Pre-World War II
In the United States, the initial stimulus for developing a classification of mental disorders was the need to collect statistical information. What might be considered the first official attempt to gather information about mental illness in the United States was the recording of the frequency of "idiocy/insanity" in the 1840 census. By the 1880 census, seven categories of mental illnesses were distinguished: mania, melancholia, monomania, paresis, dementia, dipsomania, and epilepsy.
In 1917, the American Medico-Psychological Association, together with the National Commission on Mental Hygiene, formulated a plan that was adopted by the Bureau of the Census for gathering uniform statistics across mental hospitals. Although this system devoted more attention to clinical utility than did previous systems, it was still primarily a statistical classification. The American Psychiatric Association subsequently collaborated with the New York Academy of Medicine to develop a nationally acceptable psychiatric nomenclature that would be incorporated within the first edition of the American Medical Association's Standard Classified Nomenclature of Disease. This nomenclature was designed primarily for diagnosing inpatients with severe psychiatric and neurological disorders.
In 1921, the American Medico-Psychological Association changed its name to the Committee on Statistics of the American Psychiatric Association.