Abstract
A number of worldwide studies have demonstrated that children born later in the school year are more likely to receive an ADHD diagnosis than their same school-year peers. There is, however, variation in findings between countries. We aimed to confirm whether relative age is associated with ADHD diagnosis, with or without comorbidities, and to investigate whether relative age is associated with ADHD type and severity, and if this age relationship is in common with other neurodevelopmental disorder. We used the Lombardy Region’s ADHD registry. Data on children aged 6 years and older from September 1, 2011 to December 31, 2017 were considered. We calculated incidence ratios to assess the inter-relations between relative age within the school year, using age at diagnosis of ADHD or of other psychiatric disorder, year of diagnosis, and total number of children born in Lombardy during the corresponding timeframe. Data on ADHD type, severity of diagnosed disorder clinical global impressions–severity scale, and repetition of a school-grade were also considered. 4081 children, 2856 of whom with ADHD, were identified. We confirmed that the cumulative incidence of ADHD diagnosis was greatest for younger children, in particular for boys, for whom the prevalence is greater. The relative age effect was not accounted for by ADHD comorbid disorders, ADHD of combined type or severity. The relative age effect was also observed for children with other neurodevelopmental disorders (without ADHD), with a similar profile as ADHD children: the incidence ratio was 1.78 (95% CI 1.07–2.97; p < 0.0247) for boys diagnosed before age ten. The findings have a potential implication for diagnostic and therapeutic practice, educational advice, and policies, besides to better plan and organize service systems and appropriately inform parents, children, and citizens.
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Acknowledgements
The study is part of the “Sharing diagnostic–therapeutic approaches for ADHD in Lombardy” project partially funded by the Healthcare Directorate of the Lombardy Region (D.G. sanità n.3798, 8/05/2014). The views expressed are those of the authors and not necessarily those of the regional Healthcare Directorate. We thank all the teams of the 18 participating ADHD centers who devoted. significant time and energy to this project, joining and animating the Lombardy ADHD Group, in addition to the authors: Stefano Conte, Valeria Renzetti, Laura Salvoni (Bergamo); Massimo Molteni, Sara Trabattoni (Bosisio Parini, LC); Paola Effedri, Elisa Fazzi, Elena Filippini, Elisabetta Pedercini, Edda Zanetti (Brescia); Nadia Fteita (Como); Daniele Arisi, Roberta Mapelli (Cremona); Simona Frassica, Simonetta Oriani, Christian Trevisan (Garbagnate Milanese, MI); Susanna Acquistapace, Ottaviano Martinelli, Davide Villani (Lecco); Emanuela Binaghi, Andrea Deriu, Gabriella Vasile (Legnano, MI); Arianna Borchia, Paola Morosini (Lodi); Maddalena Breviglieri, Giuseppe Capovilla, Roberto Segala (Mantova); Chiara Battaini, Claudio Bissoli, Maria Paola Canevini, Isabella Cropanese, Emiddio Fornaro, Giorgio Leonardi, Silvia Merati, Monica Saccani, Roberto Vaccari, Vera Valenti (Milan); Umberto Balottin, Matteo Chiappedi, Elena Vlacos (Pavia); Corrado Meraviglia, Maria Grazia Palmieri, Gianpaolo Ruffoni (Sondrio); Francesco Rinaldi, Federica Soardi (Vallecamonica–Sebino, BS); Chiara Luoni, Giorgio Rossi (Varese). The authors would like to acknowledge Chiara Pandolfini and Daniela Miglio for manuscript language and technical editing.
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MB had the idea for the study, designed it, and drafted the initial report. MC and MZ managed and analyzed the data. LR, AD, and MAC drafted sections of the initial report. All authors participated in study design, contributed to interpretation of data, critical review and revision of the report, and approved the final report as submitted. MB is guarantor for the study.
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The list of participants, in addition to the authors, is part of the Lombardy ADHD Group and is reported in the acknowledgements.
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Bonati, M., Cartabia, M., Zanetti, M. et al. Age level vs grade level for the diagnosis of ADHD and neurodevelopmental disorders. Eur Child Adolesc Psychiatry 27, 1171–1180 (2018). https://doi.org/10.1007/s00787-018-1180-6
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DOI: https://doi.org/10.1007/s00787-018-1180-6