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94 Chapter 6 Intellectual Developmental Disorder and Learning Disorders
disorders. Identification of bio-behavioral markers that go
beyond group-level similarities to subgroup or individual
levels of analysis provides additional opportunities for tracking
development, treatment response, and outcomes (Burack et al.,
2021; Loth & Evans, 2019).
Down Syndrome
Four brief descriptions of syndromes demonstrate this
etiology + neurobehavioral phenotype classification
approach to intellectual developmental disorder. Down
syndrome, caused by an extra chromosome 21 (trisomy 21),
is the most widely recognized and most common
chromosomal cause of intellectual disability. The vast
majority of cases of Down syndrome are nonfamilial—
that is, Down syndrome does not run in families
(Pennington, 2015). Children, adolescents, and adults with
Down syndrome usually display a pattern of physical and
physiological characteristics, including microcephaly (a
small head), distinctive facial features, heart problems, and
poor muscle tone. Intellectual challenges almost always
involve language difficulties, with expressive speech more
problematic than receptive speech (del Hoyo Soriano et al.,
2020; Hodapp & Fidler, 2021). Visual short-term memory
is often a relative strength. In contrast to many other genetic
etiologies, there is a wide range of intellectual functioning
from mild to more severe impairment, with approximately
80% displaying moderate levels of disability. There is also
significant variability in adaptive functioning (Schworer
et al., 2022; Thomas et al., 2020).
With respect to personality and psychopathology, parents
often report that their children with Down syndrome are
happy and outgoing (Dykens, 2000). Still, many children
with Down syndrome struggle with various disorders
including autism spectrum disorder, ADHD, anxiety, and
other internalizing and externalizing disorders (Hamner
et al., 2020; Hodapp & Fidler, 2021). The variability in
intellectual and adaptive functioning and specific medical
and mental health needs requires individualized patterns of
support and services across the lifespan.
Williams Syndrome
Williams syndrome, caused by a microdeletion on
chromosome 7, is associated with its own distinctive pattern
of intellectual developmental disorder (Mervis & John, 2010;
Pennington, 2015). Willi ams syndrome ha s a lower prevalence
than D own syndrome or fragi le X syndrome. Similar to Dow n
syndrome (and distinct from fragile X syndrome), Williams
syndrome does not run in families. Compared to fragile
X syndrome, where one gene product is affected, multiple
gene products are affected in Williams syndrome, which
again is like Down syndrome (Pennington, 2015).
Williams syndrome is characterized by mild intellectual
deficits, relative strengths in cognitive and language
abilities, and weaker spatial skills (Mervis, 2012). Even
though the language of children with Williams syndrome
is less impaired compared to children with other types of
IDD, many studies provide data suggesting that there are
specific language difficulties that have an impact on reading
and require educational interventions (Mervis, 2012).
Children, adolescents, and adults with Williams
syndrome are characteristically outgoing and engaging.
The hypersociability is challenging because they often have
difficulty in maintaining friendships. Their social behavior
may also make them more vulnerable to harm (Burack
et al., 2021). The most prevalent mental health issue for
individuals with Williams syndrome is anxiety. Ongoing
and high levels of anxiety compromise social and cognitive
functioning (Ng-Cordell et al., 2018).
Individuals with Williams syndrome often display an
affinity for music. Strengths are observed more in musicality
and expression than in formal music skills (Thakur et al.,
2018). Levitin et al. (2004, p. 238) provide this example of
an emotional response to music: “As the parent of a WS
child reported, her daughter began weeping after a couple
of notes were played at a Mozart concert. The girl’s reaction
was so strong that she left the concert and after returning,
once again burst into tears. After hearing a more uplifting
Mozart song some months later, she explained to her mother,
‘there are two kinds of Mozart: the kind that hurts and the
kind that does not hurt.’”
Children with specific etiologies often display a distinctive
pattern of weaknesses and strengths.
Copyright 2024 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s).
Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
Fragile X Syndrome
Fragile X syndrome, caused by atypical gene expression
on the FMR1 gene, is the most common type of inherited
intellectual developmental disorder in boys, affecting 1 in
4,000 boys and 1 in 8,000 girls. It occurs in all racial and
ethnic groups. Fragile X syndrome is a single gene disorder
in which one gene becomes inactivated via methylation.
Fragile X syndrome illustrates epigenetic processes as it
results from abnormal gene expression rather than from
a genetic mutation (Pennington, 2015). Boys, who have
only a single X gene, are likely to be more severely affected
and are more frequently diagnosed with moderate IDD.
iStock.com/DenKuvaiev
Girls are usually diagnosed with mild IDD. There are fewer
distinctive physical characteristics of fragile X syndrome,
Etiology 95
although some babies do have large head circumferences,
somewhat unusual facial features, and loose joints.
Speech and communication difficulties are part of the
fragile X cognitive profile (Abbeduto et al., 2021). Mental
health concerns associated with fragile X syndrome include
negative affect and anxiety, social avoidance, and autism
spectrum disorder. Boys are more likely to experience severe
behavioral problems such as high activity, poor attention, and
low adaptability (Abbeduto et al., 2021; Wall et al., 2019).
Fetal Alcohol Spectrum Disorder
So far, our emphasis has been on describing several genotypes
associated with intellectual developmental disorder, each of
which is typically linked with a specific neurobehavioral
profile. There are also phenotypes that include impaired
intellectual functioning that are observed when the etiology
is not genetic. Fetal alcohol spectrum disorder (FASD)
is the result of prenatal exposure to high levels of alcohol
and is the most common cause of IDD (National Institute
on Alcohol Abuse and Alcoholism, 1990). The disorder
includes four subcategories: fetal alcohol syndrome (FAS),
partial fetal alcohol syndrome (PFAS), alcohol-related
neurodevelopmental disorder (ARND), and alcohol-related
birth defects (ARBD). The type and severity of FASD
depend on the pattern of alcohol exposure, the dose and
frequency, and embryonic stage during which exposure
occurs (Mattson et al., 2019). DSM-5-TR classifies this
disorder as Neurodevelopmental Disorder associated with
Prenatal Alcohol Exposure.
Estimates of the prevalence of FASD in children and
youth is greater than 1% in over 76 countries around the
world (Lange et al., 2017). Prevalence varies by world region
and country. Countries with the highest levels of FASD are
South Africa, Croatia, and Ireland. Much higher rates are
observed in special populations, including indigenous groups,
incarcerated groups, groups receiving psychiatric care, lowSES groups, and children and youth in out-of-home care.
Prevalence rates vary not only by country but also within
countries (May et al., 2018). A comparison of rates of FASD in
first-grade children in four communities in the United States
(in the Rocky Mountain, Midwestern, Southeastern, and
Pacific Southwestern regions) ranged from 1% to 5%. Within
each community, the most conservative estimate was at least
11 to 50 children per 1000 children (and up to between
31 and 98 children per 1000 using less-conservative measures).
The FASD neurobehavioral phenotype includes physical
features such as facial anomalies and slowed growth,
neurophysiological changes in brain structure such as
reduced volume and changes in brain function across most
brain areas, and intellectual and behavioral impairment
(Mattson et al., 2019). Children and youth with FASD
display deficits in general intelligence, motor skills, attention
and executive function, language, and learning and memory.
Adaptive functioning and academic performance are also
Other psychopathologies such as ADHD, depression,
anxiety, and behavior problems are common. Children with
FASD display unusual intra-individual variability. In other
words, children with FASD are more unpredictable in their
task performance across days and times than other children.
The degree of intra-individual variability is a predictor of
neurological dysfunction (Ali et al., 2018).
Etiology
Many prenatal, perinatal, and postnatal risk factors
associated with intellectual developmental disorder have
been identified (Pennington, 2015; Schalock, 2011; refer to
Table 6.3). We have already summarized information related
to several specific genetic etiologies associated with IDD.
These often more severe forms of IDD occur independent
of family and sociocultural risk factors.
With respect to the genetic risk associated with mild (or
familial) forms of intellectual developmental disorder, we
refer back to the opening section of this chapter and the
description of genetic and environmental influences on
Table 6.3 Examples of Prenatal, Perinatal,
and Postnatal Risk Factors in Intellectual
Developmental Disorder
Prenatal:
●
Physiological: Chromosomal disorders,
metabolic disorders, transplacental infections
(e.g., rubella, HIV), exposure to toxins
●
Social: Poverty, maternal malnutrition,
domestic violence, lack of prenatal care
●
Behavioral: Parental drug use
●
Educational: Parental disability without
support, lack of educational opportunities
Perinatal:
●
Physiological: Prematurity, birth injury,
hypoxia, neonatal disorders
●
Social: Lack of access to birth care
●
Behavioral: Parental rejection of caretaking,
parental abandonment
●
Educational: Lack of referral for interventions
at hospital discharge
Postnatal:
●
Physiological: Malnutrition, traumatic brain
injury, degenerative/seizure disorder, toxins
●
Social: Lack of adequate stimulation, family
poverty, chronic illness, institutionalization
●
Behavioral: Child abuse/neglect, domestic
violence
●
Educational: Delayed diagnosis, inadequate
early intervention, inadequate special
education services; inadequate family support
Source: Schalock (2011). The evolving understanding of the construct of
intellectual disability.
Copyright 2024 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s).
Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
96 Chapter 6 Intellectual Developmental Disorder and Learning Disorders
IQ (stanine scale)
Proportion
19
0.25
IQ (stanine scale)
Proportion
19
0.25
intelligence in typically developing children. In this section,
we emphasize that for almost all children with mild forms
of IDD, there are likely numerous genetic processes and
outcomes that are disrupted.
Atypical brain development is observed across all severities
of intellectual developmental disorder (Deary, 2021). Geneby-environment-by-time processes are hypothesized to work in
similar ways for individuals at the low end of the distribution
of intellectual functioning (with IQ scores just above the
cutoff for IDD) and individuals with mild forms of IDD.
Family patterns of intellectual developmental disorder
help illustrate these different etiological explanations. For
families with a child with mild IDD, we expect that other
children in the family, who share many of the same genes as
their parents a nd their sibling with IDD, would display belowaverage intelligence, and they do (Plomin & Deary, 2015).
In contrast, for families with a child with IDD associated
with a specific genetic error, the genetic variant is not part
of a parent’s genetic makeup passed on to other children.
In these families, the siblings of the affected child display
more typical intellectual functioning. Figure 6.4 illustrates
this discontinuity in IQ score distributions for siblings
of individuals diagnosed with mild versus severe IDD
(Reichenberg et al., 2016).
As noted in earlier sections, many environmental factors
such as lower SES, child and family adverse experiences, and
poor-quality education negatively impact the development
of typical intellectual functioning. This is also true for some
types of intellectual developmental disorder, especially for
IDD in the mild and moderate range. Pre- and post-natal
nutritional deficits and malnutrition negatively impact
intellectual functioning. Pre- and post-natal exposure to
environmental toxins is also associated with IDD (Carlsson
et al., 2021; Georgieff, et al., 2018).
With FASD, the developing fetus is exposed to high
alcohol concentrations during periods of rapid growth and
differentiation. Early pregnancy is a critical phase, but damage
occurs across pregnancy. Binge drinking (defined as 4 drinks in
a short amount of time) appears more problematic than small
amounts over longer time spans (although risk remains with
lower levels of exposure). Additional risk factors include the
use of other substances, poor nutrition, and poor prenatal care
(Georgieff et al., 2018; Mattson et al., 2019). More research
is needed to explore the negative impact of lower levels of
exposure to alcohol on intellectual and adaptive functioning.
Developmental Course
Given the various etiologies, significant differences in
children’s adaptations, developmental trajectories, and
outcomes are expected and observed (Burack et al., 2021;
Schworer, 2022). In general, poorer prognoses are associated
with genetic etiologies. Not only are these genetic etiologies
related to more severe intellectual developmental disorder,
but many are also associated with serious medical conditions
such as heart problems, gastrointestinal problems, visual
and hearing impairments, and seizures. For many of the
most profoundly impaired children, outcomes may include
institutionalization, dependence on others for care, and briefer
lives. More positive health outcomes are observed in children
with mild or moderate IDD. Although both immediate
and long-term growth and health are often compromised,
advances in treatments and medical care highlight the need
for a lifespan approach to IDD (Hodapp et al., 2019).
As we th ink about many kinds of developmental t rajectories
for children and adolescents with IDD, it is important to
compare these pat hways to those of typica lly developing youth.
As in the earlier section on Zigler’s approach, we note here
Figure 6.4 Discontinuity in IQ scores of siblings of individuals with IDD related to severity of
intellectual disabilities
Siblings of
cases with
0.20
0.15
0.10
0.05
0.00
Source: Reichenberg et al. (2016). Discontinuity in the genetic and environmental causes of the intellectual disability spectrum.
Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
mild ID
Population
2 3 4 5 6 7 8
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0.20
0.15
0.10
0.05
0.00
2 3 4 5 6 7 8
Siblings of
cases with
severe ID
Population
Developmental Course 97
the difference between descriptions of developmental delays
that reflect slowed growth and lower levels of achievement
in some children and descriptions of more atypical patterns
of development in other children (Thomas, 2016). Keep in
mind as well that although many youth with IDD who share
an etiology or level of impairment display similar trajectories,
there is also meaningful variability among individuals with
the same etiology or level of impairment (Hodapp & Fidler,
2021; Thomas et al., 2020).
Leading researcher Robert Hodapp provides an important
perspective on the intersections of etiology, developmental
course, and outcome: “Depending on what it is that one is
considering, sometimes etiology matters, sometimes it does
not. In essence, etiological groups are simultaneously both
different and the same, either comparing one etiological group
with another (e.g., Williams syndrome vs. Down syndrome)
or comparing persons with a particular etiology with those
with cultural-familial ID” (Hodapp, 2021, p. 460). Hodapp
illustrates this same-and-different approach by first noting
distinctive patterns in the language and communication skills
of children with Down syndrome and children with Williams
syndrome. He then suggests that even with these differences,
the children’s school experiences will be very much alike
because both groups display similar degrees of impairment.
Language, Communication, Executive
Function, and Learning
Children with intellectual developmental disorder exhibit
different trajectories of intellectual functioning compared
to the rate and timing of growth for typically developing
children, and these trajectories vary by etiology. For many
youth with IDD, cognitive, communicative, and linguistic
profiles of strengths and weaknesses change over time, with
strengt hs becoming stronger a nd weaknesses b ecoming weaker
(Pennington, 2015). These changes are likely tied to innate
characteristics but are also influenced by the interactions of
the child’s abilities, family factors, and environmental factors.
Individuals with significantly below average IQ scores
typically display limited language and communication
abilities. With somewhat higher IQ scores, distinctive
patterns of language and communication are observed for
children, adolescents, and adults with Down syndrome
(Hodapp & Fidler, 2021), with fr agile X syndrome (Abbeduto
et al., 2021), and with Williams syndrome (Mervis, 2012).
Children with Down syndrome, for example, often struggle
with speech impairments. These impairments predict later
deficits in adaptive functioning (Stephan et al., 2021).
Comparisons of expressive language development in youth
with Down syndrome and youth with fragile X syndrome
reveal important group and individual differences related
to the language environment in which children develop
(del Hoyo Soriano et al., 2020). Similarities are also
observed. Both groups, for example, displayed an increase in
talkativeness in adolescence; this increase was accompanied,
however, by a decrease in the quality of language.
Other factors related to language and communication
are identified across multiple forms of IDD. Atypical,
disrupted sleep patterns, for instance, negatively impact the
acquisition of language in children with Down syndrome,
Williams syndrome, and fragile X syndrome (D’Souza
et al., 2020).
Executive function (EF), involving working memory,
planning, problem solving, and inhibitory control, is
impaired in many neurodevelopmental disorders and these
impairments persi st across development (Fidler & L anfranch i,
2021; Russo et al., 2012). In general, EF deficits are associated
with more problematic communication and learning (among
other difficulties). With fetal alcohol syndrome disorder, the
deficits in EF are noticeable by preschool age. These early
EF deficits become linked to deficits in social functioning by
age 8 (Rockhold et al., 2021).
General learning outcomes related to language, EF, and
academic skills vary by severity, with children with mild IDD
displaying sixth-grade academic skills by late adolescence and
children with moderate IDD displaying second- to fourthgrade skills. Attention and motivational deficits may interfere
with the development of these skills. Academic difficulties may
increase in adolescence as the gap widens between students
with and without intellectual disabilities (Tylenda et al., 2014).
One particularly relevant environmental factor is education.
In the United States, the Individuals w ith Disabilities Education
Act (IDEA) mandates diagnostic, educational, and support
services from birth to age 21, with individual education plans
developed with input from parents, teachers, and mental health
professionals. Educational approaches have changed over
previous decades and now emphasize the inclusion of children
with developmental disabilities in age-appropriate classrooms.
Success in these classrooms depends on many variables, and
behavior difficulties are often a primary reason for difficulties
in mainstream placements. Inclusion strategies designed to
enhance children’s success focus on better teacher training and
parent participation, increased classroom resources, and more
extensive supports for student learning (refer to Box 6.1).
Socioemotional Functioning,
Motivation, and Personality
The developmental course of personal and social functioning
is variable. Some groups of children with intellectual
developmental disorder show improvements over time,
others display up-and-down patterns of adjustment, and still
others exhibit declines. For all groups, however, the emphasis
remains on supporting development and functioning and
achieving a positive quality of life (Burack et al., 2021).
Referring again to Table 6.2, we expect that each child’s and
adolescent’s adaptation reflects ongoing and changing goals
related to independence, social participation, and well-being
as well as the presence of high-quality supports and services
(Schalock & Alonso, 2022).
With respect to emotion, attachment, and play in children
with IDD, multiple studies of children with Down syndrome
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Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
98 Chapter 6 Intellectual Developmental Disorder and Learning Disorders
Box 6.1 The Child in Context
Enhancing Success in Inclusive Classrooms
There is a complicated historical and legal background to the
discussion of the inclusion of children with special needs into
regular classroom settings. Despite widespread agreement that
students with special needs benefit from inclusion, translating
policy into practice requires commitment and perseverance.
Students with IDD are frequently placed in separate classrooms
for most of the school day. When students with IDD do join
their peers, they often do so for non-academic experiences such
as recess or lunch (Rao et al., 2017). Successful inclusion must
consider the academic and non-academic needs of all students
as well as teacher training and support and school resources.
Many discussions of inclusion suggest that positive
outcomes depend, in part, on teacher attitudes, and reviews of
the literature suggest that teachers have positive attitudes about
inclusion. Their attitudes and beliefs are influenced, however,
by the nature and severity of children’s special needs as well as
their concerns about training, autonomy, and performance
assessments (Avramidis et al., 2019; Woodcock & Nicoll,
2022). There are also barriers to successful implementation of
inclusive classrooms such as lack of training and lack of
resources (Fox et al., 2022).
Many investigators observe that knowledge about specific
disabilities, along with preparation, experience, and
collaborative work with other teachers, impacts teachers’
perceived competence (Greenway et al., 2013). Increasing
contact with children with intellectual developmental disorder
is also associated with positive attitudes toward inclusion
(Dessemontet et al., 2014). It is clear that additional work must
be done to document both the benefits and costs related to
inclusion for both children (and their parents) and teachers,
and these efforts must include awareness of differences across
culture and countries (Lee et al., 2015).
One approach to inclusion is illustrated by the Universal
Design for Learning (UDL) framework. The UDL framework
provides principles, guidelines, and checkpoints for the design
of curricula and instruction practices for classrooms that meet
the needs of all learners. The UDL framework describes
multiple ways of engaging students (the “why” of learning),
multiple means of representing information (the “what” of
learning), and multiple opportunities for action and expression
(the “how” of learning) (CAST, 2018). “UDL supports
inclusion that is meaningful, whereby all students are engaged
in the academic, social, and behavioral demands of the general
education setting” (Rao et al., 2017, p. 38). Flexibility and
individualized supports are in place for all students as needed.
Much of the research related to UDL examines classrooms
with typically developing students, students with learning
disorders, and students with other disorders. Additional
research is needed to explore the ways in which students with
IDD can be successful participants in UDL classrooms and
libraries, on UDL playgrounds and sports fields, and in UDLinspired extracurricular activities.
The success of inclusive classrooms depends on teachers,
students, and school communities
provide evidence that these children display basic emotion
skills, appreciate humor, and experience complex emotional
relationships. Even with this information, additional
research on the development of emotion experience and
regulation across neurodevelopmental disorders is needed
(McClure et al., 2009).
Children and adolescents with IDD also display
numerous patterns and pathways of social engagement,
social competence, and peer relationships, depending on
their etiologica l backgrounds and surrounding environments
(Burack et al., 2021; Schworer et al., 2022). Relationships,
friendships, and a social life are clearly important to many
children and adolescents with IDD. With age, youth with
Down, Williams, and Prader-Willi syndromes all increase
their participation in social activities (Sellinger et al., 2006).
Social difficulties, however, are common. These difficulties
may include less social interest or a lack of basic and/or
more sophisticated interpersonal skills. Specific deficits in
attentional control and decision-making exacerbate social
problems (Rockhold et al., 2021). Additional difficulties
may appear in adolescence, when social skills deficits
become more pronounced (Tylenda et al., 2014).
Personality characteristics contribute to the development
iStock.com/kali9
and maintenance of sociability and relationships. The child’s
or adolescent’s personality, for example, influences how
much youth benefit from social opportunities, while social
opportunities in turn influence developing personalities
(Burack et al., 2021). Social development is also embedded
in family and school contexts with varying expectations for
social interactions and varying degrees of support.
Motivation in youth with IDD has been the focus of
research for decades. Compared to typically developing
children, children with IDD often avoid difficult problemsolving tasks and are more motivated to seek and obtain
approval and positive reinforcement from others. This is likely
because of multiple experiences with failure (Burack et al.,
2021). Indeed, much of Zigler’s work focused on identifying
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Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
Developmental Course 99
and improving the environments of youth with IDD that
involved social isolation and failure. Self-esteem and perceived
competence develop over time in numerous interactions with
parents, teachers, and environments (Hodapp, 2021; Tylenda
et al., 2014).
With respect to leisure activities, et iology-associated patterns
are aga in observed, with di fferences in the selection and practice
of social activities, television and computer activities, musical
activities, and physical activities (Buttimer & Tierney, 2005). It
is important to understand that children with IDD are not just
occupying themselves or following others’ directives related
to various activities. In many cases, the selection and pursuit
of specific activities appear to be related to specific internal
strengths. Individuals with Williams syndrome, for instance,
may be assisted in their drive for relationships to make safe,
appropriate, and reciprocated overtures to others. Given their
pleasure, skill, and deep engagement in music, they also may
be encouraged, challenged, and supported in their musical
journeys (Dykens, 2006).
Maladaptive Behavior
and Comorbid Disorders
Depending on the etiology and severity of intellectual
developmental disorder, estimates of maladaptive behavior
patterns and comorbid conditions range widely. For many
children with IDD, deficits in language and communication
skills are associated with increased behavior problems
(Tylenda et al., 2014). Children and adolescents with
IDD are also diagnosed more frequently with ADHD,
anxiety and depression, self-injurious behaviors, and other
externalizing disorders. Compared to typically-developing
youth, sleep difficulties and sleep-wake disorders are more
common and more severe in children and adolescents with
IDD (Williamson et al., 2016). Some etiologies such as
Down syndrome increase the risk for autism spectrum
disorder (Schworer et al., 2022). Across etiologies,
struggles with comorbid disorders appear persistent across
development.
iStock.com/kali9
For most children with IDD, feelings of competence and social
connection contribute to resilient developmental pathways.
Adult Outcomes
With emphases on quality of life and appropriate support
for individuals with intellectual developmental disorder,
we look to the future with hope. For some individuals with
mild intellectual disabilities, leaving the academic- and
achievement-focused school system leads to meaningful
improvements in adaptation. These individuals often have the
social and vocational skills to live and work independently.
For individuals with moderate intellectual disabilities,
increased support, supervision, and assistance in living and
work are necessary. For individuals with severe and profound
intellectual disabilities, extensive and around-the-clock
assistance and supervision are required (Tylenda et al., 2014).
Many challenges are related to development and
independence, such as living with parents, siblings, or in group
settings, romantic relationships, and work opportunities. In a
study of mental health needs for young adults with IDD and
their parents, concerns included the transition to adulthood,
insurance and financial resources, professionals’ competence,
understanding individuals who communicate differently,
hospitalization, medication, alternatives to medication, and
ongoing social supports (Kramer et al., 2019).
The Role of the Family
As children with IDD develop, so do their families. As
noted previously, family background factors such as
parental education and socioeconomic status influence
the developmental pathways related to intellectual and
adaptive functioning (Burack et al., 2021). In addition,
parents and families adapt to new circumstances with a
range of emotions, beliefs, and behaviors (Hodapp et al.,
2019). The challenges and rewards of parenting a child
with IDD have often been described. Parents acknowledge
sadness, fear, and stress but also positive emotions, positive
coping experiences, and personal strength and growth
(Beighton & Wills, 2018; Hodapp et al., 2019; Sheldon
et al., 2021). Parents of children with certain etiologies may
display specific concerns. Parents of children with Williams
syndrome, for example, are more worried about their
children’s social vulnerability (Hodapp, 2021).
Levels of intellectual and adaptive functioning of
the sibling with IDD influence sibling experiences and
outcomes. Many siblings, early in their own development,
report increased caregiving responsibilities as well as
expectations for greater responsibilities as they age (Hodapp
et al., 2010). Siblings also report many benefits, including
closer relationships. Parents often provide meaningful
context and a framework for family and sibling interactions
(Shivers & Dykens, 2017).
The well-being of parents, siblings, and other caregivers
must be prioritized as these individuals play a critical role in
supporting good outcomes for youth with IDD. Many family
members may also struggle with social isolation and lack of
support (Baker et al., 2021). Significant impacts on family
time, family activities, and family finances must be addressed,
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100 Chapter 6 Intellectual Developmental Disorder and Learning Disorders
with support and ongoing resources for parents and siblings
across child, adolescent, and adult development. High-quality
services are needed to support caregivers, especially for families
in which youth display behavior difficulties and comorbid
disorders (Gardiner et al., 2020). Both child and adult service
systems play important roles related to education, the transition
from adolescence into young adulthood, and residence and
work decisions (Hodapp, 2021; Tylenda et al., 2014).
Risk and Resilience
After the diagnosis of IDD, concerns remain related to
additional risk. Adversities related to social exclusion, stigma,
discrimination, and lack of environmental support impact
current and later adaptation and well-being (Emerson,
2013). Youth with fetal alcohol spectrum disorder, for
example, are exposed to high levels of adversity in multiple
contexts. Youth with FASD are more likely to experience
ongoing exposure to substance use, maltreatment and outof-home placements, and disrupted schooling (Flannigan
et al., 2021; Pruner et al., 2020). Reducing the risks that
further complicate development and growth in children and
adolescents with IDD is an exceptionally important goal.
Resilience in children and adolescents with IDD is both
similar and different to resilience in youth without IDD
(Clark & Adams, 2022; Gilmore et al., 2013). Protective
factors associated with better outcomes include individual
assets such as optimism and self-efficacy; positive family,
teacher, and peer relationships; and environmental factors
such as positive school experiences and community
involvement. In adults with IDD, protective internal factors
include autonomy, self-acceptance, and health; protective
external factors include a social network and participation
in daily activities (Scheffers et al., 2019).
Quality of life is another outcome to consider. The ways
in which an individual’s independence, social participation,
and well-being are prioritized in day-to-day decisions and
future planning contribute to resilience across the lifespan.
Keeping in mind the Chapter 3 discussion of multilevel resilience processes as well, we also need to consider
experiences and factors related to family resilience, school
resilience, and community resilience associated with IDD.
Clinicians must evaluate whether the presence of more
specific developmental delays in speech, language, and
reading account for intellectual and adaptive delays; in those
cases, DSM-5-TR diagnoses such as Language Disorder or
Speech Disorder would be appropriate. Hearing difficulties
or hearing loss also impact cognitive and language
development and should be considered.
Early assessment and diagnosis of neurodevelopmental
disorders is essential to provide interventions before some of
the difficulties associated with these disorders become firmly
or solidly established. A transdiagnostic approach focused on
early identification of atypical physiological pathways may
use screening protocols that assess biological and behavioral
markers of disorder (Finlay-Jones et al., 2019). An example of a
specific-disorder approach involves behavioral tests combined
with physical exam data that provide potential risk scores for
infants with prenatal alcohol exposure (Bernes et al., 2022).
Assessment of Intellectual Functioning
Standardized tests of intelligence, such as the Stanford-Binet
or one of the Wechsler tests (e.g., the Wechsler Intelligence
Scale for Children or the Wechsler Preschool and Primary
Scale of Intelligence), are administered individually. In
addition to a general evaluation of intellectual functioning,
evaluations of specific cognitive processes may be included.
IQ scores two or more standard deviations below the norm
(i.e., a score of 70 or below on tests where 100 is the norm)
reflect significantly lower intellectual functioning. Note,
however, that cutoff scores are somewhat arbitrary, and
children and adolescents who score slightly above the cutoff
and slightly below are likely indistinguishable from one
another (Burack et al., 2021).
Additional assessment of intellectual functioning may
include tests of formal academic skills and school achievement.
The comparability of scores for children of different ethnic
and racial backgrounds on traditional and nontraditional
intelligence tests should be examined. Assessments of adaptive
intelligence or specific types of intelligence such as creativity
are not usually part of the comprehensive examination,
although they might provide important information about
the child’s overall intellectual functioning and individual
strengths (Gardner et al., 2018; Sternberg, 2019).
Assessment and Diagnosis
Medical and developmental histories are a key component
of the assessment of intellectual developmental disorder.
With the medical concerns that are part of the clinical
presentation of several forms of IDD, the identification of
young children with more severe forms of disorders happens
more quickly (i.e., after birth or within the first year). Delays
in achieving motor- or language-related developmental
milestones also lead to early diagnosis for some children.
Children with milder forms of IDD are often assessed and
diagnosed in the early school years, when expectations for
academic performance increase (Tylenda et al., 2014).
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Assessment of Adaptive Functioning
Of the various standardized scales for the assessment of
adaptive functioning, the most common are the Vineland
Social Maturity Scale and the AAIDD Adaptive Behavior
Scale. These instruments are designed to measure basic
skills in different domains, including communication,
self-care and health, social skills, and leisure and work.
They are usually completed by adults who know the child
or adolescent well. Given the somewhat variable course of
intellectual and adaptive functioning for different groups of
youth with IDD, repeat assessments across development are
important.
Intervention 101
Other Assessment Concerns
The clinical presentation of IDD is complex, and there
is symptom overlap with other disorders such as autism
spectrum disorder and ADHD. It is important to make
differential diagnosis and comorbidity decisions with care.
With respect to autism spectrum disorder, information
about social interactions and stereotyped behaviors may
discriminate between the disorders. Clinicians may also
explore patterns that are exhibited by youth with Down
syndrome alone, autism spectrum disorder alone, or a
combination of those two disorders (Hamner et al., 2020;
Pedersen et al., 2017) With respect to ADHD, the pattern
of deficits associated with each disorder is somewhat
distinctive. Because it is so important to identify all areas
of concern to provide appropriate interventions, evaluations
of youth may include multiple settings (e.g., at home and at
school) (Esbensen et al., 2022; Mattson et al., 2019; refer to
Figure 6.5).
Following the collection of information on significant
disabilities related to intellectual and adaptive functioning
and the diagnosis of IDD, additional assessment may
be especially valuable. Information about maladaptive
behaviors and psychopathology must be included. With
adaptations to questionnaires and interviews, children and
adolescents themselves should also provide information
about mental health difficulties (Havercamp et al., 2020).
Specific behavioral assessments, relationship assessments,
and personality measures may provide a more complete
picture of a whole child. Plans for supporting physical and
psychological well-being depend on this more comprehensive
approach.
Intervention
When considering interventions for children and
adolescents with intellectual developmental disorder, two
points are worth emphasizing. First, in general, we are not
working with youth and their families with goals focused
on children or adolescents displaying improvements so
that they no longer meet the diagnostic criteria for IDD.
Rather, we are attempting to maximize the potential of
the individual to meet developmental demands while
at the same time modifying the environment to better
match the individual’s deficits and strengths. Interventions
must address multiple problems at the same time, paying
attention to specific patterns of weakness and strength
in etiological groups and in individuals. Mental health
professionals, educators, and advocacy groups stress the
importance of intervention plans that focus on specific
person–environment contexts, target multiple points along
Figure 6.5 Overlapping and specific impairments in fetal alcohol syndrome disorder and ADHD
Impairments seen in
FASD
Lower IQ scores
Visual-spatial ability
Verbal encoding
Social cognition
Shifting attention
Encoding attention
Cognitive set-shifting
Arithmetic
Fluency
Problem solving
and planning
Shared
Impairments
Inhibition
Increased impulsivity
Executive functioning
Psychiatric disorders
Organization
Hyperactivity
Adaptive function
Verbal recall
Reading
Impairments seen in
ADHD
Verbal memory
Focused attention
Sustained attention
Retention of verbally-
learned material
Source: Mattson, Bernes, & Doyle (2019). Fetal alcohol syndrome disorders: A review of the neurobehavioral deficits associated with prenatal alcohol
exposure.
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102 Chapter 6 Intellectual Developmental Disorder and Learning Disorders
the developmental continuum, and include the range of
relevant social and educational systems within which the
child functions. These include, for example, early screening
and identification, early intervention for the child and the
family, appropriate educational and vocational services, and
coordination of the various persons and agencies involved
in the child’s care (Hodapp, 2021).
These types of quality-of-life interventions emphasize
support and inclusion in family, school, and community
environments so individuals with IDD can participate
and thrive (Schalock & Alonso, 2013; refer to Table 6.4).
Activities such as athletics, music, and scouting provide
opportunities for connections and achievements that all
children deserve. To include as many children as possible,
we need to pay attention to cultural attitudes, state and
national guidelines and practices, and stigma that may
negatively affect support and inclusion (McConkey et
al., 2013; Scior et al., 2012). Strength-based, positive
psychology approaches may be able to contribute to better
outcomes (Raley et al., 2021).
The second point to emphasize is that mental health
is an important issue for everyone, regardless of level of
intellectual functioning. We must be careful not to define
a person by a single, if salient, attribute like intellectual
developmental disorder (or, for that matter, being
intellectually gifted or a star athlete). Psychological variables
such as emotional experiences and social relationships are
every bit as relevant for individuals diagnosed with IDD as
for those who are not. Intervention strategies, then, must
be designed to address all relevant problem areas. Finally,
although exceptional progress in the treatment of mental
illness has been made, these advances are often delayed in
their application to specific populations such as children
and adolescents with IDD. The mental health field has
a clear obligation to improve its efforts to apply effective
treatment approaches to all groups, including individuals
with intellectual disabilities.
Genetic Screening and Prevention
Strategies
Genetic screening of parents, prenatal testing, and genetic
counseling afford many specific prevention and intervention
opportunities. With multiple etiologies for IDD, we
must be careful to respect many different viewpoints and
outcomes. Broad-based prevention approaches, such as
public information campaigns discouraging drinking
while pregnant, are critical. Prevention that is focused on
minimizing or eliminating a variety of poverty experiences
may lead to meaningful improvements in intellectual and
adaptive functioning for many youth. Providing parents with
resources that enhance their efforts to support their children’s
intellectual development is another basic prevention strategy.
Gene therapies and prenatal care are promising
interventions. For example, prenatal testing followed
by prenatal silencing of the extra chromosome in Down
syndrome appears to improve developmental outcomes
Table 6.4 Quality of Life (QOL) Components of
Support Systems
Component Examples
Technology-based Assistive technology,
Prosthetics Sensorimotor devices, envi-
Staff-directed Incentives, skills/knowledge,
Professional
services
Natural supports Family, friends, colleagues
Policies Public and organizational
Source: Schalock and Alonso (2013), The Impact of the Quality of Life
Concept on the Field of Intellectual Disability.
information technology
ronmental accommodation
positive behavior supports
IT, physical therapy,
occupational therapy, speech
therapy, medical services,
mental health services
policies, laws
(Riggin et al., 2020). Maternal choline supplementation
for infants exposed to alcohol is another example of
interventions to decrease the likelihood that an infant
develops a disorder (Jacobson et al., 2018; Powers et al.,
2021).
Pharmacological Treatment
Once intellectual developmental disorder has been
diagnosed, there are a variety of treatment options that
share similar goals: to develop and maintain skills, increase
Inclusion in activities that support the whole child are
essential for good outcomes.
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Learning Disorders 103
positive attributes, and decrease distress and dysfunction.
Most individuals with IDD who reside in institutions are
prescribed some sort of psychotropic medication, often
multiple medications. Accepted practice parameters,
however, suggest that individuals with IDD be prescribed
psychotropic medications cautiously, given difficulties
related to informed consent, enhanced sensitivity to drugs
and their side effects, and poor monitoring of outcomes
(Tylenda et al., 2014).
There are some drugs that are frequently prescribed for
youth with Down syndrome with mixed results (Riggan
et al., 2020). Pharmacological treatments for maladaptive
behaviors and comorbid disorders are common. For the
attention difficulties and impulsivity associated with fetal
alcohol spectrum disorder, ADHD medications are sometimes
prescribed, again with mixed results (Ritfield et al., 2022).
Psychological Treatment
Psychological treatments are complex and comprehensive,
and there is research and clinical consensus that children
and adolescents with intellectual developmental disorder
benefit from individual, family, and group therapies. Better
outcomes are associated with therapeutic practices that
account for multiple domains and contexts of development.
Therapies include behavioral treatments, cognitive
treatments, and socioemotional programs as well as family,
educational, and vocational planning (Tylenda et al., 2014).
Many researchers emphasize the need to focus on
environments and experiences that involve social isolation
and failure. In addition, they emphasize the importance of
following the child’s or adolescent’s lead in planning and
implementation of interventions (Hodapp, 2021). Several
targets of intervention are very specific, such as programs
that focus on a single key skill such as executive function.
The expectation is that improved EF skills will lead to
improvements in multiple domains (Rockhold et al., 2021).
EF interventions are useful for youth with multiple etiologies,
as are sleep interventions (Rigney et al., 2018). Related to these
single-target treatments are micro-interventions, designed to
change a specific behavior to influence a variety of outcomes.
One example of a micro-intervention involves coaching
and supporting reaching behavior in children with Down
syndrome to improve communication and social functioning.
“Just in time” interventions are provided at times when the
impact is likely to be the greatest (Fidler et al., 2021).
Educational interventions often have dramatic impact,
depending on the factors underlying impaired intellectual
functioning. As with many other treatment strategies,
early intensive efforts are associated with better outcomes.
Following educational interventions, behavior modification
therapies are among the most frequently used. The goals of
behavioral strategies include decreasing problem behaviors
and enhancing adaptive skills. Given that maladaptive
behaviors are a major source of difficulty at home and at
school, these strategies are essential.
Family Education and Support
Given the lifelong nature of intellectual developmental
disorder, the family’s role in treatment is a prime concern.
Parents often serve as co-clinicians and educational
advocates (Hodapp et al., 2019), and both education
and support are necessary. For children and adolescents
with IDD, positive adjustments and outcomes depend
on integrated, collaborative efforts that provide as much
information, support, and optimism as possible. The
difficulties associated with parenting a child with IDD are
especially important to consider and the focus of possible
intervention (Emerson & Brigham, 2014).
Gaps in services and unmet needs for youth and
families with IDD associated with a specific etiology must
be addressed. With fetal alcohol spectrum disorder, for
example, support and treatment for parents with substance
use disorders, special attention to youth with out-of-home
placements following maltreatment, and education and
support for biological parents, foster parents, and adoptive
parents are all part of a comprehensive treatment approach.
The best possible starts and outcomes for youth and families
dealing with FASD include stable, nurturing environments;
positive collaborations with caregivers; and parental supports
for safe and stable housing, respite care, honest information,
and help with major transitions (Pruner et al., 2020).
Learning Disorders
The Case of Ethan
Ethan is 10 years old and in fifth grade. He was referred
for neuropsychological assessment at the request of
his parents, who are concerned about his difficulty
completing tasks and academic underachievement.
Language processing difficulties were identified during
preschool, and he received speech and language therapy
before entering elementary school.
Ethan’s parents state that they have no current concerns
about his language skills, but they are worried about his
academic achievement. Ethan is reluctant to initiate
writing assignments, often getting upset and claiming,
“It’s impossible!” This is true even when writing is not
related to schoolwork (for example, making cards or
writing a list of weekend activities). He loves to have books
read to him but argues when his parents try to encourage
him to read on his own. His parents are concerned that an
underlying learning disorder might be contributing to his
increasing resistance to school and homework. Although
respectful of their concerns, Ethan’s teacher feels that his
issues are more likely related to anxiety and his tendency
to procrastinate.
The neuropsychologist assessing Ethan noted that he
struggled with several writing tasks. He had difficulty
forming letters, which were printed awkwardly. In
addition, his spelling and written output appeared slow
and labored. Ethan made frequent erasures as he worked,
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