Understanding initial medication adherence amongst major depressive disorder patients: A scoping review

Area of Science:

• Pharmacology
• Psychiatry
• Health Services Research

Background:

• Initial medication adherence is critical for successful pharmacotherapy in major depressive disorder (MDD).
• Inconsistent definitions and measurements of medication initiation hinder understanding of its impact on patient outcomes.

Purpose of the Study:

• To systematically review definitions, operationalization, and measurement of initial medication adherence (IMA) in MDD patients starting antidepressant medications (ADM).
• To identify variability and inform the development of standardized frameworks for evaluating IMA.

Main Methods:

• Scoping review of literature from PubMed, Embase, Scopus, and PsycInfo (inception to March 2025).
• Inclusion criteria: studies defining, measuring, and evaluating initiation in MDD patients prescribed SSRIs or SNRIs.

Main Results:

• 13 studies met inclusion criteria from 1,636 initially identified.
• Significant variability found in definitions (duration from 1 fill to 6 months) and measurement methods (claims, self-report, pill counts, electronic monitoring).
• Lack of standardization in operationalizing adherence status and differing adherence thresholds were observed, with patient demographics and prior treatment influencing initiation.

Conclusions:

• Substantial heterogeneity exists in defining and measuring IMA in MDD.
• Standardized frameworks integrating pharmacological principles and real-time adherence data are necessary for improved clinical and research applications.
• A consistent approach to define, operationalize, and evaluate IMA is needed for first-line MDD therapies.