Schizophrenia: devastating psychotic disorder that may involve characteristic disturbances in thinking (delusions), perception (hallucinations), speech, emotions, and behaviour. Catatonia: disorder of movement involving immobility or excited agitation. Paranoia: irrational delusions of grandeur or persecution: distinguished dementia praecox from bipolar disorder. Dementia praecox involves early age of onset and a poor outcome. Introduced the term schizophrenia (combined the greek words of split and mind . Believed that there was an associative splitting of the basic functions of personality (eg. cognition, emotion, perception) Disorder defined by the difficulty of keeping a consistent train of thought. Unlike many other mental disorders, schizophrenia cannot be defined by a particular behaviour, way of thinking, or emotion. People with schizophrenia do not necessarily share all the same behaviours or symptoms. Schizophrenia involves psychotic behaviour: psychotic: disorder involving delusions, hallucinations, loss of contact with reality or disorganized speech or behaviour.