nonadherence

Nonadherence, in medical contexts, refers to the extent to which a patient’s behavior falls short of agreed recommendations for treatment. It encompasses not taking medications as prescribed, missing doses, failing to follow dietary or activity guidelines, or missing follow-up appointments. Nonadherence is commonly categorized as primary nonadherence (not initiating prescribed therapy) or secondary nonadherence (starting but not continuing or adhering to the regimen). In some discussions, nonadherence to lifestyle recommendations is included.

Causes are multifactorial. Patient-related factors include beliefs about the necessity of treatment and concerns about adverse effects, forgetfulness, low health literacy, mental health issues, and socioeconomic barriers. Therapy-related factors include complex regimens, polypharmacy, side effects, and delayed perceived benefits. System-level factors include cost and access barriers, fragmented care, limited time for counseling, and poor patient–provider communication.

Measurement is challenging. Direct methods detect drug or metabolite levels but are used selectively. Indirect approaches include patient self-report instruments, pharmacy refill records, medication possession ratios, and electronic monitoring of dosing events. No single method is perfect, and multiple approaches are often used.

Consequences of nonadherence can be significant, reducing treatment effectiveness, leading to poorer disease control, higher rates of complications, hospitalizations, and increased health care costs. It can also confound assessments of therapeutic efficacy in research settings.

Strategies to improve adherence focus on simplification of regimens (eg, once-daily dosing, fixed-dose combinations), clear and ongoing patient education, shared decision-making, reminders and digital supports, addressing side effects, and reducing financial and access barriers. Effective adherence support is typically tailored to individual needs and involves coordinated care.