Bulimia typically involves rapid and out-of-control eating, which may stop when the bulimic is interrupted by another person or the stomach hurts from over-extension, followed by self-induced vomiting or other forms of purging. This cycle may be repeated several times a week or, in more serious cases, several times a day and may directly cause:

- Chronic gastric reflux after eating, secondary to vomiting

- Dehydration and hypokalemia due to renal potassium loss in the presence of alkalosis and frequent vomiting

- Electrolyte imbalance, which can lead to abnormal heart rhythms, cardiac arrest, and even death

- Esophagitis, or inflammation of the esophagus

- Mallory-Weiss tears

- Boerhaave syndrome, a rupture in the esophageal wall due to vomiting

- Oral trauma, in which repetitive insertion of fingers or other objects causes lacerations to the lining of the mouth or throat

- Russell's sign: calluses on knuckles and back of hands due to repeated trauma from incisors

- Perimolysis, or severe dental erosion of tooth enamel

- Swollen salivary glands (for example, in the neck, under the jaw line)

- Gastroparesis or delayed emptying

- Constipation

- Peptic ulcers

- Infertility

- Constant weight fluctuations are common

These are some of the many signs that may indicate whether someone has bulimia nervosa:

- A fixation on the number of calories consumed

- A fixation on and extreme consciousness of ones weight

- Low self-esteem and/or self harming

- Suicidal tendencies

- Low blood pressure

- An irregular menstrual cycle in woman

- Regular trips to the bathroom, especially soon after eating

- Depression, anxiety disorders and sleep disorders

- Frequent occurrences involving consumption of abnormally large portions of food

- The use of laxatives and diet pills

- Unhealthy/dry skin, hair, nails and lips

- A lack of energy

As with many psychiatric illnesses, delusions can occur, in conjunction with other signs and symptoms, leaving the person with a false belief that is not ordinarily accepted by others.

People with bulimia nervosa may also exercise to a point that excludes other activities.

Binge eating is the core symptom of BED; however, not everyone who binge eats has BED. An individual may occasionally binge eat without experiencing many of the negative physical, psychological, or social effects of BED. This example may be considered an eating problem (or not), rather than a disorder. Precisely defining binge eating can be problematic, however binge eating episodes in BED are generally described as having the following potential features:

- Eating much faster than normal during a binge perhaps in a short space of time

- Eating until feeling uncomfortably full

- Eating a large amount when not hungry

- Subjective loss of control over how much or what is eaten

- Binges may be planned in advance, involving the purchase of special binge foods, and the allocation of specific time for binging, sometimes at night

- Eating alone or secretly due to embarrassment over the amount of food consumed

- There may be a dazed mental state during the binge

- Not being able to remember what was eaten after the binge

- Feelings of guilt, shame or disgust following a food binge

In contrast to bulimia nervosa, binge eating episodes are not regularly followed by activities intended to prevent weight gain, such as self-induced vomiting, laxative or enema misuse, or strenuous exercise. BED is characterized more by overeating than dietary restriction and over concern about body shape. Obesity is common in persons with BED, as are depressive features, low self-esteem, stress and boredom.

These eating disorders are specified as mental disorders in standard medical manuals, such as in the ICD-10, the DSM-5, or both.

- Anorexia nervosa (AN), characterized by lack of maintenance of a healthy body weight, an obsessive fear of gaining weight or refusal to do so, and an unrealistic perception, or non-recognition of the seriousness, of current low body weight. Anorexia can cause menstruation to stop, and often leads to bone loss, loss of skin integrity, etc. It greatly stresses the heart, increasing the risk of heart attacks and related heart problems. The risk of death is greatly increased in individuals with this disease. The most underlining factor researchers are starting to take notice of is that it may not just be a vanity, social, or media issue, but it could also be related to biological and or genetic components. The DSM-5 contains many changes that better represent patients with these conditions. The DSM-IV required amenorrhea (the absence of the menstrual cycle) to be present in order to diagnose a patient with anorexia. This is no longer a requirement in the DSM-5.

- Bulimia nervosa (BN), characterized by recurrent binge eating followed by compensatory behaviors such as purging (self-induced vomiting, eating to the point of vomiting, excessive use of laxatives/diuretics, or excessive exercise). Fasting and over-exercising may also be used as a method of purging following a binge.

- Muscle dysmorphia is characterized by appearance preoccupation that one's own body is too small, too skinny, insufficiently muscular, or insufficiently lean. Muscle dysmorphia affects mostly males.

- Binge Eating Disorder (BED), characterized by recurring binge eating at least once a week for over a period of 3 months while experiencing lack of control and guilt after overeating. The disorder can develop within individuals of a wide range of ages and socioeconomic classes.

- Other Specified Feeding or Eating Disorder (OSFED) is an eating or feeding disorder that does not meet full DSM-5 criteria for AN, BN, or BED. Examples of otherwise-specified eating disorders include individuals with atypical anorexia nervosa, who meet all criteria for AN except being underweight, despite substantial weight loss; atypical bulimia nervosa, who meet all criteria for BN except that bulimic behaviors are less frequent or have not been ongoing for long enough; purging disorder; and night eating syndrome.

Bulimia nervosa is a disorder characterized by binge eating and purging, as well as excessive evaluation of one's self-worth in terms of body weight or shape. Purging can include self-induced vomiting, over-exercising, and the use of diuretics, enemas, and laxatives. Anorexia nervosa is characterized by extreme food restriction and excessive weight loss, accompanied by the fear of being fat. The extreme weight loss often causes women and girls who have begun menstruating to stop having menstrual periods, a condition known as amenorrhea. Although amenorrhea was once a required criterion for the disorder, it is no longer required to meet criteria for anorexia nervosa due to its exclusive nature for sufferers who are male, post-menopause, or who do not menstruate for other reasons. The DSM-5 specifies two subtypes of anorexia nervosa—the restricting type and the binge/purge type. Those who suffer from the restricting type of anorexia nervosa restrict food intake and do not engage in binge eating, whereas those suffering from the binge/purge type lose control over their eating at least occasionally and may compensate for these binge episodes. The most notable difference between anorexia nervosa binge/purge type and bulimia nervosa is the body weight of the person. Those diagnosed with anorexia nervosa binge/purge type are underweight, while those with bulimia nervosa may have a body weight that falls within the range from normal to obese.

With regards to interoception, people with bulimia report reduced sensitivity to many kinds of internal and external sensations. For example, some show increased thresholds to heat pain compared and report the same level of satiety after consuming more calories than do healthy subjects.

Binge eating disorder (BED) is an eating disorder characterized by frequent and recurrent binge eating episodes with associated negative psychological and social problems, but without subsequent purging episodes (e.g. vomiting).

BED is a recently described condition, which was required to distinguish binge eating similar to that seen bulimia nervosa but without characteristic purging. Individuals who are diagnosed with bulimia nervosa and binge eating disorder exhibit similar patterns of compulsive overeating, neurobiological features of dysfunctional cognitive control and food addiction, and biological and environmental risk factors. Indeed, some consider BED a milder version of bulimia nervosa, and that the conditions are on the same spectrum.

Binge eating is one of the most prevalent eating disorders among adults, though there tends to be less media coverage and research about the disorder in comparison to anorexia nervosa and bulimia nervosa.

Anorexia nervosa is an eating disorder characterized by attempts to lose weight, to the point of starvation. A person with anorexia nervosa may exhibit a number of signs and symptoms, the type and severity of which may vary and may be present but not readily apparent.

Anorexia nervosa, and the associated malnutrition that results from self-imposed starvation, can cause complications in every major organ system in the body. Hypokalaemia, a drop in the level of potassium in the blood, is a sign of anorexia nervosa. A significant drop in potassium can cause abnormal heart rhythms, constipation, fatigue, muscle damage and paralysis.

Symptoms may include:

- A low body mass index for one's age and height.

- Amenorrhea, a symptom that occurs after prolonged weight loss; causes menses to stop, hair becomes brittle, and skin becomes yellow and unhealthy.

- Fear of even the slightest weight gain; taking all precautionary measures to avoid weight gain or becoming "overweight".

- Rapid, continuous weight loss.

- Lanugo: soft, fine hair growing over the face and body.

- An obsession with counting calories and monitoring fat contents of food.

- Preoccupation with food, recipes, or cooking; may cook elaborate dinners for others, but not eat the food themselves or consume a very small portion.

- Food restrictions despite being underweight or at a healthy weight.

- Food rituals, such as cutting food into tiny pieces, refusing to eat around others and hiding or discarding of food.

- Purging: May use laxatives, diet pills, ipecac syrup, or water pills to flush food out of their system after eating or may engage in self-induced vomiting though this is a more common symptom of bulimia.

- Excessive exercise including micro-exercising, for example making small persistent movements of fingers or toes.

- Perception of self as overweight, in contradiction to an underweight reality.

- Intolerance to cold and frequent complaints of being cold; body temperature may lower (hypothermia) in an effort to conserve energy due to malnutrition.

- Hypotension or orthostatic hypotension.

- Bradycardia or tachycardia.

- Depression, anxiety disorders and insomnia.

- Solitude: may avoid friends and family and become more withdrawn and secretive.

- Abdominal distension.

- Halitosis (from vomiting or starvation-induced ketosis).

- Dry hair and skin, as well as hair thinning.

- Chronic fatigue.

- Rapid mood swings.

- Having feet discoloration causing an orange appearance.

- Having severe muscle tension + aches and pains.

- Evidence/habits of self harming or self-loathing.

- Admiration of thinner people.

The three general categories for an EDNOS diagnosis are subthreshold symptoms of anorexia or bulimia, a mixture of both anorexia or bulimia, and eating behaviors that are not particularized by anorexia and bulimia. EDNOS is no longer considered a diagnosis in "DSM-5"; those displaying symptoms of what would previously have been considered EDNOS are now classified under Other Specified Feeding or Eating Disorder.

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.

The five OSFED examples that can be considered eating disorders include atypical AN, BN (of low frequency and/or limited duration), BED (of low frequency and/or limited duration), purging disorder, and NES. Of note, OSFED is not limited to these five examples, and can include individuals with heterogeneous eating disorder presentations (i.e., OSFED-other). Another term, Unspecified Feeding or Eating Disorder (UFED), is used to describe individuals for whom full diagnostic criteria are not met but the reason remains unspecified or the clinician does not have adequate information to make a more definitive diagnosis.

- Atypical Anorexia Nervosa: In atypical AN, individuals meet all of the criteria for AN, with the exception of the weight criterion: the individual's weight remains within or above the normal range, despite significant weight loss.

- Atypical Bulimia Nervosa: In this sub-threshold version of BN, individuals meet all criteria for BN, with the exception of the frequency criterion: binge eating and inappropriate compensatory behaviors occur, on average, less than once a week and/or for fewer than 3 months.

- Binge-eating disorder (of low frequency and/or limited duration): In this sub-threshold version of BED, individuals must meet all criteria for BED, with the exception of the frequency criterion: binge eating occurs, on average, less than once a week and/or for fewer than 3 months.

- Purging Disorder: In purging disorder, purging behavior aimed to influence weight or shape is present, but in the absence of binge eating.

- Night Eating Syndrome: In NES, individuals have recurrent episodes of eating at night, such as eating after awakening from sleep or excess calorie intake after the evening meal. This eating behavior is not culturally acceptable by group norms, such as the occasional late-night munchies after a gathering. NES includes an awareness and recall of the eating, is not better explained by external influences such as changes in the individual's sleep-wake cycle, and causes significant distress and/or impairment of functioning. Though not defined specifically in "DSM-5", research criteria for this diagnosis proposed adding the following criteria (1) the consumption of at least 25% of daily caloric intake after the evening meal and/or (2) evening awakenings with ingestions at least twice per week.

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.

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.

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.

Other specified feeding or eating disorder or OSFED is the "DSM-5" category that replaces the category formerly called Eating Disorder Not Otherwise Specified (EDNOS) in "DSM-IV", and that captures feeding disorders and eating disorders of clinical severity that do not meet diagnostic criteria for anorexia nervosa (AN), bulimia nervosa (BN), binge eating disorder (BED), avoidant/restrictive food intake disorder (ARFID), pica, or rumination disorder. OSFED includes five examples: atypical AN, BN (of low frequency and/or limited duration), BED (of low frequency and/or limited duration), purging disorder, and night eating syndrome (NES).

A food addiction features compulsive overeating, such as binge eating behavior, as its core and only defining feature. There are several potential signs that a person may be suffering from compulsive overeating. Common behaviors of compulsive overeaters include eating alone, consuming food quickly, and gaining weight rapidly, and eating to the point of feeling sick to the stomach. Other signs include significantly decreased mobility and the withdrawal from activities due to weight gain. Emotional indicators can include feelings of guilt, a sense of loss of control, depression and mood swings.

Hiding consumption is an emotional indicator of other symptoms that could be a result of having a food addiction. Hiding consumption of food includes eating in secret; late at night while everybody else is asleep, in the car, and hiding certain foods until ready to consume in private. Other signs of hiding consumption are avoiding social interactions to eat the specific foods that are craved. Other emotional indicators are Inner guilt; which includes making up excuses to why the palatable food would be beneficial to consume, and then feeling guilty about it shortly after consuming.

Sense of loss of control is indicated in many ways which includes, going out of the way to obtain specific foods, spending unnecessary amounts of money on foods to satisfy cravings. Difficulty concentrating on things such as a job or career can indicate sense of loss of control by not being to organize thoughts leading to a decrease in efficiency. Other ways to indicate the sense of loss of control, are craving food despite being full. One may set rules to try to eat healthy but the cravings over rule and the rules are failed to be followed. One big indicator of loss of control due to food addiction is even though one knows they have a medical problem caused by the craved foods, they cannot stop consuming the foods, which can be detrimental to their health.

Food addiction has some physical signs and symptoms. Decreased energy; not being able to be as active as in the past, not being able to be as active as others around, also a decrease in efficiency due to the lack of energy. Having trouble sleeping; being tired all the time such as fatigue, oversleeping, or the complete opposite and not being able to sleep such as insomnia. Other physical signs and symptoms are restlessness, irritability, digestive disorders, and headaches.

In extreme cases food addiction can result in some suicidal thoughts.

A Food addiction, especially long-term, can result in negative consequences to all aspects of a person’s life, creating damaging and chronic symptoms.

Rumination syndrome in adults is a complicated disorder whose symptoms can mimic those of several other gastroesophogeal disorders and diseases. Bulimia nervosa and gastroparesis are especially prevalent among the misdiagnoses of rumination.

Bulimia nervosa, among adults and especially adolescents, is by far the most common misdiagnosis patients will hear during their experiences with rumination syndrome. This is due to the similarities in symptoms to an outside observer—"vomiting" following food intake—which, in long-term patients, may include ingesting copious amounts to offset malnutrition, and a lack of willingness to expose their condition and its symptoms. While it has been suggested that there is a connection between rumination and bulimia, unlike bulimia, rumination is not self-inflicted. Adults and adolescents with rumination syndrome are generally well aware of their gradually increasing malnutrition, but are unable to control the reflex. In contrast, those with bulimia intentionally induce vomiting, and seldom re-swallow food.

Gastroparesis is another common misdiagnosis. Like rumination syndrome, patients with gastroparesis often bring up food following the ingestion of a meal. Unlike rumination, gastroparesis causes vomiting (in contrast to regurgitation) of food, which is not being digested further, from the stomach. This vomiting occurs several hours after a meal is ingested, preceded by nausea and retching, and has the bitter or sour taste typical of vomit.

Rumination syndrome is a condition which affects the functioning of the stomach and esophagus, also known as a "functional gastroduodenal disorder." In patients that have a history of eating disorders, Rumination syndrome is grouped alongside eating disorders such as bulimia and pica, which are themselves grouped under non-psychotic mental disorder. In most healthy adolescents and adults who have no mental disability, Rumination syndrome is considered a motility disorder instead of an eating disorder, because the patients tend to have had no control over its occurrence and have had no history of eating disorders.

Drunkorexia is a colloquialism for self-imposed starvation or binge eating/purging combined with alcohol abuse. The term is generally used to denote the utilisation of extreme weight control methods (such as the aforementioned starvation or purging) as a tool to compensate for planned binge drinking.

Research on the combination of an eating disorder and binge drinking has primarily focused on the patterns of college-aged women, but the phenomenon has also been noted among young men. Studies show that college students engage in this combination of self-imposed malnutrition and binge drinking to avoid weight gain from alcohol. A study by the University of Missouri found that 30% of female college students admitted that within the last year they had restricted food in order to consume greater quantities of alcohol. The same study found that men are more likely engage in similar behavior in order to save money for purchasing alcohol. According to the study, 67% of students who restrict calories prior to alcoholic beverage consumption do so to prevent weight gain, while 21% did so to facilitate alcohol intoxication.

According to the Eating Disorder Center of Denver, of the participating college-aged females in an adjunct research study, about 75% met the criteria for alcohol abuse.

'Showbuzz', a CBS news site, has broadcast that, "Drunkorexia is a media coined term reflecting an alarmingly real trend among young women. The non-medical slang term refers to women who choose to eat less so they can party without gaining weight."

R. Andrew Chambers, MD, Assistant Professor, Institute of Psychiatric Research and Director, Laboratory for Translational Neuroscience of Dual Diagnosis Disorders notes that many celebrity blog sites report similar patterns of behavior among young actresses such as Lindsay Lohan and Paris Hilton, and that the condition could be mimicked within the entertainment industry and contemporary youth culture at large.

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.

Co-existing, and self-reinforcing starvation and alcohol disorders are gaining recognition in the fields of dual diagnosis, psychiatry, and addictionology.

Hyperthyroidism is a condition in which the thyroid gland produces too much thyroid hormone, thyroxin. This overabundance of thyroxin causes irregular and rapid heartbeat, irritability, weight loss, nervousness, anxiety and racing thoughts.

The anxiety and inability to focus is very common in hyperthyroidism and leads to racing thoughts, as well as panic attacks and difficulty concentrating.

Depressive Disorder Not Otherwise Specified (DD-NOS) is designated by the code "311" in the DSM-IV for depressive disorders that are impairing but do not fit any of the officially specified diagnoses. According to the DSM-IV, DD-NOS encompasses "any depressive disorder that does not meet the criteria for a specific disorder." In the DSM-5, it is called unspecified depressive disorder.

Examples of disorders in this category include those sometimes described as minor depressive disorder and recurrent brief depression.

"Depression" refers to a spectrum of disturbances in mood that vary from mild to severe and from short periods to constant illness. DD-NOS is diagnosed if a patients symptoms fail to meet the criteria more common depressive disorders such as major depressive disorder or dysthymia. Although DD-NOS shares similar symptoms to dysthymia, dysthymia is classified by a period of at least 2 years of constantly recurring depressed mood, where as DD-NOS is classified by much shorter periods of depressed moods.

For most people who suffer the condition, their life will be significantly affected. DD-NOS can make many aspects of a person's daily life difficult to manage, inhibiting their ability to enjoy the things that used to make them happy. Sufferers of the disorder tend to isolate themselves from their friends and families, lose interest in some activities, and experience behavioural changes and sleeping disorders. Some sufferers also experience suicidal tendencies or suicide attempts. In addition to having these symptoms, a diagnosis of DD-NOS will only be made if the symptoms cause significant distress or impairment in social, occupational, or other important areas of functioning. For the diagnosis to be accurate, a psychiatrist is required to spend extensive time with the patient.

Symptoms of the disorder may arise due to several reasons. These include:

- Distress due to medical conditions

- Environmental effects and situations

However, the effects of drugs or medication or bereavement are not classified under the diagnosis.

A person will not be diagnosed with the condition if they have or have had any of the following: a major depressive episode, manic episode, mixed episode or hypomanic episode.

A diagnosis of the disorder will look like: "Depressive Disorder NOS 311".

Minor depressive disorder is very similar to major depressive disorder in the symptoms present. Generally, a person's mood is affected by thoughts and feelings of being sad or down on themself or by a loss of interest in nearly all activities. People can experience ups and downs in their life everyday where an event, action, stress or many other factors can affect their feelings on that day. However, depression occurs when those feelings of sadness persist for longer than a few weeks.

A person is considered to have minor depressive disorder if they experience 2 to 4 depressive symptoms during a 2-week period. The Diagnostic and Statistical Manual of Mental Disorders lists the major depressive symptoms. Depressed mood most of the day and/or loss of interest or pleasure in normal activities must be experienced by the individual to be considered to have minor depressive disorder. Without either of these two symptoms, the disorder is not classified as minor depressive disorder. Other depressive symptoms include significant weight loss or weight gain without trying to diet (an increase/decrease in appetite can provide clues as well), insomnia or hypersomnia, psychomotor agitation or psychomotor retardation, fatigue or loss of energy, and feelings of worthlessness or excessive guilt.

All of these signs can compound on each other to create the last major symptom group of minor depressive disorder: thoughts of death, suicidal thoughts, plans to commit suicide, or a suicide attempt.

Minor depressive disorder differs from major depressive disorder in the number of symptoms present with 5 or more symptoms necessary for a diagnosis of major depressive disorder. Both disorders require either depressed mood or loss of interest or pleasure in normal activities to be one of the symptoms and the symptoms need to be present for two weeks or longer. Symptoms also must be present for the majority of the length of a day and present for a majority of the days in the two-week period. Diagnosis can only occur if the symptoms cause "clinically significant distress or impairment". Dysthymia consists of the same depressive symptoms, but its main differentiable feature is its longer-lasting nature as compared to minor depressive disorder. Dysthymia was replaced in the DSM-5 by persistent depressive disorder, which combined dysthymia with chronic major depressive disorder.

The causes of racing thoughts are most often associated with anxiety disorders, but many influences can cause these rapid, racing thoughts. There are also many associated conditions, in addition to anxiety disorders, which can be classified as having secondary relationships with causing racing thoughts. The conditions most commonly linked to racing thoughts are bipolar disorder, anxiety disorder, attention deficit hyperactivity disorder, sleep deprivation, amphetamine dependence, and hyperthyroidism.