Severity and type of psychotic illness as a function of personality

Eysenck (1952a) has postulated the existence of three main dimensions of personality: Extraversion, Neuroticism and Psychoticism. These are conceived of as independent of each other, and as continuous, with neurotics and psychotics respectively marking the extreme ends of the N and P dimensions. Within each dimension, the particular type of neurotic or psychotic illness is considered to be determined by the degree of extraversion of the patient; thus dysthymic and hysterical disorders mark the introverted and extraverted types of neurotic illness (Eysenck, 1947), while within the psychotic field degree of social withdrawal might be considered to be the variable most closely related to introversion/ extraversion (Venables and Wing, 1962). Hypotheses have also been formulated to account for the causal factors underlying E and N (Eysenck, 1967), although no such hypotheses have been elaborated with respect to P. A special statistical technique (criterion analysis—Eysenck, 1950) has been worked out to test the crucial question of continuity between normal and abnormal (neurotic and psychotic) populations with respect to N and P; application of this method has given support to the theory of continuity (Eysenck, 1950, 1952b).