to assess both obstacles and enablers, fostering strength-based, collaborative conversations.⁵ Recognising and addressing treatment burden is essential to reducing non-adherence and improving quality of life in an era of increasingly complex, chronic disease management.⁷

This article was written with the assistance of generative AI technology and reviewed for accuracy.

FAQ

The WHO five dimensions model reflects evidence that non-adherence is rarely caused solely by patient behaviour but emerges from complex interactions among social, economic, healthcare system, condition, therapy, and patient factors.¹Focusing narrowly on patient factors risks blaming individuals for structural or system failures beyond their control, such as unaffordable medications or inadequate healthcare access.¹The multidimensional framework guides comprehensive assessment and intervention across all levels of influence, leading to more effective and equitable adherence support.¹ A 2024 expert consensus update reaffirmed that the WHO five dimensions remain the most widely used framework in adherence research and practice globally, and that approximately 50% of patients with chronic conditions continue to be non-adherent.^1,12

Yes, the five dimensions can be operationalised through brief, structured questions that efficiently explore each domain: “How are you managing costs?” (social/economic), “Are you able to get appointments easily?” (system), “How are your symptoms?” (condition), “How is the medication regimen working for you?” (therapy), “What concerns do you have?” (patient-related).^1,2 Even brief exploration across dimensions yields richer understanding than assuming non-adherence reflects only forgetfulness or lack of motivation.² The questions can be embedded in pre-consultation intake forms or brief screening tools to reduce time burden on the clinician.

No.
Treatment burden is broader than medication burden (total number of medications) or pill burden (daily pill count), encompassing the full workload of healthcare including appointments, monitoring, lifestyle modifications, care coordination, and the financial, cognitive, emotional, and social impacts of treatment.^7,9 Reducing pill burden may decrease treatment burden, but patients may still experience high burden from frequent appointments, complex monitoring requirements, or financial strain even with a simplified medication regimen.^8,12 Validated tools such as the Treatment Burden Questionnaire (TBQ) and the Multimorbidity Treatment Burden Questionnaire (MTBQ) can assess total burden across these domains where clinical feasibility allows.^7,13

Brief conversational questions can effectively assess treatment burden without requiring formal instruments: “How much time does managing your health take each day?”, “What is the hardest part of your treatment plan?”, or “How does your treatment affect your daily life?”.⁷ These open-ended questions invite patients to share what matters most to them and are feasible within routine consultations. Formal tools like the Treatment Burden Questionnaire (TBQ) or Multimorbidity Treatment Burden Questionnaire (MTBQ) can be reserved for research settings or detailed clinical assessment when indicated.^7,13

Systematic reviews identify several effective behaviour change techniques (BCTs) for adherence, including self-monitoring, reminders and cues, problem-solving and action planning, social support, feedback on behaviour, information about health consequences, and implementation intentions.^8,15 A Cochrane review of 182 RCTs found that even the most effective interventions produced modest improvements, and no single technique consistently improved both adherence and clinical outcomes.¹⁴ Combining multiple BCTs tailored to individual determinants generally outperforms single-technique approaches, and interventions grounded in theoretical models show greater alignment with patient needs.^2,9,15

Validate the patient’s experience and engage in shared decision-making to explore alternatives, adjust goals, simplify regimens, or accept reduced treatment intensity if consistent with patient values and safety.¹¹ Non-adherence is not always irrational; patients often make trade-offs between treatment benefits, burdens, and quality of life.⁴ Acknowledging this openly supports therapeutic alliance and collaborative problem-solving rather than confrontation, and aligns with the Minimally Disruptive Medicine principle that care should be proportionate to a patient’s capacity.¹⁰

Evidence from behaviour change research suggests that strength-based approaches that identify and leverage facilitators (existing resources, motivations, and supports) alongside addressing barriers may enhance intervention effectiveness and patient engagement.⁶ Focusing exclusively on deficits can feel discouraging and overlook opportunities to build on what is already working. The TDF and COM-B both include facilitator assessment as a standard component of intervention design, and a balanced assessment of both barriers and facilitators supports more comprehensive, individualised care.⁶

Brief adapted motivational interviewing techniques—including open-ended questions, affirmations, reflective listening, and summarising—can be integrated into consultations of 10–15 minutes to explore ambivalence, support autonomy, and enhance motivation.¹⁶ A systematic review and meta-analysis of 72 randomised controlled trials found that motivational interviewing outperformed traditional advice-giving in approximately 74% of studies across a range of health behaviours including medication adherence.¹⁶ Even brief use of motivational interviewing-consistent communication improves patient satisfaction, disclosure of barriers, and adherence compared to directive styles.¹⁶

The WHO model is primarily a conceptual framework rather than a tested intervention, and direct evidence linking its systematic use to clinical outcomes is limited.¹ However, interventions informed by multidimensional frameworks that address barriers across multiple domains show greater effectiveness than single-focus interventions.^2,4A 2024 expert consensus update reaffirmed the model’s utility in guiding comprehensive adherence assessment, noting that the strongest evidence-based advances over the past two decades have been in multidimensional, theoretically grounded intervention design.¹²

Polypharmacy (concurrent use of multiple medications) contributes substantially to treatment burden through increased pill burden, cognitive demands of managing complex regimens, side effects, drug interactions, costs, and time spent obtaining and taking medications.^8,12The cumulative complexity model suggests that as polypharmacy increases, the balance between treatment workload and patient capacity is increasingly likely to become unfavourable, though the relationship varies considerably across individuals.⁸ Systematic medication review, deprescribing low-value or harmful medications, simplifying regimens, and engaging patients in shared decision-making about treatment priorities can reduce both polypharmacy and treatment burden where clinically appropriate.^10,12,15