Study Finds Relative Age Effect on ADHD Diagnosis and Prescription of Medication in Children


Autism spectrum disorder was also evaluated in the analysis, but further research is required to determine a possible association with relative age effect.

Research published in European Child and Adolescent Psychiatry demonstrates that teachers are likely to attribute signs of age-related immaturity in children to attention deficit hyperactivity disorder (ADHD) or autism spectrum disorder (ASD). Results demonstrate that the youngest students in a class with birth dates before the school entry cut-off date were overrepresented among children who received either an ADHD diagnosis or medication for ADHD management.1

Young boy with ADHD -- Image credit: |

Image credit: |

For this systemic review and meta-analysis, 2 separate searches for primary studies that investigated the effect of relative age within a school year on symptoms, diagnosis, or prescription of medication or ADHD or ASH diagnosis were conducted. The authors did not put a restriction on the dates the studies were conducted, and all observational studies were eligible for inclusion if they evaluated participants up to 18 years of age and reported a measure of ADHD symptoms, diagnosis or prescription of medication, or ASD symptoms or diagnosis that are in relation to their age within a school year (including month of birth). Studies were not considered for inclusion if they were review papers or meta-analyses; were case or conference abstracts without a full text or paper; not in English; did not report participants’ birth month in relation to school entry; only included adult participants; or commented on effect of relative age on symptoms or behaviors that were not directly relevant to either ADHD or ASD.2

A total of 32 studies were included in the analysis, of which 30 focused on ADHD and the remaining 2 on ASD. According to the findings, younger relative age was associated with both ADHD and medication, with a relative risk of 1.38 (95% CI 1.36, 1.52) and 1.28 (95% CI 1.21, 1.36), respectively, meaning that younger children are approximately 38% more likely to receive and ADHD diagnosis and 20% more likely to be prescribed medications compared to their peers. Additionally, the included studies also demonstrated higher risk ratios for younger children in their school year compared to their older classmates, with the exception of 1 study conducted in Denmark. Similarly, all studies showed a higher risk of ADHD medication prescriptions for children with younger relative ages, except for 1 study conducted in Scotland.1,2

Further, the 2 studies that evaluated ASD demonstrated that children who were the youngest in their school year were more likely to be diagnosed with ASD than their older peers. One of the 2 studies took the effect of relative age on multiple neurodevelopment disorders and reported there was a highly pronounced drop in diagnosis rate between the birth months of August and September, which are immediately before and after the school entry cut-off, according to the investigators.2

“This review shows that adults involved in identifying or raising concerns over a child’s behavior—such as parents and teachers—may be inadvertently misattributing relative immaturity as symptoms of ADHD. The child’s age in relation to their classmates—their ‘relative’ age—needs to [be] considered when making this kind of diagnosis,” said senior author Kapil Sayal, MSc, PhD, professor, School of Medicine at University of Nottingham, in a news release.1

According to the authors, limitations of the analysis include potential overlaps in the included study populations which may lead to misinterpretations of the findings, wide variability in the assessment tools included in the ADHD studies, and potential publication bias because smaller studies or ones with negative results may have been missed during the search process. Further, the authors note that there was not any information present on the training and experience of individual teachers when identifying ADHD symptoms as well as information on how long teachers have known students.2

Teachers play an important role in identifying ADHD symptoms in children. Our findings suggest that they can be more likely to rate younger students in a class as having ADHD symptoms than their older classmates. It is important teachers are supported in considering the relative age of a child in a classroom when ADHD is being queried,” said lead study author Eleni Frisira, MBBS, School of Medicine at University of Nottingham, in the news release.1


1. University of Nottingham. Younger children in school year are more commonly diagnosed with ADHD than their older classmates, says new study. News release. June 6, 2024. Accessed June 13, 2024.
2. Frisira, E, Holland, J, Sayal, K. Systematic review and meta-analysis: relative age in attention-deficit/ hyperactivity disorder and autism spectrum disorder. Eur Child Adolesc Psychiatry (2024) doi:10.1007/s00787-024-02459-x
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