Although there is no global consensus on the prevalence of attention-deficit hyperactivity disorder (ADHD) in children, adolescents and/or adults, meta-regression analyses have estimated the worldwide prevalence at between 5.29%1 and 7.1% in children and adolescents,2 and at 3.4% (range 1.2–7.3%) in adults.3 The prevalence of ADHD in very young children (aged <6 years) or later in adult life (aged >44 years), is less well-studied.2
ADHD prevalence rates may vary depending on several factors:
- Age – whilst ADHD was once considered to be a childhood disease with a decline in symptoms during maturation to adulthood,4 it is now acknowledged to persist into adulthood in an estimated 50–66% of individuals5-8
- Gender – a higher prevalence of ADHD is often reported in males2,9,10
- Presentations of ADHD – the combined inattentive-hyperactive-impulsive presentation of ADHD is considered most prevalent in children, adolescents and adults.2,11,12
ADHD is often present alongside comorbidities such as oppositional defiant disorder, conduct disorder, anxiety disorder, personality disorders and depression,10,13-16 which may further complicate understanding of true prevalence rates.
ADHD affects individuals across regions worldwide. The Diagnostic and Statistical Manual of Mental Disorders – 5th edition (DSM-5TM) suggests that cultural attitudes towards the interpretation of behaviour may contribute to differences in prevalence estimates across studies.17
A meta-analysis of studies (n=102) of children and adolescents diagnosed with ADHD found that the prevalence of ADHD in individuals aged ≤18 years of age varied between countries worldwide; the prevalence estimate for Europe specifically was just under 5% (Figure).1§
Prevalence of ADHD in children and adolescents by country (n=102 studies)1§
Geographical location was associated with significant variability between the prevalence estimates from North America and both the Middle East (p=0.01) and Africa (p=0.03), while no significant differences were reported for prevalence rates between North America and Europe (p=0.40), South America (p=0.83), Asia (p=0.85) or Oceania (p=0.45). This finding was confirmed in a meta-regression model using Europe as the comparator: significant differences in prevalence were found between Europe and both Africa (p=0.05) and the Middle East (p=0.03).1§
Estimates from individual studies have indicated that the global prevalence of ADHD in adults ranges from 1.1% in Australia to 7.3% in France (Figure).
Prevalence of ADHD in adults by country
However, review papers have concluded that ADHD prevalence data may vary widely between studies due to various factors such as: population characteristics; methodological, environmental and cultural differences; and variability in identification and diagnostic guideline tools employed in studies, rather than geographical location per se.1,2,18,19§
A worldwide meta-analysis of 86 studies in children and adolescents, and 11 studies in adults, found no significant prevalence differences between countries, after controlling for differences in the diagnostic algorithms used to define ADHD.2§ An update to this meta-analysis combined with results of another systematic review of 102 worldwide studies similarly found that country was not significantly associated in the heterogeneity of prevalence estimates in children and adolescents.1,18§ Researchers therefore argue that ADHD is not a cultural construct associated with a particular geographical location.18§
Methodological features of prevalence studies
The differences in diagnostic criteria applied to define whether ADHD is present or not, may affect prevalence estimates. The DSM-5TM and the International Classification of Mental and Behavioural Disorders 10th revision (ICD-10) have different diagnostic criteria,17,20 which although are generally consistent, hyperkinetic disorder as defined in the ICD-10 may be considered a more severe form of ADHD and a narrower diagnosis, as it requires a minimum number of symptoms across all three dimensions (impulsivity, inattention and hyperactivity).20
Additionally, different versions of each of the diagnostic criteria used may affect prevalence rates; for example, an update of two systematic literature reviews and meta-regression analyses of the prevalence of ADHD in children and adolescents found that prevalence rates based on the Diagnostic and Statistical Manual of Mental Disorders – 3rd edition - Text Revision (DSM-III-TR) and ICD-10 were 2.42% and 4.09% lower, respectively, than rates based on the DSM-IV.18§
Finally, the source of the symptom report (e.g. parent report vs teacher report), and the setting that the population comes from (e.g. community vs school) may affect whether ADHD is deemed to be present or not.1,2
§These studies were conducted prior to publication of the Diagnostic and Statistical Manual of Mental Disorders – 5th Edition (DSM-5TM).
- Polanczyk G, de Lima MS, Horta BL, et al. The worldwide prevalence of ADHD: a systematic review and metaregression analysis. Am J Psychiatry 2007; 164: 942-948.
- Willcutt EG. The prevalence of DSM-IV attention-deficit/hyperactivity disorder: a meta-analytic review. Neurotherapeutics 2012; 9: 490-499.
- Fayyad J, de Graaf R, Kessler R, et al. Cross-national prevalence and correlates of adult attention-deficit hyperactivity disorder. Br J Psychiatry 2007; 190: 402-409.
- 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.
- Barkley RA, Fischer M, Smallish L, et al. The persistence of attention-deficit/hyperactivity disorder into young adulthood as a function of reporting source and definition of disorder. J Abnorm Psychol 2002; 111: 279-289.
- 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.
- 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.
- 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.
- Murphy K, Barkley RA. Attention deficit hyperactivity disorder adults: comorbidities and adaptive impairments. Compr Psychiatry 1996; 37: 393-401.
- 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.
- Faraone SV, Biederman J, Weber W, et al. Psychiatric, neuropsychological, and psychosocial features of DSM-IV subtypes of attention-deficit/hyperactivity disorder: results from a clinically referred sample. J Am Acad Child Adolesc Psychiatry 1998; 37: 185-193.
- Wilens TE, Biederman J, Faraone SV, et al. Presenting ADHD symptoms, subtypes, and comorbid disorders in clinically referred adults with ADHD. J Clin Psychiatry 2009; 70: 1557-1562.
- Kessler RC, Adler L, Barkley R, et al. The prevalence and correlates of adult ADHD in the United States: results from the National Comorbidity Survey Replication. Am J Psychiatry 2006; 163: 716-723.
- Piñeiro-Dieguez B, Balanzá-Martínez V, García-García P, et al. Psychiatric Comorbidity at the Time of Diagnosis in Adults With ADHD: The CAT Study. J Atten Disord 2014; 1-10.
- Steinhausen HC, Nøvik TS. ADORE Study Group. Co-existing psychiatric problems in ADHD in the ADORE cohort. Eur Child Adolesc Psychiatry 2006; 15: i25-i29.
- Friedrichs B, Igl W, Larsson H, et al. Coexisting psychiatric problems and stressful life events in adults with symptoms of ADHD--a large Swedish population-based study of twins. J Atten Disord 2012; 16: 13-22.
- American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition. 2013.
- Polanczyk GV, Willcutt EG, Salum GA, et al. ADHD prevalence estimates across three decades: an updated systematic review and meta-regression analysis. Int J Epidemiol 2014; 43: 434-442.
- Skounti M, Philalithis A, Galanakis E. Variations in prevalence of attention deficit hyperactivity disorder worldwide. Eur J Pediatr 2007; 166: 117-123.
- World Health Organization. The ICD-10 Classification of Mental and Behavioural Disorders. Available at: www.who.int/entity/classifications/icd/en/bluebook.pdf. Last updated 1993; 1: 1-263. Last accessed March 2015.
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New ADHD adult and the brain animation by Dr Mitul Mehta and Professor Philip Asherson is now available.
This booklet has been created to assist with clinical assessment of adult patients with ADHD using DSM-5TM criteria and the ASRS checklist.
ADHD is often a lifelong neurobehavioural disorder, which may persist from childhood into adulthood.
Comorbidities should be taken into account when diagnosing patients and planning treatment
Following accurate assessment and diagnosis, it is important to adopt a patient-centred management approach