Peer-reviewed article
Why are the youngest in class more often prescribed pharmacological treatment for ADHD?
Nicodemo C, Nicoletti C, Vidiella-Martin J ·
Summary
Written by AI, not yet AICS's view · claude-haiku-4-5-20251001This study examines why children who start school at a younger age receive more prescriptions for ADHD treatment. Using administrative data from England and comparing children born just before and after the school entry cutoff, researchers found that early starters are 40-50% more likely to be treated for ADHD by age 15. The difference is driven by prescriptions in early childhood and is primarily explained by relative immaturity compared to peers rather than actual age differences. The authors recommend refining diagnostic guidelines and classroom grouping to reduce these diagnostic gaps.
Key points
- Early school starters are 40-50% more likely to receive ADHD treatment by age 15
- The long-term gap is entirely driven by first-time prescriptions between ages 5 and 8
- Relative age (immaturity compared to peers) is the primary long-term driver of the difference
- Absolute age and length of school exposure have only short-lived effects on prescription rates
- Authors recommend refining diagnostic guidelines and classroom grouping practices to reduce diagnostic disparities
Limitations
The study uses administrative prescription data from England only, so findings may not generalise to other countries with different healthcare systems, diagnostic practices, or school entry policies. The research cannot determine whether higher prescriptions in younger starters represent genuine overdiagnosis or underdiagnosis in older starters.
Abstract
Children who start school at a younger age are more likely to receive pharmacological treatment for attention deficit hyperactivity disorder (ADHD). This pattern is widely attributed to peer-comparison biases, but the relative importance of different underlying mechanisms remains debated. We use administrative data from England to study how school starting age affects ADHD prescription rates from ages 5 to 15. Exploiting a sharp school-entry cutoff and comparing children born just before and after September 1, we estimate both age- and grade-specific effects of early school entry. We find that early starters are 40-50% more likely to be treated for ADHD by age 15. This long-term gap is entirely driven by first-time prescriptions among children aged 5 to 8. Using a novel decomposition strategy, we isolate the roles of relative age, absolute age, the length of school exposure, and age at school entry. We find that relative age is the primary long-term driver, aligning with previous evidence on peer-comparison bias, while absolute age and the length of school exposure have only short-lived effects. Our findings suggest that early starters are more likely to receive marginal diagnoses due to their relative immaturity, and we recommend refining diagnostic guidelines and classroom grouping practices to reduce diagnostic gaps. Supplementary information The online version contains supplementary material available at 10.1007/s00148-026-01190-y.
Findings the Hub has extracted
Each claim below is labelled by its type of design and links back to this report.
- Intervention
- Comparison of ADHD prescription rates between children born just before and after the September 1 school entry cutoff in England
- Population
- Children in England aged 5 to 15, compared by school entry age
Key finding
Early starters are 40-50% more likely to be treated for ADHD by age 15