BackgroundAttention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder that often persists into adulthood, negatively impacting occupational, social, and economic outcomes. The Adult ADHD Investigator Symptom Rating Scale (AISRS) is a clinician-administered tool designed to evaluate ADHD symptom severity and treatment response. However, a validated Japanese version is not available. This study evaluated the reliability and convergent validity of the Japanese version of the AISRS (AISRS-Japanese) in adults with ADHD.MethodsFollowing linguistic validation procedures, the AISRS was translated into Japanese and reviewed by clinicians for conceptual and clinical equivalence. This was a multicenter, longitudinal, non-interventional study assessing the psychometric properties of the AISRS-Japanese. The evaluation instruments were the AISRS-Japanese, the Adult ADHD Self-Report Scale (ASRS-Japanese version), and the Clinical Global Impressions-Severity (CGI-S) scale. Reliability assessments included internal consistency (Cronbach’s alpha), test-retest, intra-rater, and inter-rater reliability (intraclass correlation coefficient [ICC] and G(q,k) coefficients). Convergent validity was evaluated via Pearson’s correlation between AISRS-Japanese and ASRS-Japanese version scores.ResultsIn total, 61 adults with ADHD were included in the analysis. The mean age of the study participants was 34 years, 52.5% (32/61) were male, and 75.4% (46/61) were moderately ill (CGI-S score of 4). The AISRS-Japanese demonstrated internal consistency for the total scale (Cronbach’s alpha = 0.83) and the hyperactivity/impulsivity and inattention subscales (0.76 and 0.75, respectively). Test-retest reliability was good (ICC: total, 0.77; hyperactivity/impulsivity, 0.79; inattention, 0.83), as was intra-rater reliability (ICC: total, 0.76; hyperactivity/impulsivity, 0.77; inattention, 0.83). Inter-rater reliability was excellent (G(q,k): total, 0.96; hyperactivity/impulsivity, 0.97; inattention, 0.96). Convergent validity of the ASRS-Japanese version was high (correlation coefficient: total, 0.89; hyperactivity/impulsivity, 0.88; inattention, 0.84).ConclusionThese results provide evidence supporting the reliability and convergent validity of AISRS-Japanese as a semi-structured tool for assessing ADHD symptoms in Japanese adults.