Abstract
There is a growing international literature investigating the relationship between attention-deficit/hyperactivity disorder (ADHD) and younger relative age within the school year, but results have been mixed. There are no published systematic reviews on this topic. This study aimed to systematically review the published studies on the relative age effect in ADHD. Systematic database searches of: Medline, Embase, PsycINFO, Web of Science, ERIC, Psychology and Behavioral Sciences Collection and The Cochrane Library were conducted. Studies were selected which investigated the relative age effect in ADHD in children and adolescents. Twenty papers were included in the review. Sixteen (of 20) papers reported a significantly higher proportion of relatively younger children being diagnosed with ADHD and/or receiving medication for this. Meta-analyses involving 17 of these 20 papers revealed a modest relative age effect in countries with higher prescribing rates, risk ratio = 1.27 (95% CI 1.19–1.35) for receipt of medication. The relative age effect is well demonstrated in countries with known higher prescribing rates. Amongst other countries, there is also increasing evidence for the relative age effect, however, there is high heterogeneity amongst studies. Further research is needed to understand the possible reasons under-pinning the relative age effect and to inform attempts to reduce it.
Highlights
Attention-deficit/hyperactivity disorder (ADHD) is a common childhood neuro-developmental disorder, characterised by three core symptoms: inattention, hyperactivity and impulsiveness causing an impairment in functioning [1]
This systematic review focuses on one debate, whether relative age within the academic year affects the likelihood of a child being diagnosed with and/or receiving medication for ADHD
Thirty records were excluded on the basis of: not relating to ADHD (9), response letters/reviews (4), case reports (5), no birth month information (8), adult data only (2) and tests of intervention (2)
Summary
Attention-deficit/hyperactivity disorder (ADHD) is a common childhood neuro-developmental disorder, characterised by three core symptoms: inattention, hyperactivity and impulsiveness causing an impairment in functioning [1]. The receipt of a clinical diagnosis of ADHD depends on evidence of symptoms affecting functioning in more than one setting, for example, both at school and at home. Despite the operationalization of the diagnostic process, since diagnosis involves clinical judgment, without an objective test, there remain a number of areas of debate within the literature [10, 11]. There is a set age at which a child starts their first year of school, with a chronological date cut-off, e.g. 1st of September. This means that one child, born early in September may be 5 years old when the academic year starts, a child born at the end of August will only recently have turned 4 years of age. It would be expected that the older child will be more developmentally
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