Chapter 12

Mental Retardation

• Mental retardation recognized perhaps longer than any other currently studied in psychology

• Written documents from ancient Egypt made oblique reference to the condition as early as about 1500 BC– was often viewed as part of mental illness

• relatively common

Defining Mental Retardation

4 assumptions outlined by AAMR

• Valid Assessment considers cultural and linguistic diversity

• Existence of limitations in adaptive skills occurs in context of community environments

• Specific adaptive limitations can coexist with strengths

• With appropriate support, life functioning will generally improve

• Communication, the ability to understand and communicate information

• Self-care skills such as toileting, eating, hygiene

• Home living, including interchange wit others

• Social skills, including interchange with others

• Community Use, including shopping and obtaining services and use of community resources

• Self-direction, such as making choices and following a schedule

• Health and safety, including eating and basic first aid

• Functional academics, skills related to learning in school that have direct application in life

• Leisure, developing a variety of leisure and recreational interests

• Work, the ability to maintain part- or full-time employment

Defining Mental Retardation

• American Association on Mental Retardation definition

– Mental retardation refers to substantial limitations in present functioning. It is characterized by significantly sub average intellectual functioning, existing concurrently with related limitations in two or more of the following applicable adaptive skill areas: communication, self-care, home living, social skills, community use, self-direction, health and safety, functional academics, leisure, and work.

•

• Definition departs from earlier efforts in several ways

• One important difference involves the manner of viewing intelligence measures

• The AAMR definition focuses on intellectual functioning primarily at the time of diagnosis and mainly considers an individual’s adaptive skills and needed environmental supports for classification and program planning

Adaptive behavior

• Part of the conceptualization of mental retardation for over 35 years

Describing and Classifying Mental Retardation

• 5 DSM-IV-TR severity classifications for mental retardation

• Mild – IQ of 50-55 to about 70

• Moderate – IQ of 35-40 to 50-55

• Severe – IQ of 20-25 to 35-40

• Profound – IQ below 20 or 25

• Unspecified – presumption of mental retardation but intelligence not testable with standardized instruments

• The term mental retardation extremely general label that covers a heterogeneous set of conditions with different developmental paths and causes

• Historically, the characteristic most typically associated with mental retardation has been reduced intellectual functioning

• The severity of the intellectual impairment has long been a common means of describing and classifying those with retardation

PREVALENCE OF MENTAL RETARDATION

• General estimates of prevalence for mental retardation

– Ranged from 1% to 3% of general population

– About 11% of all children with disabilities in US public schools, and what does this mean in terms of numbers of individuals receiving services under IDEA?

Developmental Factors Explain how development plays a role in mental retardation

• Pregnancy: unborn baby develops rapidly and is vulnerable to diseases, maternal nutritional status, and accidents

– Rubella

• Infancy/Early childhood: dependent on his/her environment for nutrition, oxygen, protection from disease and trauma

• Metabolic Disorders: Child susceptible in prenatal and early childhood

Etiology

• The causes of mental retardation are many and varied

• In some cases, pathology of a physiological or biological nature can be identified

• for as many as 30–40% of those with mental retardation, causation is unknown

Prenatal and Neonatal Causation

• Factors that may cause mental retardation during the prenatal and neonatal periods

– Genetic Factors

– Maternal Characteristics

– Clinical defects

– Birth problems due to delivery positions or atypical labor periods

– Low birth weight and inadequate gestational age

Genetic Factors

• Down syndrome

– three types of Down syndrome, each resulting from a different type of chromosomal error.

• Nondisjunction

• Translocation

• Mosaicism

Genetic Factors

• Fragile X syndrome

– name derives from the fact that the X chromosome of an affected individual will show a fragile spot when grown in an experimental culture

• phenylketonuria (PKU), an inherited metabolic disorder that occurs in about 1 of every 10,000 live births

– Affected infants lack the ability to process phenylalanine, severely damages the central nervous system

Genetic Factors

• Maple syrup urine disease

– Affected infants tend to excrete urine that has a distinctive odor of maple syrup

– may cause severe intellectual impairment, although more often than not the condition is fatal

– cause of this condition has been linked to metabolic deficiencies of three separate amino acids causing extreme CNS damage in the newborn

• Untreated maple syrup urine disease is fatal; few untreated infants survive more than a few weeks

Genetic Factors

• Galactosemia involves difficulty in carbohydrate (sugar) metabolism, rather than amino acid metabolism

• Infants with galactosemia are unable to properly process certain sugar components in milk

• Results are toxic damage to the infant’s liver, brain, and other tissues

• Not all genetic disorders are metabolic in nature

• Some sex-related (occurs in the sex chromosome portion of the genetic material)

• Other genetic disorders may produce a variety of physical and functional manifestations

Maternal Characteristics

• Maternal age

• adequate nutrition may be one of the most important factors

• Such problems become especially severe when expectant mothers do not have access to health care advice or to prenatal medical care

• However, the specific relationship remains unclear

• Sometimes the unborn fetus inadequately nourished regardless of the mother’s nutritional status

• Thyroid deficiency, chronic diabetes, and anemia may substantially affect the development of the fetus and result in premature birth

• Prematurity substantially increases the possibility of intellectual impairment

• Maternal diabetes is always considered to create some degree of risk for the baby

• Serious damage to the fetus may be caused if mother and fetus have incompatible blood types. (Rh factor)

• A variety of maternal infections

• German measles (rubella) is perhaps the viral infection most widely recognized as causing mental retardation.

• Syphilis

• Toxoplasmosis

• Chemicals, drugs, alcohol, and smoking

– a possible consequence of maternal alcohol abuse during pregnancy is fetal alcohol syndrome (FAS) or the less severe fetal alcohol effects (FAE)

Clinical Defects

• Anencephaly occurs early and results in incomplete development of the forebrain portion of cerebral tissue

• Improper closure at other parts of the neural tube may also cause damage to the central nervous system in the form of a condition known as spina bifida

• Hydrocephalus is a clinical defect that is sometimes related to improper closure of the neural tube

•

Atypical Birth

• Birth is stressful to mother and infant alike

• current thinking focuses much more narrowly on the physical trauma of atypical births

– The position of the fetus in utero

• Other fetal positions substantially raise the probability of damage

– breech presentation Several difficulties may result from a breech birth

• may place a great deal of stress on the head of the baby

Neonatal Characteristics

• Two neonatal characteristics highly related to a child’s risk of developing retardation: birth weight and gestational age

• Gestational age refers to the age of a fetus calculated from the time of conception

• Low birth weight and inadequate gestational age at birth (prematurity) are perhaps the most common neonatal risk factors

Causation during Infancy and Childhood

• Genetic disorders that cause developmental damage to the neurological system

• Psychosocial or environmental factors, where adequate stimulation to promote intellectual and social growth does not exist

Treatment of children with mental retardation

• Three types of prenatal intervention– Chromosomal analysis for Down Syndrome or

other genetic abnormalities may result decision to abort fetus

– Treatment for Rh blood incompatibility between mother and fetus may prevent fetal damage.

– Prenatal identification of a PKU problem may result in maternal dietary restrictions

• Postnatal Interventions

– Infant stimulation programs provide positive developmental environment for very young children who are at risk because of prenatal or later environmental circumstances

– Specific instruction for young children in language skills appears promising and probably should be implemented as early as possible

– Inclusion of young children of school age in classrooms with non disabled peers

Prevention of Mental Retardation

• Because of the varied causes, prevention efforts have been extremely diverse, and some approaches have involved extremely controversial methods

• In some cases, preventing mental retardation requires courses of action that are unacceptable to some segments of the population

• A close relationship between medical personnel and new parents is important in the prevention of mental retardation

• PKU screening is now routinely undertaken when a baby is born

• Prenatal screening and diagnosis can also lead to preventive intervention that may be highly controversial from a moral and ethical perspective