Intellectual Disorders

(11-14-13)

The “discovery” of the mentally retarded

Mental retardation, intellectual disability, cognitive impairment: these terms all refer to one of the oldest recognized concepts of exceptionality in Western culture. These were also one of the first basic differentiations recovered by Western civilizations after the “dark ages.” Despite this antiquity, many would argue that the concept, the population thought of as mentally challenged today is substantially different from the population historically seen as different in this manner; and that the majority of children classified as mentally retarded today would probably never have been perceived as such during much of our history.

A comment on terminology:

Many of the terms that professionals use to discuss exceptionality eventually find their way into the popular vocabulary as insults to be thrown at your siblings and others who irritate us. There was a time when “idiot”, “imbecile”, “moron” were clinical terms; these rapidly became pejorative; and were replaced with “new”, “neutral” phrases, such as “mental defective”, which in turn became terms of insult; and were replaced with “mental retardation.” Then “MR” acquired negative connotations and newer terms still, such as “developmental disability” were suggest as more acceptable labels. A number of years ago, after lecturing on mental retardation, a student politely brought to my attention the recommendations for labels that were less offensive. I listened with some sympathy to her comments but had already heard on the playgrounds of Bloomington-Normal, one child shout at another: “You DD!” Current there are efforts afoot to replace the phrase “mental retardation” with “cognitive disabiilties.” I would suggest that it will take more than just cleaning up our language every generation or so–unless we seriously examine our attitudes about those with intellectual differences, little will really change.

• Intellectual Disorders
• Intelligence Testing
• WISC-IV

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Mental Retardation

(9-18-12)

Features of Mental Retardation

• General:
  • Highly heterogeneous population: difficult to accurately characterize a “typical presentation”
  • Approximately 15-25% of cases have known, biological etiology (probably little higher now)
  • Male to female ratio approximately 1.5 to 1
• Required Elements:
  • Significantly below average cognitive functioning
  • Significantly below average adaptive functioning
  • Developmental onset
• Common Features:
  • Developmental delay
  • Socially responsive
  • Risk of behavior problems
    • Dekker and Koot (2003a, 2003b) examined a sample of Dutch children with intellectual disability and found comorbidity with psychiatric disorders and impairment high; many children with intellectual disability and psychiatric disorder do not receive mental health services
  • Need for special education
• Occasional Features:
  • Need for structured caretaking environment throughout life
  • Neurological involvement
  • Unusual appearance
• Interventions for mental retardation
  • Special education
  • Vocational habilitation
  • Development of adaptive skills & maximum participation in life
  • Psychological services
    • behavioral approaches
    • psychotherapy

Two-Group Views of Mental Retardation

HYPOTHESIS: the total observed population of indiviuals with mental retardation represent a composite of two etiologically and functionally distinct populations.

various labels have been used:

“Organic”…………………………………………. “Cultural-Familial”
“Pathological”………………………………….. “Normal variation”
“Moderate/Severe/Profound”……………. “Mild”
IQ < 50……………………………………………… IQ > 50

Organic Mental Retardation

• known biological cause of MR
• usually moderate to profound retardation
• no association with SES or ethnic group
• greater association with physical disabilities
• usually identified by parents/physician due to gross developmental delay/physical features

THEORY: child has been damaged by some powerful influence

Cultural-Familial MR

• no clear cause of retardation
• usually mild MR
• association with low SES & minority groups
• no association with physical disabilities
• associated with environmental deprivation
• other family members may show MR
• usually identified by teachers due to academic failure

THEORY: child reflects “normal” distribution of mental abilities, polygenetic influences on intelligence, negative environmental influences

Genetic influences in mental retardation:

• amilial risk and mental retardation
• general population prevalence of MR: 1-2 %
• both parents normal IQ but one
• parent has sibling with MR: 13%
• one parent has MR: 20%
• both parents have MR: 42%

Two-population models have generally received empirical support, but organic pathology cannot be identified in approximately 10% of citizens with severe MR and epilepsy, cerebral palsy, and other organic disorders are found more often in individuals with mild MR than in the general population.

Lecture references:

Hodapp, R. M., & Dykens, E. M. (1996). Mental Retardation. In E. J. Mash & R. A. Barkley (Eds.), Child Psychopathology (pp. 362-369). New York: Guilford Press.

Rao, J. M. (1990). A population-based study of mild mental handicap in children: Preliminary analysis of obstetric associations. Journal of Mental Deficiency Research , 34, 59-65.

Reed, E. W., & Reed, S. G. (1965). Mental retardation: A family study. Philadelphia: Saunders.

Sabaratnam, M., Laver, S., Butler, L., & Pembrey, M. (1994). Fragile X Syndrome in North-East Essex: Towards systematic screening: Clinical selection. Journal of Intellectual Disability Research, 38, 27-35.

Formulations of mental retardation

Development of Intellectual Testing

• Francis Galton in England
  • theoretical model: genetic, unchangable
  • sensory & motor measures
• Binet & Simon in France
  • atheoretical
  • current performance measure
  • assess skills similar to those used in school
  • use average age group achievement as standard of comparison
• Goddard at the Vineland Academy
• Terman at Stanford University
• Stanford-Binet, 5th Edition
• David Wechsler and adult ability test

WISC-III

WISC-IV

IQ Classifications based on WISC-III & WISC-IV

• “superior” = 130 and above, app. 2% of population
• “above average” = 120-129, app. 6% of population
• “high average” = 110-119, app. 17% of population
• “average” range = 90-109 , app. 50% of population
• “low average” = 80-89, app. 16% of population
• “borderline” = 70-79, app. 6% of population
• “impaired” = less than 70, app. 2% of population
  • Mild 50-55 – app. 70: 85% of group, “educable”
  • Moderate 35-40 – 50-55: 10% of group, “trainable”
  • Severe 20-25 – 35-40:3-4% of group, “custodial”
  • Profound below 20-25:1-2% of group, “custodial”

Mental Retardation in DSM-IV

Defining features of Mental Retardation in DSM-IV:

• Subaverage intellectual performance on individually administered IQ test
  • IQ less than 70 (2 standard deviations +/- s.e.)
• Associated impairments in adaptive behavior in at least two skill areas
  • communication
  • self-care
  • home living
  • social/interpersonal skills
  • use of community resources
  • self-direction
  • functional academic skills
  • work
  • leisure
  • health
  • safety
• Onset during early developmental years–beginning before age 18
• Severity of Mental Retardation
  • Mild 50-55 – app. 70: 85% of group, “educable”
  • Moderate 35-40 – 50-55: 10% of group, “trainable”
  • Severe 20-25 – 35-40:3-4% of group, “custodial”
  • Profound below 20-25:1-2% of group, “custodial”

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Wechsler Intelligence Scale for Children, Third Edition (WISC-III)

Verbal Subtests = Verbal IQ

• Information
• Similarities
• Arithmetic
• Vocabulary
• Comprehension
• (Digit Span)

Performance Subtests = Performance IQ

• Picture Completion
• Picture Arrangement
• Block Design
• Object Assembly
• Coding
• (Symbol Search)
• (Mazes)

Ten Subtests (5 Verbal + 5 Performance)= Full Scale IQ (FSIQ)

Mean (average) IQ = 100 (s.d. 15)

standard error = approx. 5