Eating Disorders and IQ: How Anorexia and Bulimia Affect Cognitive Function
Eating disorders — including Anorexia Nervosa (AN), Bulimia Nervosa (BN), Binge Eating Disorder (BED), and related conditions — are serious mental health and medical conditions characterized by disturbances in eating behavior, body image, and weight regulation. Anorexia Nervosa has the highest mortality rate of any psychiatric condition. Eating disorders affect approximately 9% of the global population over a lifetime, with women affected at higher rates than men. The relationship between eating disorders and IQ is multifaceted: malnutrition in anorexia directly impairs brain function; cognitive preoccupation with food, weight, and body image consumes working memory and attentional resources; and the emotional state associated with eating disorders — depression, anxiety, and obsessionality — further suppresses cognitive performance. Importantly, many individuals with eating disorders, especially anorexia, have above-average premorbid IQ — making the cognitive impairments imposed by the disorder particularly stark and identifiable.
How Eating Disorders Affects IQ Test Performance
Anorexia Nervosa produces the most severe cognitive impairment of the eating disorder spectrum, primarily through two mechanisms: the direct neurological effects of malnutrition (reduced brain volume, impaired myelin integrity, glucose deprivation affecting prefrontal function) and the cognitive preoccupation with food-related and body-related stimuli that consumes working memory. Studies find that active AN is associated with reductions of 7–15 IQ points on full-scale tests relative to premorbid estimates, with the largest effects on Processing Speed and Working Memory. Flexibility of thinking — cognitive set-shifting — is particularly impaired in AN, with research showing extreme difficulty shifting away from food-related or disorder-related thoughts, mirroring the rigid cognitive style of the disorder. Bulimia Nervosa shows smaller cognitive impacts in the active phase, largely affecting attention and impulse control. Binge Eating Disorder is associated with executive function and inhibitory control deficits. Recovery from eating disorders is associated with substantial cognitive improvement, though neuroimaging studies find brain changes can persist beyond behavioral recovery.
What the Research Shows
A 2010 meta-analysis in the International Journal of Eating Disorders found that active anorexia nervosa is associated with significant impairments in attention (d = 0.62), working memory (d = 0.57), and set-shifting (d = 0.59) relative to healthy controls, with smaller but meaningful impairments in visuospatial function. Research by the Cambridge Eating Disorders Group found that set-shifting — the ability to move flexibly between different tasks or concepts — is impaired in active AN and persists even after weight restoration in some individuals, suggesting both state-dependent and possible trait components to AN's cognitive profile. A landmark longitudinal study by Lena Lauer and colleagues found that IQ scores in AN patients improved substantially with weight restoration, confirming the malnutrition-driven nature of most cognitive deficits. A 2022 study in Psychological Medicine found neuroimaging evidence of reduced gray matter volume in frontal and parietal regions in active AN, with partial recovery following weight restoration — providing a structural basis for both the cognitive impairments and their partial reversibility.
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Frequently Asked Questions
Does anorexia lower IQ?
Active anorexia nervosa reduces IQ test performance, primarily through malnutrition's effects on brain function and cognitive preoccupation consuming working memory. Studies find average reductions of 7–15 points on full-scale IQ during active illness, with the largest effects on processing speed and set-shifting. Critically, most of these deficits are reversible with weight restoration and nutritional recovery — research shows significant cognitive gains following successful treatment. Many individuals with anorexia have above-average premorbid intelligence, making the illness-related cognitive suppression particularly noticeable.
Are people with eating disorders intelligent?
Research consistently finds that individuals with anorexia nervosa in particular tend to have above-average premorbid intelligence — with some studies finding mean premorbid IQ approximately 5–10 points above population norms. This may reflect the role of perfectionism, conscientiousness, and high achievement orientation in eating disorder vulnerability. Eating disorders affect people across the full IQ range, but their over-representation in high-achieving academic environments has been well-documented. The disorder's cognitive impairments are superimposed on — and often dramatically contrast with — the person's premorbid intellectual ability.
Do cognitive deficits from eating disorders recover with treatment?
For most individuals, yes. Research shows that cognitive performance improves substantially with weight restoration in anorexia and with reduced binge-purge cycles in bulimia. A landmark longitudinal study found that IQ scores improved significantly following weight restoration treatment, confirming that malnutrition-driven deficits are largely reversible. However, some research suggests that set-shifting deficits in anorexia may be partially trait-like — present before disorder onset and persisting after recovery — possibly representing a cognitive vulnerability factor rather than solely a consequence of malnutrition.
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MyIQScores Editorial Team
Researchers in cognitive psychology, psychometrics & educational science
Last updated
May 10, 2026
All content on MyIQScores is reviewed for scientific accuracy against peer-reviewed research in cognitive psychology and psychometrics. Our editorial team cross-references each article with published literature before publication and updates pages whenever new research warrants a revision.