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A study examining children with ADHD found that a greater discrepancy in sleep time between school nights and weekend nights, known as social jetlag, correlates with poorer cognitive functioning. Time spent in bed and sleep disturbances, however, did not show a relationship with cognitive performance. The study was published in the Journal of Attention Disorders.
Attention-deficit/hyperactivity disorder (ADHD) is a neurodevelopmental disorder characterized by persistent patterns of inattention, impulsivity, and hyperactivity that interfere with daily functioning. It typically begins in childhood, but can continue into adolescence and adulthood. Common symptoms include difficulty staying focused on tasks, forgetfulness, impulsiveness, restlessness, and difficulty organizing and completing tasks. ADHD can have a significant impact on various aspects of life, including academic performance, work, and relationships.
Sleep disturbances are very common in children with ADHD. Studies on this topic report that between 40% and 70% of children with ADHD experience at least some form of sleep problems. Children with ADHD who also have sleep problems tend to have more severe symptoms of ADHD. They often suffer from other types of mental health issues as well, and are more likely to experience impairments in daily functioning. Additionally, drugs typically used to treat ADHD (e.g., Ritalin) tend to increase sleep disturbances.
Study author Xueqi Qu and her colleagues wanted to explore the sleep characteristics of children with ADHD and examine whether they are associated with their cognitive performance. They focused on time spent in bed, sleep disturbances, and social jetlag. The researchers hypothesized that less time in bed, more significant sleep disturbances, and higher social jetlag would correlate with poorer cognitive performance.
“Time in bed” refers to the duration a child spends in bed, from bedtime to waking up. Sleep disturbances include disruptions in normal sleep patterns, such as difficulty falling or staying asleep, waking too early, or experiencing restless or unsatisfying sleep. Social jetlag is the discrepancy in sleep timing between school nights and weekends.
The study involved 350 children diagnosed with ADHD, aged between 5 and 12. Of these participants, 71% were boys, and 74% had commercial medical insurance. Additionally, 56% were White.
Caregivers of the children completed questionnaires about sociodemographic data and the children’s sleep characteristics and rated them on various behavioral aspects. The children underwent assessments to measure cognitive functions, including working memory, attention, processing speed, visually-based reasoning, and language-based reasoning.
The results showed that children slept an average of 10 hours on school days, with individual sleep times varying from 6.5 to 12.5 hours. On weekends and free days, the average sleep time was 10.3 hours, ranging individually from 6.5 to 14 hours. Approximately half of the children experienced at least one type of sleep disturbance, with 10% having more than three disturbances. The most common disturbances included difficulty in falling asleep, waking up, and restlessness.
Sleep time and sleep disturbances were not associated with cognitive performance, but social jetlag was. Children with longer jetlag tended to have lower processing speed, visually-based reasoning, and language-based reasoning. The average social jetlag among the studied children was one hour.
“Social jetlag among children occurs due to the changes in rules and routines within households between school/weekdays and weekends,” the study authors concluded. “Parents naturally provide more freedom over the weekends when these demands are absent, opposed to during the week. When time in bed is increasingly different between weekends and weekdays, this can perturb the natural circadian rhythms, leading to poorer cognition and mental acuity.
“Our findings suggest keeping consistent routines for children with ADHD could improve learning and attention. From the perspective of school, delaying the school start times by up to an hour has been proven to be an effective approach to reduce social jetlag.”
The study sheds light on the link between sleep characteristics and cognitive performance. However, it should be noted that the design of the study does not allow any cause-and-effect conclusions to be derived from the data. As much as it is possible that social jetlag causes worse cognitive performance, it is also possible that there is a third factor responsible both for social jetlag and worse cognitive performance. This is not the only alternative possibility.
The paper, “Association of Time in Bed, Social Jetlag, and Sleep Disturbances With Cognitive Performance in Children With ADHD”, was authored by Xueqi Qu, Luther G. Kalb, Calliope Holingue, Darlynn M. Rojo-Wissar, Alison E. Pritchard, Adam P. Spira, Heather E. Volk, and Lisa A. Jacobson.