According to the research, preschool and school-age children born in the month of August were more likely of being diagnosed with ADHD and receiving medication for their condition, as compared to children born in the month of September. Interestingly, this wasn’t the case when it came to teenagers.
Due to the fact that August 31 is the cutoff birthdate for children entering school, kids born in August tend to be the youngest in their grades; conversely, kids born in September are the oldest. Considering that, the researchers believe that a child’s age in relation to their classmates in the same grade could play a huge role in the diagnosis of ADHD and prescription of medication for the condition.
The study was based on data from a Taiwanese health insurance database of about 380,000 schoolchildren ranging in age from 4 to 17. Working from birth month to birth month, the researchers calculated the share of children diagnosed with ADHD, and also calculated the share of those who were given anti-ADHD medication over a 14-school year period. Lead author Dr. Mu-Hong Chen of the Taipei Veterans General Hospital pointed out that children in the same grade level are typically close to a year apart in age, with students born right before the August 31 cutoff being younger and less mature than those, for instance, who were born in September of the previous year.
The study revealed that preschool and school-age children born in August were 1.65 times likelier to be diagnosed with ADHD, and 1.73 times more likely to be given medication, when compared to children born in September. As Chen stressed, this is due to children born in August typically being the youngest in their grade level.
Earlier ADHD research in North America had hinted at similar trends, that the youth of a student in relation to his or her grade could play a factor in the likelihood of an ADHD diagnosis and medication. Chen believes that his team’s findings do mesh with studies from the U.S. and Canada, and are similar to those from Western countries in general.
Chen, however, admitted that he was not surprised that there was no significant difference in ADHD diagnosis rates between teenagers born in August and those born in September. He said that relative age per grade has a bigger impact on younger children than on adolescents, as the difference in neurocognitive development tends to decrease as children become older and more mature.