A group of personality disorders comprising personality types that are deeply ingrained resistant to change, and predisposed to develop into psychosis under stress. In contrast to personality trait disturbances, which center around specific characteristics such as emotional instability and aggressiveness, these are pervasive disorders in which the organization of the entire personality appears to be involved. The afflicted individuals have many features which are lesser in degree but similar in kind to one or another psychotic reaction. Although they are peculiar, difficult, or even warped, they can usually function fairly well and remain in contact with realityso long as they are not exposed to overwhelming pressure or prolonged frustration. In some cases their functioning may be improved by long-term therapy, but basic change can seldom be achieved since their personality structure can rarely be altered.The following are the major types of personality pattern disturbance. Each is described elsewhere as a separate topic.(1) Inadequate personality: characterized by ineffectuality, poor judgment, lack of physical and psychological stamina, and general inability to meet intellectual, social, emotional, and physical demands. Tends to develop schizophrenia under stress.(2) Schizoid personality: cold, aloof, unable to feel close to other people; fearful and cannot express hostility or endure competition; an introversive, eccentric day dreamer. Tends to develop schizophrenia under stress.(3) Cyclothymic personality: an ex- travert who alternates between elation and dejection without adequate external cause. Tends to develop manic-depressive reaction under stress.(4) Paranoid personality: hostile, mistrustful, self-assertive; intolerant, arrogant, hypercritical toward others but hypersensitive to criticism • of himself. Tends to develop paranoia, paranoid states, or paranoid schizophrenia under stress. See PARANOIA.(5) Hypomanic personality: lively, gregarious, uninhibited; easily swayed and carried away by enthusiasm; finds it hard to tolerate frustration or criticism. Tends to develop manic-depressive reaction under stress.(6) Melancholic personality: morose and subdued, with a persistent mild depression and inability to enjoy life; kind, sympathetic, and overconscientious; insecure and fearful of disapproval. Tends to develop manic-depressive or involutional reaction under stress.