Celiac Disease and IQ: Does It Affect Intelligence?

Celiac disease does not appear to lower IQ: in a Swedish study of 445,669 children, those diagnosed with celiac disease left compulsory school with grades no different from their classmates, a gap worth well under one IQ point that was not statistically significant. What untreated celiac disease can do is slow thinking for a while, the "brain fog" many patients describe, and small studies suggest it eases as the gut heals on a gluten-free diet.

This page covers what celiac disease is, what studies of brain fog actually measured, what large population studies show for children and older adults, and what the evidence says about gluten sensitivity without celiac disease. It describes research and is not medical advice. If you think you or your child may have celiac disease, a GP or pediatrician can arrange testing and refer you to a gastroenterologist.

Celiac disease is an immune disorder in which eating gluten, a protein found in wheat, barley and rye, damages the lining of the small intestine. The US National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) estimates that about 1% of people worldwide have it, many of them undiagnosed. The only established treatment is a lifelong gluten-free diet.

The question about intelligence arises because the damage is not confined to the gut. The NIDDK lists anemia, malnutrition and nervous system problems among the long-term complications. A damaged intestine absorbs nutrients poorly, and iron is one of the nutrients most often affected; our article on iron deficiency and IQ covers what that shortfall does to thinking. Celiac disease is also an autoimmune condition, and patients commonly report feeling mentally slow when exposed to gluten. Those reports are real, but a slow afternoon is a different thing from a lower IQ, and the research separates the two fairly clearly.

"Brain fog" is a patient term for slowed thinking, poor concentration and forgetfulness. Only a handful of studies have measured it with cognitive tests.

• The Melbourne pilot study: Lichtwark and colleagues tested 11 adults with newly diagnosed celiac disease when they started a gluten-free diet, then after 12 and 52 weeks. Scores on four tests of verbal fluency, attention and motor function improved over the year, and the improvements tracked healing of the intestine and falling antibody levels (correlations of r = 0.38 to 0.74). This is the strongest direct evidence that brain fog is real and reversible, but 11 people with no control group is a very small sample.

• The UK Biobank comparison: Iain Croall and colleagues compared 104 adults with celiac disease (average age 63) with 198 healthy people matched on age, sex, education, body mass index and blood pressure. Across five cognitive tests, the reported significant deficit was slower reaction time. The celiac group also reported more anxiety and depression, and brain scans showed subtle changes in white matter.

• The 2024 meta-analysis: Renato Beas and colleagues pooled the published studies on cognitive impairment and insomnia in celiac disease. Only 179 patients with celiac disease had been included in the cognitive studies, which shows how little data exist on the question.

There is also a rare and more serious pattern. A Mayo Clinic case series by William Hu and colleagues described 13 patients, with a median age of 64, whose cognitive decline began within two years of celiac symptoms starting or flaring. Ten of the 13 also had ataxia (problems with balance and coordination), and 3 improved or stabilised after removing gluten. A case series cannot show how often this happens, only that it can.

The best evidence on celiac disease and children's intellectual development comes from Sweden. Fredinah Namatovu and colleagues linked a national celiac register to school records for 445,669 children born between 1991 and 1994, 1,767 of whom had celiac disease diagnosed in childhood. After adjusting for family background, the children with celiac disease scored 2.4 points lower on a 320-point grade scale, a difference that was not statistically significant. With a standard deviation (the typical spread of scores) of about 64 points, that gap equals about 0.04 standard deviations, or roughly half an IQ point on a scale where the standard deviation is 15. By comparison, living with a single parent was linked to a 20.6-point gap.

A 2026 Swiss study by Sebastian Ludyga and colleagues tested 210 children with celiac disease and 234 healthy children on a standard attention task. Accuracy was identical (96% versus 97%), and the celiac group was about 19 milliseconds slower, a difference that was not statistically significant.

One Swedish register study does point the other way. Agnieszka Butwicka and colleagues followed 10,903 children with celiac disease and found higher rates of later psychiatric diagnoses, including ADHD, autism and intellectual disability, while their siblings showed no increased risk. That is an association in health records, not a measured IQ difference, and some diagnoses were already more common before celiac disease was found. The authors attributed the pattern to biological or psychological effects of the disease. It does not show that celiac disease lowers intelligence in children generally.

Because some older patients describe memory problems, researchers have asked whether celiac disease raises the risk of dementia. Benjamin Lebwohl and colleagues followed 8,846 Swedish adults aged 50 or older with biopsy-confirmed celiac disease and 43,474 matched controls for a median of 8.4 years. Dementia was diagnosed in 4.3% of patients and 4.4% of controls (hazard ratio 1.07, not significant). Risk was higher only in the first year after diagnosis, which may reflect closer medical attention around diagnosis, and there was a borderline signal for vascular dementia alone.

Many people without celiac disease avoid gluten because they believe it clouds their thinking, a condition often called "non-celiac gluten sensitivity." Blinded trials, where participants do not know whether they are eating gluten, give mixed answers.

• The Italian crossover trial: Antonio Di Sabatino and colleagues gave 59 adults with suspected gluten sensitivity either a small daily dose of gluten or a placebo in capsules for one week each. Gluten produced worse overall symptoms than placebo, including higher ratings of "foggy mind."

• The Monash trial: Jessica Biesiekierski and colleagues put 37 people on a diet low in fermentable carbohydrates, then added gluten or a placebo protein. Gluten-specific effects appeared in only 8% of participants.

• The Oslo trial: Gry Skodje and colleagues gave 59 people gluten, fructans (a carbohydrate found in wheat) or placebo in muesli bars. Fructans produced the most symptoms, and gluten scored no differently from placebo.

None of these trials measured IQ, and none tested the claim that gluten makes people less intelligent. The symptom ratings are self-reported, which is exactly where expectation has the most influence. No trial has shown that a gluten-free diet raises IQ in people without celiac disease. The NIDDK advises against starting a gluten-free diet before testing, because it can make celiac tests inaccurate. For how diet affects intelligence more broadly, see our article on whether diet or nutrition affects IQ.

Large studies find no meaningful effect. Swedish children with celiac disease finished school with grades about half an IQ-point equivalent below their peers, a gap that was not statistically significant.

Yes, in the sense that untreated patients score lower on some tests of attention, fluency and speed. In the one study that followed patients over a year, those scores improved as the intestine healed on a gluten-free diet.

There is no evidence that it does. Blinded trials of gluten sensitivity measured symptoms such as bloating and "foggy mind," not intelligence, and one found that fructans in wheat caused more symptoms than gluten.

A Swedish study of 8,846 older patients found no overall increase in dementia risk compared with matched controls. A small signal for vascular dementia needs confirmation.

Start with a GP or, for a child, a pediatrician, who can order celiac blood tests and refer to a gastroenterologist. Persistent memory or thinking problems warrant a neurologist or neuropsychologist assessment as well.

Celiac disease can make thinking feel slow while it is untreated, and in small studies that brain fog eases as the gut heals. The large population studies that come closest to measuring intelligence, school grades across Sweden and dementia rates in later life, find no meaningful lasting effect. Testing during a flare may understate ability, so if you want an accurate reading of your reasoning skills, choose a time when you feel well and take a professionally developed IQ test.

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8. Ludyga, S., Pedrini, L., Sarbach, L., Topyürek, B., Köhler, H., Furlano, R., & Légeret, C. (2026). A comparative study of cognitive function among children with coeliac disease and healthy controls. Scientific Reports, 16, 4275. [doi.org/10.1038/s41598-025-34500-7](. doi.org

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12. Biesiekierski, J. R., Peters, S. L., Newnham, E. D., Rosella, O., Muir, J. G., & Gibson, P. R. (2013). No effects of gluten in patients with self-reported non-celiac gluten sensitivity after dietary reduction of fermentable, poorly absorbed, short-chain carbohydrates. Gastroenterology, 145(2), 320-328. [doi.org/10.1053/j.gastro.2013.04.051](. doi.org

13. Skodje, G. I., Sarna, V. K., Minelle, I. H., Rolfsen, K. L., Muir, J. G., Gibson, P. R., Veierød, M. B., Henriksen, C., & Lundin, K. E. A. (2018). Fructan, rather than gluten, induces symptoms in patients with self-reported non-celiac gluten sensitivity. Gastroenterology, 154(3), 529-539. [doi.org/10.1053/j.gastro.2017.10.040](. doi.org

Hero image: CSIRO ScienceImage 385 Ears of Wheat, by CSIRO, CC BY 3.0. Via Wikimedia Commons.