County-level variation and trajectories in ADHD medication dispensing among Norwegian children and adolescents, 2005-2022: a nationwide prescription register study.

BACKGROUND

National trends in ADHD medication use in Norway have recently been described. Less is known about whether children and adolescents in different counties have followed similar or diverging medication-dispensing trajectories over time. We therefore examined county-level variation and county-level trajectories in ADHD medication dispensing among Norwegian children and adolescents from 2005 to 2022.

METHODS

We conducted a nationwide retrospective drug-utilisation study using aggregated data from the Norwegian Prescription Database and population denominators from Statistics Norway. The study included individuals aged 6-17 years who redeemed at least one prescription for an ADHD medication between 2005 and 2022. Annual dispensing prevalence was calculated by county, sex, and age group and expressed as users per 1,000 inhabitants. Analyses were stratified into children aged 6-11 years and adolescents aged 12-17 years. To quantify regional variation, we calculated the lowest and highest county rates, absolute rate differences, and high-to-low county rate ratios.

RESULTS

ADHD medication dispensing increased in all sex and age strata, but county-level trajectories differed over time. In 2022, dispensing prevalence among girls aged 6-11 years ranged from 4.6 per 1,000 inhabitants in Oslo to 15.1 per 1,000 in Møre og Romsdal, corresponding to a 3.25-fold difference. Among boys aged 6-11 years, rates ranged from 14.6 per 1,000 in Oslo to 39.9 per 1,000 in Nordland, corresponding to a 2.74-fold difference. Among adolescents aged 12-17 years, rates ranged from 15.3 per 1,000 in Agder to 35.2 per 1,000 in Trøndelag among girls, and from 25.1 per 1,000 in Oslo to 62.4 per 1,000 in Trøndelag among boys, corresponding to 2.30-fold and 2.49-fold differences, respectively.

CONCLUSIONS

This study extends previous Norwegian register-based work by showing substantial county-level variation in ADHD medication dispensing among children and adolescents. National averages may conceal important regional differences in recognition, referral pathways, diagnostic practice, treatment thresholds, prescribing practice, or service organisation. Further studies linking prescription data with diagnostic, clinical, service-level, and socioeconomic information are needed to clarify the drivers and consequences of these regional differences.