Establishing clinically important differences in adults with attention deficit/hyperactivity disorder

Background The adult attention deficit hyperactivity disorder (ADHD) Self‐Report Scale (ASRS) is one of the most widely used patient‐reported outcome measures (PROMs) for evaluating ADHD symptom severity and treatment‐related changes in clinical trials of adults with ADHD; however, clinically important differences (CIDs) for the ASRS remain poorly defined. Aims This study aimed to review how CIDs for the ASRS have been reported in randomised controlled trials (RCTs) of adult ADHD and to establish ASRS‐specific CID values for this population. Methods We first conducted a cross‐sectional literature search to examine the reporting of CID values in RCTs of adult ADHD interventions. We then conducted a secondary analysis of an RCT involving 56 adults with ADHD who received either active or sham transcranial alternating current stimulation. The ASRS total score served as the PROM. An anchor‐based approach using the Clinical Global Impression‐Improvement scale was applied. General linear mixed‐effects modelling estimated mean differences across patient‐defined improvement levels to identify categorical CID thresholds. Results None of the 11 identified studies reported CID values for the ASRS as a PROM in adults with ADHD. The mixed‐effects model indicated that a reduction of approximately 13.39 points in ASRS total score represents a clinically meaningful improvement (CID within‐group ), and a reduction of 19.51 points represents substantial improvement, corresponding to reductions of 29.2% and 42.6% from the baseline, respectively. Additionally, a between‐group difference of 6.13 points in ASRS total score represents a minimal clinically meaningful difference (CID between‐group ), and a 12.25‐point difference represents a moderately meaningful between‐group difference. Conclusions This study provides adult‐ADHD‐specific CID estimates that offer practical benchmarks for interpreting treatment response and informing power calculations in future clinical trials.