THEODORE Millon, who has died aged 85, was a leading psychologist known as "the grandfather of personality disorders" and devised the widely used diagnostic test, the Millon Clinical Multiaxial Inventory (MCMI).
Millon's clinical experience with mental illness dated back to his days as a teacher of abnormal psychology at the University of Pennsylvania in the Fifties, where he was required to show students around the nearby Allentown State Hospital so that they could observe "live" case presentations.
Housing more than 2,000 patients, Allentown was then ranked as the worst mental institution in Pennsylvania; the conditions Millon witnessed there so appalled him that he wrote in protest to the state's governor. Amid the outcry that followed, Millon was appointed to the hospital's board of trustees to oversee the reform of patient care.
He took to wandering the hospital incognito, clad in hospital garb, in order to gain deeper insight into the patients' minds. On one terrifying occasion, he became confused on waking up in the ward, after having spent a weekend there. "I began to wonder whether or not I really was a professor and a member of the board, or whether I was a patient in the hospital who merely believed that he was a professor and a member of the board," he recalled.
From 1969 he began work as chief psychologist at the University of Illinois Neuropsychiatric Institute. There he began to write in earnest on the criteria that psychologists use to describe so-called disordered thinking, and the different personality traits that made up a diagnosis. By 1980, as part of a task force assembled by the American Psychiatric Association, he had sorted these traits into 11 standardised categories or "types" (later revised to 14) which formed the basis for the third edition of the Diagnostic Statistical Manual of Mental Disorders.
Throughout the process, Millon had given much thought to how psychologists could delineate the various personality types in their daily interactions with patients. The MCMI was his solution – a personality inventory, first published in 1977, with 175 true-or-false questions, which could be completed quickly and which ranked the patient on more than 20 different scales, screening for clinical syndromes like alcohol and drug dependence as well as personality patterns (depressive, anti-social etc). Its revised version, together with Millon's version for adolescents, is still widely used today, second only to the (much longer) Minnesota Multiphasic Personality Inventory (MMPI).
An only child, Theodore Millon was born in Manhattan on August 18, 1928. His father Abraham had met his wife, Mollie, while working at her family's clothing factory in Sokoly, Poland; the couple had emigrated to the United States in the mid-1920s. An ebullient and gifted woman, Mollie was also prone to bouts of hypochondria; looking back in later years from a clinical perspective, Theodore Millon reckoned that she would have been "diagnosed" as bipolar, had the label then existed.
A quick student, Theodore attended a "gifted programme" at Hunter College, New York, before graduating from Lafayette High School in 1945. At the City College of New York he earned bachelor's degrees in psychology, physics and philosophy. His PhD dissertation, at the University of Connecticut in 1953, was on the assessment of authoritarian or fascistic personalities.
Applying his own diagnostic process in a 2005 autobiographical essay, Millon referred to himself as an example of "secure narcissism". His entry in Masters of the Mind, a dictionary of psychologists that he had compiled, described him as "invariably buoyant, if not jovial. Critics are not invariably enamoured, however, finding his work to be, at times, too speculative."
Theodore Millon married, in 1952, Renee Baratz, who survives him with their four children.