during world war i hollingworth was asked by the surgeon general’s office to administer psychological services to shell-shocked soldiers who returned from the war. from his observations of these men hollingworth developed a theory of functional neurosis, which he published in 1920 in one of the first books on clinical psychology, "the psychology of functional neurosis". in 1927 hollingworth was elected president of the american psychological association. hollingworth was also a prolific writer, publishing what essentially amounted to a book a year between 1926 and 1935. although hollingworth wrote his autobiography in 1940 it was never published. in the late 1930s hollingway returned to applied research as a favor to a friend, investigating the reasons why people chew gum.