# Re‐evaluating age‐related attention‐deficit/hyperactivity disorder (ADHD) symptom trajectories using the Japanese ADHD Rating Scale‐5

## TL;DR

This study uses a new Japanese ADHD rating scale to assess how ADHD symptoms change with age in children and how treatment affects them.

## Contribution

The study provides new insights into ADHD symptom trajectories and treatment effects using the newly developed Japanese ADHD Rating Scale-5.

## Key findings

- ADHD groups had significantly higher inattention and hyperactivity-impulsivity scores compared to non-ADHD groups.
- Hyperactivity-impulsivity scores decreased with age, while inattention scores remained stable across age groups.
- Pharmacological treatment was not linked to symptom scores but was associated with higher functional impairment scores.

## Abstract

Attention‐deficit/hyperactivity disorder (ADHD) is a neurodevelopmental disorder characterized by inattention (IA), hyperactivity, and impulsivity. In 2022, the Japanese version of the ADHD Rating Scale‐5 (ADHD‐RS‐5) was released based on DSM‐5. Although there are several changes compared to the previous version, few clinical studies have been conducted using the ADHD‐RS‐5. This study aimed to re‐evaluate ADHD‐related characteristics by age group in pediatric psychiatric outpatients, using the ADHD‐RS‐5 regardless of diagnosis, and compare these findings with previous research.

Participants were all patients aged 5–17 years who visited the Psychiatry Clinic of Tokiwa Hospital or the Tokiwa Child Development Center (Child Psychiatry Clinic) during the study period. Of 503 children, 452 met the inclusion criteria. Primary caregivers completed the ADHD‐RS‐5. Symptom and functional impairment scores were compared by ADHD diagnosis and age group. In the ADHD group, scores were also compared based on pharmacological treatment.

IA and hyperactivity–impulsivity (HI) scores were significantly higher in the ADHD group. Functional impairment scores did not differ significantly in some age groups. HI scores were lower in older age bands, whereas IA scores did not differ significantly across age groups; the cross‐sectional patterns are compatible with relative stability of inattentive symptoms but do not establish longitudinal persistence. Pharmacological treatment was not linked to symptom scores but was associated with higher impairment scores.

Our findings using the ADHD‐RS‐5 showed results consistent with previous reports regarding age‐specific symptom characteristics of ADHD, while also providing new insights into treatment options for ADHD. Clinicians may consider both symptom severity and functional impact when initiating pharmacotherapy. Given medication approval from age 6 in Japan, accurate assessment and diagnosis remain essential, and the ADHD‐RS‐5 may support decision‐making when interpreted alongside clinical judgment and multi‐informant input.