Anxiety
The philosopher Søren Kierkegaard, in "The Concept of Anxiety" (1844), described anxiety or dread associated with the "dizziness of freedom" and suggested the possibility for positive resolution of anxiety through the self-conscious exercise of responsibility and choosing. In "Art and Artist" (1932), the psychologist Otto Rank wrote that the psychological trauma of birth was the pre-eminent human symbol of existential anxiety and encompasses the creative person's simultaneous fear of – and desire for – separation, individuation, and differentiation.
Personality disorder
In 1939, psychiatrist David Henderson published a theory of 'psychopathic states' that contributed to popularly linking the term to anti-social behavior. Hervey M. Cleckley’s 1941 text, "The Mask of Sanity", based on his personal categorization of similarities he noted in some prisoners, marked the start of the modern clinical conception of psychopathy and its popularist usage.