Oct 3, 2026·Special Population & Related Conditions
Turner Syndrome and IQ: Average Overall Scores With a Visuospatial and Math Weakness
Turner syndrome IQ is usually in the average range, but verbal scores tend to run higher than visuospatial, math and speeded scores. Here is the evidence.
Dr. Russell T. WarneChief Scientist
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Most girls and women with Turner syndrome have an IQ in the average range; the 2024 international clinical guideline puts the share at about 90%. The full-scale number hides a characteristic split, with verbal ability usually average or better and visual-spatial reasoning noticeably weaker, a gap that shows up most clearly in mathematics.
This page covers the typical range and the karyotypes that shift it, the profile underneath the full-scale score, why math is so often the sticking point, and what that means for testing at different ages. The diagnostic criteria for intellectual disability are not repeated here, because they apply to only a minority of people with this condition.
The typical IQ range in Turner syndrome
Turner syndrome is the complete or partial loss of the second sex chromosome in a person who develops as female. It affects roughly 1 in 2,500 girls, a figure repeated across the research literature (Rovet, 1993; Mazzocco, 2009), and the 2024 clinical practice guideline from Gravholt and colleagues gives 25 to 50 per 100,000 females.
The guideline's summary of the neurocognitive evidence is direct: "Approximately 90% of individuals with TS have overall intellectual abilities within the average range." Hong, Scaletta Kent and Kesler's review in Developmental Disabilities Research Reviews describes the typical full-scale IQ as "average to low-average," with "a significant disjunction between verbal and performance IQ."
Clinic samples sometimes show a lower picture. Messina and colleagues tested 33 Italian girls aged 6 to 18 on Wechsler scales and found a mean full-scale IQ significantly below the normative mean, with 15.1% scoring in the intellectual disability range compared with an expected 2.3%. That is a small sample from a specialist clinic, and the same paper notes that higher rates of intellectual disability have generally been tied to one karyotype, a small ring X chromosome.
Karyotype matters
About 40% to 50% of people with Turner syndrome have the classic 45,X karyotype, according to the guideline, and the rest have mosaicism (a mix of cell lines) or a structurally altered X. The guideline notes that the classic verbal-over-spatial profile "tends to be more frequently associated with the 45,X karyotype." It also reports that people with a ring X chromosome that has lost a functioning XIST gene, the gene that normally silences the extra X, may show "a more severe cognitive phenotype," though it flags conflicting evidence on ring X outcomes overall. Because a learning difficulty and an intellectual disability are easy to confuse in this group, our explainer on the difference between intellectual disability and a learning disability is useful background.
The cognitive profile: verbal strength, spatial weakness
Hong and colleagues summarized about 50 years of research and concluded that a low Wechsler Performance IQ, or its successor indexes, is "the most consistent finding" in Turner syndrome. Older Performance IQ scores mixed reasoning with motor speed, so the deficit was hard to interpret. One study that gave both the WISC-III and the WISC-IV found girls with Turner syndrome below controls on the newer Perceptual Reasoning Index as well, which the reviewers read as a reasoning weakness that is independent of speed and motor skill.
The weak spots cluster where visual-spatial processing meets executive control. Timed Wechsler subtests such as Block Design, Object Assembly and Coding are especially vulnerable, and so are untimed tasks such as mental rotation of three-dimensional cubes and finding embedded figures. One detail is telling: a study that used letters instead of cubes found normal mental rotation, which suggests that verbally coded strategies can partly compensate. The visual-spatial index on modern Wechsler tests is the composite most likely to capture this weakness.
The verbal side is generally a strength. Hong's team describes receptive vocabulary and reading comprehension that equal or exceed those of peers, with one study finding that girls with Turner syndrome outperformed peers on the Peabody Picture Vocabulary Test. Verbal performance slips when the content carries a spatial or sequencing load, for instance following map directions or describing how relatives are related.
Klinefelter syndrome, an extra X chromosome in males, tends to show the reverse tilt, with language as the weaker side and spatial reasoning comparatively spared.
Face recognition is a further area of difficulty that several studies report. Some researchers have described the overall pattern as a nonverbal learning profile, while others argue that label does not fully explain the social difficulties (Hong et al., 2009).
Why math is so often the sticking point
Mathematics is the academic area most consistently affected. In Rovet's comparison of 67 children with Turner syndrome against 27 unaffected controls, the affected group underachieved in arithmetic, particularly numerical ability, mental calculation, geometry and reasoning. The guideline notes that reported rates of mathematics learning disability range from 10% to 79% across studies, a spread wide enough that any single figure should be read with its definition in mind.
Baker and Reiss pooled 112 comparisons from 17 studies in a meta-analysis. Their combined effect size was 0.67, meaning the average typically developing peer scored at the 74th percentile of the Turner syndrome group. The split by outcome is the most useful result for anyone reading a test report. On accuracy measures the effect was modest (0.34), while on response-time measures it was large (1.72), placing the average peer at the 96th percentile of the Turner group. The authors concluded that processing speed is "significantly more impaired" than the processes needed for accuracy.
Mazzocco reached a similar conclusion from the achievement side: most mathematical difficulties in girls with Turner syndrome "occur on timed tests or on complex problems," and on untimed tests scores may be age-appropriate. A normal untimed calculation score therefore does not rule out a math learning disability in this group. Our article on how dyscalculia is diagnosed describes the assessment process.
Testing at different ages
The guideline's developmental summary describes infants and toddlers with Turner syndrome as largely within the average range on standardized cognitive measures, with gross motor skills the main exception. The verbal-spatial discrepancy has been documented as early as age 4, and the classic profile becomes clearer in middle childhood as schoolwork turns abstract. Longitudinal studies through adolescence show girls with Turner syndrome developing in parallel with their peers in math and visual-spatial skills, with the gap persisting, and the guideline states that "the cognitive profile remains consistent throughout life."
Several practical issues follow for anyone interpreting a score:
• Index scores over the total: A full-scale IQ of 95 can average a verbal score near 105 with a visual-spatial score well below 90, so the indexes carry more information than the total.
• Speed effects: Because timed tasks are the most affected, a processing-speed weakness can pull down several subtests at once and should be interpreted separately from reasoning.
• Hearing: Hearing loss is more common in Turner syndrome, and the guideline recommends hearing screening throughout life, so an unexpectedly low verbal score warrants a hearing check before it is read as a cognitive finding.
• Attention: The guideline reports ADHD in 7% to 25% of study samples, higher than in unaffected peers, which can depress scores on working memory and speeded tasks.
Diagnosis timing also shapes who gets tested. In Stochholm and colleagues' Danish registry study, the median age at diagnosis was 15.1 years, and 38.5% of cases were diagnosed in adulthood. Many girls therefore show the profile in school before anyone knows the cause. Hormone treatment is part of standard medical care; Hong's review notes estrogen has been linked to faster processing speed and better memory in trials, but the core visual-spatial deficits persist regardless of estrogen or androgen levels.
The guideline recommends that cognitive and neuropsychological evaluation be built into care across the lifespan. In practice that means a psychologist or neuropsychologist who knows the Turner profile, working alongside the endocrinology team.
Frequently asked questions
What is the average IQ of someone with Turner syndrome?
Most people with Turner syndrome score in the average range, and reviews describe full-scale IQ as average to low-average. Verbal scores are usually higher than visual-spatial and speeded scores.
Does Turner syndrome cause intellectual disability?
Usually not. About 90% have overall ability in the average range, though intellectual disability is more common with certain karyotypes, particularly a small ring X chromosome.
Why do girls with Turner syndrome often struggle with math?
Math draws heavily on visual-spatial processing and speed, which are the weakest areas in the Turner profile. A meta-analysis found the largest differences on timed math tasks and much smaller ones on accuracy.
Is verbal IQ affected in Turner syndrome?
Composite verbal IQ is typically average, and vocabulary can be a relative strength. Verbal tasks that involve spatial relationships or sequencing are more likely to be weaker.
Who should do a cognitive evaluation for Turner syndrome?
A psychologist or neuropsychologist familiar with the Turner profile, ideally coordinating with the endocrinologist who manages the condition.
The takeaway
Turner syndrome IQ is usually average overall, and the clinically useful information sits in the gap between strong verbal scores and weaker visual-spatial scores, a gap that timed math tasks make especially visible. The profile is consistent from middle childhood into adulthood and is clearest with the 45,X karyotype. The index scores, read alongside hearing and attention, say far more about a person than one full-scale number does. If you want to see how index scores are built from subtests in the general population, you can take a professionally developed IQ test and read your own score profile.
References
1. Gravholt, C. H., Andersen, N. H., Christin-Maitre, S., Davis, S. M., Duijnhouwer, A., Gawlik, A., Maciel-Guerra, A. T., Gutmark-Little, I., Fleischer, K., Hong, D., Klein, K. O., Prakash, S. K., Shankar, R. K., Sandberg, D. E., Sas, T. C. J., Skakkebæk, A., Stochholm, K., van der Velden, J. A., International Turner Syndrome Consensus Group, & Backeljauw, P. F. (2024). Clinical practice guidelines for the care of girls and women with Turner syndrome. European Journal of Endocrinology, 190(6), G53-G151. [doi.org/10.1093/ejendo/lvae050](. doi.org
2. Hong, D., Scaletta Kent, J., & Kesler, S. (2009). Cognitive profile of Turner syndrome. Developmental Disabilities Research Reviews, 15(4), 270-278. [doi.org/10.1002/ddrr.79](. doi.org
3. Rovet, J. F. (1993). The psychoeducational characteristics of children with Turner syndrome. Journal of Learning Disabilities, 26(5), 333-341. [doi.org/10.1177/002221949302600506](. doi.org
4. Mazzocco, M. M. M. (2009). Mathematical learning disability in girls with Turner syndrome: A challenge to defining MLD and its subtypes. Developmental Disabilities Research Reviews, 15(1), 35-44. [doi.org/10.1002/ddrr.50](. doi.org
5. Messina, M. F., Zirilli, G., Civa, R., Rulli, I., Salzano, G., Aversa, T., & Valenzise, M. (2007). Neurocognitive profile in Turner's syndrome is not affected by growth impairment. Journal of Pediatric Endocrinology and Metabolism, 20(6), 677-684. [doi.org/10.1515/jpem.2007.20.6.677](. doi.org
6. Baker, J. M., & Reiss, A. L. (2016). A meta-analysis of math performance in Turner syndrome. Developmental Medicine & Child Neurology, 58(2), 123-130. [doi.org/10.1111/dmcn.12961](. doi.org
7. Stochholm, K., Juul, S., Juel, K., Naeraa, R. W., & Gravholt, C. H. (2006). Prevalence, incidence, diagnostic delay, and mortality in Turner syndrome. Journal of Clinical Endocrinology & Metabolism, 91(10), 3897-3902. [doi.org/10.1210/jc.2006-0558](. doi.org
Hero image: Plaadikas (baseplate compass and orienteering map), by Yx teine, licensed CC BY-SA 4.0 (creativecommons.org/licenses/by-sa/4.0). Via Wikimedia Commons.
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