Do people with ADHD have a lower IQ?

Not as individuals. ADHD is a separate condition from intellectual disability, and it is found across the whole IQ range, from high to low. At the group level, people with ADHD tend to score somewhat lower than control groups, with a meta-analytic effect size of d=0.61 (roughly 9 IQ points), but part of that reflects points lost to inattention and weaknesses in working memory and processing speed, and it does not mean that reasoning ability itself is lower.

Can an IQ test or the WISC tell whether someone has ADHD?

No. A doctor diagnoses ADHD by judging whether symptoms of inattention, hyperactivity, and impulsivity were present before age 12, have lasted six months or more in two or more settings such as home and school or work, and interfere with daily life. Low Working Memory or Processing Speed scores on the WISC are common in ADHD, but the same uneven profile also appears in people without ADHD, so test results alone cannot establish a diagnosis.

Does taking ADHD medication raise your IQ?

There are reports of test scores rising with medication, but that does not mean intelligence itself went up. One cohort study found that mean full-scale IQ rose from 92.6 to 97.95 after a year of medication, but it had no control group, and the rise also includes the practice effect, where scores go up simply from taking the same test twice. The more reasonable reading is that sustained attention made it easier to show the ability that was already there.

ADHD and IQ: Is Average IQ Lower? WISC Profiles and High-IQ ADHD

Published: 2026-09-28

In brief: ADHD (attention-deficit/hyperactivity disorder) is not a disorder of intelligence, and it occurs in people with high IQs as well as in people with average IQs. Compared at the group level, people with ADHD tend to score somewhat lower on IQ tests than control groups: in a meta-analysis, the full-scale IQ gap was an effect size of d=0.61, or roughly 9 IQ points (Frazier and colleagues, 2004). Most of that gap shows up in the WISC's Working Memory and Processing Speed indexes, while the verbal comprehension and reasoning indexes tend to hold up, which is the typical uneven profile. Among adults with an IQ of 120 or higher, those with ADHD had the same kinds of difficulties at home and at work as people with ADHD and an average IQ. An IQ test cannot diagnose ADHD; the diagnosis is made by a specialist based on symptoms and how much they interfere with daily life.

ADHD (attention-deficit/hyperactivity disorder) and IQ are two different things. ADHD is a neurodevelopmental condition defined by inattention, hyperactivity, and impulsivity, it is independent of how intelligent someone is, and people with an IQ of 130 can have it too. At the group level, though, people with ADHD tend to score a little lower on IQ tests, and that gap is concentrated in particular indexes within the test. Drawing on research data, this article lays out how large the gap is, where it shows up on the WISC, and what happens with high-IQ ADHD.

What ADHD is: differences in regulating attention and behavior, not in intelligence

ADHD is a condition in which inattention (being easily distracted, often forgetting things) or hyperactivity and impulsivity (being unable to stay still, unable to wait one's turn) are stronger than expected for a person's age and interfere with daily life. The DSM-5-TR diagnostic criteria require that symptoms last six months or more, that several symptoms were present before age 12, and that they appear in two or more settings, such as home and school or work (MSD Manual Professional Version).

Prevalence is estimated at a worldwide average of 3.4% in children (Polanczyk and colleagues, 2015); in adults, it is 2.58% for ADHD persisting from childhood and 6.76% for symptomatic ADHD regardless of childhood onset (Song and colleagues, 2021). The diagnostic criteria contain no IQ requirement, and ADHD is diagnosed regardless of intelligence level.

Is the average IQ lower in ADHD? The meta-analytic gap is about 9 points

A meta-analysis pooling studies that compared intelligence test performance between people with ADHD and control groups found a full-scale IQ gap with an effect size of d=0.61 (Frazier, Demaree & Youngstrom, 2004, Neuropsychology). Applied to the IQ standard deviation of 15, that corresponds to an average gap of roughly 9 points.

The normal distribution of IQ: about 68% fall within ±1 SD and 95% within ±2 SD of the mean.

But this is a difference between group averages, and the distributions overlap heavily. Even when you compare two groups on a mean-100, SD-15 distribution that are shifted 9 points apart, most people with ADHD have IQs in the same range as the control group. The numbers also include points lost when attention drifts during testing and the disadvantage on timed tasks, so the gap does not mean "reasoning ability is 9 points lower." How to read the IQ distribution is explained in average IQ and standard deviation.

Genetic research points the same way: the genetic tendency toward ADHD was modestly and inversely related to intelligence (genetic correlation −0.41) and years of education (−0.53) (Demontis and colleagues, 2019, Nature Genetics). This too is a group-level tendency and does not predict any individual's IQ.

The uneven WISC profile: working memory and processing speed

On the WISC, children with ADHD are well known to score lower on Working Memory (WMI) and Processing Speed (PSI) than on the verbal comprehension and perceptual reasoning indexes. A study of 586 children on the WISC-III and 118 on the WISC-IV found that verbal comprehension and perceptual reasoning were significantly higher than working memory and processing speed, and in the WISC-IV sample every child's lowest index was either Working Memory or Processing Speed (Mayes & Calhoun, 2006).

WISC index	Typical pattern in ADHD	Abilities involved
Verbal Comprehension (VCI)	Tends to hold up	Vocabulary, knowledge, verbal reasoning
Perceptual Reasoning (PRI) / Fluid Reasoning, Visual Spatial	Tends to hold up	Reasoning with figures and rules
Working Memory (WMI)	Tends to be low	Holding spoken information in mind while manipulating it
Processing Speed (PSI)	Tends to be low	Completing simple tasks quickly and accurately

This profile closely matches the difficulties characteristic of ADHD: keeping information in mind, and staying focused while working quickly. The same profile also appears in people without ADHD, though, so having it does not mean someone has ADHD. How to read a score report is covered in how to read WISC results, and the individual abilities in how to train working memory and how to train processing speed.

A high IQ does not change the difficulties ADHD brings

A high IQ can make the traits less visible, and they sometimes get overlooked with "they're smart, so they'll be fine." Yet a study of adults with an IQ of 120 or higher found that those with ADHD functioned worse at home and at work than people of similar IQ without ADHD, and their pattern of difficulties was similar to that of people with ADHD and an average IQ (Antshel and colleagues, 2009, Psychological Medicine). In children too, high-IQ children with ADHD showed family history, cognitive, and behavioral features consistent with the diagnosis (Antshel and colleagues, 2007).

Having both high intelligence and the traits of a developmental disorder is called being "2E" (twice-exceptional). While strong ability can compensate for the weaknesses, they may stay hidden, then become obvious at university or work, when the amount of self-management required increases. More detail is in twice-exceptional (2E): gifted with a learning difference and what does gifted mean?.

An IQ test cannot detect ADHD: how it differs from diagnosis

An IQ test measures cognitive abilities such as reasoning and memory; it is not a test for whether someone has ADHD. To diagnose ADHD, a doctor judges when the symptoms started, in which settings they appear, and how much they interfere with daily life, using interviews, behavior rating scales, and information from school and family. Intelligence tests such as the WISC are used not as the diagnosis itself but as material for understanding strengths and weaknesses and planning support and learning strategies.

The same goes for online IQ tests: they cannot tell you whether you have ADHD. If you are concerned about symptoms, the reliable route is to consult a pediatrician or child psychiatrist for a child, or a psychiatrist or an adult ADHD clinic for an adult.

Does ADHD medication change IQ scores?

There are reports of intelligence test scores rising with medication. A cohort study following treated children with ADHD found that mean full-scale IQ rose from 92.6 to 97.95 after a year of medication (Johnson and colleagues, 2021, Journal of Psychiatric Research). However, it had no control group, and the rise also includes the practice effect, where scores go up simply from taking the same test twice.

Rather than medication raising intelligence itself, the reasonable reading is that sustained attention made it easier to show one's actual ability on the test. For the same reason, it is worth remembering that intelligence test results for people with ADHD are especially sensitive to how they feel and how well they can concentrate on the day.

How to check your own reasoning ability

An IQ test cannot tell you whether you have ADHD, but separately from that, you can get a rough sense of your own reasoning ability. BrainRank's free IQ test scores 20 questions (about 10 minutes) across four domains, spatial reasoning, pattern recognition, logical reasoning, and classification, using item response theory (IRT), and returns an estimated IQ on a mean-100, SD-15 scale along with your strengths and weaknesses by domain. Taking it is free with no signup; viewing the results, including the estimated IQ, is a one-time payment of ¥300 (tax included), with no subscription or auto-renewal (the result can be reopened for 24 hours after it is first shown, and saved as an image or PDF during that window). Results are estimates for entertainment and self-understanding, not a medical or diagnostic test.

Frequently asked questions

Do people with ADHD have a lower IQ?: Not as individuals. ADHD is a separate condition from intellectual disability, and it is found across the whole IQ range, from high to low. At the group level, people with ADHD tend to score somewhat lower than control groups, with a meta-analytic effect size of d=0.61 (roughly 9 IQ points), but part of that reflects points lost to inattention and weaknesses in working memory and processing speed, and it does not mean that reasoning ability itself is lower.
Can an IQ test or the WISC tell whether someone has ADHD?: No. A doctor diagnoses ADHD by judging whether symptoms of inattention, hyperactivity, and impulsivity were present before age 12, have lasted six months or more in two or more settings such as home and school or work, and interfere with daily life. Low Working Memory or Processing Speed scores on the WISC are common in ADHD, but the same uneven profile also appears in people without ADHD, so test results alone cannot establish a diagnosis.
Does taking ADHD medication raise your IQ?: There are reports of test scores rising with medication, but that does not mean intelligence itself went up. One cohort study found that mean full-scale IQ rose from 92.6 to 97.95 after a year of medication, but it had no control group, and the rise also includes the practice effect, where scores go up simply from taking the same test twice. The more reasonable reading is that sustained attention made it easier to show the ability that was already there.

Share this article

Editorial note & disclaimer

BrainRank Editorial Team

This article was written and edited by the BrainRank Editorial Team with reference to academic literature on psychometrics, including CHC theory and Item Response Theory (IRT). Statistics and percentages are calculated from a normal distribution model with a mean of 100 and a standard deviation of 15.

The tests on this site provide estimates for entertainment and self-understanding purposes only. They are not medical or clinical assessments, nor official psychological (intelligence) tests.

Sourcing standards and correction policy →