OBJECTIVES: To validate the Medication Adherence Reasons Scale (MAR-Scale) in an adult attention-deficit/hyperactivity disorder (ADHD) population and to describe reasons for nonadherence to oral stimulants among adults with ADHD.

METHODS: Adults (aged ≥18 years) who self-reported being diagnosed with ADHD and were currently being treated with oral stimulants (for ≥3 months) participated in this cross-sectional observational survey. The survey included questions regarding sociodemographic characteristics, ADHD symptom level (Adult ADHD Self-Report Scale Version 1.1 Symptom Checklist [ASRS-v1.1]), medication adherence (MAR-Scale and Morisky Green Levine Medication Adherence Scale [MGLS]), and work productivity loss and non-work activity impairment (Work Productivity and Activity Impairment-General Health [WPAI-GH] questionnaire). MAR-Scale reliability was evaluated using Cronbach’s α, with an α >0.70 being considered acceptable. Pearson correlations assessed MAR-Scale validity versus the MGLS, ASRS-v1.1, and WPAI-GH. Reasons for nonadherence, based on the 19-item MAR-Scale, are reported descriptively using percentages.

RESULTS: A total of 602 respondents completed the survey. The mean ± SD age of respondents was 40.26±14.51 years. Most respondents were female (77.1%), white (89.5%), and employed (65.0%). MAR-Scale overall score demonstrated acceptable reliability when its items were treated as 4 separate domains (Cronbach’s α=0.79) and when all 19 items were considered as one scale (Cronbach’s α=0.80). MAR-Scale and MGLS overall scores were significantly correlated (r=0.65; P<0.001), with both scales classifying approximately 65% of respondents as nonadherent. The most frequently reported reason for nonadherence was “I would have taken it but simply missed it” (33.7%). The MAR-Scale overall score was significantly and positively correlated (all P<0.001) with overall work productivity impairment (r=0.32), activity impairment (r=0.19), and ADHD symptom level (r=0.25).

CONCLUSIONS: The MAR-Scale demonstrated acceptable validity in adults with ADHD. MAR-Scale overall score was significantly and positively correlated with the MGLS overall score, ADHD symptom level, work productivity loss, and non-work activity impairment.