There have been indications that infants who have difficulty sleeping are more likely to later develop ADHD in childhood. Would this hold up in a large nationwide cohort study?
Noting that "Norway has several national health registries with compulsory and automatically collected information," and "registries can be linked on an individual level, making it possible to conduct large cohort studies," a Norwegian team of researchers studied the association between sleep-inducing medications prescribed to infants under three years old and diagnoses of ADHD between the ages of five and eleven.
Norway has a national health insurance system that covers all residents, and pays in full for youths under 16 years old. Norwegian pharmacies must register all dispensed prescriptions into a national register as a prerequisite for reimbursement.
The study included all children born in Norway from 2004 through 2010, minus those who died or emigrated, leaving a total of 410,555 children.
In addition to traditional hypnotic and sedative drugs and melatonin, the study looked at antihistamines, which though intended for respiratory use, are frequently used for gentle sedation.
The two most frequently prescribed drugs were found to be dexchlorpheniramine (girls 7%, boys 8%) and trimeprazine(girls 3%, boys 4%), both of which are antihistamines.
After adjusting for parental education as an indicator of family socioeconomic status, and parental ADHD as indicated by prescription of ADHD medications, girls who had been prescribed sleeping medications on at least two occasions were twice as likely to subsequently develop ADHD, and boys about 60 percent more likely. For, dexchlorpheniramine equivalent associations were not statistically significant for either boys or girls. But girls prescribed trimeprazine on at least two occasions were almost three times as likely to subsequently develop ADHD, and boys were well over twice as likely.
A limitation of the study was that there was no direct data for sleep diagnosis. The authors noted, "The Norwegian prescription database does not contain diagnosis unless medications are reimbursed and hypnotics are not reimbursed for insomnia or sleep disturbances in general. Sleep diagnoses were also not available from the Norwegian Patient Registry, as there seems to be a clinical tradition for not using the ICD- 10G47 Sleep Disorders diagnosis for children."
The authors concluded, "It has previously been shown that infant regulation problems, including sleep problems, are associated with ADHD diagnosis. We replicate this finding in a large cohort, where continuous data collection ensures no recall bias and no loss to follow-up. We find that the use of hypnotic drugs before 3 years of age, signifying substantial sleeping problems, increases the risk of a later ADHD diagnosis. This was especially true for the antihistaminic drug, trimeprazine."
Ingvild Holdo¸, Jorgen G. Bramness, Marte Handal, Berit Hjelde Hansen, Vidar Hjellvik, Svetlana Skurtveit, "Association Between Prescribed Hypnotics in Infants and Toddlers and Later ADHD: A Large Cohort Study from Norway," Child Psychiatry & Human Development (2020), https://doi.org/10.1007/s10578-020-01039-9.
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