Up until the end of the 18th century mental disorders were divided into roughly four categories: idiocy (congenital intellectual impairment), dementia (acquired intellectual impairment), mania (insanity associated with many delusions and disturbed behaviour), and melancholia (insanity associated with circumscribed delusions and social withdrawal).
Morel in France was one of the first people to put forward the view that that mental disorders could in fact be further separated and classified. In 1852 he gave the name démence précoce to describe a disorder which he described as starting in adolescence and leading first to a withdrawal, odd mannerisms, self-neglect and eventually to intellectual deterioration.
Kraepelin working in the late nineteenth century took inspiration from general paralysis of the insane – a disease with unity of cause, course and outcome – and argued that there were a discrete and discoverable number of psychiatric disorders. He sought to distinguish between ‘dementia praecox’ and affective psychosis. Dementia praecox described patients with a global disruption of perceptual and cognitive processes (dementia) together with early onset (praecox). Affective psychosis contrasted with relatively intact thinking, later onset and episodic nature of the illness.
It was Bleuler who first used the phrase ‘schizophrenia’. It is commonly thought that this means ‘split personality’ but Bleuler actually meant the name to reflect the ‘loosening of the associations’; he thought this the essence of the disease. He described four fundamental symptoms which he deemed essential for the diagnosis: loosened associations (between different functions of the mind, so that thoughts become disconnected and co-ordination between emotional and volitional processes become weaker), ambivalence (the presence of conflicting emotions and desires), incongruous affect (e.g. vacuous giggling on hearing sad news), and autism (active withdrawal from reality in order to live in an inner world of fantasy)
Unlike Kraeplin, Bleuler felt that affective psychosis and schizophrenia were not strictly delineated but on lay on a continuum. He also demoted hallucinations and delusions, which to Kraeplin were central, to ‘secondary symptoms’.
More recently, working in the 1950s, Kurt Schneider’s work was fundamentally pragmatic. He lent on the earlier work of Karl Jaspers – a philosopher psychiatrist who had concentrated on the phenomenology of mental disorders, in particular the un-understandability of psychotic delusions – and aimed to identify characteristics that were peculiar to schizophrenia and which would therefore provide the best guide to the practising clinician. He identified eleven first rank symptoms of the disorder, all of which were forms of hallucination, delusion or passivity experience.
We can see from the above brief summary of the evolution of schizophrenia as an idea that what is central to the diagnosis has significantly altered as it has passed through the hands of these thinkers. For Kraepelin the crucial features were intellectual, for Bleuler cognitive and emotional, whereas Schneider pinpointed hallucinations and delusions. Their ideas are still important as DSM IV/ICD-10 criteria for schizophrenia are a patchwork of the ideas of all three. Therefore although operationalized criteria have improved the reliability of the schizophrenia diagnosis and outside psychiatry it is considered to be a crystallized entity, not only does there still remain no firm aetiology or diagnostic test for schizophrenia but its very character is still up for question.