Psychosis (from the Ancient Greek ψυχή “psyche”, for mind/soul, and -ωσις “-osis”, for abnormal condition or derangement) refers to an abnormal condition of the mind, and is a generic psychiatric term for a mental state often described as involving a “loss of contact with reality“. People suffering from psychosis are described as psychotic. Psychosis is given to the more severe forms of psychiatric disorder, during which hallucinations and delusions and impaired insight may occur.
The term psychosis is very broad and can mean anything from relatively normal aberrant experiences through to the complex and catatonic expressions of schizophrenia and bipolar type 1 disorder. Moreover a wide variety of central nervous system diseases, from both external poisons and internal physiologic illness, can produce symptoms of psychosis. This led many professionals to say that psychosis is not specific enough as a diagnostic term. Despite this, “psychosis” is generally given to noticeable deficits in normal behavior (negative signs) and more commonly to diverse types of hallucinations or delusional beliefs (positive signs).
An excess in dopaminergic, and a deficit in glutamate(specifically NMDA) signalling correspond to positive and negative symptoms respectively. The NMDA antagonist MK-801 is used in animal models of schizophrenia, while paranoid and persecutory delusions are typical of methamphetamine users. In those with an organic psychosis, a complex cluster of genetic and environmental factors are involved in the creation of the endogenous imbalance of neurotransmitters observed in those with psychosis.
People experiencing psychosis may exhibit personality changes and thought disorder. Depending on its severity, this may be accompanied by unusual or bizarre behavior, as well as difficulty with social interaction and impairment in carrying out daily life activities.
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. 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 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. 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.
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., ethnicity, religious beliefs, superstitious belief).
Catatonia describes a profoundly agitated state in which the experience of reality is generally considered to be impaired. There are two primary manifestations of catatonic behavior. The classic presentation is a person who does not move or interact with the world in any way while awake. This type of catatonia presents with waxy flexibility. Waxy flexibility is when someone physically moves part of a catatonic person’s body and the person stays in the position even if it is bizarre and otherwise nonfunctional (such as moving a person’s arm straight up in the air and the arm stays there).
The other type of catatonia is more of an outward presentation of the profoundly agitated state described above. It involves excessive and purposeless motor behavior as well as extreme mental preoccupation which prevents intact experience of reality. An example would be someone walking very fast in circles to the exclusion of anything else with a level of mental preoccupation (meaning not focused on anything relevant to the situation) that was not typical of the person prior to the symptom onset. In both types of catatonia there is generally no reaction to anything that happens outside of them. It is important to distinguish catatonic agitation from severe bipolar mania although someone could have both.
 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“.