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What Is a Developmental Disability?
What Is an Intellectual Disability?
How many people have Intellectual Disabilities?
What are the causes of Intellectual Disabilities?
Can intellectual disabilities be prevented?
Can intellectual disabilities be cured?
What Is a Developmental Disability?
A severe and chronic disability of a person which is:
Attributed to a mental or physical impairment or combination of
impairments;
Is manifested before the person becomes 18;
Is likely to continue indefinitely;
Results in substantial functional limitations in three or more of the
following areas of major life activity:
Self care (basic living skills)
Receptive and expressive language
Learning
Mobility
Self-direction (making choices and decisions on one’s own)
Capacity for independent living
Economic self-sufficiency
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What Is an Intellectual Disability?
An individual is considered to have an intellectual disability based on
the following three criteria (Diagnostic and Statistical Manual-IV of
the American Psychiatric Association):
Significantly sub-average intellectual functioning: an IQ of
approximately 70 or below in an individually administered IQ test.
Concurrent deficits or impairments in present adaptive functioning
(i.e., the person’s effectiveness in meeting the standards expected for
his or her age by his or her cultural group) in at least two of the
following areas: Communication, Self-Care, Home Living,
Social/interpersonal skills, use of community resources, self-direction,
functional academic skills, work, leisure, health, and safety.
The onset is before age 18.
The DSM-IV diagnosis is also based on degree of severity reflecting the
level of intellectual impairment:
Mild Intellectual Disabilities: IQ level 50-55 to 70
Moderate Intellectual Disabilities: IQ level 35-40 to 50-55
Severe Intellectual Disabilities: IQ level of 20-25 to 35-40
Profound Intellectual Disabilities: IQ level below 20-25
The AAID (American Association on Intellectual and Developmental
Disabilities) method of classification looks at strengths and weaknesses
and the level of supports the person needs to overcome limits in
adaptive skills. The level or intensity of support is defined as:
Intermittent (as needed)
Limited (time-limited)
Extensive (daily)
Pervasive (daily, across all life areas)
Severity
IQ Range
Mental Age (MA) Equivalent
% of Persons with ID
Mild
50-70
8 yrs. To 11.25 yrs.
85%
Moderate
35-40 to 50-55
5 yrs. 9 mos. To 8 yrs. 9 mos.
10%
Severe
20-25 to 35-40
4 yrs. 3 mos. To 6 yrs. 6 mos.
3-4%
Profound
Below 20-25
Less than 4 yrs.
1-2%
Intelligence: Refers to general mental or cognitive capacity or the
person’s ability to reason, plan, solve problems, think abstractly,
comprehend complex ideas, learn quickly, learn from experience, and to
make general inferences from that experience. It is measured by
standardized IQ tests such as the Wechsler Adult Intelligence Scale,
Stanford-Binet, or others.
Adaptive Behavior: Refers to the person’s ability to function or cope
within the demands of their environment. A standardized test is used
such as the Vineland Adaptive Behaviors Scales or the AAID Adaptive
Behavior Scale.
Occurs before the age of 18: The cause of the Intellectual Disability
must have occurred during the developmental period of life (essentially
from conception to the age of 18).
Mental Age: Means that the individual received the same number of
correct responses on a standardized IQ test as the average person of
that age. It does not mean that an older person with an intellectual
disability is like or has the mind or understanding of a younger person.
A person with a chronological age of 40, but a Mental Age of 8, still
has the experiences, wants, needs and interests of a 40-year-old, and
not those of an 8-year-old.
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How many people have Intellectual Disabilities?
Approximately 2.5 to 3 percent of the general population has an
intellectual disability. Intellectual disabilities cut across the lines
of racial, ethnic, educational, social and economic backgrounds. It can
occur in any family.
What are the causes of Intellectual Disabilities?
An intellectual disability can be caused by any condition which impairs
development of the brain before birth, during birth, or during
childhood. Several hundred causes have been discovered, but in about
one-third of the people affected, the cause remains unknown. The three
major known causes of mental retardation are Down syndrome, fetal
alcohol syndrome and fragile X syndrome.
The causes can be categorized as follows:
Genetic conditions – These result from abnormality of genes inherited
from parents, errors when genes combine, or from other disorders of the
genes caused during pregnancy by infections, overexposure to x-rays and
other factors. More than 500 genetic diseases are associated with
intellectual disabilities. Some examples include PKU 9pheylketonuria), a
single gene disorder also referred to as an inborn error of metabolism
because it is caused by a defective enzyme. Down syndrome is an example
of a chromosomal disorder. Chromosomal disorders happen sporadically and
are caused by too many or too few chromosomes, or by a change in
structure of a chromosome. Fragile X syndrome is a single gene disorder
located on the X chromosome and is the leading inherited cause of
intellectual disabilities.
Problems during pregnancy – Use of alcohol or drugs by the pregnant
mother can cause intellectual disabilities. Recent research has
implicated smoking in increasing the risk of intellectual disabilities.
Other risks include malnutrition, certain environmental contaminants,
and illnesses of the mother during pregnancy, such as toxoplasmosis,
cytomegalovirus, rubella and syphilis. Pregnant women who are infected
with HIV may pass the virus to their child, leading to future
neurological damage.
Problems at birth – Although any birth condition of unusual stress may
injure the infant’s brain, prematurity and low birth weight predict
serious problems more often than any other conditions.
Problems after birth – Childhood diseases such as whooping cough,
chicken pox, measles, and Hib disease which may lead to meningitis and
encephalitis can damage the brain, as can accidents such as a blow to
the head or near drowning. Lead, mercury and other environmental toxins
can cause irreparable damage to the brain and nervous system.
Poverty and environmental deprivation – Children from deprived
environments may become intellectual disabled because of malnutrition,
disease-producing conditions, inadequate medical care and environmental
health hazards, physical and emotional deprivation, child abuse and
neglect, and lack of stimulation. Research suggests that such
under-stimulation can result in irreversible damage and can serve as a
cause of intellectual disabilities.
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Can intellectual disabilities be prevented?
During the last 30 years, significant advances in research have
prevented many cases of intellectual disabilities. Screening and
treatment of newborns for several conditions which lead to mental
retardation (PKU, congenital hypothyroidism, Rh disease), vaccines
against measles, rubella and Hib, removing lead from the environment,
child safety seats, bicycle helmets to reduce head trauma, early
intervention for high-risk infants, and good prenatal care are all
interventions which can prevent intellectual disabilities. Research
continues on the many causes of mental retardation which we cannot
prevent.
Can intellectual disabilities be cured?
The short answer is no. Intellectual disabilities cannot be cured. A
person’s IQ level is unlikely to increase once that person has reached
adulthood, although it may decrease due to trauma, stroke, etc. An
intellectual disability is considered a lifelong condition. What can
change more fluidly is the level of supports or the person’s adaptive
behavior. Adaptive functioning can change, meaning that all individuals
can learn and grow, increasing their level of independence or decreasing
their dependence on others for supports.
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Contact: Susan Berneike,
Director of Residential Services at 216-504-9846 |