Regional variation in ADHD treatment and diagnosis in Denmark

Introduction

Attention-deficit/hyperactivity disorder (ADHD) treatment and diagnoses show marked international and regional variation, not fully explained by underlying morbidity. In Denmark, earlier studies reported substantial regional differences, raising concerns about inequities in access to care. We examined nationwide patterns of ADHD medication use and diagnosis in 2024 and assessed system-level factors potentially contributing to geographic variation.

Methods

We conducted a register-based cross-sectional study of all Danish residents aged 4-17 years in 2024, using data from the National Patient Register, National Prescription Registry, Civil Registration System, and administrative sources. Pharmacological treatment of ADHD was defined as at least one redeemed prescription for ADHD drugs, while ADHD diagnoses were defined as at least one hospital contact with International Classification of Diseases, 10th revision codes F90.x/F98.8. Prevalence estimates were calculated overall and stratified by subgroups of sex and age. Associations with municipal socioeconomic index, regional hospital waiting times, and private child psychiatrist capacity were evaluated using Spearman’s rank correlations and regression analyses.

Results

Among 4-17-year-olds, ADHD medication prevalence ranged sixfold across municipalities (9.6-58 per 1,000). ADHD diagnoses showed parallel patterns (15-74 per 1,000). Variation was largest among adolescents (more than sevenfold). Municipal socioeconomic status was weakly and inversely correlated with medication use (ρ = -0.20, p = 0.049), but not diagnoses. Regional waiting times and specialist capacity varied but showed no significant associations with the prevalence of either medication use or diagnoses.

Conclusion

Marked geographic variation in ADHD medication use and diagnoses persists in Denmark despite a uniform healthcare framework. Observed differences were only weakly related to socioeconomic context, specialist capacity, or waiting times, suggesting that the unwarranted variation is driven by other factors. Ensuring equitable access will require addressing both structural resources and local practice variation.

Significant Outcomes

ADHD medication and diagnosis prevalence among Danish children and adolescents in 2024 varied more than sixfold across municipalities.

Socioeconomic context, specialist capacity, and waiting times explained little of the observed geographic variation.

Limitations

Waiting time data were available only for hospital-based services, excluding the referral phase and private practices.

Specialist capacity was measured only for private psychiatrists under agreements with the public health insurance system, limiting coverage of capacity for public hospitals and private non-contracted services.

Regional-level analyses were constrained by the small number of regions (n=5), reducing statistical power and precision.