Psychosis

In psychopathology, psychosis is a condition in which one is unable to distinguish, in one's experience of life, between what is and is not real. Examples of psychotic symptoms are delusions, hallucinations, and disorganized or incoherent thoughts or speech. Psychosis is a description of a person's state or symptoms, rather than a particular mental illness, and it is not related to psychopathy (a personality construct characterized by impaired empathy and remorse, along with bold, disinhibited, and egocentric traits).

Common causes of chronic (i.e. ongoing or repeating) psychosis include schizophrenia or schizoaffective disorder, bipolar disorder, and brain damage (usually as a result of alcoholism). Acute (temporary) psychosis can also be caused by severe distress, sleep deprivation, sensory deprivation, some medications, and drug use (including alcohol, cannabis, hallucinogens, and stimulants). Acute psychosis is termed primary if it results from a psychiatric condition and secondary if it is caused by another medical condition or drugs. The diagnosis of a mental-health condition requires excluding other potential causes. Tests can be done to check whether psychosis is caused by central nervous system diseases, toxins, or other health problems.

Treatment may include antipsychotic medication, psychotherapy, and social support. Early treatment appears to improve outcomes. Medications appear to have a moderate effect. Outcomes depend on the underlying cause.

Psychosis is not well-understood at the neurological level, but dopamine (along with other neurotransmitters) is known to play an important role. In the United States about 3% of people develop psychosis at some point in their lives. Psychosis has been described as early as the 4th century BC by Hippocrates and possibly as early as 1500 BC in the Ebers Papyrus.

A hallucination is defined as a sensory perception in the absence of external stimuli. Hallucinations are different from illusions and perceptual distortions, which are the misperception of external stimuli. Hallucinations may occur in any of the senses and take on almost any form. They may consist of simple sensations (such as lights, colors, sounds, tastes, or smells) or more detailed experiences (such as seeing and interacting with animals and people, hearing voices, and having complex tactile sensations). Hallucinations are generally characterized as being vivid and uncontrollable. Auditory hallucinations, particularly experiences of hearing voices, are the most common and often prominent feature of psychosis.

Up to 15% of the general population may experience auditory hallucinations (though not all are due to psychosis). The prevalence of auditory hallucinations in patients with schizophrenia is generally put around 70%. Reported prevalence in bipolar disorder ranges between 11% and 68%. During the early 20th century, auditory hallucinations were second to visual hallucinations in frequency, but they are now the most common manifestation of schizophrenia, although rates vary between cultures and regions. Auditory hallucinations are most commonly intelligible voices. When voices are present, the average number has been estimated at three. Content, like frequency, differs significantly, especially across cultures and demographics. People who experience auditory hallucinations can frequently identify the loudness, location of origin, and may settle on identities for voices. Western cultures are associated with auditory experiences concerning religious content, frequently related to sin. Hallucinations may command a person to do something potentially dangerous when combined with delusions.

So-called "minor hallucinations", such as extracampine hallucinations, or false perceptions of people or movement occurring outside of one's visual field, frequently occur in neurocognitive disorders, such as Parkinson's disease.

Visual hallucinations occur in roughly a third of people with schizophrenia, although certain studies show rates higher than 60%, suggesting that the prevelance of visual hallucinatinations may be higher in certain samples than traditionally thought. The reported prevalence in bipolar disorder is around 15%. Content commonly involves animate objects, although perceptual abnormalities such as changes in lighting, shading, streaks, or lines may be seen. Visual abnormalities may conflict with proprioceptive information, and visions may include experiences such as the ground tilting. Lilliputian hallucinations are less common in schizophrenia, and are more common in various types of encephalopathy, such as peduncular hallucinosis.