Intentional and Unintentional Medication Adherence with the MMAS-8: Insights from Academic Research

Medication adherence—taking medications as prescribed—is a cornerstone of managing chronic conditions, yet many patients struggle to follow their regimens. The 8-item Morisky Medication Adherence Scale (MMAS-8) is a widely used tool that helps researchers and clinicians understand why patients may not adhere, distinguishing between intentional non-adherence (e.g., deliberately skipping doses) and unintentional non-adherence (e.g., forgetting to take a dose). In this blog, we explore key academic studies that have leveraged the MMAS-8 to investigate these dimensions of adherence, with a special focus on a groundbreaking 2010 study in Diabetes Research and Clinical Practice that validated the scale and highlighted its ability to differentiate intentional and unintentional non-adherence.
What is the MMAS-8?
The MMAS-8 is a straightforward, self-reported questionnaire with eight questions designed to capture medication-taking behaviors. It includes items like “Do you sometimes forget to take your medication?” (unintentional) and “Have you ever cut back or stopped taking your medication without telling your doctor because you felt worse when you took it?” (intentional). Scored from 0 to 8, a score of 8 indicates high adherence, 6 to <8 medium adherence, and <6 low adherence. Its ability to separate intentional and unintentional non-adherence makes it invaluable for tailoring interventions to specific patient needs.
Let’s dive into the studies that showcase the MMAS-8’s impact, starting with the pivotal 2010 study.
1. The Groundbreaking 2010 Study: Validating MMAS-8 in Diabetes Care
Article Title: Validation and Reliability of an Eight-Item Morisky Medication Adherence Scale (MMAS-8) in Type 2 Diabetes
Source: Diabetes Research and Clinical Practice
Publication Date: 2010
Details: This landmark study introduced a groundbreaking perspective by validating the MMAS-8 in patients with type 2 diabetes. Conducted with a diverse cohort, the study confirmed the scale’s reliability (Cronbach’s α ≈ 0.83) and validity, demonstrating its ability to distinguish intentional non-adherence (e.g., stopping medication due to side effects or beliefs about efficacy) from unintentional non-adherence (e.g., forgetfulness or carelessness). Factor analysis revealed two distinct dimensions, allowing researchers to isolate these behaviors. The study showed that intentional non-adherence was often linked to patient beliefs, while unintentional non-adherence correlated with logistical barriers. This differentiation paved the way for targeted interventions, such as education for intentional non-adherence and reminders for unintentional non-adherence.
Key Takeaway: This study established the MMAS-8 as a robust tool for assessing adherence in diabetes, highlighting its unique ability to separate intentional and unintentional non-adherence for more effective interventions.
2. MMAS-8 in Psychiatric Care: Adherence in Mental Health
In a 2014 study published in the International Journal of Clinical and Health Psychology, researchers applied the Spanish MMAS-8 to 967 psychiatric outpatients. The scale demonstrated strong construct validity and a single-factor structure, effectively distinguishing intentional non-adherence (e.g., avoiding medication due to side effects) from unintentional non-adherence (e.g., forgetting doses). It correlated significantly with tools like the Drug Attitude Inventory and revealed adherence variations across mental health diagnoses.
Citation: De las Cuevas, C., et al. (2014). Psychometric properties of the eight-item Morisky Medication Adherence Scale (MMAS-8) in a psychiatric outpatient setting. International Journal of Clinical and Health Psychology.
Key Takeaway: The MMAS-8 helps pinpoint whether psychiatric patients’ non-adherence is driven by beliefs or practical barriers, enabling tailored mental health interventions.
3. Cancer Pain Management: Intentional vs. Unintentional Non-Adherence
A 2021 study in Oncology Nursing Forum used the MMAS-8 to assess adherence to analgesics in cancer patients. It found that 51% of participants took only up to 60% of prescribed doses. The MMAS-8 identified intentional non-adherence (e.g., stopping medication when feeling better or worse) and unintentional non-adherence (e.g., forgetting doses), helping uncover barriers like misconceptions about analgesics or logistical challenges.
Citation: Meghani, S. H., et al. (2021). A pilot study to identify correlates of intentional versus unintentional nonadherence to analgesic treatment for cancer pain. Oncology Nursing Forum.
Key Takeaway: The MMAS-8 is critical for understanding adherence challenges in cancer pain management, guiding targeted support strategies.
4. Diabetes and MMAS-8: Two Factors of Non-Adherence
A 2016 study in SAGE Open Medicine explored the French MMAS-8 in type 2 diabetes patients. Factor analysis identified two sub-scales: one for intentional non-adherence (e.g., altering doses due to beliefs and another for one for unintentional non-adherence (e.g., forgetting). This structure allowed separate assessment of these behaviors, supporting the findings of the 2010 study and reinforcing the scale’s utility for targeted interventions.
Citation: Zongo, A., et al. (2016). Revisiting the internal consistency and factorial validity of the 8-item Morisky Medication Adherence Scale. SAGE Open Medicine.
Key Takeaway: The MMAS-8’s two-factor structure enhances its ability to address specific adherence issues in diabetes care.
5. Chronic Pain: Cultural Adaptations of MMAS-8
A 2021 study in Annals of Palliative Medicine evaluated a modified MMAS-8 in Chinese chronic pain patients. Factor analysis confirmed two dimensions—intentional and unintentional non-adherence—explaining 62.978% of variance. Cultural differences affected some item loadings, but the scale distinguished intentional (e.g., altering doses) from unintentional (e.g., forgetting) behaviors, highlighting the need for cultural adaptations.
Citation: Yang, Y., et al. (2021). Reliability and validity of a modified 8-item Morisky Medication Adherence Scale in patients with chronic pain. Annals of Palliative Medicine.
Key Takeaway: The MMAS-8 can be adapted for chronic pain populations, though cultural nuances may require tweaks for accuracy.
6. Community Health: Adherence in General Populations
A 2015 study in Journal of Environmental and Public Health used the Italian MMAS-8 during a health promotion event. It found that 60.9% of non-adherent participants showed intentional non-adherence (e.g., stopping medication without consulting a doctor), while 13.4% were unintentionally non-adherent (e.g., forgetting). Education and smoking habits influenced adherence.
Citation: Napolitano, et al. (2015). Self-assessment of adherence to medication: A case study in Campania region community-dwelling population. Journal of Environmental and Public Health.
Key Takeaway: The MMAS-8 reveals adherence patterns in community settings, linking intentional non-adherence to misconceptions.
Why These Studies Matter
The 2010 Diabetes Research and Clinical Practice study set the stage for the MMAS-8’s widespread use by validating its ability to distinguish intentional and unintentional non-adherence. This breakthrough has shaped subsequent research, enabling clinicians to understand whether non-adherence stems from patient beliefs (intentional) or practical barriers (unintentional). Across conditions—diabetes, mental health, cancer, and chronic pain—the MMAS-8 helps design interventions like patient education for intentional non-adherence or reminders for medication adherence, improving patient outcomes.
Limitations to Understand
The MMAS-8 isn’t flawless. Its internal consistency is moderate (Cronbach’s α ≈ 0.67–0.77 in some studies), and cultural differences can affect responses. Its sensitivity may be low in certain populations, such as those with treatment-resistant hypertension (26%). Additionally, the scale’s copyrighted status requires permission for use, prompting some to consider alternatives like the Medication Adherence Questionnaire (MAQ) or MARS-5.
Wrapping Up
From the pioneering 2010 study to recent applications, the MMAS-8 has revolutionized how we approach medication adherence. By separating intentional and unintentional non-adherence, it offers actionable insights for improving patient outcomes across diverse conditions. Whether addressing misconceptions in diabetes care or logistical barriers in cancer pain management, the MMAS-8 remains a cornerstone of adherence research.
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Note: This blog is based on research available as of June 10, 2025, at 2:30 PM PDT.*