This document discusses intellectual disability, including its definition, levels of severity, measurement, etiology, and common comorbidities. Intellectual disability is defined by both intellectual functioning (IQ) and adaptive functioning. It is categorized into four levels of severity - mild, moderate, severe, and profound - based on adaptive functioning scores. Common causes include genetic factors like Down syndrome, environmental factors like prenatal infections, and developmental factors such as prematurity. Comorbid conditions like autism, mood disorders, and seizures are more prevalent among those with intellectual disability.

1. INTELLECTUAL DISABILITY

3. Intellectual Function
 Cognitive abilities (IQ)
Adaptive Function
 Social functioning
 Understanding of societal norms
 Performance of everyday tasks

4.  Levels of severity of ID are determined on the basis of
adaptive functioning, not on IQ scores
 This change in emphasis from prior diagnostic manuals
has been adopted by DSM-5 because adaptive
functioning determines the level of support that is
required

8. MEASUREMENT
 If the clinician chooses to use a standardized test of intelligence which is still common practice-the term
signicantly
subaverage is defined as an IQ of approximately 70 or below or two standard deviations below the mean
for the particular
test
 Adaptive functioning can be measured by using a standardized scale,
Vineland Adaptive Behavior Scale
 Scores communications, daily living skills, socialization, and motor skills (up to 4 years, 1 1 months) and generates
an
adaptive behavior composite that is correlated with the expected skills at a given age

10. MILD INTELLECTUAL DISABILITY
 IQ for this level of adaptive function may typically range from 50 to 70
 Mild intellectual disability represents approximately 85 percent of persons with intellectual disability
 Children with mild intellectual disability often are not identified until the first or second grade, when academic
demands increase
 By late adolescence, they often acquire academic skills at approximately a sixth-grade level
 Many adults with mild intellectual disability can live independently with appropriate support and raise their own
families

11. MODERATE INTELLECTUAL DISABILITY
 IQ for this level of adaptive function may typically range from 35 to 50
 About 10 percent of persons with intellectual disability
 Most children with moderate intellectual disability acquire language and can communicate adequately
during early childhood

12. MODERATE INTELLECTUAL DISABILITY
 They are challenged academically ad often ae not able to achieve above a second to third grade level
 During adolescence, socialization difficulties often set these persons apart, and a great deal of social and
vocational support is beneficial
 As adults, individuals with moderate intellectual disability may be able to perform semiskilled work
under appropriate supervision

13. SEVERE INTELLECTUAL DISABILITY
 IQ in individuals with this level of adaptive function may typically range from 20 to 35
 Represents about 4 percent of individuals with intellectual disability
 May be able to develop communication skills in childhood and often can learn to count as well as
recognize words that are critical to functioning

14. SEVERE INTELLECTUAL DISABILITY
 In this group, the cause for the intellectual disability is more likely to be identified than in milder forms
of intellectual disability
 In adulthood, persons with severe intellectual disability may adapt well to supervised living situations,
such as group homes, and may be able to perform work-related tasks under supervision

15. PROFOUND INTELLECTUAL DISABILITY
 IQ in individuals with this level of adaptive function may typically be less than 20.
 constitutes approximately 1 to 2 percent of individuals with intellectual disability
 Most individuals with profound intellectual disability have identifiable causes for their condition
 Children with profound intellectual disability may be taught some self-care skills and lear to communicate their needs
given the appropriate training

16. COMORBIDITY
 The severity of intellectual disability influenced the risk for particular comorbid psychiatric disorders
 Disruptive and conduct-disorder behaviors occurred more frequently in those diagnosed with mild intellectual
disability,
 severe intellectual disability were more likely to meet criteria for autism spectrum disorder and exhibited symptoms
such as self-stimulation and self-mutilation
 Children diagnosed with severe intellectual disability have a particularly high rate of comorbid autism spectrum
disorder

17. COMORBIDITY
 2-3% meet the criteria for schizophrenia
 Up to 50% meet the criteria for mood disorder
 negative self-image, low self-esteem, poor frustration tolerance, interpersonal dependence, and a rigid problem-
solving style are frequent
 Seizure disorders occur more frequently in individuals with intellectual disability

18. PSYCHOSOCIAL FEATURES
 A negative self-image and poor self-esteem are common features of mildly and moderately intellectually disabled
persons
 Communication difficulties further increase their vulnerability to feelings of ineptness and frustration
 The perpetual sense of isolation and inadequacy has been linked to feelings of anxiety, anger, dysphoria, and
depression

19. ETIOLOGY
 Genetic - chromosomal and inherited conditions
 Developmental or environmental factors - prenatal exposure to infections and toxins, prenatal trauma (e.g.,
prematurity)
 Sociocultural factors - deprivation of nutrition, nurturance, and social stimulation can potentially contribute to the
development of at least mild forms of intellectual disability

20. GENETIC INTELLECTUAL DISABILITY AND BEHAVIORAL PHENOTYPE
 Syndrome of observable behaviors that occur with a significantly greater probability than expected among those
individuals with a specific genetic abnormality
 Examples of behavioral phenotypes occur in genetically determined syndromes such as:
 fragile X syndrome – high rates of ADHD
 Prader-Willi syndrome - compulsive eating disturbances, hyperphagia, and obesity
 Down syndrome

21. FRAGILE X SYNDROME
 Mutation in the FMR1 gene
 One of the most well-known single gene causes of intellectual disability
 It is the most common and first X-linked gene to be identified as a direct cause of intellectual disability
 Deficits in language function include rapid perseverative speech with abnormalities in combining words into phrases
and sentences
 Intellectual functions seem to decline in the pubertal period

22. DOWN SYNDROME
 Prototype of a cytogenetically visible abnormality
 Accounts for about two-thirds of the 15% of intellectual disability attributable to visible
abnormal cytogenetics
 Other microscopically visible chromosomal abnormalities associated with intellectual
disability include deletions, translocations, and supernumerary marker chromosomes

23. DOWN SYNDROME
 Most children with Down syndrome are mildly to moderately intellectually disabled, with a minority having an IQ
above 50
 Cognitive development appears to progress normally from birth to 6 months of age
 IQ scores gradually decrease from near normal at 1 year of age to about 30 to 50 as development proceeds
 According to anecdotal clinical reports, children with Down syndrome are typically placid, cheerful, and cooperative
and adapt easily at home
 With adolescence, the picture changes: youth with Down syndrome may experience more social and emotional
difficulties and behavior disorders, and there is an increased risk for psychotic disorders.

24. DOWN SYNDROME
 Language function is a relative weakness
 Sociability and social skills, such as interpersonal cooperation and conformity with social conventions, are relative
strengths
 Typically manifest deficits in scanning the environment; they are more likely to focus on a single stimulus  difficulty
noticing environmental change
 Characterized by deterioration in language, memory, self-care skills, and problem-solving by the third decade of life

25. PHENYLKETONURIA
 Deficiency of phenylalanine hydroxylase
 Most patients with PKU are severely intellectually disabled
 Children with PKU are reported to be hyperactive and irritable
 Frequently exhibit temper tantrums and often display bizarre movements of their bodies and upper extremities,
including
twisting hand mannerisms
 Verbal and nonverbal communication is commonly severely impaired or nonexistent
 Coordination is poor, and they have many perceptual difficulties

26. RETT SYNDROME
 Diagnosed in the DSM-5 as a form of ASD
 Deterioration in communications skills, motor behavior, and social functioning starts at about 1 year of age
 Symptoms include ataxia, facial grimacing, teeth-grinding, and loss of speech
 Intermittent hyperventilation and a disorganized breathing patter are characteristic while the child is awake
 Stereotypical hand movements, including hand-wringing, are typical
 Cerebral atrophy occurs with decreased pigmentation of the substantia nigra, which suggests abnormalities of the
dopaminergic nigrostiatal system.

27. LESCH-NYHAN SYNDROME
 rare disorder caused by a deficiency of an gene involved in purine metabolism
 Patients have intellectual disability, microcephaly, seizures, choreoathetosis, and spasticity
 The syndrome is also associated with severe compulsive self-mutilation by biting the mouth and fingers

28. ACQUIRED AND DEVELOPMENTAL FACTORS
Prenatal period
 Maternal chronic illnesses and conditions affecting the normal development of the fetus's CNS
 Uncontrolled diabetes, anemia, emphysema, hypertension, and long-term use of alcohol and narcotic substances
 Maternal infections during pregnancy, especially viral infections, have been known to cause fetal damage and
intellectual disability
 The extent of fetal damage depends on such variables as the type of viral infection, the gestational age of the fetus,
and the severity of the illness

29. ACQUIRED AND DEVELOPMENTAL FACTORS
Prenatal period
 Although numerous infectious diseases have been reported to affect the fetus's CNS, the following maternal illnesses have
been identified to increase risk of intellectual disability in the newborn:
1. Rubella (German measles) - major cause of congenital malformations and intellectual disability caused by maternal infection
2. Syphilis
3. Toxoplasmosis
4. CMV
5. Herpes simplex
6. HIV

30. ACQUIRED AND DEVELOPMENTAL FACTORS
Prenatal period
 Fetal alcohol syndrome
 one of the leading preventable causes of intellectual disability and physical disabilities
 Often, the affected children have learning disorders and ADHD, and in some cases
intellectual disability

31. ACQUIRED AND DEVELOPMENTAL FACTORS
Prenatal period
 Drug exposure
 The long-term sequelae of prenatal opioid exposure are not fully known
 Developmental milestones and intellectual functions may be within the normal range, but they have an increased risk for
impulsivity and behavioral problems

32. ACQUIRED AND DEVELOPMENTAL FACTORS
Prenatal period
 Complications of Pregnancy
 Toxemia of pregnancy ad uncontrolled maternal diabetes present hazards to the fetus
 Can potentially result in intellectual disability
 The use of lithium during pregnancy was recently implicated in some congenital malformations, especially of the
cardiovascular system

33. ACQUIRED AND DEVELOPMENTAL FACTORS
Perinatal period
 Infants who sustain intracranial hemorrhages or show evidence of cerebral ischemia are especially vulnerable
to cognitive abnormalities
 Very premature children and those who had intrauterine growth retardation were found to be at high risk for
developing both social problems and academic difficulties
 Socioeconomic deprivation can also affect the adaptive function of these vulnerable infants

34. ACQUIRED CHILDHOOD DISORDERS
 Infection
 Head trauma
 Asphyxia
 Long-term exposures - Intracranial tumors of various types and origins, surgery, and chemotherapy can also adversely
affect brain function

35. ENVIRONMENTAL AND SOCIOCULTURAL FACTORS
 Malnutrition
 Teenage pregnancies are at risk for mild intellectual disability in the baby due to the increased risk of obstetrical
complications, prematurity, and low birth weight
 Child neglect and inadequate caretaking may deprive an infant of both physical and emotional nurturances, leading
to failure to thrive syndromes

36. DIAGNOSIS
 History
 Standardized intellectual assessment
 Standardized measure of adaptive function
 Examination of physical signs, neurological abnormalities, and in some cases, laboratory tests can be used to
ascertain the cause and prognosis.

37. PSYCHIATRIC INTERVIEW
 Requires a high level of sensitivity in order to elicit information at the appropriate intellectual level while remaining
respectful of the patient's age and emotional development
 Patients with milder forms of intellectual disability are often well aware of their differences from others and their
failures, and may be anxious and ashamed during the interview
 Should reveal how the patient has coped with stages of development
 Frustration tolerance, impulse control, and over-aggressive motor and sexual behavior are important areas of attention in the
interview
 It is equally important to elicit the patient's self-image, areas of self-confidence, and an assessment of tenacity, persistence,
curiosity, and willingness to explore the environment

38. STRUCTURED INSTRUMENTS, RATING SCALES, AND PSYCHOLOGICAL
ASSESSMENT
 Wechsler Intelligence Test for Children (6-16 years old)
 Wechsler Preschool and Primary Scale of Intelligence-Revised (3-6 years old)
 Stanford-Binet Intelligence Scale, 4th ed (starting 2 years old)
 Kaufman Assessment Battery for Children (2-12 years old)
 Kaufman Adolescent and Adult Intelligence Test (11-85 years old)

39. STRUCTURED INSTRUMENTS, RATING SCALES, AND PSYCHOLOGICAL
ASSESSMENT
 Vineland Adaptive Behavior Scales

40. PHYSICAL EXAMINATION
 May demonstrate identifying characteristics of specific perinatal and prenatal events or conditions associated with
intellectual disabilities
 Dermatoglyphics may offer another diagnostic tool, because uncommon ridge patters and flexion creases on the
hand are often found in persons who are intellectually disabled

41. NEUROLOGIC EXAMINATION
 Sensory impairments occur frequently among persons with intellectual disabilities
 Hearing impairment occurs in 10% of persons with intellectual disability
 Visual disturbances can range from blindness to disturbances of spatial concepts, design recognition, and concepts of
body image
 Seizure disorders occur in about 10% of intellectually disabled populations and in one third of those with severe
intellectual disability
 Neurological abnormalities increase in incidence and severity in direct proportion to the degree of intellectual
disability.

42. LABORATORY EXAMINATION
 Laboratory tests that may elucidate the causes of intellectual disability
 Chromosomal analysis
 Urine and blood testing for metabolic disorders
 EEG
 Neuroimaging
 Hearing and speech evaluations

43. COURSE AND PROGNOSIS
 Although the underlying intellectual impairment does not improve, in most cases of intellectual disability, level of
adaptation increases with age and can be influenced positively by an enriched and supportive environment
 In general, persons with mild and moderate mental intellectual disabilities have the most flexibility in adapting to
various environmental conditions
 Comorbid psychiatric disorders negatively impact overall prognosis

44. DIFFERENTIAL DIAGNOSIS
 In some cases, severe child maltreatment in the form of neglect or abuse may contribute to delays in development,
which can appear to be intellectual disability
 Sensory disabilities, especially deafness and blindness, can be mistaken for intellectual disability when a lack of
awareness of the sensory deficit leads to inappropriate testing
 Chronic, debilitating medical diseases may depress and delay a child’s functioning and achievement, despite normal
intelligence

45. DIFFERENTIAL DIAGNOSIS
 Specific organic syndromes leading to isolated handicaps such as:
 failure to read (alexia)
 failure to write (agraphia)
 failure to communicate (aphasia)

46. DIFFERENTIAL DIAGNOSIS
 Intellectual disability and ASD often coexist
 70-75% of those with ASD have an IQ below 70
 Children with ASD have relatively more severe impairment in social relatedness and language than other children with the same
level of intellectual disability.

47. TREATMENT
 Newborn screening
 Abstinence from substance use
during pregnancy
 Public health strategies
 Family and genetic counseling
 Educational interventions
 Behavioral and cognitive
interventions
 Family education
 Social interventions – support
groups, etc
 Psychopharmacolgic
interventions
PRIMARY PREVENTION SECONDARY PREVENTION

48. PSYCHOPHARMACOLOGIC INTERVENTIONS
 Aggression, Irritability and Self-injurious Behavior
 Risperidone has been well documented as an efficacious treatment for irritability in children with ASD
 Children and adolescents with intellectual disability appear to be at higher risk for the development
of tardive dyskinesia after use of antipsychotic medications

49. PSYCHOPHARMACOLOGIC INTERVENTIONS
 ADHD
 Studies of methylphenidate (Ritalin) treatment in those mildly intellectually disabled with ADHD have shown significant
improvement in the ability to maintain attention and to stay focused on tasks
 Methylphenidate treatment studies have not shown evidence of long-term improvement in social skills or learning
 Risperidone also has been found to be beneficial in reducing symptoms of ADHD in this population
 It is prudent to begin with a trial of a stimulant medication before the use of antipsychotic agents for the treatment of ADHD
symptoms in intellectual disorder

50. PSYCHOPHARMACOLOGIC INTERVENTIONS
 ADHD
 Amphetamine-based preparations have been shown to be efficacious in treating ADHD in typically developing
children
 It does not appear that these stimulant preparations have been specifically studied in children with intellectual disability.
 Clonidine has been used clinically in this population, especially to ameliorate hyperactivity and impulsivity
 Atomoxetine has been shown to be efficacious in children diagnosed with ASD and prominent ADHD features, and it is used
clinically in the intellectually disabled population

51. PSYCHOPHARMACOLOGIC INTERVENTIONS
 Depressive disorders
 The identification of depressive disorders among individuals with intellectual disability requires careful evaluation
 There have been anecdotal reports of disinhibition in response to SSRis (e.g., fluoxetine and sertaline) in intellectually disabled
individuals with ASD
 Given the relative safety of SSRI antidepressants, a trial is indicated when a depressive disorder is diagnosed in a child or
adolescent with intellectual disability

52. PSYCHOPHARMACOLOGIC INTERVENTIONS
 Stereotypical Motor Movements
 Antipsychotic medications-historically, haloperidol (Haldol) and chlorpromazine, and currently, the
atypical antipsychotics-are used in the treatment of repetitive self-stimulatory behaviors in children
with intellectual disability when these behaviors are either harmful to the child or disruptive.
 Obsessive-compulsive symptoms often overlap with the repetitive stereotypical behaviors seen in
children and adolescents
with intellectual disability, particularly in those with comorbid ASD
 SSRis such as fluoxetine, fluvoxamine (Luvox), paroxetine, and sertraline have been shown to have efficacy in
treating obsessive-compulsive symptoms in children and adolescents and may have some efficacy for
stereotyped motor movements

53. PSYCHOPHARMACOLOGIC INTERVENTIONS
 Explosive Rage Behavior
 Antipsychotic medications, particularly risperidone, have been shown to be efficacious for the treatment of explosive rage
 B-Adenergic receptor antagonists (betablockers), such as propranolol (Inderal), have been reportedly anecdotally to result in
fewer explosive rages in some children with intellectual disability and ASD