Objectives: To explore whether regional variations in the initiation of attention-deficit hyperactivity disorder (ADHD) medication among school-age children are explained by differences in sociodemographic composition and/or ADHD prescribing practice, especially in children who face social adversity (low parental education and single parenthood).
Methods: A cohort of Danish school-age children (ages 5-17) without previous psychiatric conditions (N = 813,416) was followed during 2010-2011 for incident ADHD prescribing in the individual-level Danish registers. Register information was retrieved for both children and their parents. Regional differences were decomposed into contributions from differences in sociodemographic composition and in prescribing practices. Incidence rate ratios (IRR) with 95% confidence interval (CI) of ADHD prescribing were calculated using demographically standardized multivariable Poisson regression models.
Results: Compared with the Capital, prescribing rates were significantly higher in regions North and Zealand (IRR, 1.19; 95% CI, 1.08-1.32 and 1.17; 1.08-1.28, respectively) and lower in South (IRR, 0.60; 95% CI, 0.54-0.66). After inclusion of the interaction term (region*social adversity), the multivariable analyses revealed a higher rate for the most disadvantaged children in North (IRR, 2.00; 95% CI, 1.51-2.66) and a lower rate in South (IRR, 0.47; 95% CI, 0.3-0.65). Prescribing rates were the highest for disadvantaged children in all regions, demonstrating the steepest social gradient in North and the smoothest in South. Demographic composition explained little of the variation: 3% for North and 13% for Zealand.
Conclusions: Differences in sociodemographic composition explain little of regional variation in incident ADHD prescribing for children. However, large regional differences prevail in prescribing practices for children facing social adversity, indicating that local cultures shape the interpretation and handling of children with ADHD-like behaviors.