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a hallucination is defined as sensory perception in the absence of external stimuli. hallucinations are different from illusions, or perceptual distortions, which are the misperception of external stimuli.[2] hallucinations may occur in any of the five senses and take on almost any form, which may include simple sensations (such as lights, colors, tastes, and smells) to more meaningful experiences such as seeing and interacting with fully formed animals and people, hearing voices, and having complex tactile sensations.
auditory hallucinations, particularly experiences of hearing voices, are a common and often prominent feature of psychosis. hallucinated voices may talk about, or to, the person, and may involve several speakers with distinct personas. auditory hallucinations tend to be particularly distressing when they are derogatory, commanding or preoccupying. however, the experience of hearing voices need not always be a negative one. one research study has shown that the majority of people who hear voices are not in need of psychiatric help.[3] the hearing voices movement has subsequently been created to support voice hearers, regardless of whether they are considered to have a mental illness or not.
[edit]delusions
psychosis may involve delusional beliefs, some of which are paranoid in nature. karl jaspers has classified psychotic delusions into primary and secondary types. primary delusions are defined as arising suddenly and not being comprehensible in terms of normal mental processes, whereas secondary delusions may be understood as being influenced by the person's background or current situation (e.g., ethnic or sexual orientation, religious beliefs, superstitious belief).[4]
[edit]thought disorder
thought disorder describes an underlying disturbance to conscious thought and is classified largely by its effects on speech and writing. affected persons show loosening of associations, that is, a disconnection and disorganization of the semantic content of speech and writing. in the severe form speech becomes incomprehensible and it is known as "word-salad".
[edit]causes
causes of symptoms of mental illness were customarily classified as "organic" or "functional". organic disorders were those held to be caused by physical illness affecting the brain (that is, psychiatric disorders secondary to other conditions), while functional disorders were considered to be disorders of the functioning of the mind in the absence of physical disorders (that is, primary psychological or psychiatric disorders). the materialistic view of the mind-body problem holds that mental disorders arise from physical processes; in this view, the distinction between brain and mind, and therefore between organic and functional disease, is an artificial one. subtle physical abnormalities have been found in illnesses traditionally considered functional, such as schizophrenia. the dsm-iv-tr avoids the functional/organic distinction, and instead lists traditional psychotic illnesses, psychosis due to general medical conditions, and substance-induced psychosis.
[edit]psychiatric disorders
primary psychiatric causes of psychosis include the following:[5][6][7]
schizophrenia and schizophreniform disorder
affective (mood) disorders, including severe depression, and severe depression or mania in bipolar disorder (manic depression). people experiencing a psychotic episode in the context of depression may experience persecutory or self-blaming delusions or hallucinations, while people experiencing a psychotic episode in the context of mania may form grandiose delusions.
schizoaffective disorder, involving symptoms of both schizophrenia and mood disorders
brief psychotic disorder, or acute/transient psychotic disorder
delusional disorder (persistent delusional disorder)
chronic hallucinatory psychosis
psychotic symptoms may also be seen in[7]
schizotypal disorder
certain personality disorders at times of stress (including paranoid personality disorder, schizoid personality disorder, and borderline personality disorder)
induced delusional disorder
and occasionally in obsessive-compulsive disorder
stress is known to contribute to and trigger psychotic states. a history of psychologically traumatic events, and the recent experience of a stressful event, can both contribute to the development of psychosis. short-lived psychosis triggered by stress is known as brief reactive psychosis, and patients may spontaneously recover normal functioning within two weeks.[8] in some rare cases, individuals may remain in a state of full-blown psychosis for many years, or perhaps have attenuated psychotic symptoms (such as low intensity hallucinations) present at most times.
[edit]normal states
brief hallucinations are not uncommon in those without any psychiatric disease. causes or triggers include[7]
falling asleep and waking: hypnagogic and hypnopompic hallucinations, which are entirely normal[9]
bereavement, in which hallucinations of a deceased loved one are common[7]
severe sleep deprivation[10][11][12]
sensory deprivation and sensory impairment
[edit]medical conditions
a very large number of medical conditions can cause psychosis, sometimes called secondary psychosis.[7] examples include:
disorders causing delirium (toxic psychosis), in which consciousness is disturbed
neurodevelopmental disorders and chromosomal abnormalities, including velocardiofacial syndrome
neurodegenerative disorders, such as alzheimer's disease[13], dementia with lewy bodies[14], and parkinson's disease[15]
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