Psychosis (from the Greek ψυχή "psyche", for mind/soul, and -ωσις "-osis", for abnormal condition) means 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. Some professionals say that the term psychosis is not sufficient as some illnesses grouped under the term "psychosis" have nothing in common (Gelder, Mayou & Geddes 2005).
The terms psychosis and psychotic are very broad and can mean anything from relatively normal aberrant experiences through to the florid and catatonic expressions of schizophrenia and bipolar type 1 disorder Despite this, psychosis is a term generally given to noticeable deficits in normal behavior (known as deficit or negative signs) or more commonly to the florid experiences of hallucinations or delusional beliefs. 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. It is also important to note that psychosis usually refers to negative expressions, that is paranoia, stereotypy etc. rather than ecstatic experience such as religious ecstasy, though with such a broad term, there are no hard and fast rules.
A wide variety of central nervous system diseases, from both external poisons and internal physiologic illness, can produce symptoms of psychosis.