The Weiss Functional Impairment Rating Scale Self-Report has been translated into nine languages and has been widely used in assessing functional impairment of adults with ADHD. This study is a psychometric validation of the WFIRS-S in Japanese. The WFIRS-S-J and other questionnaires were administered to 46 adults with attention-deficit-hyperactivity disorder (ADHD), 104 control adults, and 889 university students. ADHD diagnoses were made using the Japanese semi-structured diagnostic interview for adult ADHD, which is compatible with the DSM-5. All subscales of the WFIRS-S-J had Cronbach's α values of around 0.80. Total scores on the WFIRS-S-J had high test-retest reliability after a 2-week interval. The total score, subscale scores, and 59 of the individual item scores of the 70 items in the WFIRS-S-J were significantly higher in the ADHD group than in the other two groups, although more than half of the items in subdomain G (risk) showed floor effects and did not reach significance. Generally WFIRS-S-J subdomain scores were moderately correlated with scores on the Japanese version of Conners' Adult ADHD Rating Scales Self-Report subscales. WFIRS-S-J scores were also correlated (albeit more weakly; 0.31 ≤ r ≤ 0.55) with Beck Depression Inventory II total scores. The WFIRS-S-J showed acceptable psychometric properties, although further study is necessary.
Keywords: Attention-deficit–hyperactivity disorder (ADHD); Functional impairment; Psychometric properties; Weiss Functional Impairment Rating Scale Self-Report (WFIRS-S).