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Attention-deficit/hyperactivity disorder (ADHD) is marked by age-inappropriate levels of inattention and activity. A report from Finland examines how relative immaturity in the first years of school could increase the risk of ADHD medication use.
Although the age of children in a specific grade in school are typically the same, there can be several months in between the oldest child in the grade and the youngest child. Particularly in the early years of school, this gap can make a significant difference. A report from Finland in Pediatrics looks at whether a link exists between a child’s birth month and medication rates for attention-deficit/hyperactivity disorder (ADHD).1
The researchers ran a population-based study. They identified a first purchase of ADHD medication in 7054 children who were born in 2005 to 2007. The medications used to identify ADHD cases included methylphenidate, atomoxetine, dexamphetamine, and lisdexamphetamine. The children were put into 3 groups based on the month of birth: group 1 was born in January to April; group 2 was born in May to August; and group 3 was born in September to December. In Finland, children must spend at least 1 year in kindergarten before starting compulsory school and the first year of compulsory education is when a child turns 6 years of age. The cutoff date for school eligibility is December 31. The researchers noted that delayed school entry was rare in Finland and is also decreasing.
Among the children, the risk of ADHD medication use was found to increase throughout the year by birth month. When looking at the boys who were born in September to December, the link was stable across the year cohorts (hazard ratio [HR]: 1.3; 95% CI: 1.1–1.5). However, among girls born in the same part of the year, the HR in the 2005 cohort was 1.4 (95% CI: 1.1–1.8) and increased to 1.7 (95% CI: 1.3–2.2) in the 2007 cohort. Following restricted follow-up, which concluded at the end of the year when a child had his or her eighth birthday, the HRs for boys and girls who were born in September to December 2007 were 1.5 (95% CI: 1.3–1.7) and 2.0 (95% CI: 1.5–2.8), respectively.
The investigators concluded that the relative immaturity of a child increased the likelihood of using ADHD medication. The link was found to more pronounced in the first school years. They said that clinicians and teachers should be aware of this link.
1. Vuori M, Martikainen J, Koski-Pirilä A, et al. Children’s relative age and ADHD medication use: a finnish population-based study. Pediatrics. September 21, 2020. Epub ahead of print. doi:10.1542/peds.2019-4046