Schizophrenia is among the most serious of all unsolved diseases. This was the opinion expressed 60 years ago in Medical Research: A Mid-Century Survey, sponsored by the American Foundation. Because of a worldwide lifetime prevalence of approximately 0.85 percent and particularly because of its onset early in life, its chronicity, and the associated social, vocational, and personal disabilities, the same conclusion is justified today (see Carpenter and Buchanan).
Neurologists and psychiatrists currently accept the idea that schizophrenia comprises a group of closely related disorders characterized by a particular type of disordered thinking, affect, and behavior. The syndrome by which these disorders manifest themselves differs from those of delirium, confusional states, dementia, and depression in ways that will become clear in the following pages. Unfortunately, the diagnosis of schizophrenia depends on the recognition of characteristic psychologic disturbances largely unsupported by physical findings and laboratory data. This inevitably results in a certain degree of diagnostic imprecision. In other words, any group classified as schizophrenic will include patients with diseases that only resemble schizophrenia, whereas variant or incomplete cases of schizophrenia may not have been included. Moreover, there is not full agreement as to whether all the conditions that are called schizophrenic are the expression of a single disease process. In the United States, for example, paranoid schizophrenia is usually considered to be a subtype of the common syndrome, whereas in some parts of Europe it is thought to be a separate disease.
Present views of the disease now called schizophrenia originated with Emil Kraepelin, a Munich psychiatrist, who first clearly separated it from bipolar psychosis. He called it dementia praecox (adopting the term introduced earlier by Morel) to refer to a deterioration of mental function at an early age, from a previous level of normalcy. At first, Kraepelin believed that "catatonia" and "hebephrenia," which had previously been described by Kahlbaum and by Hecker, respectively, as well as the paranoid form of schizophrenia, were separate diseases, but later, by 1898, he had concluded that several subtypes were a single disease. He emphasized an onset in adolescence or early adult life and a chronic course, often ending in marked deterioration of personality as the defining attributes of all forms of the disease. Early in the twentieth century, the Swiss psychiatrist Eugen Bleuler substituted the term schizophrenia for dementia praecox. This was an improvement insofar as the term dementia was already being used to specify the clinical effects of another category of disease; unfortunately, however, the new name implied a "split personality" or "split mind." By the "splitting" of psychic functions, Bleuler meant the lack of correspondence between ideation and emotional display—the inappropriateness of the patient's affect in relation to his thoughts and behavior. In contrast, in bipolar disease, the patient's mood and affect accurately express his morbid thoughts. Bleuler also introduced the term autism ("thinking divorced from reality") as an aspect of the thought disorder.