Motion sickness susceptibility patterns of psychotic illness.

Motion sickness susceptibility can be used as a neurophysiologic index to establish a polar spectrum of personality difference. Previous observations on a psychiatric patient population have shown that persons in transition between these extremes enter the hospital at a younger age, have a longer stay, and are more likely to receive a diagnosis of schizophrenia. The relationship of this midspectrum, early-onset disorder to other psychotic illnesses has been unclear. Examination of a large sample shows that a midspectrum psychiatric illness, which is most common in young men and is usually diagnosed as schizophrenia, is balanced at the extremes of susceptibility by an older-onset illness, which is most common in women and is often diagnosed as affective in nature. A gradual transition appears to exist between the two types of illness.