First graders
Credit: GreatSchool

Younger children in a certain grade level were more likely to be diagnosed with attention-deficit hyperactivity disorder (ADHD) compared with older children, a population-based study of a Finnish cohort found.

There was a “relative age effect” for children ages 7 to 9 years even in the same grade, as children born in September to December (“younger children”) had a higher cumulative incidence of ADHD diagnosis versus children born from January to April (“older children”), reported Kapil Sayal, PhD, of the University of Nottingham in England, and colleagues.

This effect was seen regardless of sex, with younger boys and girls having a higher cumulative incidence of ADHD diagnosis than older boys and girls in the same grade, the authors wrote in Lancet Psychiatry.

They noted that prior research found that “relative age” (defined as a child’s age within their school year compared with the age of other children within the school year) was a risk factor for mental health problems in children, with interest growing in the “contributory role of young relative […]