Dissociative disorders (DD) are conditions that involve disruptions or breakdowns of memory, awareness, identity, or perception. People with dissociative disorders use dissociation, as a defence mechanism, pathologically and involuntarily. Dissociative disorders are sometimes triggered by psychological trauma, but may be preceded only by stress, psychoactive substances, or no identifiable trigger at all.

The dissociative disorders listed in the American Psychiatric Association's DSM-5 are as follows:

- Dissociative identity disorder (formerly multiple personality disorder): the alternation of two or more distinct personality states with impaired recall among personality states. In extreme cases, the host personality is unaware of the other, alternating personalities; however, the alternate personalities can be aware of all the existing personalities. This category now includes the old derealization disorder category.

- Dissociative amnesia (formerly psychogenic amnesia): the temporary loss of recall memory, specifically episodic memory, due to a traumatic or stressful event. It is considered the most common dissociative disorder amongst those documented. This disorder can occur abruptly or gradually and may last minutes to years depending on the severity of the trauma and the patient.

- Dissociative fugue (formerly psychogenic fugue) is now subsumed under the dissociative amnesia category. It is described as reversible amnesia for personal identity, usually involving unplanned travel or wandering, sometimes accompanied by the establishment of a new identity. This state is typically associated with stressful life circumstances and can be short or lengthy.

- Depersonalization disorder: periods of detachment from self or surrounding which may be experienced as "unreal" (lacking in control of or "outside" self) while retaining awareness that this is only a feeling and not a reality.

- The old category of dissociative disorder not otherwise specified is now split into two: Other specified dissociative disorder, and unspecified dissociative disorder. These categories are used for forms of pathological dissociation that do not fully meet the criteria of the other specified dissociative disorders, or if the correct category has not been determined.

Both dissociative amnesia and dissociative fugue usually emerge in adulthood and rarely occur after the age of 50. The ICD-10 classifies conversion disorder as a dissociative disorder while the DSM-IV classifies it as a somatoform disorder.

According to the fifth "Diagnostic and Statistical Manual of Mental Disorders" ("DSM-5"), DID symptoms include "the presence of two or more distinct personality states" accompanied by the inability to recall personal information, beyond what is expected through normal forgetfulness. Other DSM-5 symptoms include a loss of identity as related to individual distinct personality states, and loss referring to time, sense of self and consciousness. In each individual, the clinical presentation varies and the level of functioning can change from severely impaired to adequate. The symptoms of dissociative amnesia are subsumed under the DID diagnosis but can be diagnosed separately. Individuals with DID may experience distress from both the symptoms of DID (intrusive thoughts or emotions) and the consequences of the accompanying symptoms (dissociation rendering them unable to remember specific information). The majority of patients with DID report childhood sexual or physical abuse, though the accuracy of these reports is controversial. Identities may be unaware of each other and compartmentalize knowledge and memories, resulting in chaotic personal lives. Individuals with DID may be reluctant to discuss symptoms due to associations with abuse, shame, and fear. DID patients may also frequently and intensely experience time disturbances.

Around half of people with DID have fewer than 10 identities and most have fewer than 100; as many as 4,500 have been reported. The average number of identities has increased over the past few decades, from two or three to now an average of approximately 16. However, it is unclear whether this is due to an actual increase in identities, or simply that the psychiatric community has become more accepting of a high number of compartmentalized memory components. The primary identity, which often has the patient's given name, tends to be "passive, dependent, guilty and depressed" with other personalities being more active, aggressive or hostile, and often containing a current time line that lacks childhood memory. Most identities are of ordinary people, though fictional, mythical, celebrity and animal parts have been reported.

The psychiatric history frequently contains multiple previous diagnoses of various disorders and treatment failures. The most common presenting complaint of DID is depression, with headaches being a common neurological symptom. Comorbid disorders can include substance abuse, eating disorders, anxiety, post traumatic stress disorder (PTSD), and personality disorders. A significant percentage of those diagnosed with DID have histories of borderline personality disorder and bipolar disorder. Further, data supports a high level of psychotic symptoms in individuals with DID, and that both individuals diagnosed with schizophrenia and those diagnosed with DID have histories of trauma. Other disorders that have been found to be comorbid with DID are somatization disorders, major depressive disorder, as well as history of a past suicide attempt, in comparison to those without a DID diagnosis. Individuals diagnosed with DID demonstrate the highest hypnotizability of any clinical population. The large number of symptoms presented by individuals diagnosed with DID has led some clinicians to suggest that, rather than being a separate disorder, diagnosis of DID is actually an indication of the severity of the other disorders diagnosed in the patient.

Dissociative disorder not otherwise specified (DDNOS) is a mental health diagnosis for pathological dissociation that matches the DSM-5 criteria for a dissociative disorder, but does not fit the full criteria for any of the specifically identified subtypes, which include dissociative identity disorder, dissociative amnesia, and depersonalization/derealization disorder. The International Statistical Classification of Diseases and Related Health Problems (ICD-10) refers to the diagnosis as "Other dissociative and conversion disorders".

Examples of DDNOS include chronic and recurrent syndromes of mixed dissociative symptoms, identity disturbance due to prolonged and intense coercive persuasion, disorders similar to dissociative identity disorder, acute dissociative reactions to stressful events, and dissociative trance.

DDNOS is the most common dissociative disorder and is diagnosed in 40% of dissociative disorder cases. It is often co-morbid with other mental illnesses such as complex posttraumatic stress disorder, major depressive disorder, generalized anxiety disorder, personality disorders, substance abuse disorders and eating disorders.

The core symptom of depersonalization-derealization disorder is the subjective experience of "unreality in one's self", or detachment from one's surroundings. People who are diagnosed with depersonalization also experience an urge to question and think critically about the nature of reality and existence.

Individuals who experience depersonalization can feel divorced from their own personal physicality by sensing their body sensations, feelings, emotions and behaviors as not belonging to themselves. As such, a recognition of one's self breaks down. Depersonalization can result in very high anxiety levels, which can intensify these perceptions even further.

Individuals with depersonalization describe feeling disconnected from their physicality; feeling as if they are not completely occupying their own body; feeling as if their speech or physical movements are out of their control; feeling detached from their own thoughts or emotions; and experiencing themselves and their lives from a distance. While depersonalization involves detachment from one's "self", individuals with derealization feel detached from their "surroundings", as if the world around them is foggy, dreamlike, or visually distorted. Some people with depersonalization disorder also have visual alterations such as rapid fluctuations in light. While the exact cause of these perceptual changes has not been determined, it is thought that they may be due to previous drug use. These perceptual changes differ from true hallucinatory phenomena, as they are closer to being optical distortions or illusions rather than psychotic breaks from reality. Individuals with the disorder commonly describe a feeling as though time is "passing" them by and they are not in the notion of the present. These experiences which strike at the core of a person's identity and consciousness may cause a person to feel uneasy or anxious.

Factors that tend to diminish symptoms are comforting personal interactions, intense physical or emotional stimulation, and relaxation. Distracting oneself (by engaging in conversation or watching a movie, for example) may also provide temporary relief. Some other factors that are identified as relieving symptom severity are diet and/or exercise, while alcohol and fatigue are listed by some as worsening their symptoms.

First experiences with depersonalization may be frightening, with patients fearing loss of control, dissociation from the rest of society and functional impairment. The majority of people with depersonalization-derealization disorder misinterpret the symptoms, thinking that they are signs of serious psychosis or brain dysfunction. This commonly leads to an increase of anxiety experienced by the patient, and obsession, which contributes to the worsening of symptoms.

Occasional, brief moments of mild depersonalization can be experienced by many members of the general population; however, depersonalization-derealization disorder occurs when these feelings are strong, severe, persistent, or recurrent and when these feelings interfere with daily functioning.

Dissociative identity disorder (multiple personality disorder)

Cause: People with dissociative identity disorder usually have close relatives who have also had similar experiences.

Treatment: Long-term psychotherapy that helps the patient merge his/her multiple personalities into one personality. “The trauma of the past has to be explored and resolved with proper emotional expression. Hospitalization may be required if behavior becomes bizarre or destructive”. Dissociative identity disorder has a tendency to recur over a period of several years, and may become less of a problem after mid-life.

Dissociative amnesia

Cause: A way to cope with trauma.

Treatment: Psychotherapy (e.g. talk therapy) counseling or psychosocial therapy which involves talking about your disorder and related issues with a mental health provider. Psychotherapy often involves hypnosis (help you remember and work through the trauma); creative art therapy (using creative process to help a person who cannot express his or her thoughts); cognitive therapy (talk therapy to identify unhealthy and negative beliefs/behaviors); and medications (antidepressants, anti-anxiety medications or tranquilizers). These medications help control the mental health symptoms associated with the disorders, but there are no medications that specifically treat dissociative disorders. However, the medication Pentothal can sometimes help to restore the memories. The length of an event of dissociative amnesia may be a few minutes or several years. If an episode is associated with a traumatic event, the amnesia may clear up when the person is removed from the traumatic situation.

Dissociative fugue

Cause: A stressful event that happens in adulthood.

Treatment: Hypnosis is often used to help patient recall true identity and remember events of the past. Psychotherapy is helpful for the person who has traumatic, past events to resolve. Once dissociative fugue is discovered and treated, many people recover quickly. The problem may never happen again.

Depersonalization disorder

Cause: Dissociative disorders usually develop as a way to cope with trauma. The disorders most often form in children subjected to chronic physical, sexual or emotional abuse or, less frequently, a home environment that is otherwise frightening or highly unpredictable; however, this disorder can also acutely form due to severe traumas such as war or the death of a loved one.

Treatment: Same treatment as dissociative amnesia, and same drugs. An episode of depersonalization disorder can be as brief as a few seconds or continue for several years.

Conversion disorder is now contained under the umbrella term functional neurological symptom disorder. In cases of conversion disorder, there is a psychological stressor.

The diagnostic criteria for functional neurological symptom disorder, as set out in DSM-V, are:

Specify type of symptom or deficit as:

- With weakness or paralysis

- With abnormal movement (e.g. tremor, dystonic movement, myoclonus, gait disorder)

- With swallowing symptoms

- With speech symptoms (e.g. dysphonia, slurred speech)

- With attacks or seizures

- With amnesia or memory loss

- With special sensory symptom (e.g. visual, olfactory, or hearing disturbance)

- With mixed symptoms.

Specify if:

- Acute episode: symptoms present for less than six months

- Persistent: symptoms present for six months or more.

Specify if:

- Psychological stressor (conversion disorder)

- No psychological stressor (functional neurological symptom disorder)

The ICD-10 includes a diagnostic guideline for the wide group of personality and behavioural disorders. However, every disorder has its own diagnostic criteria. In case of the organic personality disorder, patient has to show at least three of the following diagnostic criteria over a six or more months period. organic personality disorder is associated with a large variety of symptoms, such as deficits in cognitive function, dysfunctional behaviours, psychosis, neurosis, emotional changes, alterations in expression function and irritability. Patients with organic personality disorder can present emotional lability that means their emotional expressions are unstable and fluctuating. In addition, patients show reduction in ability of perseverance with their goals and they express disinhibited behaviours, which are characterised by inappropriate sexual and antisocial actions. For instance, patients can show dissocial behaviours, like stealing. Moreover, according to diagnostic guideline of ICD-10, patients can suffer from cognitive disturbances and they present signs of suspiciousness and paranoid ideas. Additionally, patients may present alteration in process of language production that means there are changes in language rate and flow. Furthermore, patients may show changes in their sexual preference and hyposexuality symptoms.

Another common feature of personality of patients with organic personality disorder is their dysfunctional and maladaptive behaviour that causes serious problems in these patients, because they face problems with pursuit and achievement of their goals. It is worth to be mentioned that patients with organic personality disorder express a feeling of unreasonable satisfaction and euphoria. Also, the patients show aggressive behaviours sometimes and these serious dysfunctions in their behaviour can have effects on their life and their relationships with other people. Specifically patients show intense signs of anger and aggression because of their inability to handle their impulses. The type of this aggression is called "impulsive aggression". Furthermore, it is worth to be mentioned that the pattern of organic personality disorder presents some similarities with pattern of temporal lobe epilepsy (TLE). Specifically patients who suffer from this chronic disorder type of epilepsy, express aggressive behaviours, likewise it happens to patients with organic personality disorder. Another similar symptom between Temporal lobe epilepsy and organic personality disorder is the epileptic seizure. The symptom of epileptic seizure has influence on patients' personality that means it causes behavioural alterations". The Temporal lobe epilepsy (TLE) is associated with the hyperexcitability of the medial temporal lobe (MTL) of patients. Finally, patients with organic personality disorder may present similar symptoms with patients, who suffer from the Huntington's disease as well. The symptoms of apathy and irritability are common between these two groups of patients.

Depersonalization disorder (DPD), also known as depersonalization/derealization disorder, is a mental disorder in which the person has persistent or recurrent feelings of depersonalization or derealization. Symptoms can be classified as either depersonalization or derealization. Depersonalization is described as feeling disconnected or estranged from one's self. Individuals experiencing depersonalization may report feeling as if they are an outside observer of their own thoughts or body, and often report feeling a loss of control over their thoughts or actions. In some cases, individuals may be unable to accept their reflection as their own, or they may have out-of-body experiences. While depersonalization is a sense of detachment from one's self, derealization is described as detachment from one's surroundings. Individuals experiencing derealization may report perceiving the world around them as foggy, dreamlike/surreal, or visually distorted. In addition to these depersonalization-derealization disorder symptoms, the inner turmoil created by the disorder can result in depression, self-harm, low self-esteem, panic attacks, phobias, etc. It can also cause a variety of physical symptoms, including chest pain, blurry vision, visual snow, nausea, and the sensation of pins and needles in one's arms or legs.

Depersonalization-derealization disorder is thought to be caused largely by severe traumatic lifetime events, including childhood abuse, accidents, natural disasters, war, torture, and bad drug experiences. It is unclear whether genetics plays a role; however, there are many neurochemical and hormonal changes in individuals with depersonalization disorder. The disorder is typically associated with cognitive disruptions in early perceptual and attentional processes.

Diagnostic criteria for depersonalization-derealization disorder include, among other symptoms, persistent or recurrent feelings of detachment from one's mental or bodily processes or from one's surroundings. A diagnosis is made when the dissociation is persistent and interferes with the social and/or occupational functions of daily life. However, accurate descriptions of the symptoms are hard to provide due to the subjective nature of depersonalization/derealization and persons' ambiguous use of language when describing these episodes. In the DSM-5, it was combined with Derealization Disorder and renamed Depersonalization/Derealization Disorder (DDPD). In the DSM-5, it remains classified as a dissociative disorder, while the ICD-10 calls it depersonalization-derealization syndrome and classifies it as a neurotic disorder. Although the disorder is an alteration in the subjective experience of reality, it is not a form of psychosis, as the person is able to distinguish between their own internal experiences and the objective reality of the outside world. During episodic and continuous depersonalization, the person can distinguish between reality and fantasy. In other words, the grasp on reality remains stable at all times.

While depersonalization-derealization disorder was once considered rare, lifetime experiences with it occur in about 1–2% of the general population. The chronic form of the disorder has a reported prevalence of 0.8 to 1.9%. While these numbers may seem small, depersonalization/derealization experiences have been reported by a majority of the general population, with varying degrees of intensity. While brief episodes of depersonalization or derealization can be common in the general population, the disorder is only diagnosed when these symptoms cause substantial distress or impair social, occupational, or other important areas of functioning.

As it has already been mentioned, the organic personality disorder is included in a wide group of personality and behavioural disorders. This mental health disorder can be caused by disease, brain damages or dysfunctions in specific brain areas in frontal lobe. The most common reason for this profound change in personality is the traumatic brain injury (TBI). Children, whose brain areas have injured or damaged, may present Attention Deficit Hyperactivity Disorder (ADHD), oppositional defiant disorder (ODD) and organic personality disorder. Moreover, this disorder is characterised as "frontal lobe syndrome". This characteristic name shows that the organic personality disorder can usually be caused by lesions in three brain areas of frontal lobe. Specifically, the symptoms of organic personality disorder can also be caused by traumatic brain injuries in orbitofrontal cortex, anterior cingulate cortex and dorsolateral prefrontal cortex. It is worth to be mentioned that organic personality disorder may also be caused by lesions in other circumscribed brain areas.

Conversion disorder begins with some stressor, trauma, or psychological distress. Usually the physical symptoms of the syndrome affect the senses or movement. Common symptoms include blindness, partial or total paralysis, inability to speak, deafness, numbness, difficulty swallowing, incontinence, balance problems, seizures, tremors, and difficulty walking. These symptoms are attributed to conversion disorder when a medical explanation for the afflictions cannot be found. Symptoms of conversion disorder usually occur suddenly. Conversion disorder is typically seen in individuals aged 10 to 35, and affects between 0.011% and 0.5% of the general population.

Conversion disorder can present with motor or sensory symptoms including any of the following:

Motor symptoms or deficits:

- Impaired coordination or balance

- Weakness/paralysis of a limb or the entire body (hysterical paralysis or motor conversion disorders)

- Impairment or loss of speech (hysterical aphonia)

- Difficulty swallowing (dysphagia) or a sensation of a lump in the throat

- Urinary retention

- Psychogenic non-epileptic seizures or convulsions

- Persistent dystonia

- Tremor, myoclonus or other movement disorders

- Gait problems (astasia-abasia)

- Loss of consciousness (fainting)

Sensory symptoms or deficits:

- Impaired vision (hysterical blindness), double vision

- Impaired hearing (deafness)

- Loss or disturbance of touch or pain sensation

Conversion symptoms typically do not conform to known anatomical pathways and physiological mechanisms. It has sometimes been stated that the presenting symptoms tend to reflect the patient's own understanding of anatomy and that the less medical knowledge a person has, the more implausible are the presenting symptoms. However, no systematic studies have yet been performed to substantiate this statement.

Symptoms of a dissociative fugue include mild confusion, and once the fugue ends, possible depression, grief, shame and discomfort. People have also experienced a post-fugue anger.

A doctor may suspect dissociative fugue when people seem confused about their identity or are puzzled about their past or when confrontations challenge their new identity or absence of one. The doctor carefully reviews symptoms and does a physical examination to exclude physical disorders that may contribute to or cause memory loss. A psychological examination is also done.

Sometimes dissociative fugue cannot be diagnosed until people abruptly return to their pre-fugue identity and are distressed to find themselves in unfamiliar circumstances. The diagnosis is usually made retroactively when a doctor reviews the history and collects information that documents the circumstances before people left home, the travel itself, and the establishment of an alternative life.

Functional amnesia can also be situation specific, varying from all forms and variations of traumas or generally violent experiences, with the person experiencing severe memory loss for a particular trauma. Committing homicide; experiencing or committing a violent crime such as rape or torture; experiencing combat violence; attempting suicide; and being in automobile accidents and natural disasters have all induced cases of situation-specific amnesia (Arrigo & Pezdek, 1997; Kopelman, 2002a). As Kopelman (2002a) notes, however, care must be exercised in interpreting cases of psychogenic amnesia when there are compelling motives to feign memory deficits for legal or financial reasons. However, although some fraction of psychogenic amnesia cases can be explained in this fashion, it is generally acknowledged that true cases are not uncommon. Both global and situationally specific amnesia are often distinguished from the organic amnesic syndrome, in that the capacity to store new memories and experiences remains intact. Given the very delicate and often times dramatic nature of memory loss in these such cases, there usually is a concerted effort to help the person recover their identity and history. This will allow the subject to sometimes be recovered spontaneously when particular cures are encountered.

Ganser syndrome is a rare dissociative disorder previously classified as a factitious disorder. It is characterized by nonsensical or wrong answers to questions or doing things incorrectly, other dissociative symptoms such as fugue, amnesia or conversion disorder, often with visual pseudohallucinations and a decreased state of consciousness. It is also sometimes called nonsense syndrome, balderdash syndrome, syndrome of approximate answers, hysterical pseudodementia or prison psychosis. This last name, prison psychosis, is sometimes used because the syndrome occurs most frequently in prison inmates, where it may be seen as an attempt to gain leniency from prison or court officials.

Ganser is an extremely rare variation of dissociative disorder. It is a reaction to extreme stress and the patient thereby suffers from approximation or giving absurd answers to simple questions. The syndrome can sometimes be diagnosed as merely malingering, but it is more often defined as dissociative disorder.

Symptoms include a clouding of consciousness, somatic conversion symptoms, confusion, stress, loss of personal identity, echolalia, and echopraxia. The psychological symptoms generally resemble the patient's sense of mental illness rather than any recognized category. Individuals also give approximate answers to simple questions. For example, "How many legs are on a cat?", to which the subject may respond 'Three'.

The syndrome may occur in persons with other mental disorders such as schizophrenia, depressive disorders, toxic states, paresis, alcohol use disorders and factitious disorders. EEG data does not suggest any specific organic cause.

The symptoms of the syndrome of subjective doubles are not clearly defined in medical literature, however, there are some defining features of the delusion:

- The existence of the delusion, by definition, is not a widely accepted cultural belief.

- The patient insists that the double he/she sees is real even when presented with contradictory evidence.

- Paranoia and/or spatial visualization ability impairments are present.

Similarities to other disorders are often noted in literature. Prosopagnosia, or the inability to recognize faces, may be related to this disorder due to the similarity of symptoms. Subjective doubles syndrome is also similar to delusional autoscopy, also known as an out-of-body experience, and therefore is occasionally referred to as an "autoscopic type" delusion. However, subjective doubles delusion differs from an autoscopic delusion: autoscopy often occurs during times of extreme stress, and can usually be treated by relieving the said stressor.

The syndrome of subjective doubles is usually accompanied by another mental disorder or organic brain syndrome, and may appear during or after the onset of the other disorder. Often, co-occurrence of subjective doubles with other types of delusional misidentification syndromes, especially Capgras syndrome, also occurs.

Several variations of the syndrome have been reported in literature:

- The doubles may appear at different ages of oneself.

- Some patients describe their double as both a physically and psychologically identical copy, rather than a purely physical copy. This is also known as clonal pluralization of the self, another type of delusional misidentification syndrome that may or may not be the same type of disorder (see #Controversy, below). In this case, depersonalization may be a symptom.

- Reverse subjective doubles occurs when the patient believes his/her own self (either physical or mental) is being transformed into another person. (see the case of Mr. A in #Presentation)

The main symptoms of paraphrenia are paranoid delusions and hallucinations. The delusions often involve the individual being the subject of persecution, although they can also be erotic, hypochondriacal, or grandiose in nature. The majority of hallucinations associated with paraphrenia are auditory, with 75% of patients reporting such an experience; however, visual, tactile, and olfactory hallucinations have also been reported. The paranoia and hallucinations can combine in the form of “threatening or accusatory voices coming from neighbouring houses [and] are frequently reported by the patients as disturbing and undeserved". Patients also present with a lack of symptoms commonly found in other mental disorders similar to paraphrenia. There is no significant deterioration of intellect, personality, or habits and patients often remain clean and mostly self-sufficient. Patients also remain oriented well in time and space.

Paraphrenia is different from schizophrenia because, while both disorders result in delusions and hallucinations, individuals with schizophrenia exhibit changes and deterioration of personality whereas individuals with paraphrenia maintain a well-preserved personality and affective response.

The original description by Sigbert Josef Maria Ganser in 1898 pointed out their hysterical twilight state. They may also describe hallucinations which are usually more than those in schizophrenia. They may also have disorders of sensation similar to those in conversion disorder. They may be inattentive or drowsy.

Some workers believe there is a genuine psychosis underlying this, others believe it is a dissociative disorder, while still others believe it is the result of malingering. Over the years, opinions have seemed to move from the last view more towards the first.

Ganser syndrome is currently classified under dissociative disorders, to which it moved in the DSM IV from the factitious disorders.

"The following case describes a patient who was diagnosed with psychotic depression, bipolar disorder, and the syndrome of subjective doubles:"

Taken from Kamanitz et al., 1989:

"The following case describes a patient who has been diagnosed with schizoaffective disorder along with multiple delusional misidentification syndromes (subjective doubles, Capgras delusion, intermetamorphosis)":

Taken from Silva et al., 1994:

"The following case describes a patient who has been diagnosed with chronic paranoid schizophrenia and reverse subjective doubles:"

Taken from Vasavada and Masand, 1992:

The diagnosis of PTSD was originally developed for adults who had suffered from a single event trauma, such as rape, or a traumatic experience during a war. However, the situation for many children is quite different. Children can suffer chronic trauma such as maltreatment, family violence, and a disruption in attachment to their primary caregiver. In many cases, it is the child's caregiver who caused the trauma. The diagnosis of PTSD does not take into account how the developmental stages of children may affect their symptoms and how trauma can affect a child’s development.

The term developmental trauma disorder (DTD) has also been suggested. This developmental form of trauma places children at risk for developing psychiatric and medical disorders. Bessel van der Kolk explains DTD as numerous encounters with interpersonal trauma such as physical assault, sexual assault, violence or death. It can also be characterized by subjective events like betrayal, defeat or shame.

Repeated traumatization during childhood leads to symptoms that differ from those described for PTSD. Cook and others describe symptoms and behavioural characteristics in seven domains:

- "Attachment" – "problems with relationship boundaries, lack of trust, social isolation, difficulty perceiving and responding to others' emotional states"

- "Biology" – "sensory-motor developmental dysfunction, sensory-integration difficulties, somatization, and increased medical problems"

- "Affect or emotional regulation" – "poor affect regulation, difficulty identifying and expressing emotions and internal states, and difficulties communicating needs, wants, and wishes"

- "Dissociation" – "amnesia, depersonalization, discrete states of consciousness with discrete memories, affect, and functioning, and impaired memory for state-based events"

- "Behavioural control" – "problems with impulse control, aggression, pathological self-soothing, and sleep problems"

- "Cognition" – "difficulty regulating attention, problems with a variety of 'executive functions' such as planning, judgement, initiation, use of materials, and self-monitoring, difficulty processing new information, difficulty focusing and completing tasks, poor object constancy, problems with 'cause-effect' thinking, and language developmental problems such as a gap between receptive and expressive communication abilities."

- "Self-concept" – "fragmented and disconnected autobiographical narrative, disturbed body image, low self-esteem, excessive shame, and negative internal working models of self".

Paraphrenia (from – beside, near + φρήν – intellect, mind) is a mental disorder characterized by an organized system of paranoid delusions with or without hallucinations (the positive symptoms of schizophrenia) without deterioration of intellect or personality (its negative symptom).

This disorder is also distinguished from schizophrenia by a lower hereditary occurrence, less premorbid maladjustment, and a slower rate of progression. Onset of symptoms generally occurs later in life, near the age of 60. The prevalence of the disorder among the elderly is between 0.1 and 4%

Paraphrenia is not included in the DSM-5; psychiatrists often diagnose patients presenting with paraphrenia as having atypical psychoses, delusional disorder, psychoses not otherwise specified, schizoaffective disorders, and persistent persecutory states of older adults. Recently, mental health professionals have also been classifying paraphrenia as very late-onset schizophrenia-like psychosis.

In the Russian psychiatric manuals paraphrenia (or paraphrenic syndrome) is the last stage of development of paranoid schizophrenia. "Systematized paraphrenia" (with systematized delusions i. e. delusions with complex logical structure) and "expansive-paranoid paraphrenia" (with expansive/grandiose delusions and persecutory delusions) are the variants of paranoid schizophrenia (). You see sometimes "systematized paraphrenia" with delusional disorder ().

Depersonalization is the third most common psychological symptom, after feelings of anxiety and feelings of depression. Depersonalization is a symptom of anxiety disorders, such as panic disorder. It can also accompany sleep deprivation (often occurring when suffering from jet lag), migraine, epilepsy (especially temporal lobe epilepsy), obsessive-compulsive disorder, stress, anxiety, and some cases of low latent inhibition. Interoceptive exposure is a non-pharmacological method that can be used to induce depersonalization.

A similar and overlapping concept called ipseity disturbance (ipse is Latin for "self" or "itself") may be part of the core process of schizophrenia spectrum disorders. However, specific to the schizophrenia spectrum seems to be "a "dis"location of first-person perspective such that self and other or self and world may seem to be non-distinguishable, or in which the individual self or field of consciousness takes on an inordinate significance in relation to the objective or intersubjective world" (emphasis in original).

For the purposes of evaluation and measurement depersonalisation can be conceived of as a construct and scales are now available to map its dimensions in time and space. A study of undergraduate students found that individuals high on the depersonalization/derealization subscale of the Dissociative Experiences Scale exhibited a more pronounced cortisol response. Individuals high on the absorption subscale, which measures a subject's experiences of concentration to the exclusion of awareness of other events, showed weaker cortisol responses.

Individuals who experience depersonalization feel divorced from their own personal self by sensing their body sensations, feelings, emotions, behaviors etc. as not belonging to the same person or identity. Often a person who has experienced depersonalization claims that things seem unreal or hazy. Also, a recognition of a self breaks down (hence the name). Depersonalization can result in very high anxiety levels, which further increase these perceptions.

Depersonalization is a subjective experience of unreality in one's self, while derealization is unreality of the outside world. Although most authors currently regard depersonalization (self) and derealization (surroundings) as independent constructs, many do not want to separate derealization from depersonalization.

Adults with C-PTSD have sometimes experienced prolonged interpersonal traumatization as children as well as prolonged trauma as adults. This early injury interrupts the development of a robust sense of self and of others. Because physical and emotional pain or neglect was often inflicted by attachment figures such as caregivers or older siblings, these individuals may develop a sense that they are fundamentally flawed and that others cannot be relied upon.

This can become a pervasive way of relating to others in adult life described as insecure attachment. The diagnosis of dissociative disorder and PTSD in the current DSM-5 (2013) do not include insecure attachment as a symptom. Individuals with Complex PTSD also demonstrate lasting personality disturbances with a significant risk of revictimization.

Six clusters of symptoms have been suggested for diagnosis of C-PTSD:

- alterations in regulation of affect and impulses;

- alterations in attention or consciousness;

- alterations in self-perception;

- alterations in relations with others;

- somatization;

- alterations in systems of meaning.

Experiences in these areas may include:

- Difficulties regulating emotions, including symptoms such as persistent dysphoria, chronic suicidal preoccupation, self injury, explosive or extremely inhibited anger (may alternate), or compulsive or extremely inhibited sexuality (may alternate).

- Variations in consciousness, including forgetting traumatic events (i.e., psychogenic amnesia), reliving experiences (either in the form of intrusive PTSD symptoms or in ruminative preoccupation), or having episodes of dissociation.

- Changes in self-perception, such as a chronic and pervasive sense of helplessness, paralysis of initiative, shame, guilt, self-blame, a sense of defilement or stigma, and a sense of being completely different from other human beings.

- Varied changes in the perception of the perpetrator, such as attributing total power to the perpetrator, becoming preoccupied with the relationship to the perpetrator, including a preoccupation with revenge, idealization or paradoxical gratitude, seeking approval from the perpetrator, a sense of a special relationship with the perpetrator or acceptance of the perpetrator's belief system or rationalizations.

- Alterations in relations with others, including isolation and withdrawal, persistent distrust, anger and hostility, a repeated search for a rescuer, disruption in intimate relationships and repeated failures of self-protection.

- Loss of, or changes in, one's system of meanings, which may include a loss of sustaining faith or a sense of hopelessness and despair.

- Disconnection from surroundings accompanied by feelings of terror and confusion.

Secondary functional delusional parasitosis occurs when the delusions are associated with a psychiatric condition such as schizophrenia or clinical depression.

Because these are frequently found in cases of autistic disorders, criteria could be met for multiple neurological disorders, or cause severe symptoms.

Some examples include:

1. Learning difficulties symptoms such as dyslexia, dysgraphia, dyscalcula, NVLD, slow learning, poor memory, etc.

2. AD/HD symptoms such as poor concentration, poor decision making, poor judgement, impulsiveness, difficulty sitting still, etc.

3. Synesthesia.

4. Neurological sleep disorders such as narcolepsy, insomnia, circadian rhythm disorder, etc.

5. Conditions affecting perceptions and/or cognition, such as agnosia, aphasia, etc.

6. Tourette syndrome or Tic disorder.

7. Epilepsy or Seizure disorder.

8. Parkinsonian syndrome features such as tremors, stiff movements, etc.