ADHD exists in all cultures and countries worldwide. The frequency of occurrence is called prevalence.
Prevalence can define different terms:
(Diagnostic) prevalence: Frequency of existing medical diagnoses of a disease in the total population (e.g., within the last 12 months). Depends on diagnostic scale and expertise of diagnosing persons.
True prevalence / field prevalence: Frequency of a disease when a representative group is thoroughly examined by experts, extrapolated to the total population. This value also depends
depends on the instruments used.
Treatment prevalence: Prevalence determined on the basis of treatment/preventive care contacts. Dependent on the treatment commitment of those affected.
Administrative prevalence: Prevalence determined from routine statistics (e.g. cancer registry). Hardly possible for ADHD.
Point prevalence: number of existing cases at a point in time.
Period prevalence: all occurring cases in a period.
Incidence: Frequency of new diagnoses of a disease in the total population (e.g., within the last 12 months).
The diagnostic prevalence of ADHD, i.e., the frequency with which practicing physicians and psychologists detect ADHD, has risen sharply in recent years as ADHD has become better understood and physicians and psychologists are now better trained. In contrast, the true prevalence, that is, the frequency with which ADHD actually exists, has not changed. In test studies in which representative groups are examined by specialists, the true prevalence of ADHD is unchanged.
Where we use the term prevalence without further explanation, we will refer to diagnostic prevalence in the future. As of April 2021, this differentiation has not yet been consistently verified, which is complicated by the fact that several studies do not formulate this transparently.
1. Population prevalence
The overall average prevalence in 2007 from studies conducted from 1978 to 2005 was 5.29%. Little difference was found between North America and Europe, while deviating values were found for Africa and the Middle East.
in 2018, one study identified a prevalence of around 5% in children and adolescents and another 5% just below the cutoff for a diagnosis. in 2012, a meta-analysis of 86 studies with n = 163,688 children and adolescents determined a prevalence cutoff of 5.9% to 7.1% according to DSM IV and 11 studies with n = 14,112 adults of around 5%.
The following differences in (diagnostic) prevalence in different regions of the world are likely to represent differences in diagnostic methodology rather than the true prevalence of ADHD.
The first KiGGS study in 2006 found that just under 5% of children and adolescents in Germany aged 3-17 had already received a medical diagnosis of ADHD (diagnosis prevalence). In addition, a further 5% were to be classified as suspected cases
The second KiGGS study from 2017 speaks of 4.4% of children and adolescents who had already received a medical diagnosis once. These are reports from the parents or guardians. The statement that an ADHD diagnosis was made once does not mean that this diagnosis must still exist at the time of the study survey.
The overall prevalence of ADHD in children and adolescents was found to be 2.2% in the 2007 Bella study (which we consider too low). A Bella sub-study with n= 2500 subjects between 7 and 17 years names the prevalence in parent assessment with about 5%. Both representations confirm a strong discrepancy of the prevalence according to social classes. According to the 2007 Bella study, the middle class is burdened with the average prevalence, while the lower social class has a prevalence 4 times higher than the upper class, at 3.9%. The Bella sub-study reports a prevalence of ADHD in the lower social stratum (at 7.2%) approximately 2.3 times higher than in the upper stratum at 2.8% (for 3 strata).
In older adults, one study determined an ADHD field prevalence of:
- 40-59-year-olds: 3.1
- 60-80 years old: 2.1 %
With regard to current ADHD symptomatology, the result of the self-assessment instrument used coincided 92.1% with that of the external observation instrument.
In Germany, 20% of psychiatric and psychotherapeutic patients are said to be affected by ADHD.
33.3% of all Germans and 38.8% of all EU citizens suffer from a mental disorder (within 12 months). Men and women are affected with roughly the same frequency, but with different types of disorders. The age group most frequently affected is 18 to 34 years.
Of these 33.3%, 1/3 (i.e. a total of 11.1% of all Germans) suffer from more than one disorder. In these cases, there is an open comorbidity of several disorders from different diagnostic groups. The comorbidity with regard to different individual diagnoses from the same group is again significantly higher.
Comorbidities increase with age.
The lifetime prevalence of ADHD in Germany is about the same as that of diabetes.
Continuing on the prevalence distribution of ADHD: http://www.adhs.info/fuer-paedagogen/allgemein-stoerungsbild/praevalenzraten.html
A cohort study in Denmark found a prevalence of 5.9% in boys under 18 years of age according to ICD 10. Another study among all children born from 1990 to 199 found a prevalence of 3.68%.
In Finland, a national cohort study observed an increase in ADHD medication administration in children from 1.26% in 2008 to 4.42% in 2018 and in adolescents from 0.93% in 2008 to 4.21% in 2018. At the same time, the proportion of females on medication increased.
The prevalence of ADHD in children aged 6 to 12 has been reported as 3.5% to 5.6%. Another study gives a value of 0.3%, which seems too low.
1.2.5. Czech Republic
In a representative population cross-section, the diagnostic prevalence in 2019 was 3%, and the field prevalence (according to the very simple ASRS) was 7.84%.
1.3. North America
In the U.S., the frequency of diagnosis of all developmental disabilities, including ADHD, increased significantly from 2009 to 2018:
- Children aged 3 to 17 years with ADHD diagnosis (diagnosis prevalence)
- 2010: 8 %
- 2017: 8.5 % to 9.5 %
- 2018: 9,8 %
- By age (2018)
- 3-4: Learning disability 3.2%, ADHD 1.2%
5-11: learning disability 6.7%, ADHD 9%
12-17: learning disability 9.4%, ADHD 13.6%
- Children aged 4 to 17 years in a nationwide telephone survey (diagnosis prevalence)
- 2003: 7,8 %
- 2007: 9.5%; 4.8% taking ADHD medication
- 2019/2020: 8,5 %
- Children 5 to 11 years of age in California (diagnosis prevalence)
Hispanic children were less likely to receive an ADHD diagnosis (2010: 4%; 2018: 6.9%) than non-Hispanic white (2010: 10%; 2018: 10.9%) or non-Hispanic black (2010: 11%; 2018: 13.1%) children. Children of couples with one white and one American Indian/Alaska Native parent had an ADHD prevalence of 26.4% in 2018
Children of single mothers were about twice as likely to show learning disabilities (1010: 12%; 2018: 11.3%) or ADHD (2010: 13%; 2018: 12.6%) as children in two-parent families (learning disabilities 2010: 6%, 2018: 5.9%; ADHD 2010: 7%, 2018: 8.8%). Children of single fathers had only 5% learning disabilities and 6.7% ADHD in 2018.
Children with moderate or poor health were about five times more likely to show learning disabilities (2010: 28% at 6%; 2018: 32.3% at 5.9%) and about twice as likely to show ADHD (2010: 18% at 7%; 2018: 16.2% at 8.8%) as children with excellent or very good health. In good health, ADHD was barely more common in 2018 (15.4%) than in moderate or poor health.
Children in large cities over 1 million population were less likely to receive an ADHD diagnosis in 2018 (8.2%) than children in cities under 1 million (12%) or outside large cities (11.6%).
Among war veterans, an increase of approximately 250% in annual ADHD prevalence was observed between 2009 and 2016, from 0.23 to 0.84%.
Friedmann reports that the lifetime prevalence of ADHD in the U.S. has increased from 7.8% in 2003 to 11% in 2011. This does not result from an increase in ADHD (true prevalence), but from the fact that ADHD is now better recognized and more reliably diagnosed (diagnostic prevalence).
A 20-year study from 1997 to 2016 in the United States found at diagnosis prevalences in children and adolescents:
- 6.1 % in 1997/1998
- 10.2 % in 2015/2016, of which
- Boys 14.0 %
- Girls 6,3 %
- hispanic 6.1 %
- non-Hispanic white 12.0%
- non-Hispanic black 12.8%
The increase in diagnostic prevalence is likely explained by improved diagnosis of ADHD. The true prevalence of ADHD in children in the United States did not change from 2003 to 2007.
One study found widely varying ADHD prevalences by county. The data were obtained through parent reports, which massively compromises their validity:
USA national: 12.9% (11.5% to 14.4%)
Areas with high ADHD prevalence:
- West South Central: 55.1% of counties had a prevalence of 16% or greater
- East South Central: 53.6% of counties had a prevalence of 16% or greater
- New England: 49.3% of counties had a prevalence of 16% or more
- South Atlantic: 46.2% of counties had a prevalence of 16% or greater
Areas with low ADHD prevalence:
- East North Central: 11.7% of counties had a prevalence of 16% or greater
- Pacific: 6.9% of counties had a prevalence of 16% or more
- West North Central: 5.8% of counties had a prevalence of 16% or greater
- Mid Atlantic: 4% of counties had a prevalence of 16% or more
- Mountain: 2.1% of counties had a prevalence of 16% or more
In Canadian children, ADHD has been diagnosed in
In contrast, the calculated true prevalence was
- 4 - 17 years
- 2008: 6,92 %
- 2015: 8,57 %
- Girls: 6.5 %
- Boys: 10.1 %
- 18 - 34 years
- 2008: 5,73 %
- 2015: 7,33 %
- 35 - 64 years
- 2008: 5,20 %
- 2015: 5,54 %
1.4. South America
Among Paisa children in Colombia, one study found an ADHD prevalence of 16.4% (boys 19.8%, girls 12.3%).
In China, the prevalence was found to be 6.26% in children and adolescents (63 studies from 1983 to 2015, 70% of which were from 2005 to 2015), with significant regional differences.
Among Japanese adults, ADHD prevalence is reported to be 1.7%.
Among Japanese female students (∅ 19.2 years), ADHD-HI was found in 27.2% and ADHD-I in 1.1%. Another study reported 27% ADHD among Japanese students (29.7% men, 25.3% women).
One study reported 31.1% ADHD by parent report (n = 7,566) and 4.3% ADHD by teacher report (n = 9,9 56), for an overall prevalence of 7.2% to 7.9% among Japanese preschool children. It is possible that parent reports are not robust in Japan for cultural reasons. Another study also finds evidence of inflated parent ratings for young children in Japan. While parents of 4 to 12 year olds identified an ADHD rate of 7.7%, teacher ratings of children identified ADHD (according to DSM III) in only 3.19%.
One large study found an increase in new ADHD diagnoses by ICD 9 from 7.92/10000 person-years in 2000 to 13.92/10000 person-years in 2011, with the male-to-female ratio decreasing from 3.61 to 2.90. The largest increase was found in young adults (19-30 years), followed by preschoolers (0-6 years).
A large study named the prevalence of ADHD in India in 2017 as 0.3%. The prevalence of ASD was reported to be 3.2%.
A rural area of northern India was found to have a prevalence of AD
In Ethiopia, a 2022 study of children and adolescents aged 6 to 17 years found a field prevalence of 13%. in 2015, a study of 6- to 17-year-olds found a prevalence of 7.3%. It affected 80% more boys than girls, children of single parents were 5 times more likely to be affected, and children from families with low socioeconomic status were 2.4 times more likely to be affected. Another study found a field prevalence of 9.9%
A 2016 study in Ghana found a prevalence of 1.64% among children 7 to 15 years of age.
A study in Somalia found a prevalence of 2.8% in children 7 to 15 years of age.
1.7. Middle East
In Iran, a study published in 2019 found a prevalence of 4% (5.2% in boys, 2.7% in girls) between 6 and 18 years of age.
1.7.2. Saudi Arabia
A study of 2280 students from 11 colleges at King Abdulaziz University, one of the largest universities in Saudi Arabia, were personally assessed with a validated Arabic version of the Adult ADHD Self-Report Scale. Of the 2059 students (90%) who completed the questionnaire (mean age: 21.2 years), 11.9% of the sample met criteria for adult ADHD. Only 6.5% had been diagnosed with ADHD in childhood, and only 0.8% had taken medication for it.
This is one of the few studies on the true prevalence (field prevalence) of ADHD.
The ADHD risk correlated with
- high family income
- bad grades in the last semester
- Divorce of parents
ADHD diagnosis in childhood
- previous depression diagnosis
- higher severity of current depression and anxiety
- Cigarette smoking.
2. Differences in different ethnic groups
One meta-study found the following ADHD prevalence rates by ethnicity among children and adolescents:
Whites: 16.8%, n = 835,505, k = 25
Blacks: 15.9% n = 218,445, k = 26
Asians: 12.4%, n = 66,413, k = 7
Latin American: 10.1%, n = 493,417, k = 24
N indicates the number of subjects, K the number of studies evaluated. There were no significant differences in prevalence by ethnicity.
A study of 5.2 million patients concluded that the prevalence of ADHD was population dependent:
- Whites: 102.8
- Indigenous: 0.56%-1.14%
- Hispanic or Latino: 0.25%-0.65%
- Colored: 0.22 %-0.69 %
- Asian-Americans: 0.11%-0.35%
- Pacific Islanders: 0.11%-0.39%
- Individuals of other ethnicities: 0.29%-0.71%
This is not the lifetime prevalence of the total population, but the frequency of diagnoses given within a year to patients using a particular medical record system.
Since ADHD is largely genetic, a difference in prevalence between different ethnic groups would not be surprising.
A cohort study of Scottish schoolchildren found the following relative prevalence distribution by ethnicity. 100% would be an even distribution. Asians and Blacks were thus significantly less likely to have ADHD than would have been expected based on the proportion of subjects
Asians: 8.3 %
Notes on the concepts of population and race:
- The term race characterizes humanity as a whole. There are no different races of people.
- The English term race does not designate a genetic definition, but a social construct.
- The genetic differences between continents are gradual. For example, there are groups of people in Africa (e.g. the San) who have lighter skin than groups of people in Europe (e.g. in Andalusia). The light skin color of Europeans was formed only a few thousand years ago. Before that, all people were more or less “black”.
- Over a family tree of 4000 years, every human being is related by blood to every other human being.
3.1. Prison Inmates
One study found an ADHD field prevalence (“true prevalence”) among adult prison inmates in the United Kingdom of 25%. In France (11%) and Canada (17%), field prevalence was found in prisons with more stringent diagnostic criteria.
Field prevalence is determined by examinations of a representative group of subjects by specialists and is to be distinguished from treatment prevalence (diagnosis prevalence), which measures the frequency of existing diagnoses on the part of the normal medical profession.
Among Spanish prison inmates, a lifetime prevalence of 54.4% was found for ADHD, with an acute prevalence of 16.4%. The lifetime prevalence of Axis 1 disorder was 81.4%.
3.2. Refugees and asylum seekers under 18 years of age
Among refugees and asylum seekers under 18 years of age, a meta-study of 8 studies found an ADHD prevalence of 8.6% (1% to 16%), with concurrent findings of PTSD (22.71%), anxiety disorders (15.77%), depression (13.81%), and ODD (1.77%). In our opinion, the high levels of PTSD, anxiety disorders, and depression may have masked the true prevalence of ADHD in the studied target group.
4. Prevalence in psychiatric hospitals
Among adult inpatients in a German psychiatric hospital, 59% were diagnosed with ADHD (12-month prevalence).
Adult patients of outpatient treatment centers were found to have ADHD prevalence ranging from 14.7% to 26.1%.