Early preterm birth linked to increased ADHD symptoms
Helga Ask, Ph.D., from the Norwegian Institute of Public Health in Oslo, and colleagues recruited pregnant women in a prospective, population-based cohort study. The correlation between gestational age at birth and symptoms of ADHD in preschool and school-age children was compared after adjustment for unmeasured genetic and environmental risk factors. Data were included for 113,227 children, including 33,081 siblings who were part of a sibling-comparison design.
The researchers found that compared with term-born children, children born early preterm were rated with more symptoms of ADHD, inattention, and hyperactivity/impulsivity. Children born early preterm had a mean score that was 0.24, 0.33, and 0.23 standard deviation (SD) higher on ADHD symptom tests, inattention tests, and hyperactivity/impulsivity tests, respectively, than children born at gestational week 40 after adjustment for unmeasured genetic and environmental factors. The correlation of gestational age with preschool ADHD symptoms was moderated by sex, with the association strongest among girls. Compared with their term-born sisters, early preterm girls scored a mean of 0.8 SD higher.
"This study demonstrates the importance of differentiating between inattention and hyperactivity/impulsivity and stratifying on sex in the study of childhood ADHD," the authors write.
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