What is the prevalence of ADHD?
A mean worldwide prevalence of attention-deficit hyperactivity disorder (ADHD), or hyperkinetic disorder (HKD), of ~2.2% overall (range, 0.1–8.1%) has been estimated in children and adolescents (aged <18 years). The mean prevalence of ADHD in adults (aged 18–44 years) from a range of countries in Asia, Europe, the Americas and the Middle East was reported as ~2.8% overall (range, 0.6–7.3%).1
How does the prevalence of ADHD in children and adolescents differ across the world?
Few studies exist regarding ADHD prevalence rates in pre-school children (aged ≤6 years); however, prevalence rates in Norway, Germany and Spain have been estimated to be 1.9%, 1.8% and 5.4%, respectively.2-4 An epidemiological study of 20 countries from the World Health Organization World Mental Health Surveys found that across high-, upper-middle-, and low-/lower-middle-income countries, prevalence rates of ADHD in children and adolescents were highest in the USA (8.1%) and lowest in Iraq (0.1%), Poland (0.3%) and Romania (0.4%) [Figure 1].1
Figure 1: Global prevalence of childhood ADHD based on retrospective recall in adults aged 18–44 years. Figure developed using data from Fayyad J et al. Atten Defic Hyperact Disord 2017; 9: 47-65.1
How does the prevalence of ADHD in adults differ across the world?
Once considered to be a childhood disorder,5 ADHD is now acknowledged to persist into adulthood in ~50–65% of individuals.1,6,7 Predictors for persistence into adulthood over time may include severity of symptoms,8 psychosocial adversity and psychiatric comorbidities as reported in women with ADHD.9 The reported prevalence rates of ADHD can vary due to population characteristics, methodological, environmental and cultural differences, and variability in identification and diagnostic guideline tools employed in studies.10
The prevalence of ADHD in adults (n=26,744) aged 18–44 years from a range of countries in Asia, Europe, the Americas and the Middle East was ~2.8% overall; the lowest prevalence was reported in Iraq (0.6%) and Romania (0.6%) and the highest was reported in France (7.3%) [Figure 2].1
Figure 2: Global prevalence of adults aged 18–44 years with ADHD. Figure developed using data from Fayyad J et al. Atten Defic Hyperact Disord 2017; 9: 47-65 and Ebejer JL et al. PLoS One 2012; 7: e47404.1,7
Persistence of ADHD from childhood to adulthood
Once considered to be a childhood disorder,5 ADHD is now acknowledged to persist into adulthood in ~50–65% of individuals.1,6,7
Does the prevalence of ADHD differ between genders?
Data suggest that the prevalence of ADHD is greater in males than females.11,12 The large European ADORE (Attention-Deficit Hyperactivity Disorder Observational Research in Europe) study was a 24-month naturalistic longitudinal observational study in 10 European countries of children (aged 6–18 years). In total, 1478 individuals were analysed: 231 girls (15.7%) and 1222 boys (84.3%) [gender data were missing for n=25]. Gender ratios varied by country ranging from 1:3 to 1:16 in females:males.11 ADHD was more commonly diagnosed in adult males compared with adult females. A worldwide meta-regression analysis of 11 studies of adults with ADHD found that although the ratio of males to females with ADHD decreased with age, a gender ratio of 1 to 1.6 (females to males) was still present in adults aged ≥19 years.12
Do symptoms of ADHD differ between genders?
Some studies have indicated that girls with ADHD may be up to twice as likely as boys to have the inattentive type of ADHD and may experience more from internalising symptoms and inattention, in contrast with the hyperactive and aggressive symptoms sometimes shown by boys.13-15 Differences in ADHD presentation between boys and girls may explain the lower prevalence rates of ADHD in females. However, the large European ADORE study of clinically referred children (n=1478; mean age: girls=8.8 years, boys=9.0 years) found no evidence to suggest that core ADHD symptomatology differed between genders.11 Research in adults with ADHD has indicated that both genders have similar phenotypic features following adolescence.16
Does the prevalence of ADHD symptoms vary with age?
Symptoms of ADHD can vary between individuals in terms of severity and combination of inattentive, hyperactive and impulsive symptoms. ADHD, its symptoms and impact, may also vary through an individual’s lifespan.17-20 A worldwide meta-analysis of 86 studies in children and adolescents and 11 studies in adults indicated that the predominantly inattentive type of ADHD was the most common subtype in all samples, with the exception of pre-school children, in whom predominantly hyperactive-impulsive type was the most common (Figure 3).12
Figure 3: The prevalence of ADHD presentations varies with age, according to preliminary evidence from a cross-sectional meta-analysis of 97 studies (n=175,800). Reproduced with permission from Willcutt EG. Neurotherapeutics 2012; 9: 490-499.12
- Fayyad J, Sampson NA, Hwang I, et al. The descriptive epidemiology of DSM-IV Adult ADHD in the World Health Organization World Mental Health Surveys. Atten Defic Hyperact Disord 2017; 9: 47-65.
- Wichstrøm L, Berg-Nielsen TS, Angold A, et al. Prevalence of psychiatric disorders in preschoolers. J Child Psychol Psychiatry 2012; 53: 695-705.
- Schlack R, Hölling H, Kurth BM, et al. The prevalence of attention-deficit/hyperactivity disorder (ADHD) among children and adolescents in Germany. Initial results from the German Health Interview and Examination Survey for Children and Adolescents (KiGGS). Bundesgesundheitsblatt Gesundheitsforschung Gesundheitsschutz 2007; 50: 827-835.
- Canals J, Morales-Hidakgo P, Jane M, et al. Prevalence in Spanish preschoolers: comorbidity, socio-demographic factors, and functional consequences. J Atten Disord 2016; 22: 143-153.
- Biederman J, Mick E, Faraone SV. Age-dependent decline of symptoms of attention deficit hyperactivity disorder: impact of remission definition and symptom type. Am J Psychiatry 2000; 157: 816-818.
- Faraone SV, Biederman J, Mick E. The age-dependent decline of attention deficit hyperactivity disorder: a meta-analysis of follow-up studies. Psychol Med 2006; 36: 159-165.
- Ebejer JL, Medland SE, van der Werf J, et al. Attention deficit hyperactivity disorder in Australian adults: prevalence, persistence, conduct problems and disadvantage. PLoS One 2012; 7: e47404.
- Lara C, Fayyad J, De Graaf R, et al. Childhood predictors of adult attention-deficit/hyperactivity disorder: results from the World Health Organization World Mental Health Survey Initiative. Biol Psychiatry 2009; 65: 46-54.
- Biederman J, Petty CR, O’Connor KB, et al. Predictors of persistence in girls with attention deficit hyperactivity disorder: results from an 11-year controlled follow-up study. Acta Psychiatr Scand 2012; 125: 147-156.
- Skounti M, Philalithis A, Galanakis E. Variations in prevalence of attention deficit hyperactivity disorder worldwide. Eur J Pediatr 2007; 166: 117-123.
- Nøvik TS, Hervas A, Ralston SJ, et al. Influence of gender on attention-deficit/hyperactivity disorder in Europe–ADORE. Eur Child Adolesc Psychiatry 2006; 15(Suppl 1): I15-I24.
- Willcutt EG. The prevalence of DSM-IV attention-deficit/hyperactivity disorder: a meta-analytic review. Neurotherapeutics 2012; 9: 490-499.
- Biederman J, Mick E, Faraone SV, et al. Influence of gender on attention deficit hyperactivity disorder in children referred to a psychiatric clinic. Am J Psychiatry 2002; 159: 36-42.
- Biederman J, Faraone SV. The Massachusetts General Hospital studies of gender influences on attention-deficit/hyperactivity disorder in youth and relatives. Psychiatr Clin North Am 2004; 27: 225-232.
- Newcorn JH, Halperin JM, Jensen PS, et al. Symptom profiles in children with ADHD: effects of comorbidity and gender. J Am Acad Child Adolesc Psychiatry 2001; 40: 137-146.
- Biederman J, Faraone SV, Monuteaux MC, et al. Gender effects on attention-deficit/hyperactivity disorder in adults, revisited. Biol Psychiatry 2004; 55: 692-700.
- Caci H, Asherson P, Donfrancesco R, et al. Daily life impairments associated with childhood/adolescent attention-deficit/hyperactivity disorder as recalled by adults: results from the European Lifetime Impairment Survey. CNS Spectr 2015; 20: 112-121.
- Caci H, Doepfner M, Asherson P, et al. Daily life impairments associated with self-reported childhood/adolescent attention-deficit/hyperactivity disorder and experiences of diagnosis and treatment: results from the European Lifetime Impairment Survey. Eur Psychiatry 2014; 29: 316-323.
- Holmberg K, Bölte S. Do symptoms of ADHD at ages 7 and 10 predict academic outcome at age 16 in the general population? J Atten Disord 2014; 18: 635-645.
- Biederman J, Faraone SV, Spencer TJ, et al. Functional impairments in adults with self-reports of diagnosed ADHD: a controlled study of 1001 adults in the community. J Clin Psychiatry 2006; 67: 524-540.
