Insomnia in children with ADHD affects daytime behaviour and cognitive functioning

Insomnia may play a role in manifestation of attention deficit hyperactivity disorder (ADHD) symptoms and has a negative effect on cognitive abilities of children with ADHD, according to a cross-sectional study by the University of Hong Kong (HKU), the Chinese University of Hong Kong (CUHK) and Alice Ho Miu Ling Nethersole Hospital.

“[Although] insomnia is a common comorbidity in ADHD, with prevalence rates ranging from 25 percent to as high as 71 percent, previous studies only measured sleep problems in general and did not look into whether insomnia symptoms would have impacts on daytime behaviour and cognitive functioning in children with ADHD,” said the researchers.

To investigate these associations, a total of 84 children aged 6–12 years (male, 70 percent) were recruited, including 36 children with ADHD and insomnia, 27 children with ADHD without insomnia, and 21 age-matched healthy controls. [J Clin Sleep Med 2022;doi:10.5664/jcsm.10060]

“Children with ADHD and insomnia showed the highest Children’s Sleep Habits [CSHQ] total score, followed by children with ADHD without insomnia and healthy controls [56.78 vs 51 vs 42.95; p<0.0001],” reported the researchers. “Children with ADHD and insomnia had the highest scores on CSHQ bedtime resistance [10 vs 8.33 vs 7.24; p=0.001], sleep onset delay [2.19 vs 1.41 vs 1.24; p<0.001], and night waking [3.86 vs 3.44 vs 3.1; p=0.002] subscales than children with ADHD without insomnia and healthy controls, with no significant differences between the latter two groups.”

“Insomnia symptoms in children with ADHD were associated with more severe behavioural manifestations of ADHD, including inattention and hyperactivity,” noted the researchers. After controlling for potential confounders (ie, sex, age, and AHDH medication), children with ADHD and insomnia had the highest scores on strengths and weaknesses of ADHD symptoms and normal behaviour scale (SWAN) vs children with ADHD without insomnia and healthy controls (1.48 vs 0.65 vs -0.91; both p<0.01). A similar trend was observed in both SWAN inattention (1.60 vs 0.70 vs -0.73; p<0.01) and hyperactivity (1.38 vs 0.62 vs -1.07; p<0.01) subscales. “This observation was in line with that of previous studies conducted in adults with ADHD, which indicated that insomnia symptoms were significantly associated with ADHD symptomatology, independent of age and sex,” the researchers noted.

After controlling for age, sex, ADHD medication, and SWAN total score, children with ADHD and insomnia also showed significantly poorer performance in cognitive tests, including the Continuous Performance Test (CPT) for sustained attention and the letter-digital test for processing speed (both p<0.05), vs children with ADHD without insomnia and healthy controls.

“These findings highlighted the potential role of insomnia in the manifestation of ADHD symptoms and its negative effect on cognitive abilities [sustained attention and processing speed] in children with ADHD, which might potentially give rise to their frustration, low self-esteem, and academic difficulties,” wrote the researchers.

“Our findings underscored the need to address sleep problems in children with ADHD in a timely manner,” they noted. “Future studies with a longitudinal design are needed to further explore the long-term impacts of insomnia and the effects of sleep-focused intervention on cognitive functioning in children with ADHD.”