The global prevalence of ADHD in children and adolescents has been estimated at 5.29%. However, various systematic reviews report a community prevalence* of ADHD between 2.2% and 7.2%, which may reflect variation in study methodology or regional differences. Based on diagnosis, the administrative prevalence† of ADHD in the US ranges from 0.93% (2–5-year-olds in 2002) to 11.0% (4–17-year-olds in 2003–2011). In the UK, the administrative prevalence of ADHD based on prescribed medication, rather than diagnosis alone, is lower and is between 0.19% (6–17-year-olds in 1998) and 0.76% (5–15-year-olds in 2011–2012). Both community prevalence and administrative prevalence studies indicate that the incidence of ADHD is consistently higher in males than in females, with a UK study (The Health Improvement Network, 2010–2012) reporting a 5-times greater prevalence, suggesting that ADHD is relatively under-recognised in females. Some community prevalence studies have stratified the incidence of ADHD according to socioeconomic deprivation and indicate that individuals from families defined as “more deprived” were between 1.5–4-times more likely to have ADHD. Although administrative prevalence studies in the US are mixed regarding the correlation between socioeconomic deprivation and incidence of ADHD, studies in which access to public healthcare is available and accessible generally confirm an association between administrative prevalence of ADHD and deprivation.
Regional discrepancies in the incidence of ADHD within countries may reflect difficulties in the diagnosis and treatment of ADHD and rates of prescribing medication for ADHD in some parts of the US exceed what is expected from epidemiological studies. Data from 2004 indicate that in the UK, less than 50% of children diagnosed with ADHD receive treatment, therefore under-recognition of ADHD in many countries may reflect certain barriers that prevent access to treatment for children and adolescents with ADHD. Identified barriers include: being female, older age, non-white ethnicity, rural residence and lower family socioeconomic status. One recent systematic review highlighted that increasing knowledge of ADHD among parents, teachers and primary care clinicians may help improve access to care and that streamlining care pathways may help overcome these barriers.
The associated cost of ADHD can have a considerable and persistent impact on the individual with ADHD, their family and society. In the US, the total annual costs of ADHD are estimated at $143–266 billion and are primarily associated with the cost burden on healthcare and educational services for children and adolescents with ADHD, and with loss of income and productivity for adults with ADHD. In the UK (based on 2010 prices), one study estimated the total costs to the National Health Service, social care and education services to be around £670 million. Delays in receiving a clinical diagnosis of ADHD also incur greater long-term costs, particularly when individuals are not diagnosed until adulthood.
In line with global differences in the prevalence of ADHD, clinical care for individuals with ADHD is also different and often reflects variations in healthcare systems, historical and cultural differences in the acceptance of ADHD as a disorder, and the use of pharmacological and non-pharmacological treatment. In the US, the majority of healthcare provision is delivered privately, with primary healthcare professionals working in isolation, and guidelines recommend medication as a first-line treatment option. In the UK, several healthcare and non-medical professionals may agree on a care pathway, and although medication is an appropriate treatment in severe cases, behavioural management is recommended initially where possible. Several studies have assessed the clinical guidelines and treatment recommendations for ADHD (e.g. the Multimodal Treatment of ADHD study, a Cochrane review, the National Institute for Health and Care Excellence [NICE]) and collectively, evidence suggests that although behavioural treatments and non-pharmacological interventions benefit many children with ADHD, medication is more likely to reduce symptoms in children aged 6–18 years.
Transition of adolescents with ongoing needs to adult services poses particular challenges. Management of ADHD within children’s services is common, but few individuals are referred to adult services. In the UK, NICE guidelines recommend that for adolescents with ADHD who require transitioning into adult mental health services, pharmacological treatment should be reviewed and shared between specialist mental health and primary healthcare services. Poor transitioning of adolescents with ADHD to adult services can result in individuals disengaging from services and ultimately having worse outcomes. Findings from the Clinical Practice Research Datalink in the UK show that there is a 95% drop in drug prescriptions for individuals with ADHD between the ages of 15 and 21 years, therefore it is important that those with ADHD are provided with the appropriate clinical care pathway.
This systematic review highlighted several differences between the reported prevalence, cost, management and healthcare provision in the UK and the US. Differences in healthcare systems and the rates of prescribing medication for individuals with ADHD are likely to impact on the reported prevalence of the disorder between countries. The article also emphasised the importance of improving transitioning between child and adult services, as ADHD in adulthood is now a recognised disorder.
Read more about ADHD in the UK and US here
*Community prevalence is defined as the number of people with ADHD in a representative population sample according to predefined criteria
†Administrative prevalence describes the number of individuals with clinically diagnosed ADHD as a proportion of the whole population
Sayal K, Prasad V, Daley D, et al. ADHD in children and young people: prevalence, care pathways, and service provision. Lancet Psychiatry 2018; 5: 175-186.