Psychoanalysis is a psychological theory; a form of psychotherapy, especially for the treatment of neurotic and character or personality disorders; and a method for investigating psychological phenomena. Psychoanalysis was created and developed by Sigmund Freud, who presented his method, clinical observations, and theory in Interpretation of Dreams and other major works, including The Psychopathology of Everyday Life and Three Essays on the Theory of Sexuality, as well as in many of his case studies.