Introduction: ADHD is a neurodevelopmental disorder characterized by hyperactivity, inattention and impulsivity. For many the core symptoms become less troubling in adulthood. Treatment with stimulants is considered the most efficacious treatment for ADHD. Large high-quality studies have estimated the prevalence of AHDH to be 3,4-7,2% for children and adolescents and 2,5-6,8% for young adults. The aim of this study was to estimate the proportion of Icelanders who have received an ADHD diagnosis based on ADHD-medication prescriptions since an ADHD diagnosis is a prerequisite for such prescriptions in Iceland.
Methods: This population-based retrospective cohort study included all Icelanders 7-70 years old who received a prescription for an ADHD drug from 1.1.2004-31.12.2023. Every citizen receiving a prescription is included in the Icelandic Prescription Medicines Registry (IPMR).
Results: In 2023 14,7% of youth, 7-17 years of age, received a prescription for an ADHD medication, 17,7% of boys and 11,6% of girls. Among 12-17 years old youth the proportion was higher still, 17,6%, 20,1% for boys and 14,6% for girls. For 18-44 years old adults the proportion was 10,2%, 9,4% for males and 11,0% for females. From 2010-2023 the increase in prescriptions for 7-17 years old boys has been 93% but 224% for girls. For 18-44 years old males the increase has been 414% for males and 543% for females during this period. The incidence of new ADHD prescriptions for 7-17 years old boys from 2021-2023 was 10,9 and 13,5 for girls per 1000, respectively. For 18-44 years old the incidence in the years 2021-2023 was 18,7 for males and 19,2 for females per 1000, respectively.
Conclusion: The prevalence of Icelanders who have received an ADHD diagnosis is double to treble that observed in the best available studies in other populations. We therefore call for an urgent review of how ADHD diagnoses are made in Iceland because it is obvious that the current system leads to overdiagnosis and inappropriate treatment.
Keywords: ADHD; diagnosis; medication; prevalence.