Episodes of skin picking are often preceded or accompanied by tension, anxiety, or stress. In some cases, following picking, the affected person may feel depressed. During these moments, there is commonly a compulsive urge to pick, squeeze, or scratch at a surface or region of the body, often at the location of a perceived skin defect. When picking one may feel a sense of relief or satisfaction.

The region most commonly picked is the face, but other frequent locations include the arms, legs, back, gums, neck, shoulders, scalp, abdomen, chest, and extremities such as the fingernails, cuticles, and toenails. Most patients with excoriation disorder report having a primary area of the body that they focus their picking on, but they will often move to other areas of the body to allow their primary picking area to heal. Individuals with excoriation disorder vary in their picking behaviour; some do it briefly multiple times a day while others can do one picking session that can last for hours. The most common way to pick is to use the fingers although a significant minority of people use tools such as tweezers or needles.

Skin picking often occurs as a result of some other triggering cause. Some common triggers are feeling or examining irregularities on the skin and feeling anxious or other negative feelings.

Complications arising from excoriation disorder include: infection at the site of picking, tissue damage, and septicemia. Damage from picking can be so severe as to require skin grafting. Severe picking can cause epidermal abscesses. Severe cases of excoriation disorder can cause life-threatening injuries. For example, in one reported case a female picked a hole through the bridge of her nose, which required surgery to fix, and a 48-year-old female picked through the skin on her neck exposing the carotid artery. Pain in the neck or back can arise due to prolonged bent-over positions while engaging in the behavior. Besides physical injuries, excoriation disorder can cause severe physical scarring and disfigurement.

Excoriation disorder can cause feelings of intense helplessness, guilt, shame, and embarrassment in individuals, and this greatly increases the risk of self-harm. Studies have shown that excoriation disorder presented suicidal ideation in 12% of individuals with this condition, suicide attempts in 11.5% of individuals with this condition, and psychiatric hospitalizations in 15% of individuals with this condition.

Trichotillomania is defined as a self-induced and recurrent loss of hair. It includes the criterion of an increasing sense of tension before pulling the hair and gratification or relief when pulling the hair. However, some people with trichotillomania do not endorse the inclusion of "rising tension and subsequent pleasure, gratification, or relief" as part of the criteria; because many individuals with trichotillomania may not realize they are pulling their hair, patients presenting for diagnosis may deny the criteria for tension prior to hair pulling or a sense of gratification after hair is pulled.

Trichotillomania may lie on the obsessive-compulsive spectrum, also encompassing obsessive-compulsive disorder (OCD), body dysmorphic disorder (BDD), nail biting (onychophagia) and skin picking (dermatillomania), tic disorders and eating disorders. These conditions may share clinical features, genetic contributions, and possibly treatment response; however, differences between trichotillomania and OCD are present in symptoms, neural function and cognitive profile. In the sense that it is associated with irresistible urges to perform unwanted repetitive behavior, trichotillomania is akin to some of these conditions, and rates of trichotillomania among relatives of OCD patients is higher than expected by chance. However, differences between the disorder and OCD have been noted, including: differing peak ages at onset, rates of comorbidity, gender differences, and neural dysfunction and cognitive profile. When it occurs in early childhood, it can be regarded as a distinct clinical entity.

Because trichotillomania can be present in multiple age groups, it is helpful in terms of prognosis and treatment to approach three distinct subgroups by age: preschool age children, preadolescents to young adults, and adults.

Trichotillomania is often not a focused act, but rather hair pulling occurs in a "trance-like" state; hence, trichotillomania is subdivided into "automatic" versus "focused" hair pulling. Children are more often in the automatic, or unconscious, subtype and may not consciously remember pulling their hair. Other individuals may have focused, or conscious, rituals associated with hair pulling, including seeking specific types of hairs to pull, pulling until the hair feels "just right", or pulling in response to a specific sensation. Knowledge of the subtype is helpful in determining treatment strategies.

Whereas vanity involves a quest to aggrandize the appearance, BDD is experienced as a quest to merely normalize the appearance. Although delusional in about one of three cases, the appearance concern is usually nondelusional, an overvalued idea.

The bodily area of focus can be nearly any, yet is commonly face, hair, stomach, thighs, or hips. Some half dozen areas can be a roughly simultaneous focus. Many seek dermatological treatment or cosmetic surgery, which typically do not resolve the distress. On the other hand, attempts at self-treatment, as by skin picking, can create lesions where none previously existed.

BDD shares features with obsessive-compulsive disorder, but involves more depression and social avoidance. BDD often associates with social anxiety disorder. Some experience delusions that others are covertly pointing out their flaws. Cognitive testing and neuroimaging suggest both a bias toward detailed visual analysis and a tendency toward emotional hyperarousal.

Most generally, one experiencing BDD ruminates over the perceived bodily defect up to several hours daily, uses either social avoidance or camouflaging with cosmetics or apparel, repetitively checks the appearance, compares it to that of other persons, and might often seek verbal reassurances. One might sometimes avoid mirrors, repetitively change outfits, groom excessively, or restrict eating.

BDD's severity can wax and wane, and flareups tend to yield absences from school, work, or socializing, sometimes leading to protracted social isolation, with some becoming housebound for extended periods. Social impairment is usually greatest, sometimes approaching avoidance of all social activities. Poor concentration and motivation impair academic and occupational performance. The distress of BDD tends to exceed that of either major depressive disorder or type-2 diabetes, and rates of suicidal ideation and attempts are especially high.

The inability to control the urge to pick is similar to the urge to compulsively pull one's own hair, i.e., trichotillomania. Researchers have noted the following similarities between trichotillomania and excoriation disorder: the symptoms are ritualistic but there are no preceding obsessions; there are similar triggers for the compulsive actions; both conditions appear to play a role in modifying the arousal level of the subject; and the age of onset for both conditions is similar. There is also a high level of comorbidity between those that have trichotillomania and those that have excoriation disorder. A notable difference between these conditions is that skin picking seems to be dominated by females whereas trichotillomania is more evenly distributed across genders.

Research has also suggested that excoriation disorder may be thought of as a type of obsessive compulsive disorder (OCD). Excoriation disorder and OCD are similar in that they both involve "repetitive engagement in behaviors with diminished control" and also both generally decrease anxiety.

Nevertheless, Odlaug and Grant have suggested that excoriation disorder is more akin to substance abuse disorder than OCD. They argue that excoriation disorder differs from OCD in the following fundamental ways: (1) there is a much greater share of females with excoriation disorder; (2) excoriation disorder may be inherently pleasurable whereas OCD is not; (3) the treatments that are generally effective for patients with OCD (i. e., SSRIs and exposure therapy) are not as successful in patients with excoriation disorder; and (4) unlike OCD, picking the skin is rarely driven by obsessive thoughts. Odlaug and Grant have recognized the following similarities between individuals with dermatillomania and patients with addictions: (1) a compulsion to engage in the negative behavior despite knowledge of the harm; (2) a lack of control over the problematic behavior; (3) a strong urge to engage in the behavior prior to engagement; and (4) a feeling of pleasure while engaging in the behavior or a feeling of relief or reduced anxiety after engaging in the behavior. One study that supported the addiction theory of picking found that 79% of patients with excoriation disorder reported a pleasurable feeling when picking.

Odlaug and Grant also argue that dermatillomania could have several different psychological causes, which would explain why some patients seem more likely to have symptoms of OCD, and others, of an addiction. They suggest that treating certain cases of excoriation as an addiction may yield more success than treating them as a form of OCD.

Trichotillomania (TTM), also known as hair pulling disorder, is an impulse control disorder characterised by a long term urge that results in the pulling out of one's hair. This occurs to such a degree that hair loss can be seen. Efforts to stop pulling hair typically fail. Hair removal may occur anywhere; however, the head and around the eyes are most common. The hair pulling is to such a degree that it results in distress.

The disorder may run in families. It occurs more commonly in those with obsessive compulsive disorder. Episodes of pulling may be triggered by anxiety. People usually acknowledge that they pull their hair. On examination broken hairs may be seen. Other conditions that may present similarly include body dysmorphic disorder, however in that condition people remove hair to try to improve what they see as a problem in how they look.

Treatment is typically with cognitive behavioral therapy. The medication clomipramine may also be helpful. Trichotillomania is estimated to affect one to four percent of people. Trichotillomania most commonly begins in childhood. Women are more commonly affected than men. The name was created by François Henri Hallopeau in 1889, from the Greek θρίξ/τριχ; "thrix" (meaning "hair"), along with τίλλειν; "tíllein" (meaning "to pull"), and μανία; "mania" (meaning "madness").

Body dysmorphic disorder (BDD) is a mental disorder characterized by the obsessive idea that some aspect of one's own appearance is severely flawed and warrants exceptional measures to hide or fix it. In BDD's delusional variant, the flaw is imagined. If the flaw is actual, its importance is severely exaggerated. Either way, thoughts about it are pervasive and intrusive, occupying up to several hours a day. The "DSM-5" categorizes BDD in the obsessive–compulsive spectrum, and distinguishes it from anorexia nervosa.

BDD is estimated to affect up to 2.4% of the population. It usually starts during adolescence, and affects men and women roughly equally. The BDD subtype muscle dysmorphia, perceiving the body as too small, affects mostly males. Besides thinking about it, one repetitively checks and compares the perceived flaw, and can adopt unusual routines to avoid social contact that exposes it. Fearing the stigma of vanity, one usually hides the preoccupation. Commonly unsuspected even by psychiatrists, BDD has been underdiagnosed. Severely impairing quality of life via educational and occupational dysfunction and social isolation, BDD has high rates of suicidal thoughts and suicide attempts.

The onset of ORS may be sudden, where it usually follows after a precipitating event, or gradual.

The defining feature of ORS is excessive thoughts of having offensive body odor(s) which are detectable to others. The individual may report that the odor comes from: the nose and/or mouth, i.e. halitosis (bad breath), the anus, the genitals, the skin generally, or specifically the groin, armpits or feet. The source(s) of the supposed odor may also change over time. There are also some who are unsure of the exact origin of the odor. The odor is typically reported to be continuously present. The character of the odor may be reported as similar to bodily substances, e.g. feces, flatus, urine, sweat, vomitus, semen, vaginal secretions; or alternatively it may be an unnatural, non-human or chemical odor, e.g. ammonia, detergent, rotten onions, burnt rags, candles, garbage, burning fish, medicines, old cheese. Again, the reported character of the odor complaint may change over time. Halitosis appears to be the most common manifestation of ORS, with 75% complaining of bad breath, alone or in combination with other odors. The next most common complaint was sweat (60%).

Although all individuals with ORS believe they have an odor, in some cases the individual reports they cannot perceive the odor themselves. In the latter cases, the belief arises via misinterpretation of the behavior of others or with the rationale that a disorder of smell which prevents self detection of the odor (i.e. anosmia) exists. In the cases where the non-existent odor can be detected, this is usually considered as phantosmia (olfactory hallucination). Olfactory hallucination can be considered the result of the belief in an odor delusion, or the belief a result of the olfactory hallucination. In one review, the individual with ORS was unreservedly convinced that he or she could detect the odor themselves in 22% of cases, whilst in 19% there was occasional or intermittent detection and in 59% lack of self-detection was present.

Some distinguish "delusional" and "non-delusional" forms of ORS. In the delusional type, there is complete conviction that the odor is real. In the non-delusional type, the individual is capable of some insight into the condition, and can recognize that the odor might not be real, and that their level of concern is excessive. Others argue that reported cases of ORS present a spectrum of different levels of insight. Since sometimes the core belief of ORS is not of delusional intensity, it is argued that considering the condition as a form of delusional disorder, as seems to occur in the DSM, is inappropriate. In one review, in 57% of cases the beliefs were fixed, held with complete conviction, and the individual could not be reassured that the odor was non existent. In 43% of cases the individual held the beliefs with less than complete conviction, and was able to varying degrees to consider the possibility that the odor was not existent.

Other symptoms may be reported and are claimed to be related to the cause of the odor, such as malfunction of the anal sphincter, a skin disease, "diseased womb", stomach problems or other unknown organic disease. Excessive washing in ORS has been reported to cause the development of eczema.

Koro is a culture-specific syndrome delusional disorder in which an individual has an overpowering belief that one's genitalia are retracting and will disappear, despite the lack of any true longstanding changes to the genitals. Koro is also known as shrinking penis, and it is listed in the "Diagnostic and Statistical Manual of Mental Disorders". The syndrome occurs worldwide, and mass hysteria of genital-shrinkage anxiety has a history in Africa, Asia, and Europe. In the United States and Europe, the syndrome is commonly known as genital retraction syndrome. The condition can be diagnosed through psychological assessment along with physical examination to rule out genuine disorders of the genitalia that could be causing true retraction.

Most patients report acute anxiety attacks due to perceived genital retraction and/or genital shrinkage, despite a lack of any objectively visible biological changes in the genitalia that are longstanding. "Longstanding" refers to changes that are sustained over a significant period and do not appear reversible, unlike the effect of cold temperatures on some genital regions that cause retraction. These changes may trigger a koro attack when observed, although the effects of cold temperatures are objectively reversible. According to literature, episodes usually last several hours, though the duration may be as long as two days. There are cases in which koro symptoms persist for years in a chronic state, indicating a potential co-morbidity with body dysmorphic disorder. In addition to retraction, other symptoms include a perception of alteration of penis shape and loss of penile muscle tone. In cases when sufferers have no perception of retraction, some patients may complain of genital paraesthesia or genital shortening. Among females, the cardinal symptom is nipple retraction in the breast, generally into the breast as a whole.

Psychological components of koro anxiety include fear of impending death, penile dissolution and loss of sexual power. Feelings of impending death along with retraction and perceived spermatorrhea has a strong cultural link with Chinese traditional beliefs. This is demonstrated by the fact that Asians generally believe koro symptoms are fatal, unlike most patients in the West. Other ideational themes are intra-abdominal organ shrinkage, sex change to female or eunuch, non-specific physical danger, urinary obstruction, sterility, impending madness, spirit possession and a feeling of being bewitched.

Extremely anxious sufferers and their family members may resort to physical methods to prevent the believed retraction of the penis. A man may perform manual or mechanical penile traction, or "anchoring" by a loop of string or some clamping device. Similarly, a woman may be seen grabbing her own breast, pulling her nipple, or even having iron pins inserted into the nipple. Physical injury may occur from these attempts. These forceful attempts often lead to injuries, even death.

The differential diagnoses of anorexia nervosa (AN) includes various types of medical and psychological conditions, which may be misdiagnosed as AN. In some cases, these conditions may be comorbid with AN because the misdiagnosis of AN is not uncommon. For example, a case of achalasia was misdiagnosed as AN and the patient spent two months confined to a psychiatric hospital. A reason for the differential diagnoses that surround AN arise mainly because, like other disorders, it is primarily, albeit defensively and adaptive for, the individual concerned.

Anorexia Nervosa is a psychological disorder characterized by extremely reduced intake of food. People suffering from Aneroxia Nervosa have a low self-image and consider themselves overweight.

Common behaviors and signs of someone suffering from AN:

- Forcing oneself to vigorously exercise even in adverse conditions or when their health does not permit it.

- Forcing own self to urinate and excrete waste product from the body.

- Using substituted amphetamines (stimulants that can reduce appetite) to reduce appetite.

- Skin turning yellow

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.

An intrusive thought is an unwelcome involuntary thought, image, or unpleasant idea that may become an obsession, is upsetting or distressing, and can feel difficult to manage or eliminate. When such thoughts are associated with obsessive-compulsive disorder (OCD), depression, body dysmorphic disorder (BDD), and sometimes attention-deficit hyperactivity disorder (ADHD), the thoughts may become paralyzing, anxiety-provoking, or persistent. Intrusive thoughts may also be associated with episodic memory, unwanted worries or memories from OCD, posttraumatic stress disorder, other anxiety disorders, eating disorders, or psychosis. Intrusive thoughts, urges, and images are of inappropriate things at inappropriate times, and generally have aggressive, sexual, or blasphemous themes.

Many people experience the type of bad or unwanted thoughts that people with more troubling intrusive thoughts have, but most people can dismiss these thoughts. For most people, intrusive thoughts are a "fleeting annoyance". Psychologist Stanley Rachman presented a questionnaire to healthy college students and found that virtually all said they had these thoughts from time to time, including thoughts of sexual violence, sexual punishment, "unnatural" sex acts, painful sexual practices, blasphemous or obscene images, thoughts of harming elderly people or someone close to them, violence against animals or towards children, and impulsive or abusive outbursts or utterances. Such bad thoughts are universal among humans, and have "almost certainly always been a part of the human condition".

When intrusive thoughts occur with obsessive-compulsive disorder (OCD), patients are less able to ignore the unpleasant thoughts and may pay undue attention to them, causing the thoughts to become more frequent and distressing. The thoughts may become obsessions which are paralyzing, severe, and constantly present, and can range from thoughts of violence or sex to religious blasphemy. Distinguishing them from normal intrusive thoughts experienced by many people, the intrusive thoughts associated with OCD may be anxiety provoking, irrepressible, and persistent.

How people react to intrusive thoughts may determine whether these thoughts will become severe, turn into obsessions, or require treatment. Intrusive thoughts can occur with or without compulsions. Carrying out the compulsion reduces the anxiety, but makes the urge to perform the compulsion stronger each time it recurs, reinforcing the intrusive thoughts. According to Lee Baer, suppressing the thoughts only makes them stronger, and recognizing that bad thoughts do not signify that one is truly evil is one of the steps to overcoming them. There is evidence of the benefit of acceptance as an alternative to suppression of intrusive thoughts. A study showed that those instructed to suppress intrusive thoughts experienced more distress after suppression, while patients instructed to accept the bad thoughts experienced decreased discomfort. These results may be related to underlying cognitive processes involved in OCD. However, accepting the thoughts can be more difficult for persons with OCD. In the 19th century, OCD was known as "the doubting sickness"; the "pathological doubt" that accompanies OCD can make it harder for a person with OCD to distinguish "normal" intrusive thoughts as experienced by most people, causing them to "suffer in silence, feeling too embarrassed or worried that they will be thought crazy".

The possibility that most patients suffering from intrusive thoughts will ever act on those thoughts is low. Patients who are experiencing intense guilt, anxiety, shame, and upset over these thoughts are different from those who actually act on them. The history of violent crime is dominated by those who feel no guilt or remorse; the very fact that someone is tormented by intrusive thoughts and has never acted on them before is an excellent predictor that they will not act upon the thoughts. Patients who are not troubled or shamed by their thoughts, do not find them distasteful, or who have actually taken action, might need to have more serious conditions such as psychosis or potentially criminal behaviors ruled out. According to Lee Baer, a patient should be concerned that intrusive thoughts are dangerous if the person does not feel upset by the thoughts, or rather finds them pleasurable; has ever acted on violent or sexual thoughts or urges; hears voices or sees things that others do not see; or feels uncontrollable irresistible anger.

There are multiple medical conditions which may be misdiagnosed as a primary psychiatric disorder, complicating or delaying treatment. These may have a synergistic effect on conditions which mimic an eating disorder or on a properly diagnosed eating disorder.

- Lyme disease which is known as the "great imitator", as it may present as a variety of psychiatric or neurological disorders including anorexia nervosa.

- Gastrointestinal diseases, such as celiac disease, Crohn's disease, peptic ulcer, eosinophilic esophagitis or non-celiac gluten sensitivity, among others. Celiac disease is also known as the "great imitator", because it may involve several organs and cause an extensive variety of non-gastrointestinal symptoms, such as psychiatric and neurological disorders, including anorexia nervosa.

- 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.

- Gastric adenocarcinoma is one of the most common forms of cancer in the world. Complications due to this condition have been misdiagnosed as an eating disorder.

- Hypothyroidism, hyperthyroidism, hypoparathyroidism and hyperparathyroidism may mimic some of the symptoms of, can occur concurrently with, be masked by or exacerbate an eating disorder.

- Toxoplasma seropositivity: even in the absence of symptomatic toxoplasmosis, toxoplasma gondii exposure has been linked to changes in human behavior and psychiatric disorders including those comorbid with eating disorders such as depression. In reported case studies the response to antidepressant treatment improved only after adequate treatment for toxoplasma.

- Neurosyphilis: It is estimated that there may be up to one million cases of untreated syphilis in the US alone. "The disease can present with psychiatric symptoms alone, psychiatric symptoms that can mimic any other psychiatric illness". Many of the manifestations may appear atypical. Up to 1.3% of short term psychiatric admissions may be attributable to neurosyphilis, with a much higher rate in the general psychiatric population. (Ritchie, M Perdigao J,)

- Dysautonomia: a wide variety of autonomic nervous system (ANS) disorders may cause a wide variety of psychiatric symptoms including anxiety, panic attacks and depression. Dysautonomia usually involves failure of sympathetic or parasympathetic components of the ANS system but may also include excessive ANS activity. Dysautonomia can occur in conditions such as diabetes and alcoholism.

Psychological disorders which may be confused with an eating disorder, or be co-morbid with one:

- 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.

- 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. Persons with this disorder may present with complaints of pain while swallowing.

- 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 39% of eating disorder cases. BDD is a chronic and debilitating condition which may lead to social isolation, major depression and 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 a new atrophy in the frontotemporal region.

Research data indicates that steroids affect the serotonin and dopamine neurotransmitter systems of the brain. In an animal study, male rats developed a conditioned place preference to testosterone injections into the nucleus accumbens, an effect blocked by dopamine antagonists, which suggests that androgen reinforcement is mediated by the brain. Moreover, testosterone appears to act through the mesolimbic dopamine system, a common substrate for drugs of abuse. Nonetheless, androgen reinforcement is not comparable to that of cocaine, nicotine, or heroin. Instead, testosterone resembles other mild reinforcers, such as caffeine, or benzodiazepines. The potential for androgen addiction remains to be determined.

Anabolic steroids are not psychoactive and cannot be detected by stimuli devices like a pupilometer which makes them hard to spot as a source of neuropsychological imbalaces in some AAS users.

Symptoms and complications vary according to the nature and severity of the eating disorder:

Some physical symptoms of eating disorders are weakness, fatigue, sensitivity to cold, reduced beard growth in men, reduction in waking erections, reduced libido, weight loss and failure of growth. Unexplained hoarseness may be a symptom of an underlying eating disorder, as the result of acid reflux, or entry of acidic gastric material into the laryngoesophageal tract. Patients who induce vomiting, such as those with anorexia nervosa, binge eating-purging type or those with purging-type bulimia nervosa are at risk for acid reflux. Polycystic ovary syndrome (PCOS) is the most common endocrine disorder to affect women. Though often associated with obesity it can occur in normal weight individuals. PCOS has been associated with binge eating and bulimic behavior. Other possible manifestations are dry lips, burning tongue, parotid gland swelling, and temporomandibular disorders.

Other psychological issues 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. Some people have a previous disorder which may increase their vulnerability to developing an eating disorder and some develop them afterwards. The presence of Axis I or Axis II psychiatric comorbidity has been shown to affect the severity and type of anorexia nervosa symptoms in both adolescents and adults.

Obsessive-compulsive disorder (OCD) and obsessive-compulsive personality disorder (OCPD) are highly comorbid with AN, particularly the restrictive subtype. Obsessive-compulsive personality disorder is linked with more severe symptomatology and worse prognosis. The causality between personality disorders and eating disorders has yet to be fully established. Other comorbid conditions include depression, alcoholism, borderline and other personality disorders, anxiety disorders, attention deficit hyperactivity disorder, and body dysmorphic disorder (BDD). Depression and anxiety are the most common comorbidities, and depression is associated with a worse outcome.

Autism spectrum disorders occur more commonly among people with eating disorders than in the general population. Zucker "et al." (2007) proposed that conditions on the autism spectrum make up the cognitive endophenotype underlying anorexia nervosa and appealed for increased interdisciplinary collaboration.

Interoception has an important role in homeostasis and regulation of emotions and motivation. Anorexia has been associated with disturbances to interoception. People with anorexia concentrate on distorted perceptions of their body exterior due to fear of looking overweight. Aside from outer appearance, they also report abnormal bodily functions such as indistinct feelings of fullness. This provides an example of miscommunication between body and brain. Further, people with anorexia experience abnormally intense cardiorespiratory sensations, particularly of the breath, most prevalent before they consume a meal. People with anorexia also report inability to distinguish emotions from bodily sensations in general, called alexithymia. In addition to metacognition, people with anorexia also have difficultly with social cognition including interpreting other’s emotions, and demonstrating empathy. Abnormal interoceptive awareness like these examples have been observed so frequently in anorexia that they have become key characteristics of the illness.

The Diagnostic Statistical Manual IV (DSM IV) and the International Classification of Diseases, Volume 10 (ICD 10) differ in the way they regard Anabolic-Androgenic Steroids' (AAS) potential for producing dependence.

DSM IV regards AAS as potentially dependence producing. ICD 10 however regards them as non-dependence producing. Anabolic steroids are not physically addictive but users can develop a psychological dependence on the physical result.