WEDNESDAY, Oct. 2, 2019 (HealthDay News) — Children who are younger compared with their school peers have an increased risk for diagnosis of attention-deficit/hyperactivity disorder (ADHD), intellectual disability, and depression in childhood, according to a study published online Sept. 23 in JAMA Pediatrics.

Adrian Root, Ph.D., from the London School of Hygiene and Tropical Medicine, and colleagues used electronic medical record data from the U.K. Clinical Practice Research Datalink to identify 1,042,106 children (aged 4 to 15 years; 51.1 percent male) seen at more than 700 general practices. Children’s relative age within the school year was determined by month of birth.

The researchers found that being born in the last quarter of the school year (i.e., being the youngest group in a school year) was associated with a diagnosis of intellectual disability (adjusted hazard ratio [aHR], 1.30; 95 percent confidence interval [CI], 1.18 to 1.42), ADHD (aHR, 1.36; 95 percent CI, 1.28 to 1.45), and depression (aHR, 1.31; 95 percent CI, 1.08 to 1.59) compared with being born in the first quarter. For the intermediate age groups, there was a graded association with a smaller increased risk for each diagnosis compared with the oldest group: aHRs for intellectual disability for those born in the second quarter and third quarter: 1.06 (95 percent CI, 0.96 to 1.17) and 1.20 (95 percent CI, 1.09 to 1.32), respectively; aHRs for ADHD for those born in the second quarter and third quarter: 1.15 (95 percent CI, 1.08 to 1.23) and 1.31 (95 percent CI, 1.23 to 1.40), respectively; aHRs for depression for those born in the second quarter and third quarter: 1.05 (95 percent CI, 0.85 to 1.29) and 1.13 (95 percent CI, 0.92 to 1.38), respectively.

“Effective interventions may be needed to minimize the negative intellectual ability and mental and physical health consequences of relative youth,” the authors write.

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