Theoretical Frameworks in Medication Adherence Research: A Systematic Review Using the ABC Taxonomy

Despite the availability of various frameworks for studying medication adherence, most fail to account for the distinct characteristics of each phase of medication-taking behavior based on the ABC Taxonomy (initiation, implementation, and discontinuation). To address this gap, existing frameworks should be systematically mapped in alignment with the ABC taxonomy to reflect unique conceptual distinctions across these phases.

To assess and classify the theoretical frameworks used in medication adherence research based on the ABC taxonomy.

A systematic literature search was conducted in PubMed and Scopus on 4 June 2025, without publication year restrictions. Eligible studies were empirical medication adherence studies that explicitly applied an identifiable theoretical or conceptual framework to understand, explain, or predict medication adherence and its determinants, or to design, guide, or evaluate interventions aimed at improving medication adherence. The identified frameworks were subsequently mapped to the three medication adherence phases defined by the ABC Taxonomy. The methodological quality of the included studies was critically appraised using the Mixed Methods Appraisal Tool (MMAT), version 2018.

Of 855 retrieved records, 29 met the inclusion criteria, representing 27 distinct theoretical frameworks. Most studies were conducted in the United States (n = 8; 27.58%) and among patients with multiple chronic conditions (n = 6; 20.68%). Only three frameworks (11.1%) addressed all three phases of medication adherence, whereas 20 frameworks (74.07%) focused solely on the implementation phase; three frameworks (11.11%) on implementation and discontinuation, and one examined initiation (3.7%). Most studies (n = 23; 79.31%) used frameworks to conceptualize and explain the multifaceted determinants of medication adherence.

While numerous frameworks have been proposed to understand medication adherence, most predominantly emphasize the implementation phase, leaving the initiation and discontinuation phases underexplored. Current frameworks are predominantly employed to explain factors, predictors, and underlying mechanisms that influence adherence behaviors.