Objective: The youngest children in a classroom have a higher risk of attention-deficit/hyperactivity disorders (ADHDs) and depression than their relatively older peers. However, there has been a lack of research on how relative age is related to second-generation antipsychotic (SGA) medication use.
Methods: This study used the Finnish National Prescription Register data and comprised all 669,726 Finnish children and adolescents aged 7–17 in 2018. We extracted data for those who were dispensed SGAs (risperidone, quetiapine, aripiprazole, and olanzapine) and ADHD medication (methylphenidate, atomoxetine, dexamphetamine, and lisdexamfetamine). Odds ratios (OR) and 95% confidence intervals (CI) were calculated for medication dispensed to schoolchildren born from January to April (the relatively oldest), May to August, and September to December (the relatively youngest). Dispensed prescriptions were a proxy for medication use.
Results: SGAs were dispensed to 9146 (1.4%) individuals in 2018. Their use was lower among girls aged 12–17 years born from September to December than January to April (OR 0.89; 95% CI 0.83–0.97), with no association between SGA use and birth month among boys. However, younger relative age was associated with combined SGA and ADHD medication, which was used by 2556 (0.4%) of the cohort: 2074 (0.6%) boys and 482 (0.1%) girls. The OR was 1.27 for boys aged 12–17 born from September to December (95% CI 1.10–1.46), compared with January to April. The OR for girls born from May to August was 1.35 (95% CI 1.04–1.76) and from September to December it was 1.33 (95% CI 1.02–1.74), compared with January to April.
Conclusions: A novel discovery of this study was that using both SGA and ADHD medication at the age of 12–17 years was more common among the youngest subjects in a school year than their relatively older peers.