<![CDATA[Adherence to antiretroviral therapy (ART) remains a pivotal determinant of virological suppression and long-term clinical outcomes among people living with HIV (PLHIV). Nevertheless, adherence estimates and determinants frequently differ across settings, partly because of variation in adherence measurement and contextual influences. This narrative review synthesises evidence on factors influencing ART adherence among PLHIV. A literature search was conducted using Google Scholar and ScienceDirect and complemented by manual screening of reference lists to identify relevant studies published between 2015 and 2025. Studies were included if they reported adherence outcomes and/or determinants among PLHIV receiving ART. Five eligible studies were narratively synthesised because adherence measurement tools and reporting formats were heterogeneous, including pharmacy-based indicators such as proportion of days covered, validated questionnaires such as the Simplified Medication Adherence Questionnaire and the Morisky Green Levine Scale, self-report measures, and biological proxies based on antiretroviral concentrations in hair. Across the included studies, adherence levels ranged from suboptimal to high depending on the metric applied, indicating limited comparability across methods. Determinants that recurrently emerged comprised regimen- and treatment-related factors, psychosocial influences, and health-system or structural constraints, particularly pill burden, adverse effects, regimen line, family or partner support, stigma, mental health, service accessibility, appointment logistics, and continuity of care. Overall, the evidence indicates that ART adherence is shaped by an interplay of individual, treatment, and system-level factors, suggesting that adherence interventions should be multi-component and context-tailored, while future research should improve standardisation and transparency in adherence measurement to strengthen comparability.]]>
