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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). Schizophrenia has been found in every racial and social group so far studied. On average, 35 new cases per 100,000 population appear annually (Jablensky). Studies of prevalence suggest that at any given time 0.85 percent of the world population is suffering from schizophrenia and expectancy rates are estimated to be as high as 1 chance in 100 that a person will manifest the condition during his or her lifetime. The Global Burden of Disease Study derived from multiple sources (Charlson et al) gives estimates in 2016 of 0.28 percent of the world’s population, which do not vary greatly cross populations or regions. Despite the low incidence, the resultant number of years of life with disability are enormous.

The incidence of schizophrenia has remained more or less the same over the past several decades. Males and females are affected with equal frequency. For unknown reasons, the incidence is higher in social classes showing high mobility and disorganization. It has been suggested that this is a by-product of “downward drift”—a result of deteriorating function in those with the disease that forces them into the lowest socioeconomic stratum where one finds poverty, crowding, limited education, and associated handicaps—and the same data have been used to support the idea that schizophrenia can be caused by such social factors.

Schizophrenic patients occupy about half the beds in psychiatric hospitals—more hospital beds than are allocated to any other single disease—and they constitute 20 to 30 percent of all new admissions to psychiatric institutions (100,000 to 200,000 new cases per year in the United States). The age of admission generally is between 20 and 40 years, with a peak between 28 and 34 years. The economic burden created by this disease is enormous—the direct and indirect costs in the United States have been estimated to be over $50 billion.

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 ...

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