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Before the mid-1800s, medical causes of ID were unknown. Instead, causes were attributed to divinity. Then the tide gradually turned. Medical understanding was improving. With this new understanding, the treatment of people with ID began to improve. In this section, we review some of these medical milestones.
John Langston Down is well known for his identification of Down syndrome. Down syndrome is a leading genetic cause of intellectual disability. His 1866 paper, "Observations on the Ethnic Classification of Idiots," he proposed that physical ethnic characteristics could help physicians to pinpoint different conditions.
Down noticed similar characteristics among a certain group of individuals. However, he did not have the technology or genetic knowledge to understand the underlying genetic disorder. Down syndrome results from a genetic abnormality. People with Down syndrome have an extra chromosome. An error in cell division during prenatal development results in a third chromosome 21. The extra chromosome is also referred to as Trisomy 21. This key genetic information was later discovered by other researchers.
Down thought the flat face and almond-shaped eyes of people with Trisomy 21 resembled Mongolian people. This of course is inaccurate. Nonetheless, the term "Mongoloid" was used for years. During the 1960s, the World Health Organization renamed Mongolian syndrome as Down syndrome.
William Ireland attributed most of the cases of intellectual disability to heredity. He wrote an influential article in the 1882 edition of the Edinburgh Medical Journal. It was titled, "On the Diagnosis and Prognosis of Idiocy and Imbecility." He associated ID with the existence of neurotic disorders and insanity. He also noted that IDs were more common in certain families. Ireland believed that illnesses could contribute to the occurrence of intellectual disability. He further postulated that nervous conditions such as epilepsy might result in intellectual disability. Ireland suggested that infant tantrums might cause irreversible brain injury. Although not completely accurate, Ireland was a pioneer. We now know that certain infections, brain injury, and genetics can cause ID. There is more information about causes of ID here.
Ireland's observations identified the many physical features associated with certain causes of ID. The physical features he identified were a smaller head size than usual, and deformities in the palate and teeth. His descriptions of cleft palates and widely spaced teeth were quite detailed.
As knowledge and information about these disabilities improved, the cultural climate changed. Reform movements began to emerge. Advocates pushed for more compassionate and respectful treatment of people with ID. During the late 1800s, Dorothea Dix pressed the United States federal and state governments to provide care and housing for individuals with mental illnesses and intellectual disability. Her efforts were tireless. She achieved success in convincing many states to build hospitals for people with ID and mental illnesses. Although many hospitals were built and staffed, they did not receive the treatment Dix envisioned. Many were severely neglected and mistreated in these institutions.
John Locke's vision of the mind as a "blank slate" with unlimited potential inspired Edouard Seguin, M.D. During the 1800s, Sequin pioneered the development of techniques for educating children with ID. Seguin's teaching approach involved using the five senses. His methods were founded upon the belief that intellectual functioning and the senses were related. He stressed mastery of practical self-help skills and vocational education.
The first step in Seguin's system involved sensory training. This training strengthened the individual's hearing, vision, taste, smell, and hand-eye coordination. Daily living and work skills were taught using positive reinforcement. The curriculum focused on imitation, memory, and generalization skills. Perception and coordination activities helped students evolve their skills and knowledge.
In 1876, Seguin founded a professional organization known today as the American Association on Intellectual and Developmental Disabilities (formerly AAMR). The AAIDD is considered the world's oldest and largest trans-disciplinary professional organization for intellectual disabilities. Seguin's techniques were quite successful. Many of his educational techniques are still in use today (albeit in modified form).
As progress continued, IDs began to be formally classified as a mental condition with medical causes. The origins of the American Diagnostic and Statistical Manual of Mental Disorders date back to the 1840s. These early efforts to name, classify, and record cases of mental illness led to our modern system of diagnosis and classification. When the DSM-I was first published in 1952, intellectual disability was among the sixty recorded disorders. At that time, intellectual disabilities were called mental retardation.
