ADHD diagnosis

Researchers investigated the relationship between age and ADHD diagnosis to uncover if a child’s age within the school year impacts chances of a diagnosis.

Behavioural symptoms that include hyperactivity, impulsivity, and inattention are well-known features of children diagnosed with Attention Deficit Hyperactivity Disorder (ADHD). There are many factors that contribute to the chances of receiving a diagnosis of ADHD. Researchers in Finland are investigating whether there is an association between relative age and ADHD diagnosis.

Previous research has concluded that there is a mixed relationship associated with younger relative age in school year and ADHD.  The relative age refers to the actual age of the child when compared to their peers in the same school grade. These Finnish researchers sought to investigate the relative age associated with ADHD to determine such an association; specifically, are children with a younger relative age diagnosed at higher or lower frequencies compared to their peers?

A national population-based registry of all Finnish babies born between January 1, 1991, and December 31, 2004, was used to identify children with an ADHD diagnosis at the start of school age, which is seven years.

As published in Lancet Psychiatry, the researchers revealed that they were able to identify 6,136 children with ADHD for the period January 1998 to December 2011. The results showed a higher incidence of ADHD diagnosis in children born September to December than in children born January to April.  This means that the younger children were more likely to be diagnosed than their older counterparts in the same grade. When the researchers looked at only the data from 2004 – 2011, this association became even more pronounced.

The results of this study show that children of a younger relative age are more likely to receive a diagnosis of ADHD than their older peers. This increases the chances of false positives and incorrect diagnoses.  Conversely, children with a higher relative age than their peers are more likely to be missed for a referral or a diagnosis. Teachers, educators, and clinicians must take into account the relative age of their students when assessing behaviour and abilities, in order to more accurately refer children for assessments, and diagnose ADHD.

Written by Dr. MòNique J. Grant Coke, DNP, MPH, BSN, Medical Writer


Sayal, K., Chudal, R., Hinkka-Yi-Salomaki, S., Joelsson, P., & Sourander, A. (2017). Relative age within the school year and diagnosis of attention-deficit hyperactivity disorder: a nationwide population-based study. The

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