Clinicians have provided rich descriptions of schizophrenia-prone individuals. These descriptions are primarily anecdotal and speculative, but they provide a valuable source of hypotheses for testing in more rigorous research. Both Kraepelin ([1913] 1919) and Bleuler (1924), working from case history information as well as from observations of relatives of schizophrenic patients, described schizophreniaprone individuals as having deviant but nonpsychotic symptoms. The symptoms were often milder or transient versions of the types of symptoms displayed by psychotic patients. They interpreted these symptoms as early signs of the disorder but reported that only a portion of persons who show these symptoms of schizophrenia proneness actually develop full-fledged schizophrenia.

The construct of schizophrenia proneness

“Schizophrenia proneness” refers to a predisposition or diathesis to schizophrenia. Most researchers in the field guide their work by a diathesis-stress model. Well-known examples include those of Gottesman (1991), and Meehl (1962), and Slater and Cowie (1971). It is usually assumed that the diathesis is genetic, but that assumption is not necessary for the logic of the model. Although there is clearly a strong genetic predisposition to schizophrenia (Gottesman 1991), other contributions to the predisposition could be environmental. The stress component of diathesis-stress is considered to be only environmental, although the concept of environmental stress is broad, and includes much more than interpersonal stress. For example, one variety of environmental stress is the difficulty of coping with the problems of life for a person with a poor genetic endowment, such as genetically weak physique or low intelligence.