Anorexia nervosa is not OCD, but the two disorders share striking similarities in brain function, genetics, and behavior. They are classified as separate conditions: anorexia falls under eating disorders, while OCD falls under obsessive-compulsive and related disorders. Still, up to 54% of people with anorexia also meet criteria for an OCD diagnosis, and the overlap between them runs deeper than most people realize.
Why They Look So Similar
Both anorexia and OCD involve rigid, repetitive behaviors that feel impossible to stop. A person with OCD might count objects or wash their hands following a strict internal script. A person with anorexia might cut food into exact pieces, eat in a fixed sequence, or exercise according to inflexible rules. From the outside, these rituals can look nearly identical.
The International OCD Foundation highlights a useful distinction through a specific example: a person with OCD might count mouthfuls of food because the number needs to feel “correct” or “just right,” while a person with anorexia counts mouthfuls to limit how much they eat and lose weight. Similarly, someone with OCD might wash their hands obsessively out of contamination fear, while someone with anorexia might do the same thing to remove traces of oil that they believe could cause weight gain if ingested. The behavior is the same. The motivation behind it is different.
The Brain Circuits They Share
Neuroimaging research shows that both anorexia and OCD involve disruptions in frontostriatal circuits, the brain pathways that connect the prefrontal cortex to deeper structures and help regulate self-control. These circuits loop information from the cortex to the subcortex and back again, governing your ability to shift between tasks, suppress urges, and respond flexibly to changing situations.
When these circuits malfunction, the result is an impaired capacity for self-regulatory control. In OCD, that impairment interacts with intrusive thoughts, producing compulsions. In anorexia, it interacts with preoccupation about body shape, weight, and food, producing self-starvation and rigid eating rituals. The underlying mechanism appears analogous, even though the surface-level symptoms point in different directions.
Cognitive Inflexibility in Both Conditions
People with anorexia and OCD think in remarkably similar ways. Research published in Frontiers in Psychiatry tested both groups on tasks measuring cognitive flexibility (the ability to shift mental gears) and found they performed almost identically. On a trail-making task that requires rapid switching between categories, both groups had significantly longer reaction times than healthy controls, but did not differ from each other. Both groups also reported comparably elevated levels of experienced cognitive inflexibility, with large effect sizes compared to controls.
This shared pattern of rigid thinking, strong detail focus, and difficulty seeing the bigger picture may be driven by those same dysfunctional brain pathways. It also helps explain why people with either condition can get “stuck” on rules, routines, and specific fears in ways that feel overwhelming and hard to interrupt.
How Much Genetic Overlap Exists
Genome-wide association studies have calculated a genetic correlation of 0.49 between anorexia and OCD, meaning roughly half of the genetic risk factors for one condition overlap with those for the other. A separate twin study found a similar figure (0.52) and also showed that anorexia was significantly more common in relatives of people with OCD compared to relatives of matched controls.
This is a meaningful overlap, but it’s not the whole story. The majority of genetic variance remains unique to each disorder, and non-shared environmental influences are largely specific to one condition or the other. In plain terms: the two disorders grow from partially common roots, but they branch in distinct directions.
One Key Difference: How People Feel About Their Symptoms
Perhaps the most important clinical distinction is how people experience their own thoughts. In OCD, intrusive thoughts are typically “ego-dystonic,” meaning they feel foreign and unwanted. A person with OCD who has contamination fears usually recognizes the thoughts as irrational and distressing. They don’t want to keep washing their hands; they feel compelled to.
In anorexia, the relationship with intrusive thoughts is more complicated. Research in Psychiatry Research found that eating-related intrusive thoughts can function as ego-syntonic, meaning the person experiences them as consistent with their goals and identity. When someone with anorexia has the thought “you shouldn’t eat that,” they may interpret it as a helpful reminder rather than an unwanted intrusion. When these thoughts were perceived as ego-syntonic, patients tried to act on them. When they were perceived as ego-dystonic, patients tried to neutralize them. This distinction shapes how willing someone is to resist their symptoms, which has major implications for treatment.
Treatment Approaches That Cross Over
Exposure and response prevention (ERP), the gold-standard therapy for OCD, has been adapted for anorexia with promising results. In the adapted version, patients are exposed to feared eating situations, like holding a sandwich and eating it, without using anxiety-reducing rituals such as breaking it into tiny pieces. The therapist helps the patient stay in contact with the feared food and experience their anxiety naturally decreasing over time.
A randomized controlled pilot study found that patients who received this adapted ERP increased their caloric intake during test meals by an average of 49 calories, while a control group actually decreased by 77 calories. The difference was statistically significant with a large effect size. Improvement in food intake was also directly linked to improvement in eating-related anxiety, suggesting the mechanism works the same way it does in OCD treatment: confront the fear, experience the anxiety dropping, and gradually loosen the grip of the compulsion.
Medication tells a different story. While SSRIs are a well-established treatment for OCD, there is no FDA-approved medication for anorexia, and available drug treatments have limited effectiveness. SSRIs may help with relapse prevention and mood symptoms in people with anorexia who have already restored their weight, but they don’t address the core eating disorder the way they can address OCD symptoms. This divergence in medication response is one reason researchers believe anorexia and OCD, despite their similarities, involve distinct enough biology to remain separate diagnoses.
Related but Not the Same
The question of whether anorexia should be reclassified as an obsessive-compulsive spectrum disorder has been debated for years. The evidence for partial overlap is strong: shared genetics, shared brain circuitry, shared cognitive profiles, high comorbidity rates (35 to 54% of anorexia patients also have OCD), and some shared treatment approaches. But the evidence for separation is equally compelling: the majority of genetic risk is unique to each condition, the motivation behind similar-looking behaviors differs, the relationship to one’s own symptoms differs, and medication responses diverge significantly.
If you or someone you know has symptoms of both conditions, that’s common and well-documented. Having both doesn’t mean one is causing the other. It means these two disorders share enough underlying biology that they frequently travel together, while still requiring their own targeted treatment approaches.