The diagnostic workup typically includes complete medical and psychosocial history and follows a rational and formulaic approach to the diagnosis. Neuroimaging using fMRI, MRI, PET and SPECT scans have been used to detect cases in which a lesion, tumor or other organic condition has been either the sole causative or contributory factor in an eating disorder. "Right frontal intracerebral lesions with their close relationship to the limbic system could be causative for eating disorders, we therefore recommend performing a cranial MRI in all patients with suspected eating disorders" (Trummer M "et al." 2002), "intracranial pathology should also be considered however certain is the diagnosis of early-onset anorexia nervosa. Second, neuroimaging plays an important part in diagnosing early-onset anorexia nervosa, both from a clinical and a research prospective".(O'Brien "et al." 2001).

After ruling out organic causes and the initial diagnosis of an eating disorder being made by a medical professional, a trained mental health professional aids in the assessment and treatment of the underlying psychological components of the eating disorder and any comorbid psychological conditions. The clinician conducts a clinical interview and may employ various psychometric tests. Some are general in nature while others were devised specifically for use in the assessment of eating disorders. Some of the general tests that may be used are the Hamilton Depression Rating Scale and the Beck Depression Inventory. longitudinal research showed that there is an increase in chance that a young adult female would develop bulimia due to their current psychological pressure and as the person ages and matures, their emotional problems change or are resolved and then the symptoms decline.

Previously considered a topic for further research exploration, binge eating disorder was included in the "Diagnostic and Statistical Manual of Mental Disorders" in 2013. Until 2013, binge eating disorder was categorized as an Eating Disorder Not Otherwise Specified, an umbrella category for eating disorders that don't fall under the categories for anorexia nervosa or bulimia nervosa. Because it was not a recognized psychiatric disorder in the "DSM-IV" until 2013, it has been difficult to obtain insurance reimbursement for treatments. The disorder now has its own category under "DSM-5", which outlines the signs and symptoms that must be present to classify a person's behavior as binge eating disorder. Studies have confirmed the high predictive value of these criteria for diagnosing BED.

According to DSM-5, the following criteria must be present to make a diagnosis of binge eating disorder. Studies have confirmed the high predictive value of these criteria for diagnosing BED.

A. Recurrent episodes of binge eating. An episode of binge eating is characterized by both of the following:

1. Eating, in a discrete period of time (e.g., within any 2-hour period), an amount of food that is definitely larger than what most people would eat in a similar period of time under similar circumstances.

2. A sense of lack of control over eating during the episode (e.g., a feeling that one cannot stop eating or control what or how much one is eating).

B. The binge-eating episodes are associated with three (or more) of the following:

1. Eating much more rapidly than normal.

2. Eating until feeling uncomfortably full.

3. Eating large amounts of food when not feeling physically hungry.

4. Eating alone because of feeling embarrassed by how much one is eating.

5. Feeling disgusted with oneself, depressed, or very guilty afterward.

C. Marked distress regarding binge eating is present.

D. The binge eating occurs, on average, at least once a week for 3 months.

E. The binge eating is not associated with the recurrent use of inappropriate compensatory behavior as in bulimia nervosa and does not occur exclusively during the course of bulimia nervosa or anorexia nervosa.

Individuals suffering from BED often have a lower overall quality of life and commonly experience social difficulties.

Early behavior change is an accurate prediction of remission of symptoms later.

Individuals who have BED commonly have other comorbidities such as major depressive disorder, personality disorder, bipolar disorder, substance abuse, body dysmorphic disorder, kleptomania, irritable bowel syndrome, fibromyalgia, or an anxiety disorder. There may also be panic attacks and a history of attempted suicide.

While people of a healthy weight may overeat occasionally, an ongoing habit of consuming large amounts of food in a short period of time may ultimately lead to weight gain and obesity. Binging episodes usually include foods that are high in fat, sugar, and/or salt, but low in vitamins and minerals, as these types of foods tend to trigger greatest emotional reward. The main physical health consequences of this type of eating disorder are brought on by the weight gain resulting from the binging episodes. Up to 70% of individuals with BED may also be obese, and therefore obesity-associated morbidities such as high blood pressure and coronary artery disease type 2 diabetes mellitus gastrointestinal issues (e.g., gallbladder disease), high cholesterol levels, musculoskeletal problems and obstructive sleep apnea may also be present.

Few studies to date have examined OSFED prevalence. The largest community study is by Stice (2013), who examined 496 adolescent females who completed annual diagnostic interviews over 8 years. Lifetime prevalence by age 20 for OSFED overall was 11.5%. 2.8% had atypical AN, 4.4% had subthreshold BN, 3.6% had subthreshold BED, and 3.4% had purging disorder. Peak age of onset for OSFED was 18–20 years. NES was not assessed in this study, but estimates from other studies suggest that it presents in 1% of the general population.

A few studies have compared the prevalence of EDNOS and OSFED and found that though the prevalence of atypical eating disorders decreased with the new classification system, the prevalence still remains high. For example, in a population of 215 young patients presenting for ED treatment, the diagnosis of EDNOS to OSFED decreased from 62.3% to 32.6%. In another study of 240 females in the U.S. with a lifetime history of an eating disorder, the prevalence changed from 67.9% EDNOS to 53.3% OSFED. Although the prevalence appears to reduce when using the categorizations of EDNOS vs. OSFED, a high proportion of cases still receive diagnoses of atypical eating disorders, which creates difficulties in communication, treatment planning, and basic research.

Medical tests to check for signs of physical deterioration in anorexia nervosa may be performed by a general physician or psychiatrist, including:

- Complete Blood Count (CBC): a test of the white blood cells, red blood cells and platelets used to assess the presence of various disorders such as leukocytosis, leukopenia, thrombocytosis and anemia which may result from malnutrition.

- Urinalysis: a variety of tests performed on the urine used in the diagnosis of medical disorders, to test for substance abuse, and as an indicator of overall health

- Chem-20: Chem-20 also known as SMA-20 a group of twenty separate chemical tests performed on blood serum. Tests include cholesterol, protein and electrolytes such as potassium, chlorine and sodium and tests specific to liver and kidney function.

- Glucose tolerance test: Oral glucose tolerance test (OGTT) used to assess the body's ability to metabolize glucose. Can be useful in detecting various disorders such as diabetes, an insulinoma, Cushing's Syndrome, hypoglycemia and polycystic ovary syndrome.

- Serum cholinesterase test: a test of liver enzymes (acetylcholinesterase and pseudocholinesterase) useful as a test of liver function and to assess the effects of malnutrition.

- Liver Function Test: A series of tests used to assess liver function some of the tests are also used in the assessment of malnutrition, protein deficiency, kidney function, bleeding disorders, and Crohn's Disease.

- Lh response to GnRH: Luteinizing hormone (Lh) response to gonadotropin-releasing hormone (GnRH): Tests the pituitary glands' response to GnRh a hormone produced in the hypothalamus. Hypogonadism is often seen in anorexia nervosa cases.

- Creatine Kinase Test (CK-Test): measures the circulating blood levels of creatine kinase an enzyme found in the heart (CK-MB), brain (CK-BB) and skeletal muscle (CK-MM).

- Blood urea nitrogen (BUN) test: urea nitrogen is the byproduct of protein metabolism first formed in the liver then removed from the body by the kidneys. The BUN test is primarily used to test kidney function. A low BUN level may indicate the effects of malnutrition.

- BUN-to-creatinine ratio: A BUN to creatinine ratio is used to predict various conditions. A high BUN/creatinine ratio can occur in severe hydration, acute kidney failure, congestive heart failure, and intestinal bleeding. A low BUN/creatinine ratio can indicate a low protein diet, celiac disease, rhabdomyolysis, or cirrhosis of the liver.

- Electrocardiogram (EKG or ECG): measures electrical activity of the heart. It can be used to detect various disorders such as hyperkalemia

- Electroencephalogram (EEG): measures the electrical activity of the brain. It can be used to detect abnormalities such as those associated with pituitary tumors.

- Thyroid Screen TSH, t4, t3 :test used to assess thyroid functioning by checking levels of thyroid-stimulating hormone (TSH), thyroxine (T4), and triiodothyronine (T3)

A variety of medical and psychological conditions have been misdiagnosed as anorexia nervosa; in some cases the correct diagnosis was not made for more than ten years.

The distinction between the diagnoses of anorexia nervosa, bulimia nervosa and eating disorder not otherwise specified (EDNOS) is often difficult to make as there is considerable overlap between people diagnosed with these conditions. Seemingly minor changes in a people's overall behavior or attitude can change a diagnosis from anorexia: binge-eating type to bulimia nervosa. A main factor differentiating binge-purge anorexia from bulimia is the gap in physical weight. Someone with bulimia nervosa is ordinarily at a healthy weight, or slightly overweight. Someone with binge-purge anorexia is commonly underweight. People with the binge-purging subtype of AN may be significantly underweight and typically do not binge-eat large amounts of food, yet they purge the small amount of food they eat. In contrast, those with bulimia nervosa tend to be at normal weight or overweight and binge large amounts of food. It is not unusual for a person with an eating disorder to "move through" various diagnoses as their behavior and beliefs change over time.

Few studies guide the treatment of individuals with OSFED. However, cognitive behavioral therapy (CBT), which focuses on the interplay between thoughts, feelings, and behaviors, has been shown to be the leading evidence-based treatment for the eating disorders of BN and BED. For OSFED, a particular cognitive behavioral treatment can be used called CBT-Enhanced (CBT-E), which was designed to treat all forms of eating disorders. This method focuses not only what is thought to be the central cognitive disturbance in eating disorders (i.e., over-evaluation of eating, shape, and weight), but also on modifying the mechanisms that sustain eating disorder psychopathology, such as perfectionism, core low self-esteem, mood intolerance, and interpersonal difficulties. CBT-E showed effectiveness in two studies (total N = 219) and well maintained over 60-week follow-up periods. CBT-E is not specific to individual types of eating disorders but is based on the concept that common mechanisms are involved in the persistence of atypical eating disorders, AN, and BN.

Clinicians will often follow a diagnostic checklist to test whether or not an individual is exhibiting behaviors and characteristics that may lead to a diagnosis of ARFID. Clinicians will look at the variety of foods an individual consumes, as well as the portion size of accepted foods. They will also question how long the avoidance or refusal of particular foods has lasted, and if there are any associated medical concerns, such as malnutrition. Unlike most eating disorders, there may be a higher rate of ARFID in young boys, than there is in young girls.

There are two main types of treatment given to those suffering with bulimia nervosa; psychopharmacological and psychosocial treatments.

Some researchers have also claimed positive outcomes in hypnotherapy.

Rather than providing specific diagnostic criteria for EDNOS, the fourth revision of the "Diagnostic and Statistical Manual of Mental Disorders" ("DSM-IV") listed six non-exhaustive example presentations, including individuals who:

1. Meet all criteria for anorexia nervosa except their weight falls within the normal range

2. Meet all criteria for bulimia nervosa except they engage in binge eating or purging behaviors less than twice per week or for fewer than three months

3. Purge after eating small amounts of food while retaining a normal body weight

4. Repeatedly chew and spit out large amounts of food without swallowing

5. Do not meet criteria for binge eating disorder

Despite its subclinical status in "DSM-IV", available data suggest that EDNOS is no less severe than the officially recognized "DSM-IV" eating disorders. In a comprehensive meta-analysis of 125 studies, individuals with EDNOS exhibited similar levels of eating pathology and general psychopathology to those with anorexia nervosa and binge eating disorder, and similar levels of physical health problems as those with anorexia nervosa. Although individuals with bulimia nervosa scored significantly higher than those with EDNOS on measures of eating pathology and general psychopathology, those with EDNOS exhibited more physical health problems than those with bulimia nervosa.

Eating disorder not otherwise specified (EDNOS) is an eating disorder that does not meet the criteria for: anorexia nervosa, bulimia nervosa, or binge eating. Individuals with EDNOS usually fall into one of three groups: sub-threshold symptoms of anorexia or bulimia, mixed features of both disorders, or extremely atypical eating behaviors that are not characterized by either of the other established disorders.

People with EDNOS have similar symptoms and behaviors to those with anorexia and bulimia, and can face the same dangerous risks.

EDNOS is the most prevalent eating disorder; about 60% of adults treated for eating disorders are diagnosed with EDNOS. EDNOS occurs in both sexes.

Children can benefit from a four stage in-home treatment program based on the principles of systematic desensitization. The four stages of the treatment are record, reward, relax and review.

- In the record stage, children are encouraged to keep a log of their typical eating behaviors without attempting to change their habits as well as their cognitive feelings.

- The reward stage involves systematic desensitization. Children create a list of foods that they might like to try eating some day. These foods may not be drastically different from their normal diet, but perhaps a familiar food prepared in a different way. Because the goal is for the children to try new foods, children are rewarded when they sample new foods.

- The relaxation stage is most important for those children that suffer severe anxiety when presented with unfavorable foods. Children learn to relax to reduce the anxiety that they feel. Children work through a list of anxiety-producing stimuli and can create a story line with relaxing imagery and scenarios. Often these stories can also include the introduction of new foods with the help of a real person or fantasy person. Children then listen to this story before eating new foods as a way to imagine themselves participating in an expanded variety of foods while relaxed.

- The final stage, review, is important to keep track of the child's progress. It is important to include both one-on-one sessions with the child, as well as with the parent in order to get a clear picture of how the child is progressing and if the relaxation techniques are working.

There are numerous ways in which individuals can reduce emotional distress without engaging in emotional eating. The most salient choice is to minimize maladaptive coping strategies and to maximize adaptive strategies. A study conducted by Corstorphine et al. in 2007 investigated the relationship between distress tolerance and disordered eating. These researchers specifically focused on how different coping strategies impact distress tolerance and disordered eating. They found that individuals who engage in disordered eating often employ emotional avoidance strategies. If an individual is faced with strong negative emotions, they may choose to avoid the situation by distracting themselves through overeating. Discouraging emotional avoidance is thus an important facet to emotional eating treatment. The most obvious way to limit emotional avoidance is to confront the issue through techniques like problem solving. Corstorphine et al. showed that individuals who engaged in problem solving strategies enhance one's ability to tolerate emotional distress. Since emotional distress is correlated to emotional eating, the ability to better manage one's negative affect should allow an individual to cope with a situation without resorting to overeating.

One way to combat emotional eating is to employ mindfulness techniques. For example, approaching cravings with a nonjudgmental inquisitiveness can help differentiate between hunger and emotionally-driven cravings. An individual may ask his or herself if the craving developed rapidly, as emotional eating tends to be triggered spontaneously. An individual may also take the time to note his or her bodily sensations, such as hunger pangs, and coinciding emotions, like guilt or shame, in order to make conscious decisions to avoid emotional eating.

Emotional eating disorder predisposes individuals to more serious eating disorders and physiological complications. Therefore, combatting disordered eating before such progression takes place has become the focus of many clinical psychologists.

Disordered eating describes a variety of abnormal eating behaviors that, by themselves, do not warrant diagnosis of an eating disorder.

Disordered eating includes behaviors that are common features of eating disorders, such as:

- Chronic restrained eating.

- Compulsive eating.

- Binge eating, with associated loss of control.

- Self-induced vomiting.

Disordered eating also includes behaviors that are not characteristic of any eating disorder, such as:

- Irregular, chaotic eating patterns.

- Ignoring physical feelings of hunger and satiety (fullness).

- Use of diet pills.

- Emotional eating.

- Night eating.

- "Secretive food concocting": the consumption of embarrassing food combinations, such as mashed potatoes mixed with sandwich cookies. See also Food craving § Pregnancy and Nocturnal sleep-related eating disorder § Symptoms and behaviors.

Typically the eating is done rapidly and a person will feel emotionally numb and unable to stop eating.

Most people who have eating binges try to hide this behavior from others, and often feel ashamed about being overweight or depressed about their overeating. Although people who do not have any eating disorder may occasionally experience episodes of overeating, frequent binge eating is often a symptom of an eating disorder.

Binge-eating disorder, as the name implies, is characterized by uncontrollable, excessive eating, followed by feelings of shame and guilt. Unlike those with bulimia, those with binge-eating disorder symptoms typically do not purge their food, fast, or excessively exercise to compensate for binges. Additionally, these individuals tend to diet more often, enroll in weight-control programs and have a history of family obesity. However, many who have bulimia also have binge-eating disorder.

→Swollen of salivary glands lead to the change of facial shape

→If gastric juice is flown to the esophagus constantly, it will lead to a corrosion of the wall of esophagus(long term harmful effect)

→If gastric juice is flown to the oral cavity, it will lead to a corrosion of the oral tissue, dissolve the enamel and consequently cause the loss of teeth/increase chances for tooth decay

Disordered eating can represent a change in eating patterns caused by other mental disorders (e.g. clinical depression), or by factors that are generally considered to be unrelated to mental disorders (e.g. extreme homesickness).

Certain factors among adolescents tend to be associated with disordered eating, including perceived pressure from parents and peers, nuclear family dynamic, body mass index, negative affect (mood), self-esteem, perfectionism, drug use, and participation in sports that focus on leanness. These factors are similar among boys and girls alike. However, the reported incidence rates of are consistently and significantly higher in female than male participants, with 61% of females and 28% of males reporting disordered eating behaviors in a study of over 1600 adolescents.

Emotional eating may qualify as avoidant coping and/or emotion-focused coping. As coping methods that fall under these broad categories focus on temporary reprieve rather than practical resolution of stressors, they can initiate a vicious cycle of maladaptive behavior reinforced by fleeting relief from stress. Additionally, in the presence of high insulin levels characteristic of the recovery phase of the stress-response, glucocorticoids trigger the creation of an enzyme that stores away the nutrients circulating in the bloodstream after an episode of emotional eating as visceral fat, or fat located in the abdominal area. Therefore, those who struggle with emotional eating are at greater risk for abdominal obesity, which is in turn linked to a greater risk for metabolic and cardiovascular disease.

Some of the differential or comorbid medical diagnoses may include:

- achalasia – There have been cases where achalasia, a disorder of the esophagus which affects peristalsis, has been misdiagnosed as AN. It has been reported in cases where there is sub-clinical manifestation of anorexia nervosa and also in cases where the full diagnostic criteria AN have been met.

- acute pandysautonomia is one form of an autonomic neuropathy, which is a collection of various syndromes and diseases which affect the autonomic neurons of the autonomic nervous system (ANS). Autonomic neuropathies may be the result of an inherited condition or they may be acquired due to various premorbid conditions such as diabetes and alcoholism, bacterial infection such as Lyme disease or a viral illness. Some of the symptoms of ANS which may be associated with an ED include nausea, dysphagia, constipation, pain in the salivary glands, early saiety. It also affects peristalsis in the stomach. Acute pandysautonomia may cause emotional instability and has been misdiagnosed as various psychiatric disorders including hysterical neurosis and anorexia nervosa.

- Lupus: various neuropsychiatric symptoms are associated with systemic lupus erythematosus (SLE), including depression. Anorexia and weight loss also may occur with SLE and while rare it may be misdiagnosed as AN.

- Lyme disease is known as the "great imitator", as it may present as a variety of psychiatric or neurologic disorders including anorexia nervosa. "A 12 year old boy with confirmed Lyme arthritis treated with oral antibiotics subsequently became depressed and anorectic. After being admitted to a psychiatric hospital with the diagnosis of anorexia nervosa, he was noted to have positive serologic tests for Borrelia burgdorferi. Treatment with a 14 day course of intravenous antibiotics led to a resolution of his depression and anorexia; this improvement was sustained on 3 year follow-up." Serologic testing can be helpful but should not be the sole basis for diagnosis. The Centers for Disease Control (CDC) issued a cautionary statement (MMWR 54;125) regarding the use of several commercial tests. Clinical diagnostic criteria have been issued by the CDC (CDC, MMWR 1997; 46: 531-535).

- Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is a rare genetic disorder characterized by gastrointestinal dysmotility, severe cachexia progressive external ophthalmoplegia, post-prandial emesis (vomiting after eating), peripheral neuropathy, and diffuse leukoencephalopathy. Onset is prior to age 20 in 60% of cases. ""Miss A" was a 21-year-old Indian woman diagnosed as having treatment-resistant anorexia nervosa." It was subsequently proven to be MNGIE

- superior mesenteric artery syndrome (SMA syndrome) "is a gastrointestinal disorder characterized by the compression of the third or transverse portion of the duodenum against the aorta by the superior mesenteric artery resulting in chronic partial, incomplete, acute or intermittent duodenal obstruction". It may occur as a complication of AN or as a differential diagnosis. There have been reported cases of a tentative diagnosis of AN, where upon treatment for SMA syndrome the patient is asymptomatic.

- Addison's disease is a disorder of the adrenal cortex which results in decreased hormonal production. Addison's disease, even in subclinical form, may mimic many of the symptoms of anorexia nervosa.

- Brain tumors: There are multiple cases were the neuropsychiatric symptoms of a brain tumor were attributed to AN, resulting in misdiagnosis. The tumors in these cases were noted in various regions of the brain including the medulla oblongata, hypothalamus, pituitary gland, pineal gland and the obex.

- Simmond's disease (organic hypopituitarism) – "A 20-year-old Japanese man with a hypothalamic tumor which caused hypopituitarism and diabetes insipidus was mistakenly diagnosed as anorexia nervosa because of anorexia, weight loss, denial of being ill, changes in personality, and abnormal behavior resembling the clinical characteristics of anorexia nervosa"

- Brain calcification either dystrophic calcification or metastatic calcification can present with neuropsychiatric symptoms including those associated with AN and comorbid disorders such as obsessive compulsive disorder.

- cysts that occur in the central nervous system such as dermoid cysts and arachnoid cysts can cause neuropsychiatric symptoms including psychosis.

- Celiac disease is an inflammatory disorder triggered by peptides from wheat and similar grains which cause an immune reaction in the small intestine. "information on the role of the gastrointestinal system in causing or mimicking eating disorders is scarce."(Leffler DA "et al.")

- Gall bladder disease which may be caused by inflammation, infection, gallstones, obstruction of the gallbladder or torsion of the gall bladder – Many of the symptoms of gall bladder disease may mimic anorexia nervosa (AN). Laura Daly, a woman from Missouri, suffered from an inherited disorder in which the gall bladder was not properly attached; the resultant complications led to multiple erroneous diagnoses of AN. Upon performance of a CCK test, standard imaging techniques are done with the patient lying prone, in this instance it was done with the patient in an upright position. The gall bladder was shown to be in an abnormal position having flipped over the liver. The gallbladder was removed and the patient has since recovered. The treatment was performed by William P. Smedley in Pennsylvania.

- colonic tuberculosis misdiagnosed as anorexia nervosa in a physician at the hospital where she worked – "This patient, who had severe wasting, was misdiagnosed as having anorexia nervosa despite the presence of other symptoms suggestive of an organic disease, namely, fever and diarrhea"(Madani, A 2002).

- Crohn's disease: "We report three cases of young 18 to 25 year-old girls, initially treated for anorexia nervosa in a psychiatric department. Diagnosis of Crohn's disease was made within 5 to 13 years."(Blanchet C, Luton JP. 2002)"This disease should be diagnostically excluded before accepting anorexia nervosa as final diagnosis". (Wellmann W "et al.")

- hypothyroidism, hyperthyroidism, hypoparathyroidism and hyperparathyroidism may mimic some of the symptoms of, can occur concurrently with, be masked by or exacerbate an eating disorder and/or various comorbid disorders such as anxiety and depression.

- Insulinomas are (pancreatic tumors) that cause an overproduction of insulin, causing hypoglycemia. Various neurological deficits have been ascribed to this condition including misdiagnosis as an eating disorder.

- Multiple sclerosis (encephalomyelitis disseminata) is a progressive autoimmune disorder in which the protective covering (myelin sheath) of nerve cells is damaged as a result of inflammation and resultant attack by the bodies own immune system. In its initial presentation, MS has been misdiagnosed as an eating disorder.

Binge eating is a pattern of disordered eating which consists of episodes of uncontrollable eating. It is sometimes a symptom of binge eating disorder or compulsive overeating disorder. During such binges, a person rapidly consumes an excessive quantity of food. A diagnosis of binge eating is associated with feelings of loss of control.

Rumination syndrome is diagnosed based on a complete history of the individual. Costly and invasive studies such as gastroduodenal manometry and esophageal Ph testing are unnecessary and will often aid in misdiagnosis. Based on typical observed features, several criteria have been suggested for diagnosing rumination syndrome. The primary symptom, the regurgitation of recently ingested food, must be consistent, occurring for at least six weeks of the past twelve months. The regurgitation must begin within 30 minutes of the completion of a meal. Patients may either chew the regurgitated matter or expel it. The symptoms must stop within 90 minutes, or when the regurgitated matter becomes acidic. The symptoms must not be the result of a mechanical obstruction, and should not respond to the standard treatment for gastroesophageal reflux disease.

In adults, the diagnosis is supported by the absence of classical or structural diseases of the gastrointestinal system. Supportive criteria include a regurgitant that does not taste sour or acidic, is generally odourless, is effortless, or at most preceded by a belching sensation, that there is no retching preceding the regurgitation, and that the act is not associated with nausea or heartburn.

Patients visit an average of five physicians over 2.75 years before being correctly diagnosed with rumination syndrome.

There are various other psychological issues that may factor into anorexia nervosa, some fulfill the criteria for a separate Axis I diagnosis or a personality disorder which is coded Axis II and thus are considered comorbid to the diagnosed eating disorder. Axis II disorders are subtyped into 3 "clusters", A, B and C. The causality between personality disorders and eating disorders has yet to be fully established. Some people have a previous disorder which may increase their vulnerability to developing an eating disorder. Some develop them afterwards. The severity and type of eating disorder symptoms have been shown to affect comorbidity. These comorbid disorders themselves have multiple differential diagnoses, such as depression which may be caused by such disparate causes such as Lyme disease or hypothyroidism.

- Body dysmorphic disorder (BDD) is listed as a somatoform disorder that affects up to 2% of the population. BDD is characterized by excessive rumination over an actual or perceived physical flaw. BDD has been diagnosed equally among men and women. While BDD has been misdiagnosed as anorexia nervosa, it also occurs comorbidly in 25% to 39% of AN cases.

BDD is a chronic and debilitating condition which may lead to social isolation, major depression, suicidal ideation and attempts. Neuroimaging studies to measure response to facial recognition have shown activity predominately in the left hemisphere in the left lateral prefrontal cortex, lateral temporal lobe and left parietal lobe showing hemispheric imbalance in information processing. There is a reported case of the development of BDD in a 21 year old male following an inflammatory brain process. Neuroimaging showed the presence of new atrophy in the frontotemporal region.

- Emetophobia is an anxiety disorder characterized by an intense fear of vomiting. A person so afflicted may develop rigorous standards of food hygiene, such as not touching food with their hands. They may become socially withdrawn to avoid situations which in their perception may make them vomit. Many who suffer from emetophobia are diagnosed with anorexia or self-starvation. In severe cases of emetophobia they may drastically reduce their food intake.

- Food avoidance emotional disorder is an eating disorder that affects children which involves a fear of eating which is not accompanied by a fear of weight gain which may be misdiagnosed as anorexia nervosa.

- phagophobia is an anxiety disorder characterized by a fear of eating, it is usually initiated by an adverse experience while eating such as choking or vomiting. Individuals with this disorder may present with complaints of pain while swallowing. There have been cases of it being misdiagnosed as AN. A similar phobic anxiety disorder, swallowing phobia may also lead to a misdiagnosis of anorexia nervosa; such individuals do not want to lose weight but typically want to put weight back on that they have lost due to their phobia.

The distinction between the diagnoses of anorexia nervosa, bulimia nervosa and eating disorder not otherwise specified (EDNOS) is often difficult to make as there is considerable overlap between patients diagnosed with these conditions. Seemingly minor changes in a patient's overall behavior or attitude can change a diagnosis from "anorexia: binge-eating type" to bulimia nervosa. It is not unusual for a person with an eating disorder to "move through" various diagnoses as his or her behavior and beliefs change over time.

Purging disorder is an eating disorder characterized by recurrent purging (self-induced vomiting, misuse of laxatives, diuretics, or enemas) to control weight or shape in the absence of binge eating episodes.

Purging disorder differs from bulimia nervosa (BN) because individuals with purging disorder do not consume a large amount of food before they purge. In current diagnostic systems, purging disorder is a form of Other specified feeding or eating disorder (OSFED). Research indicates that purging disorder may be as common as bulimia nervosa or anorexia nervosa in women, that the syndrome is associated with clinically significant levels of distress, and that it appears to be distinct from bulimia nervosa on measures of hunger and ability to control food intake. Some of the signs of purging disorder are frequent trips to the bathroom directly after a meal, frequent use of laxatives, and obsession over one's appearance and weight. Other signs include swollen cheeks, popped blood vessels in the eyes, and clear teeth which are all signs of excessive vomiting.

Accurately assessing for a specific Depressive Disorder diagnosis requires an expenditure of time that is deemed unreasonable for most primary care physicians. For this reason, physicians often use this code as a proxy for a more thorough diagnosis. There is concern that this may lead to a "wastebasket" mindset for certain disorders. In addition reimbursement through Medicare may be lower for certain non specific diagnosis.