ADHD in Numbers: Verified Figures With Primary Sources

Last verified: 13 September 2026 Every figure here comes from a paper that was reachable on the day of checking, and the number is actually in it. Anything I could not verify has been left out.

The numbers

1. 2.58 % of adults worldwide have persistent ADHD, meaning symptoms that began in childhood. Systematic review and meta-analysis, adjusted for the global age structure in 2020.¹
2. 6.76 % show symptomatic ADHD, regardless of documented childhood onset. That works out to roughly 366 million people.¹
3. 5.29 % is the worldwide pooled prevalence among children and adolescents, calculated by metaregression across studies from every inhabited continent.²
4. 43 % of adults with clinically significant ADHD symptoms report significant insomnia symptoms. Against the general population that is a 2.7-fold increased risk (OR = 2.66; 95 % CI 1.74–4.07). Population sample, n = 4,618.³
5. 41 % of that same group sleep six hours or less per night.³
6. 84 % of children with ADHD had ferritin levels below 30 µg/l. In the control group it was 18 %.⁴
7. 208 empirically supported statements about ADHD were compiled by the World Federation of ADHD, endorsed by 80 experts from 27 countries. Only studies with more than 2,000 participants, or meta-analyses of at least five studies, were included.⁵

Why the list is this short

Seven figures is not many for a statistics page. The reason is simple: I checked every entry for whether the cited paper exists, whether year and journal match, and whether the number is really in there. Whatever failed that is gone, however plausible it sounded.

There is a second reason. A percentage without a denominator tells you nothing. With "68 % of those affected" you never learn who was asked, or how many. So every figure here says which group it came from.

How common is ADHD?

For adults, the answer depends on how you ask. Require documented childhood onset and prevalence sits at 2.58 %. Count everyone meeting the criteria today and it is 6.76 %.¹ Both numbers come from the same meta-analysis. Setting them against each other compares two definitions, not two populations.

Among children and adolescents the worldwide pooled estimate is 5.29 %.² The same paper shows that the striking differences between countries come mostly from how the data was collected, not from where.

How badly is sleep affected?

43 % of adults with clinically significant ADHD symptoms report significant insomnia symptoms, measured with the Insomnia Rating Scale in a population sample of 4,618 people.³ 41 % sleep six hours or less.

That puts the risk of clinically relevant insomnia at 2.7 times the general population.

What about iron?

In a study of children with ADHD, 84 % had ferritin levels below 30 µg/l; in the control group it was 18 %.⁴ Ferritin reflects iron stores, and iron is involved in dopaminergic signalling.

This is an association, not proof of a cause. The paper shows that low stores are more common in this group. It does not show that they cause ADHD, and certainly not that supplements change anything.

What is missing here

Three figures that often turn up on statistics pages are deliberately absent.

For average age at diagnosis and sex ratio I found no primary source whose number I can support. And the frequently quoted share of adults with RSD goes back to an estimate in a magazine article rather than a study. Estimated is not measured.

If solid papers turn up for any of these, I will add the numbers.

Checking the sources

Every source is listed below with DOI and PubMed link. The figures can be read in the abstracts, no paywall.

Footnotes

1. Song, P., et al. (2021). The prevalence of adult attention-deficit hyperactivity disorder: A global systematic review and meta-analysis. Journal of Global Health, 11, 04009. DOI 10.7189/jogh.11.04009 · PubMed 33692893 ↩ ↩² ↩³

2. Polanczyk, G., et al. (2007). The worldwide prevalence of ADHD: a systematic review and metaregression analysis. American Journal of Psychiatry, 164(6), 942–948. DOI 10.1176/ajp.2007.164.6.942 · PubMed 17541055 ↩ ↩²

3. Wynchank, D., et al. (2018). The Association Between Insomnia and Sleep Duration in Adults With ADHD: Results From a General Population Study. Journal of Clinical Sleep Medicine, 14(3), 349–357. DOI 10.5664/jcsm.6976 · PubMed 29458702 ↩ ↩² ↩³

4. Konofal, E., et al. (2004). Iron deficiency in children with attention-deficit/hyperactivity disorder. Archives of Pediatrics & Adolescent Medicine, 158(12), 1113–1115. DOI 10.1001/archpedi.158.12.1113 · PubMed 15583094 ↩ ↩²

5. Faraone, S. V., et al. (2021). The World Federation of ADHD International Consensus Statement: 208 Evidence-based conclusions about the disorder. Neuroscience & Biobehavioral Reviews, 128, 789–818. DOI 10.1016/j.neubiorev.2021.01.022 · PubMed 33549739 ↩