Longitudinal Associations Between Sleep Habits and Attention-Deficit Hyperactivity Disorder Symptoms in Japanese Children Attending Regular Classrooms.

AIMS: To characterize cross-sectional and one‑year longitudinal associations between sleep disturbance and attention-deficit hyperactivity disorder (ADHD) symptom severity in Japanese children diagnosed with ADHD.

METHODS

Forty-five children (six to 13-years-old) with clinically diagnosed ADHD, who were unmedicated and attending regular classrooms, were recruited online. At baseline, parents completed the Conners 3 (Japanese parent form), the Social Responsiveness Scale, Second Edition (SRS-2), and the Japanese Sleep Questionnaire for Elementary Schoolers (JSQ‑ES). Thirty-eight participants completed identical assessments at one‑year follow‑up. Pearson's correlation coefficients examined relationships between JSQ‑ES total T‑scores and Conners 3 Global Index (CGI) and its six factor scales, cross‑sectionally and in change scores (follow‑up minus baseline). Hierarchical multiple regression analyses assessing which ADHD dimensions were predicted by sleep problems after controlling for demographic and autism spectrum disorder (ASD) variables were conducted.

RESULTS

Cross‑sectionally, JSQ‑ES total T‑scores correlated significantly with CGI (r = 0.376, p = 0.010) and with the inattention (IN), hyperactivity/impulsivity (HY), learning problems (LP), and aggression (AG) subscales (all p < 0.05). Longitudinally, only HY changes correlated with JSQ‑ES change scores (r = 0.394, p = 0.014). Regression models confirmed that sleep problems independently predicted overall ADHD severity and AG at baseline, in addition to predicting HY over time.

CONCLUSIONS

Sleep disturbances are closely linked to ADHD symptom severity, particularly longitudinal hyperactive/impulsive behaviors, in children, even those without clinical sleep disorder diagnoses. These findings highlight the importance of assessing sleep quality in all children with ADHD, even without major sleep disorders. To draw definitive conclusions about whether improving sleep hygiene reduces HY, further intervention studies are warranted.