Development and preliminary validation of the treatment adherence rating scale

Background and objectives: Patient adherence to treatment is an important barrier to the implementation of evidence-based psychological treatments (EBPTs). There is a need for simple and deployable measures of patient adherence to treatment for use across EBPTs. The Treatment Adherence Rating Scale (TARS) was developed and validated in two samples. Methods: This study includes two samples: adults with Major Depressive Disorder who received Cognitive Therapy for depression (Sample 1; N = 48, mean age = 44.27 years), and at-risk adolescents who received either the Transdiagnostic Sleep and Circadian Intervention or Psychoeducation (Sample 2; N = 176, mean age = 14.77 years). Factor structure of the TARS scores was examined via Exploratory Factor Analyses (EFA) in Sample 1 and Confirmatory Factor Analyses (CFA) in Sample 2. Internal consistency, predictive validity, and construct validity of the TARS scores were examined. Results: Results from EFA in Sample 1 supported a one-factor model. Results from CFA in Sample 2 suggested that a two-factor model (i.e., agreement and compliance) fit better than a one-factor model. TARS scores from both samples demonstrated adequate predictive validity with primary clinical outcomes and construct validity with treatment expectations. Limitations: The sample was small with two specific populations. Future research should focus on other patient populations, a larger population, and other EBPTs. Future research examining patient ratings of these items are needed for further validation of the TARS. Conclusions: Preliminary findings support the use of a two-factor model and highlight the potential utility of a simple measure of patient adherence to treatment across age and diagnostic groups.