Psychosis (from the Ancient Greek ψυχή "psyche", for mind/soul, and -ωσις "-osis", for abnormal condition or derangement) 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). Indeed, a complex constellation of neurological and psychological factors can result in the altered signalling observed in psychosis. In otherwise normal individuals, exogenous ligands can produce psychotic symptoms. NMDA receptor antagonists, such as ethanol and ketamine, can replicate a similar psychosis to that experienced in schizophrenia.