Intellectual and Developmental Disabilities
Definitions
Intellectual disability refers to a group of disorders characterized by a limited mental capacity and difficulty with adaptive behaviors such as managing money, schedules and routines, or social interactions. Intellectual disability originates before the age of 18 and may result from physical causes, such as autism or cerebral palsy, or from nonphysical causes, such as lack of stimulation and adult responsiveness.
Developmental disability is a severe, long term disability that can affect cognitive ability, physical functioning, or both. These disabilities appear before age 22 and are likely to be life-long. The term “developmental disability” encompasses intellectual disability but also includes physical disabilities. Some developmental disabilities may be solely physical, such as blindness from birth. Others involve both physical and intellectual disabilities stemming from genetic or other causes, such as Down syndrome and fetal alcohol syndrome.
Research
The National Institutes of Health (NIH) in Rockville, Maryland funds the development of new technologies for newborn screening. The goals are to develop fast, reliable, and cost-effective means to screen newborns and to expand the number of conditions these tests can assess. Such screening makes it possible to begin treatment early, when chances for success are greatest.
Research into the causes and early diagnosis of intellectual disabilities is a priority of the NIH-sponsored Eunice Kennedy Shriver Intellectual and Developmental Disabilities Research Centers. Researchers affiliated with these centers conduct studies to better understand the causes of such disorders and to pursue new avenues for treatment. Investigators at one center, for example, identified a source of adult stem cells in the brain. Such cells, which can develop new tissue, could one day be used to delay or prevent developmental diseases.
Health disparities in survival and access to care are another priority for NIH research. People from disadvantaged backgrounds are less likely to receive screening services, diagnostic evaluations, or treatment interventions. Future studies will seek to identify factors that contribute to these disparities and develop new approaches that ensure equal access to early screening, therapeutic services, and treatment.
Fragile X syndrome affects one in 2,500 births, resulting in intellectual disability, sleep problems, attention deficit disorder, aggression, and compulsive behavior. NIH-funded scientists working with mice having the same genetic mutation found in Fragile X syndrome learned that the mice have increased activity in the metabotropic glutamate receptor (mGluR), which sits atop brain cells. Researchers hope that drugs that block the mGluR receptor might one day be used to lessen the disorder’s effects in humans. Advances in screening for this disorder also may one day give doctors a cheaper, more precise test for diagnosing the condition.
Hypoxic ischemic encephalopathy—loss of blood or oxygen to an infant’s brain during birth— may lead to brain damage or death. Researchers supported by the NIH discovered that lowering a baby’s body temperature in the first six hours of life could help prevent disability. NIH is supporting studies to learn how best to use this new technique so that it soon may be used routinely.
Duchenne muscular dystrophy occurs in about 1 in every 3,500 males. Symptoms include muscle weakness and difficulty walking and talking. Death usually occurs by age 20. In dogs with a canine form of Duchenne muscular dystrophy, researchers used DNA-like molecules called morpholinos to cover up the genetic error that causes the disease. The treatment restored functioning to the skeletal muscles, but was unable to prevent deterioration of the animals’ hearts. Researchers are now seeking more effective ways to deliver the treatment to the heart.
