Children who suffer regular sleep disturbances may be more likely to receive an ADHD diagnosis in early adolescence, according to a new study.
The study examined the relationship between sleep and ADHD in a large group of Brazilian children born in the same year, and found “a consistent association” between sleep problems like nightmares, restlessness, and difficulty going to sleep at 24 to 48 months of age, and an ADHD diagnosis at 11 years of age.
Researchers said the study of nearly 3,500 children aimed to better understand sleep characteristics as early predictors of attention deficit hyperactivity disorder. While sleep problems are among the most frequent challenges associated with ADHD, few researchers have studied day-time and night-time sleep duration, sleep trajectories, and sleep disturbances as precursors to an ADHD diagnosis.
Analysis revealed that children who experienced difficulties going to sleep at 24 months were about twice as likely (OR=2.05) as their peers to receive an ADHD diagnosis later in childhood. Children who had nightmares at 24 and 48 months were 1.7 and 1.6 times as likely, respectively, of having ADHD. Children who had restless sleep at 48 months were about 1.6 times as likely to receive an ADHD diagnosis.
The new study used data on night-time and day-time sleep duration and sleep disturbances from the 2004 Pelotas Birth Cohort — a longitudinal study of hospital childbirths in the Brazilian city of Pelotas. Researchers analyzed this data from participating children at 12, 24, 48 months, and then 11 years of age, and used it to construct and calculate sleep trajectories and total sleep duration. At the 11-year mark, specialists assessed the children for ADHD and mental health disorders, of which a total of 144 adolescents were diagnosed.
The cohort study derived sleep duration data from maternal reports that answered questions like, “In the last two weeks, at what time did your child go to bed at night?”; “At what time did your child wake up in the morning?”; and, “In the last two weeks, approximately how many naps did your child take during the day?” Data on sleep disturbances also came from yes/no questions posed to mothers about the presence of nightmares and restless sleep.
While trouble falling asleep, nightmares, and restless sleep all appear correlated to a higher likelihood of having ADHD, the researchers found that sleep duration and trajectories were not associated with ADHD. The results also showed that sleep problems may be common to different psychiatric disorders.
“The results suggest that sleep disturbances may be more important ADHD predictors than sleep duration or sleep duration trajectories,” part of the study reads. “However, it may also be considered early markers of other mental disorders.”
The study was limited in some factors. Data on sleep at 11 years and data from ADHD evaluations made at other points was not available, for instance, and sleep and mental health outcomes were evaluated only by mothers’ reports. Still, researchers said the cohort was large and had high follow-up rates.
“This study shows that the relationship between sleep/circadian rhythms and ADHD may be more complex than previously shown by other empirical studies,” the study reads. “Further research exploring temporality and sleep trajectories in the sleep – ADHD association as well as studies exploring the specificity of this relationship are still necessary to narrow this gap in the literature.”