Demographic and socioeconomic factors influencing ADHD diagnosis in children and adolescents: a population-based nested case–control study

Attention deficit hyperactivity disorder (ADHD) is among the most commonly diagnosed psychiatric disorders in childhood, with an estimated prevalence in children and adolescents of 5.9% in Navarre (2019) and 6.8% in Spain (2012). However, demographic and socioeconomic factors influencing diagnosis remain insufficiently explored. The aim was to examine associations between demographic factors (month of birth, migration status, number of siblings) or socioeconomic variables (household income, residence type, school type) and ADHD diagnosis in children and adolescents. Population-based case-control study nested in a cohort of individuals born between 1991 and 2011 and followed from 2007 to 2019 using linked health and educational records from Navarre, Spain. Incident ADHD cases were age and sex-matched to three controls (1:3). Data were analyzed with multivariate conditional logistic regression. Lower family income (< €18,000/year) was associated with a 23% increased risk of ADHD diagnosis (OR = 1.23, 95%CI: 1.15–1.31). Large sized rural areas showed less likely diagnostic rates compared to urban residence (OR = 0.88, 95%CI: 0.82–0.93). The month of birth significantly influenced diagnosis likelihood, with those born later in the year showing increased odds, peaking at 69% higher odds in October-December (OR = 1.69, 95%CI: 1.55–1.83). Having ≥ 3 siblings reduced diagnosis likelihood by 17% compared to only children (OR = 0.83, 95%CI: 0.76–0.91). Migration status and school type interaction analysis revealed that migrant children in public schools had significantly lower ADHD diagnoses compared to non-migrant peers; this difference diminished in charter schools. This study confirms, in a large population cohort, the significant impact of socio-demographic factors on the likelihood of ADHD diagnosis, such as socio-economic status, month of birth, migrant status, number of siblings, and place of residence, and provides new insights into the role of school type and the interaction between school type and migrant status, this interaction representing a relatively understudied factor. These associations highlight disparities and potential diagnostic biases. Strategies to address these inequalities are essential for consistent ADHD diagnostic practices and equitable healthcare interventions.