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Brain Dev. 2014 Oct;36(9):778-85. doi: 10.1016/j.braindev.2013.11.004. Epub 2013 Dec 2.

A clinical study of attention-deficit/hyperactivity disorder in preschool children--prevalence and differential diagnoses.

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Center for Developmental Clinical Psychology and Psychiatry, Nagoya University, Nagoya, Japan. Electronic address:
Center for Developmental Clinical Psychology and Psychiatry, Nagoya University, Nagoya, Japan.
Kanie Health Center, Aichi, Japan.
Graduate School of Education, Naruto University of Education, Naruto, Japan.
Faculty of Humanities and Social Sciences, Shizuoka University, Shizuoka, Japan.



We aimed to examine (1) the prevalence and characteristics of ADHD in preschool children, and (2) differential diagnoses among children who display symptoms of inattention and hyperactivity-impulsivity in early childhood.


The participants were children living in Kanie-cho, in Japan's Aichi Prefecture, who underwent their age 5 exams at the municipal health center between April 2009 and March 2011. We first extracted children who were observed to be inattentive or hyperactive-impulsive during their age 5 exams and considered as possibly having ADHD. We conducted follow-ups with these children using post-examination consultations, visits to preschools, and group rehabilitation. The results of the age 5 exams were combined with behavior observations and interview content obtained during subsequent follow-ups. A child psychiatrist and several clinical psychologists discussed these cases and made a diagnosis in accordance with the DSM-IV-TR.


91 (15.6%) of the 583 children selected were considered as possibly having ADHD; we were able to conduct follow-ups with 83 of the 91 children. Follow-up results showed that 34 children (5.8% of all participants) remained eligible for a diagnosis of ADHD. Diagnoses for the remaining children included: pervasive developmental disorders (six children, or 6.6% of suspected ADHD children), intellectual comprehension problems (four children, or 4.4%), anxiety disorders (seven children, or 7.7%), problems related to abuse or neglect (four children, or 4.4%), a suspended diagnosis for one child (1.1%), and unclear diagnoses for 29 children (31.9%).


ADHD tendencies in preschool children vary with changing situations and development, and the present study provides prevalence estimates that should prove useful in establishing a diagnostic baseline.


Attention-deficit/hyperactivity disorder (ADHD); Differential diagnoses; Preschool children; Prevalence

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