Gender and socioeconomic dimensions of relative age effects on ADHD prescriptions: Evidence from Denmark

This paper examines the impact of relative age on Attention Deficit Hyperactivity Disorder (ADHD) prescriptions among school-aged children. Using a regression discontinuity design, we leverage the quasi-experimental variation in school starting age. We use administrative data for all children aged 6–16 from 2010 to 2019 in Denmark. We find a significant decrease in ADHD prescription rates for girls who are relativly old compared to their class mates. We do not find any significant results for boys. We further test the social gradient in relative age on ADHD prescriptions and find that the effect is entirely driven by girls from low income families. • The study uses a regression discontinuity design to examine how relative age affects ADHD prescription rates among Danish children from 2010 to 2019. • We find a significant decrease in ADHD prescription rates for girls who are relatively old compared to their classmates. There are no significant effects for boys. • The result is driven by girls from low-income families, indicating heterogeneous effects.