ADHD Prevalence: The Global Burden Under Age 20 in 204 Countries

In 2021 an estimated 46,890,733 people under the age of 20 in the world had ADHD. That is the figure from a new study using Global Burden of Disease 2021 (GBD 2021) data. The number is large, but to read it correctly you need to know how it was calculated and what the authors themselves say. The authors write themselves at the end of the abstract that these estimates may fall below the truth.

Who the study comes from and where

The authors of the study are Samuele Cortese, Min Seo Kim, Jong Hoon Han, Sarah Soyeon Oh, Dong Keon Yon, Jae Il Shin and Marco Solmi. The study was published in the journal Molecular Psychiatry in June 2026. Its type, in the abstract's own words, is a global, population-based analysis. That is, there is no study here that examined anyone one by one or tried out a medication or therapy. Estimates were produced with GBD 2021 data for everyone under the age of 20, for 204 countries and territories, from 1990 to 2021. The title also includes the phrase "critical appraisal," which suggests that the limits of the numbers were looked at as well.

This article is a summary of the paper published open access in Molecular Psychiatry. The paper was published under the Creative Commons Attribution 4.0 (CC BY 4.0) license. The findings belong to the authors of the paper; the account and assessment here are mine. One more note: I rely not on the whole paper but only on its abstract. So I do not know the details of the method, its tables or the authors' discussion section, and I will not make guesses about them.

What prevalence, incidence and DALY mean

The study looks at three measures, and at first glance all three seem to say the same thing, but they are different things.

Prevalence is the proportion or number of people in that age group who have ADHD in a given year. The answer to the question "how many people under 20 had ADHD in 2021."

Incidence is the proportion or number of people counted as newly having ADHD within that year. Prevalence can be thought of as a photograph, and incidence as a flow within a year.

DALY means "disability-adjusted life year." A measure that adds up, into a single number, the years lost early because of a disease and the years lived with the disease. In public health it is used to answer the question "how large is this disease's burden on society." The abstract does not break down what parts the DALY of ADHD is made of, it gives only the total number and the rate.

Next to the numbers, the parentheses say "95 percent uncertainty interval." This shows the reasonable limits around the estimate. If the interval is wide, the estimate is not certain, and here it is quite wide: the true value is expected to lie within these limits, but exactly where is not known.

The numbers for 2021

The figures in the abstract are as follows:

• Number of prevalent cases: 46,890,733 (uncertainty interval between 32,136,904 and 67,271,064).
• Number of incident cases: 4,111,621 (between 2,775,203 and 5,954,941).
• DALYs: 574,979 (between 294,277 and 977,557).
• Global prevalence rate: 1.78 percent (between 1.22 and 2.55 percent).
• Global incidence rate: 0.16 percent (between 0.11 and 0.23 percent).
• DALY rate: 21.8 per 100,000 people (between 11.2 and 37.1).

Looking at the intervals, the plainest fact is this: between the lower and upper limits of the estimate there is a difference of more than twofold. For prevalence we are somewhere between 1.22 percent and 2.55 percent. This shows that it should not be read as "the frequency of ADHD in the world is exactly 1.78 percent."

Among countries the highest prevalence and incidence rates came out in Australia: 5.62 percent (between 4.16 and 7.46 percent) and 0.49 percent (between 0.34 and 0.66 percent). The abstract does not rank other countries. It does not give a figure for Turkey either. It does not explain why Australia came out highest. As I see it, it is too early to read a difference like this as "there is more ADHD there," because between countries the habit of diagnosing, access to data and the method of measurement may differ too. This is my interpretation, not a claim in the abstract.

Change from 1990 to 2021

The authors report that between 1990 and 2021 the global prevalence and incidence rates fell "slightly": by 6.0 percent and 5.81 percent respectively. That is, the rates stayed roughly the same over these years, with a slight decrease.

There is a detail you need to watch here. This is a decline in a "rate," not a decline in the "number of people." Because the population changes, the rate and the number do not have to move in the same direction. The abstract does not give the change in the number of people over time. Nor does it explain the reason for the decline, and whether this reason is ADHD truly decreasing or a change in measurement or data sources does not come out of the abstract. A conclusion like "ADHD is decreasing" is not possible with this data.

Boys and girls, income level

In all GBD regions prevalence came out higher in boys than in girls: 2.52 percent and 0.99 percent. The gap between them is two and a half times. The abstract does not explain the reason for this difference. That ADHD in girls is noticed later and less is a subject known from other research, so I wrote about it separately in the article on ADHD in girls. But I cannot say from the abstract that there is data in this study that supports or refutes this.

The study has a second relationship too: prevalence rises as the sociodemographic index (SDI) rises. SDI is a composite measure used in the GBD. It is calculated from indicators such as income, level of education and fertility. That is, as the level of development rises, the rate of ADHD has risen too. The abstract again does not explain the reason. Here too, instead of "there is more ADHD in rich countries," it is necessary to keep in mind the possibility that "ADHD may be more recognized and measured in rich countries." This is also not a conclusion from the abstract, it is my cautious reading.

The authors' own warning: the estimate may have come out low

The last sentence of the abstract is important. The authors say the findings are guiding for policymakers, but immediately add that possible limitations of method may be making the prevalence, incidence and burden of ADHD look lower than they are. The abstract does not list what the limitations are.

So reading the 1.78 percent that came out not as "this is the real rate" but as "at least this much, probably more" is closer to the authors' own framing. You may have seen higher figures in other sources on the frequency of ADHD. The abstract makes no comparison with those figures, but it already says that its own estimate may have come out low.

What this finding means for you

In the daily life of a family, a teacher or a young person with ADHD, these numbers change nothing. Whether a child has ADHD is decided not by the prevalence in the world but by that child's symptoms and assessment. If you want to look at the subject from that side, the articles on ADHD symptoms in children and how ADHD is diagnosed in children will be more useful to you.

The value of this study lies elsewhere: in scale. It shows that ADHD exists in almost every part of the world, in millions of children and young people, and that this is a health matter that needs to be planned for. It is also a good reminder against the feeling of "this exists only in me." If you are curious about the causes of ADHD, the article what causes ADHD is a separate subject.

What this study does not say

Let me write out a few limits plainly.

This is an estimate. It is not data counted child by child. The uncertainty intervals are wide.

The abstract does not give in detail how many children there are in which country, it gives only the global numbers and Australia. It says nothing about Turkey.

The reason for the boy-girl difference and for the SDI relationship is not in the abstract. These are an observational picture, they do not show a cause-and-effect relationship.

There is also a limit regarding age: the study looks only at those under 20. The frequency and burden of ADHD in adults is outside the subject of this study. For what happens to ADHD in adulthood you can look at the article does ADHD go away.

What I think

I read this study in two ways. First, it is useful because it gives a rough scale: ADHD is not rare, it exists everywhere in the world and concerns millions of young people. Second, as the authors themselves say, because these numbers are not exact and probably stay low, one should not lean too heavily on the figures. When discussing a number, looking at it together with its interval is more honest than news headlines.

What strikes me most is the difference between girls and boys. I received my diagnosis at 22. So the question of in whom and when ADHD is noticed holds a separate place in me. The abstract does not give the reason for the difference, and neither will I. But I think it is not right to wave this difference away by looking at the numbers and saying "it's less in girls anyway."