Relative age within the school year and diagnosis of attention-deficit hyperactivity disorder: a nationwide population-based study
Background There are mixed findings on the relationship between ADHD and younger relative age in class. This study examines whether relative age is associated with ADHD diagnosis in a country where treatment prevalence rates are low and whether any such association has changed over time or relate...
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| Format: | Article |
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Elsevier
2017
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| Online Access: | https://eprints.nottingham.ac.uk/46726/ |
| _version_ | 1848797385965174784 |
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| author | Sayal, Kapil Chudal, Roshan Hinkka-Yli-Salomäki, Susanna Joelsson, Petteri Sourander, Andre |
| author_facet | Sayal, Kapil Chudal, Roshan Hinkka-Yli-Salomäki, Susanna Joelsson, Petteri Sourander, Andre |
| author_sort | Sayal, Kapil |
| building | Nottingham Research Data Repository |
| collection | Online Access |
| description | Background
There are mixed findings on the relationship between ADHD and younger relative age in class. This study examines whether relative age is associated with ADHD diagnosis in a country where treatment prevalence rates are low and whether any such association has changed over time or relates to comorbid disorders.
Methods
Using nationwide population-based registers, all Finnish children born between 1991 and 2004 who were diagnosed with ADHD from age 7 years onwards (school starting age), between 1998 and 2011, were identified (n=6136). Incidence ratios (IRs) were used to examine the inter-relationships between relative age, actual age at ADHD diagnosis, and year of diagnosis (1998-2003 vs. 2004-2011).
Findings
The cumulative incidence of ADHD diagnosis was greatest for younger children within the schoolyear - IRs of 1.26 (boys) and 1.31 (girls). The association between relative age and ADHD diagnosis reflected children diagnosed before the age of 10 years. The strength of this association increased during recent years – for 2004-2011, IRs were 1.37 (95% CI 1.24,1.53) for May-August and 1.64 (95% CI 1.48,1.81) for September-December compared with January-April births (oldest). The relative age effect was not explained by comorbid disorders.
Interpretation
In a health service system with low prescribing rates for ADHD, younger relative age is associated with an increased likelihood of receiving a clinical diagnosis of ADHD. This influence has increased in recent years. Teachers, parents and clinicians should take relative age into account when considering the possibility of ADHD in a child or encountering a child with a pre-existing diagnosis. |
| first_indexed | 2025-11-14T20:03:03Z |
| format | Article |
| id | nottingham-46726 |
| institution | University of Nottingham Malaysia Campus |
| institution_category | Local University |
| last_indexed | 2025-11-14T20:03:03Z |
| publishDate | 2017 |
| publisher | Elsevier |
| recordtype | eprints |
| repository_type | Digital Repository |
| spelling | nottingham-467262020-05-04T19:11:30Z https://eprints.nottingham.ac.uk/46726/ Relative age within the school year and diagnosis of attention-deficit hyperactivity disorder: a nationwide population-based study Sayal, Kapil Chudal, Roshan Hinkka-Yli-Salomäki, Susanna Joelsson, Petteri Sourander, Andre Background There are mixed findings on the relationship between ADHD and younger relative age in class. This study examines whether relative age is associated with ADHD diagnosis in a country where treatment prevalence rates are low and whether any such association has changed over time or relates to comorbid disorders. Methods Using nationwide population-based registers, all Finnish children born between 1991 and 2004 who were diagnosed with ADHD from age 7 years onwards (school starting age), between 1998 and 2011, were identified (n=6136). Incidence ratios (IRs) were used to examine the inter-relationships between relative age, actual age at ADHD diagnosis, and year of diagnosis (1998-2003 vs. 2004-2011). Findings The cumulative incidence of ADHD diagnosis was greatest for younger children within the schoolyear - IRs of 1.26 (boys) and 1.31 (girls). The association between relative age and ADHD diagnosis reflected children diagnosed before the age of 10 years. The strength of this association increased during recent years – for 2004-2011, IRs were 1.37 (95% CI 1.24,1.53) for May-August and 1.64 (95% CI 1.48,1.81) for September-December compared with January-April births (oldest). The relative age effect was not explained by comorbid disorders. Interpretation In a health service system with low prescribing rates for ADHD, younger relative age is associated with an increased likelihood of receiving a clinical diagnosis of ADHD. This influence has increased in recent years. Teachers, parents and clinicians should take relative age into account when considering the possibility of ADHD in a child or encountering a child with a pre-existing diagnosis. Elsevier 2017-10-09 Article PeerReviewed Sayal, Kapil, Chudal, Roshan, Hinkka-Yli-Salomäki, Susanna, Joelsson, Petteri and Sourander, Andre (2017) Relative age within the school year and diagnosis of attention-deficit hyperactivity disorder: a nationwide population-based study. Lancet Psychiatry, 4 (11). pp. 868-875. ISSN 2215-0374 http://www.sciencedirect.com/science/article/pii/S2215036617303942?via%3Dihub doi:10.1016/S2215-0366(17)30394-2 doi:10.1016/S2215-0366(17)30394-2 |
| spellingShingle | Sayal, Kapil Chudal, Roshan Hinkka-Yli-Salomäki, Susanna Joelsson, Petteri Sourander, Andre Relative age within the school year and diagnosis of attention-deficit hyperactivity disorder: a nationwide population-based study |
| title | Relative age within the school year and diagnosis of attention-deficit hyperactivity disorder: a nationwide population-based study |
| title_full | Relative age within the school year and diagnosis of attention-deficit hyperactivity disorder: a nationwide population-based study |
| title_fullStr | Relative age within the school year and diagnosis of attention-deficit hyperactivity disorder: a nationwide population-based study |
| title_full_unstemmed | Relative age within the school year and diagnosis of attention-deficit hyperactivity disorder: a nationwide population-based study |
| title_short | Relative age within the school year and diagnosis of attention-deficit hyperactivity disorder: a nationwide population-based study |
| title_sort | relative age within the school year and diagnosis of attention-deficit hyperactivity disorder: a nationwide population-based study |
| url | https://eprints.nottingham.ac.uk/46726/ https://eprints.nottingham.ac.uk/46726/ https://eprints.nottingham.ac.uk/46726/ |