A single manic episode, in the absence of secondary causes, (i.e., substance use disorder, pharmacologic, general medical condition) is sufficient to diagnose bipolar I disorder. Hypomania may be indicative of bipolar II disorder. Manic episodes are often complicated by delusions and/or hallucinations; should the psychotic features persist for a duration significantly longer than the episode of mania (two weeks or more), a diagnosis of schizoaffective disorder is more appropriate. Certain of "obsessive-compulsive spectrum" disorders as well as impulse control disorders share the name "mania," namely, kleptomania, pyromania, and trichotillomania. Despite the unfortunate association implied by the name, however, no connection exists between mania or bipolar disorder and these disorders.

B deficiency can also cause characteristics of mania and psychosis.

Hyperthyroidism can produce similar symptoms to those of mania, such as agitation, elevated mood, increased energy, hyperactivity, sleep disturbances and sometimes, especially in severe cases, psychosis.

A "manic episode" is defined in the American Psychiatric Association's diagnostic manual as a "distinct period of abnormally and persistently elevated, expansive, or irritable mood and abnormally and persistently increased activity or energy, lasting at least 1 week and present most of the day, nearly every day (or any duration if hospitalization is necessary)," where the mood is not caused by drugs/medication or a medical illness (e.g., hyperthyroidism), and (a) is causing obvious difficulties at work or in social relationships and activities, or (b) requires admission to hospital to protect the person or others, or (c) the person is suffering psychosis.

To be classed as a manic episode, while the disturbed mood and an increase in goal directed activity or energy is present at least three (or four if only irritability is present) of the following must have been consistently present:

1. Inflated self-esteem or grandiosity.

2. Decreased need for sleep (e.g., feels rested after 3 hours of sleep).

3. More talkative than usual or pressure to keep talking.

4. Flights of ideas or subjective experience that thoughts are racing.

5. Increase in goal directed activity, or psychomotor acceleration.

6. Distractibility (too easily drawn to unimportant or irrelevant external stimuli).

7. Excessive involvement in activities with a high likelihood of painful consequences.(e.g., extravagant shopping, improbable commercial schemes, hypersexuality).

Though the activities one participates in while in a manic state are not "always" negative, those with the potential to have negative outcomes are far more likely.

If the person is concurrently depressed, they are said to be having a mixed episode.

The World Health Organization's classification system defines "a manic episode" as one where mood is higher than the person's situation warrants and may vary from relaxed high spirits to barely controllable exuberance, accompanied by hyperactivity, a compulsion to speak, a reduced sleep requirement, difficulty sustaining attention and often increased distractibility. Frequently, confidence and self-esteem are excessively enlarged, and grand, extravagant ideas are expressed. Behavior that is out of character and risky, foolish or inappropriate may result from a loss of normal social restraint.

Some people also have physical symptoms, such as sweating, pacing, and weight loss. In full-blown mania, often the manic person will feel as though his or her goal(s) trump all else, that there are no consequences or that negative consequences would be minimal, and that they need not exercise restraint in the pursuit of what they are after. Hypomania is different, as it may cause little or no impairment in function. The hypomanic person's connection with the external world, and its standards of interaction, remain intact, although intensity of moods is heightened. But those who suffer from prolonged unresolved hypomania do run the risk of developing full mania, and indeed may cross that "line" without even realizing they have done so.

One of the most signature symptoms of mania (and to a lesser extent, hypomania) is what many have described as racing thoughts. These are usually instances in which the manic person is excessively distracted by objectively unimportant stimuli. This experience creates an absent-mindedness where the manic individual's thoughts totally preoccupy him or her, making him or her unable to keep track of time, or be aware of anything besides the flow of thoughts. Racing thoughts also interfere with the ability to fall asleep.

Manic states are always relative to the normal state of intensity of the afflicted individual; thus, already irritable patients may find themselves losing their tempers even more quickly and an academically gifted person may, during the hypomanic stage, adopt seemingly "genius" characteristics and an ability to perform and articulate at a level far beyond that which would be capable during euthymia. A very simple indicator of a manic state would be if a heretofore clinically depressed patient suddenly becomes inordinately energetic, cheerful, aggressive, or "over happy." Other, often less obvious, elements of mania include delusions (generally of either grandeur or persecution, according to whether the predominant mood is euphoric or irritable), hypersensitivity, hyper vigilance, hypersexuality, hyper-religiosity, hyperactivity and impulsivity, a compulsion to over explain, (typically accompanied by pressure of speech) grandiose schemes and ideas, and a decreased need for sleep (for example, feeling rested after only 3 or 4 hours of sleep); in the case of the latter, the eyes of such patients may both look and feel abnormally "wide" or "open," rarely blinking, and this often contributing to some clinicians’ erroneous belief that these patients are under the influence of a stimulant drug, when the patient, in fact, is either not on any mind-altering substances or is actually on a depressant drug, in a misguided attempt to ward off any undesirable manic symptoms. Individuals may also engage in out-of-character behavior during the episode, such as questionable business transactions, wasteful expenditures of money (e.g., spending sprees), risky sexual activity, abuse of recreational substances, excessive gambling, reckless behavior (as "speed driving" or daredevil activity), abnormal social interaction (as manifest via, for example, over familiarity and conversing with strangers), or highly vocal arguments. These behaviours may increase stress in personal relationships, lead to problems at work and increase the risk of altercations with law enforcement. There is a high risk of impulsively taking part in activities potentially harmful to self and others.

Although "severely elevated mood" sounds somewhat desirable and enjoyable, the experience of mania is ultimately often quite unpleasant and sometimes disturbing, if not frightening, for the person involved and for those close to them, and it may lead to impulsive behaviour that may later be regretted. It can also often be complicated by the sufferer's lack of judgment and insight regarding periods of exacerbation of characteristic states. Manic patients are frequently grandiose, obsessive, impulsive, irritable, belligerent, and frequently deny anything is wrong with them. Because mania frequently encourages high energy and decreased perception of need or ability to sleep, within a few days of a manic cycle, sleep-deprived psychosis may appear, further complicating the ability to think clearly. Racing thoughts and misperceptions lead to frustration and decreased ability to communicate with others.

Mania may also, as earlier mentioned, be divided into three “stages.” Stage I corresponds with hypomania and may feature typical hypomanic characteristics, such as gregariousness and euphoria. In stages II and III mania, however, the patient may be extraordinarily irritable, psychotic or even delirious. These latter two stages are referred to as acute and delirious (or Bell’s), respectively.

Schizoaffective disorder is defined by "mood disorder-free psychosis" in the context of a long-term psychotic and mood disorder. Psychosis must meet criterion A for schizophrenia which may include delusions, hallucinations, disorganized speech, thinking or behavior and negative symptoms. Both delusions and hallucinations are classic symptoms of psychosis. Delusions are false beliefs which are strongly held despite evidence to the contrary. Beliefs should not be considered delusional if they are in keeping with cultural beliefs. Delusional beliefs may or may not reflect mood symptoms (for example, someone experiencing depression may or may not experience delusions of guilt). Hallucinations are disturbances in perception involving any of the five senses, although auditory hallucinations (or "hearing voices") are the most common. A lack of responsiveness or negative symptoms include alogia (lack of spontaneous speech), blunted affect (reduced intensity of outward emotional expression), avolition (loss of motivation), and anhedonia (inability to experience pleasure). Negative symptoms can be more lasting and more debilitating than positive symptoms of psychosis.

Mood symptoms are of mania, hypomania, mixed episode, or depression, and tend to be episodic rather than continuous. A mixed episode represents a combination of symptoms of mania and depression at the same time. Symptoms of mania include elevated or irritable mood, grandiosity (inflated self-esteem), agitation, risk-taking behavior, decreased need for sleep, poor concentration, rapid speech, and racing thoughts. Symptoms of depression include low mood, apathy, changes in appetite or weight, disturbances in sleep, changes in motor activity, fatigue, guilt or feelings of worthlessness, and suicidal thinking.

The disorder is characterized by a sudden onset of psychotic symptoms, which may include delusions, hallucinations, disorganized speech or behavior, or catatonic behavior. The symptoms must not be caused by schizophrenia, schizoaffective disorder, delusional disorder or mania in bipolar disorder. They must also not be caused by a drug (such as amphetamines) or medical condition (such as a brain tumor). The term bouffée délirante describes an acute nonaffective and nonschizophrenic psychotic disorder, which is largely similar to DSM-III-R and DSM-IV brief psychotic and schizophreniform disorders.

Symptoms generally last at least a day, but not more than a month, and there is an eventual return to full baseline functioning. It may occur in response to a significant stressor in one's life, or in other situations where a stressor is not apparent, including in the weeks following birth. In diagnosis, a careful distinction is considered for culturally appropriate behaviors, such as religious beliefs and activities. It is believed to be connected to or synonymous with a variety of culture-specific phenomena such as latah, koro, and amok.

There are three forms of brief psychotic disorder:

1. Brief psychotic disorder with a stressor, such as a trauma or death in the family.

2. Brief psychotic disorder without a stressor, there is no obvious stressor.

3. Brief psychotic disorder with postpartum onset. Usually occurs about four weeks after giving birth.

Mania is a distinct period of at least one week of elevated or irritable mood, which can range from euphoria to delirium, and those experiencing hypo- or mania may exhibit three or more of the following behaviors: speak in a rapid, uninterruptible manner, short attention span, racing thoughts, increased goal-oriented activities, agitation, or they may exhibit behaviors characterized as impulsive or high-risk, such as hypersexuality or excessive spending. To meet the definition for a manic episode, these behaviors must impair the individual's ability to socialize or work. If untreated, a manic episode usually lasts three to six months.

People with hypomania or mania may experience a decreased need of sleep, impaired judgment, and speak excessively and very rapidly. Manic individuals often have a history of substance abuse developed over years as a form of "self-medication". At the more extreme, a person in a full blown manic state can experience psychosis; a break with reality, a state in which thinking is affected along with mood. They may feel unstoppable, or as if they have been "chosen" and are on a "special mission", or have other grandiose or delusional ideas. This may lead to violent behavior and, sometimes, hospitalization in an inpatient psychiatric hospital. The severity of manic symptoms can be measured by rating scales such as the Young Mania Rating Scale, though questions remain about the reliability of these scales.

The onset of a manic or depressive episode is often foreshadowed by sleep disturbances. Mood changes, psychomotor and appetite changes, and an increase in anxiety can also occur up to three weeks before a manic episode develops.

Hypomania is the milder form of mania, defined as at least four days of the same criteria as mania, but does not cause a significant decrease in the individual's ability to socialize or work, lacks psychotic features such as delusions or hallucinations, and does not require psychiatric hospitalization. Overall functioning may actually increase during episodes of hypomania and is thought to serve as a defense mechanism against depression by some. Hypomanic episodes rarely progress to full blown manic episodes. Some people who experience hypomania show increased creativity while others are irritable or demonstrate poor judgment.

Hypomania may feel good to some persons who experience it, though most people who experience hypomania state that the stress of the experience is very painful. Bipolar people who experience hypomania, however, tend to forget the effects of their actions on those around them. Even when family and friends recognize mood swings, the individual will often deny that anything is wrong. What might be called a "hypomanic event", if not accompanied by depressive episodes, is often not deemed problematic, unless the mood changes are uncontrollable, volatile, or mercurial. Most commonly, symptoms continue for a few weeks to a few months.

People with psychosis normally have one or more of the following:

- hallucinations

- delusions

- catatonia

- thought disorder.

Impairments in social cognition also occur.

Individuals with schizophrenia may experience hallucinations (most reported are hearing voices), delusions (often bizarre or persecutory in nature), and disorganized thinking and speech. The last may range from loss of train of thought, to sentences only loosely connected in meaning, to speech that is not understandable known as word salad. Social withdrawal, sloppiness of dress and hygiene, and loss of motivation and judgment are all common in schizophrenia.

Distortions of self-experience such as feeling as if one's thoughts or feelings are not really one's own to believing thoughts are being inserted into one's mind, sometimes termed passivity phenomena, are also common. There is often an observable pattern of emotional difficulty, for example lack of responsiveness. Impairment in social cognition is associated with schizophrenia, as are symptoms of paranoia. Social isolation commonly occurs. Difficulties in working and long-term memory, attention, executive functioning, and speed of processing also commonly occur. In one uncommon subtype, the person may be largely mute, remain motionless in bizarre postures, or exhibit purposeless agitation, all signs of catatonia. People with schizophrenia often find facial emotion perception to be difficult. It is unclear if the phenomenon called "thought blocking", where a talking person suddenly becomes silent for a few seconds to minutes, occurs in schizophrenia.

About 30 to 50 percent of people with schizophrenia fail to accept that they have an illness or comply with their recommended treatment. Treatment may have some effect on insight.

People with schizophrenia may have a high rate of irritable bowel syndrome but they often do not mention it unless specifically asked. Psychogenic polydipsia, or excessive fluid intake in the absence of physiological reasons to drink, is relatively common in people with schizophrenia.

Schizophreniform disorder is a type of mental illness that is characterized by psychosis and closely related to schizophrenia. Both schizophrenia and schizophreniform disorder, as defined by the "Diagnostic and Statistical Manual of Mental Disorders" (DSM-IV-TR), have the same symptoms and essential features except for two differences: the level of functional impairment and the duration of symptoms. Impairment in social, occupational, or academic functioning is usually present in schizophrenia, particularly near the time of first diagnosis, but such impairment may or may not be present in schizophreniform disorder. In schizophreniform disorder, the symptoms (including prodromal, active, and residual phases) must last at least 1 month but not more than 6 months, while in schizophrenia the symptoms must be present for a minimum of 6 months.

If the symptoms have persisted for at least one month, a provisional diagnosis of schizophreniform disorder can be made while waiting to see if recovery occurs. If the symptoms resolve within 6 months of onset, the provisional qualifier is removed from the diagnosis. However, if the symptoms persist for 6 months or more, the diagnosis of schizophreniform disorder must be revised. The diagnosis of brief psychotic disorder may be considered when the duration of symptoms is less than one month.

The main symptoms of both schizophreniform disorder and schizophrenia may include:

- delusions,

- hallucinations,

- disorganized speech resulting from formal thought disorder,

- disorganized or catatonic behavior, and negative symptoms, such as

- an inability to feel a range of emotions (flat affect),

- an inability to experience pleasure (anhedonia),

- impaired or decreased speech (aphasia),

- a lack of desire to form relationships (asociality), and

- a lack of motivation (avolition).

Schizophrenia is often described in terms of positive and negative (or deficit) symptoms. "Positive symptoms" are those that most individuals do not normally experience, but are present in people with schizophrenia. They can include delusions, disordered thoughts and speech, and tactile, auditory, visual, olfactory and gustatory hallucinations, typically regarded as manifestations of psychosis. Hallucinations are also typically related to the content of the delusional theme. Positive symptoms generally respond well to medication.

"Negative symptoms" are deficits of normal emotional responses or of other thought processes, and are less responsive to medication. They commonly include flat expressions or little emotion, poverty of speech, inability to experience pleasure, lack of desire to form relationships, and lack of motivation. Negative symptoms appear to contribute more to poor quality of life, functional ability, and the burden on others than positive symptoms do. People with greater negative symptoms often have a history of poor adjustment before the onset of illness, and response to medication is often limited.

The validity of the positive and negative construct has been challenged by factor analysis studies observing a three dimension grouping of symptoms. While different terminology is used, a dimension for hallucinations, a dimension for disorganization, and a dimension for negative symptoms are usually described.

The following specifiers for schizophreniform disorder may be used to indicate the presence or absence of features that may be associated with a better prognosis:

- With Good Prognostic Features, used if at least two of the following features are present:

- Onset of prominent psychotic symptoms within 4 weeks of the first noticeable change in usual behavior or functioning

- Confusion or perplexity at the height of the psychotic episode

- Good premorbid social and occupational functioning

- Absence of blunted or flat affect

- Without Good Prognostic Features, used if two or more of the above features have not been present.

The presence of negative symptoms and poor eye contact both appear to be prognostic of a poor outcome. Many of the anatomic and functional changes seen in the brains of patients with schizophrenia also occur in patients with schizophreniform disorder. However, at present there is no consensus among scientists regarding whether or not ventricular enlargement, which is a poor prognostic factor in schizophrenia, has any prognostic value in patients with schizophreniform disorder. According to the American Psychiatric Association, approximately two-thirds of patients diagnosed with "provisional" schizophreniform disorder are subsequently diagnosed with schizophrenia; the remaining keep a diagnosis of schizophreniform disorder.

Cycloid psychosis is a psychosis that progresses from normal to full-blown, usually between a few hours to days, not related to drug intake or brain injury. The cycloid psychosis has a long history in European psychiatry diagnosis. The term "cycloid psychosis" was first used by Karl Kleist 1926. Despite the significant clinical relevance, this diagnosis is neglected both in literature as in nosology. The cycloid psychosis has attracted much interest in the international literature of the past 50 years, but the number of scientific studies have greatly decreased over the past 15 years, possibly partly explained by the misconception that the diagnosis has been included incorporated in current diagnostic classification systems. The cycloid psychosis is therefore only partially described in the diagnostic classification systems used. "polymorph acute psychotic disorder", with or without schizophrenic symptoms. (F23.0 ICD 10). Cycloid psychosis is nevertheless its own specific disease that is distinct from both the manic-depressive disorder, and from schizophrenia, and this despite the fact that the cycloid psychosis can include both bipolar (basic mood shifts) as well as schizophrenic symptoms. The disease is an acute, usually self-limiting, functionally psychotic state, with a very diverse clinical picture that almost consistently is characterized by the existence of some degree of confusion or distressing perplexity, but above all, of the multifaceted and diverse expressions the disease takes. The main features of the disease is thus that the onset is acute, the multifaceted picture of symptoms and typically reverses to a normal state and that the long-term prognosis is good. In addition, diagnostic criteria include at least four of the following symptoms:

- Confusion

- Mood-incongruent delusions

- Hallucinations

- Pan-anxiety, a severe anxiety not bound to particular situations or circumstances

- Happiness or ecstasy of high degree

- Motility disturbances of akinetic or hyperkinetic type

- Concern with death

- Mood swings to some degree, but less than what is needed for diagnosis of an affective disorder

Cycloid psychosis occurs in people of generally 15–50 years of age.

Individuals with psychotic depression experience the symptoms of a major depressive episode, along with one or more psychotic symptoms, including delusions and/or hallucinations. Delusions can be classified as mood congruent or incongruent, depending on whether or not the nature of the delusions is in keeping with the individual's mood state. Common themes of mood congruent delusions include guilt, persecution, punishment, personal inadequacy, or disease. Half of patients experience more than one kind of delusion. Delusions occur without hallucinations in about one-half to two-thirds of patients with psychotic depression. Hallucinations can be auditory, visual, olfactory (smell), or haptic (touch), and are congruent with delusional material. Affect is sad, not flat. Severe anhedonia, loss of interest, and psychomotor retardation are typically present.

Cyclothymia is characterized by short cycles of baseline, stable periods of not over two months and numerous swings between depression and hypomania that fail to meet the severity of sustained duration criterion for major affective syndromes for at least two years.

Depressive/dysthymic episodes. Symptoms of the "depressive/dysthymic phase" may include any of the following conditions:difficulty making decisions, problems concentrating, poor memory recall, guilt, self-criticism, low self-esteem, pessimism, self-destructive thinking, constant sadness, apathy, hopelessness, helplessness and irritability. Also common are quick temper, poor judgment, lack of motivation, social withdrawal, appetite change, lack of sexual desire, self-neglect, fatigue, insomnia and sleepiness.

Hypomanic episodes. Symptoms of the "hypomanic episode" may include any of the following conditions: unusually good mood or cheerfulness (euphoria), extreme optimism, inflated self-esteem, rapid speech, racing thoughts, aggressive or hostile behavior, lack of consideration for others, agitation, massively increased physical activity, risky behavior, spending sprees, increased drive to perform or achieve goals, increased sexual drive, decreased need for sleep, tendency to be easily distracted, and inability to concentrate.

The DSM-IV-TR defines a hypomanic episode as including, over the course of at least four days, elevated mood plus three of the following symptoms OR irritable mood plus four of the following symptoms:

- pressured speech

- inflated self-esteem or grandiosity

- decreased need for sleep

- flight of ideas or the subjective experience that thoughts are racing

- easily distracted and attention-deficit; the inability to 'follow-through' with complete tasks, as similar to attention deficit hyperactivity disorder

- increase in psychomotor agitation, or occasionally in some, increased irritability

- hypersexuality

- involvement in pleasurable activities that may have a high potential for negative psycho-social or physical consequences (e.g., the person engages in unrestrained buying sprees, sexual indiscretions, reckless driving, physical and verbal conflicts, foolish business investments, quitting a job to pursue some grandiose goal, etc).

Psychotic symptoms are often missed in psychotic depression, either because patients do not think their symptoms are abnormal or they attempt to conceal their symptoms from others. On the other hand, psychotic depression may be confused with schizoaffective disorder. Due to overlapping symptoms, differential diagnosis includes also dissociative disorders.

Specifically, hypomania is distinguished from mania by the absence of psychotic symptoms and grandiosity, and by its lesser degree of impact on functioning.

Hypomania is a feature of bipolar II disorder and cyclothymia, but can also occur in schizoaffective disorder. Hypomania is also a feature of bipolar I disorder; it arises in sequential procession as the mood disorder fluctuates between normal mood (euthymia) and mania. Some individuals with bipolar I disorder have hypomanic as well as manic episodes. Hypomania can also occur when moods progress downwards from a manic mood state to a normal mood. Hypomania is sometimes credited with increasing creativity and productive energy. Numerous people with bipolar disorder have credited hypomania with giving them an edge in their theater of work.

People who experience hyperthymia, or "chronic hypomania", encounter the same symptoms as hypomania but on a longer-term basis.

Diagnosis of a specific type of delusional disorder can sometimes be made based on the content of the delusions. The "Diagnostic and Statistical Manual of Mental Disorders" (DSM) enumerates seven types:

- Erotomanic type (erotomania): delusion that another person, often a prominent figure, is in love with the individual. The individual may breach the law as he/she tries to obsessively make contact with the desired person.

- Grandiose type: delusion of inflated worth, power, knowledge, identity or believes themself to be a famous person, claiming the actual person is an impostor or an impersonator.

- Jealous type: delusion that the individual's sexual partner is unfaithful when it is untrue. The patient may follow the partner, check text messages, emails, phone calls etc. in an attempt to find "evidence" of the infidelity.

- Persecutory type: This delusion is a common subtype. It includes the belief that the person (or someone to whom the person is close) is being malevolently treated in some way. The patient may believe that he/she has been drugged, spied upon, harassed and so on and may seek "justice" by making police reports, taking court action or even acting violently.

- Somatic type: delusions that the person has some physical defect or general medical condition

- Mixed type: delusions with characteristics of more than one of the above types but with no one theme predominating.

- Unspecified type: delusions that cannot be clearly determined or characterized in any of the categories in the specific types.

Schizophrenia is a mental disorder that is expressed in abnormal mental functions and disturbed behavior.

The signs and symptoms of childhood schizophrenia are nearly the same as adult-onset schizophrenia. Some of the earliest signs that a young child may develop schizophrenia are lags in language and motor development. Some children engage in activities such as flapping the arms or rocking, and may appear anxious, confused, or disruptive on a regular basis. Children may experience symptoms such as hallucinations, but these are often difficult to differentiate from just normal imagination or child play. It is often difficult for children to describe their hallucinations or delusions, making very early-onset schizophrenia especially difficult to diagnose in the earliest stages. The cognitive abilities of children with schizophrenia may also often be lacking, with 20% of patients showing borderline or full intellectual disability.

Very early-onset schizophrenia refers to onset before the age of thirteen. The prodromal phase, which precedes psychotic symptoms, is characterized by deterioration in school performance, social withdrawal, disorganized or unusual behavior, a decreased ability to perform daily activities, a deterioration in self-care skills, bizarre hygiene and eating behaviors, changes in affect, a lack of impulse control, hostility and aggression, and lethargy.

Auditory hallucinations are the most common "positive symptom" in children. Positive symptoms have come to mean psychopathological disorders that are actively expressed, such as delusions, hallucinations, thought disorder etc.). A child's auditory hallucinations may include voices that are conversing with each other or voices that are speaking directly to the children themselves. Many children with auditory hallucinations believe that if they do not listen to the voices, the voices will harm them or someone else. Tactile and visual hallucinations seem relatively rare. The children often attribute the hallucinatory voices to a variety of beings, including family members or other people, evil forces ("the Devil", "a witch", "a spirit"), animals, characters from horror movies (Bloody Mary, Freddy Krueger) and less clearly recognizable sources ("bad things," "the whispers"). Command auditory hallucinations (also known as imperative hallucinations) were common and experienced by more than ½ of the group in a research at the Bellevue Hospital Center's Children's Psychiatric Inpatient Unit. And voices repeat and repeat: "Kill somebody!", "Kill her, kill her!". Delusions are reported in more than half of children with schizophrenia, but they are usually less complex than those of adults. Delusions often connected with hallucinatory experiences.. In a research delusions were characterized as persecutory for the most part, but some children reported delusions of control. Many said they were being tortured by the beings causing their visual and auditory hallucinations, some thought that if they disobeying their voices would cause them harm.

Some degree of thought disorder was observed in a test group of children in Bellevue Hospital. They displayed illogicality, tangentialiry (a serious disturbance in the associative thought process), and loosening of associations.

Negative ("deficit") symptoms in schizophrenia reflect mental deficit states such as apathy and aboulia, avolition, flattened affect, asthenia etc.

Schizoaffective disorder (SZA, SZD or SAD) is a mental disorder characterized by abnormal thought processes and deregulated emotions. The diagnosis is made when the person has features of both schizophrenia and a mood disorder—either bipolar disorder or depression—but does not strictly meet diagnostic criteria for either alone. The bipolar type is distinguished by symptoms of mania, hypomania, or mixed episode; the depressive type by symptoms of depression only. Common symptoms of the disorder include hallucinations, paranoid delusions, and disorganized speech and thinking. The onset of symptoms usually begins in young adulthood, currently with an uncertain lifetime prevalence because the disorder was redefined, but DSM-IV prevalence estimates were less than 1 percent of the population, in the range of 0.5 to 0.8 percent. Diagnosis is based on observed behavior and the person's reported experiences.

Genetics, neurobiology, early and current environment, behavioral, social, and experiential components appear to be important contributory factors; some recreational and prescription drugs may cause or worsen symptoms. No single isolated organic cause has been found, but extensive evidence exists for abnormalities in the metabolism of tetrahydrobiopterin (BH4), dopamine, and glutamic acid in people with schizophrenia, psychotic mood disorders, and schizoaffective disorder. People with schizoaffective disorder are likely to have co-occurring conditions, including anxiety disorders and substance use disorder. Social problems such as long-term unemployment, poverty and homelessness are common. The average life expectancy of people with the disorder is shorter than those without it, due to increased physical health problems from an absence of health promoting behaviors such as a sedentary lifestyle, and a higher suicide rate.

The mainstay of current treatment is antipsychotic medication combined with mood stabilizer medication or antidepressant medication, or both. There is growing concern by some researchers that antidepressants may increase psychosis, mania, and long-term mood episode cycling in the disorder. When there is risk to self or others, usually early in treatment, hospitalization may be necessary. Psychiatric rehabilitation, psychotherapy, and vocational rehabilitation are very important for recovery of higher psychosocial function. As a group, people with schizoaffective disorder diagnosed using DSM-IV and criteria have a better outcome than people with schizophrenia, but have variable individual psychosocial functional outcomes compared to people with mood disorders, from worse to the same. Outcomes for people with DSM-5 diagnosed schizoaffective disorder depend on data from prospective cohort studies, which haven't been completed yet.

In DSM-5 and ICD-10, schizoaffective disorder is in the same diagnostic class as schizophrenia, but not in the same class as mood disorders. The diagnosis was introduced in 1933, and its definition was slightly changed in the DSM-5, published in May 2013, because the DSM-IV schizoaffective disorder definition leads to excessive misdiagnosis. The changes made to the schizoaffective disorder definition were intended to make the DSM-5 diagnosis more consistent (or reliable), and to substantially reduce the use of the diagnosis. Additionally, the DSM-5 schizoaffective disorder diagnosis can no longer be used for first episode psychosis.

Cyclothymia (), also called cyclothymic disorder, is a type of chronic mood disorder widely considered to be a more chronic but milder or subthreshold form of bipolar disorder. Cyclothymia is characterized by numerous mood swings, with periods of hypomanic symptoms that do not meet criteria for a manic episode, alternating with periods of mild or moderate symptoms of depression that do not meet criteria for a major depressive episode.

An individual with cyclothymia may feel stable at a baseline level but experience a noticeable shift to an emotional high during subthreshold hypomanic episodes of elation or euphoria, with symptoms similar to those of mania but less severe, and often cycle to emotional lows with moderate depressive symptoms. To meet the diagnostic criteria for cyclothymia, a person must experience this alternating pattern of emotional highs and lows for a period of at least two years with no more than two consecutive symptom-free months. For children and adolescents, the duration must be at least one year.

The diagnosis of cyclothymia is rare compared to other mood disorders. Diagnosis of cyclothymia entails the absence of any major depressive episode, manic episode or mixed episode, which would qualify the individual for diagnosis of other mood disorders. When a major episode manifests after an initial diagnosis of cyclothymia, the individual may qualify for a diagnosis of bipolar I or bipolar II disorder. Although estimates vary greatly, 15–50% of cases of cyclothymia later advance to the diagnostic criteria for bipolar I and/or bipolar II disorder (with cyclothymic features). Although the emotional highs and lows of cyclothymia are less extreme than those of bipolar disorder and generally do not cause the same conditions, the symptomatology, longitudinal course, family history and treatment response of cyclothymia are consistent with bipolar spectrum.

Lifetime prevalence of cyclothymic disorder is 0.4–1%. Frequency appears similar in men and women, though women more often seek treatment. People with cyclothymia during periodic hypomania (euphoria) tend to feel an inflated self-worth, self-confidence and elation, often with rapid speech, racing thoughts, not much need to sleep, increased aggression and impulsive behavior, showing little regard for consequences of decisions—but may sometimes be somewhat, fully or hyper-productive for a period of several days at a time.

The following can indicate a delusion:

1. The patient expresses an idea or belief with unusual persistence or force.

2. That idea appears to have an undue influence on the patient's life, and the way of life is often altered to an inexplicable extent.

3. Despite his/her profound conviction, there is often a quality of secretiveness or suspicion when the patient is questioned about it.

4. The individual tends to be humorless and oversensitive, especially about the belief.

5. There is a quality of "centrality": no matter how unlikely it is that these strange things are happening to him/her, the patient accepts them relatively unquestioningly.

6. An attempt to contradict the belief is likely to arouse an inappropriately strong emotional reaction, often with irritability and hostility.

7. The belief is, at the least, unlikely, and out of keeping with the patient's social, cultural, and religious background.

8. The patient is emotionally over-invested in the idea and it overwhelms other elements of their psyche.

9. The delusion, if acted out, often leads to behaviors which are abnormal and/or out of character, although perhaps understandable in the light of the delusional beliefs.

10. Individuals who know the patient observe that the belief and behavior are uncharacteristic and alien.

Additional features of delusional disorder include the following:

1. It is a primary disorder.

2. It is a stable disorder characterized by the presence of delusions to which the patient clings with extraordinary tenacity.

3. The illness is chronic and frequently lifelong.

4. The delusions are logically constructed and internally consistent.

5. The delusions do not interfere with general logical reasoning (although within the delusional system the logic is perverted) and there is usually no general disturbance of behavior. If disturbed behavior does occur, it is directly related to the delusional beliefs.

6. The individual experiences a heightened sense of self-reference. Events which, to others, are nonsignificant are of enormous significance to him or her, and the atmosphere surrounding the delusions is highly charged.

The exact incidence and prevalence of brief psychotic disorder is not known, but it is generally considered uncommon. Internationally, it occurs twice as often in women than men, and even more often in women in the United States. It typically occurs in the late 30s and early 40s. The exact cause of brief psychotic disorder is not known. One theory suggests a genetic link, because the disorder is more common in people who have family members with mood disorders, such as depression or bipolar disorder. Another theory suggests that the disorder is caused by poor coping skills, as a defense against or escape from a particularly frightening or stressful situation. These factors may create a vulnerability to develop brief psychotic disorder. In most cases, the disorder is triggered by a major stress or traumatic event. Childbirth may trigger the disorder in some women. Approximately 1 in 10,000 women experience brief psychotic disorder shortly after childbirth. There are general medical causes of brief psychosis that should also be considered when being evaluated. Post-natal depression, HIV and AIDS, malaria, syphilis, Alzheimer's disease, Parkinson's disease, hypoglycaemia (an abnormally low level of glucose in the blood), lupus, multiple sclerosis, brain tumor and PANS.

Though less common than stimulant psychosis, stimulants such as cocaine and amphetamines as well as the dissociative drug phencyclidine (PCP, angel dust) may also cause a theorized severe and life-threatening condition known as excited delirium. This condition manifests as a combination of delirium, psychomotor agitation, anxiety, delusions, hallucinations, speech disturbances, disorientation, violent and bizarre behavior, insensitivity to pain, elevated body temperature, and superhuman strength. Despite some superficial similarities in presentation excited delirium is a distinct (and more serious) condition than stimulant psychosis. The existence of excited delirium is currently debated.

Symptoms of psychotic breaks vary greatly, usually depending on the circumstances of diagnosis or any contributary substance ingested. Symptoms can range from harmless, sometimes unnoticed delusions, to violent outbursts and major depression. The sufferer may also be unable to distinguish reality from fantasy (for example, believing that a dream really happened or experiencing hallucinations that appear to be real). When a bipolar disorder is involved: crying, grandiosity, insomnia, irritability, and persecutory delusions may all or severally manifest themselves as symptoms.