Dementia Praecox (premature or precocious madness) is a term which came into use over 100 years ago as an umbrella term to refer to what are now known as the schizophrenias. It was the work of German psychiatrist Emil Kraepelin (1856-1926) that originally made the term popular. He was heavily influenced by Karl Ludwig Kahlbaum (1828-1899) who carried out systematic studies of the symptoms of young psychotic patients and began to name different syndromes.It is important to note that the study of mental illness and the increasingly scientific approach to data gathering and categorising sets of symptoms is an important stage in the history of the discipline of psychology.
Appreciating the step forward in diagnosis and prognosis that could be made by such systematic study, Kraepelin undertook longitudinal studies of his patients. The methodical data collection he carried out helped him to discover patterns which led him to categorise two forms of insanity in his textbook Psychiatrie (updated and reprinted several times in the 1890s). These were manic depressive illness (which affected mood and could respond to treatment and even be completely recovered from) and dementia praecox (in which, he claimed, the prognosis was poor and chronic deterioration inevitable and this made the name appropriate due to the onset of the disease in adolescence). The latter category he characterised as being a disintegration of cognitive functions leading to memory loss, attention deficit and a lack of adherence to goal fulfilment.
So at that time this category comprised what the International Statistical Classification of Diseases and Related Health Problems (ICD), produced by the World Health Organization now calls the paranoid, catatonic and hebephrenic types of schizophrenia. Paranoid schizophrenia is characterised by symptoms of delusion or hallucination, catatonic by immoblity or purposeless movement and hebephrenic by disorganised thought.
Swiss psychiatrist Paul Eugen Bleuler (1857-1939) agreed with Kraepelin's concept of dementia praecox as a degenerative brain disease but argued that the term was not accurate because onset was not necessarily in adolescence and also 'dementia' suggested an inevitable decline which was not always the case. He began to use the term schizophrenia and although the terms schizophrenia and dementia praecox were used interchangeably until the 1950s, schizophrenia is now the term for this group of mental disorders.
In 1909, Carl Gustav Jung (1875 -1961) who began his career as an assistant to Bleuler, wrote On the Psychology of Dementia Praecox where, heavily influenced by the work of Sigmund Freud, he used psychoanalytical methods to interpret the actions of his patients at the Burghözli Mental Hospital instead of dismissing them as incomprehensible madness. This is considered a key early work by a man who would later be seen as the founder of analytical psychology.