CHAPTER 8

Neurodevelopmental Disorders

Leonard Abbeduto, Ph.D.

Sally Ozonoff, Ph.D.

Angela John Thurman, Ph.D.

Andrea McDuffie, Ph.D.

Julie Schweitzer, Ph.D.

In this chapter, we consider the DSM-5 diagnostic class of neurodevelopmental disorders (American Psychiatric Association 2013). Included in this class are disorders that emerge during childhood or adolescence and that affect behaviors important for functioning in formal and informal contexts, from school to social interactions. The disorders in this class differ from one another in the specific domains of behavior impacted, with some disorders impacting multiple domains (e.g., intellectual disabilities) and other disorders being more circumscribed in their effects (e.g., specific learning disorder, motor disorders). Critical to the diagnosis of all neurodevelopmental disorders is the assessment of multiple domains of behavior, including cognition, language, and motor behaviors, with consideration of delays in achieving developmental milestones and/or the display of atypical behaviors.

Intellectual Disabilities

The DSM-5 intellectual disabilities subclass includes intellectual disability (intellectual developmental disorder) (Box 8-1), global developmental delay (Box 8-2), and unspecified intellectual disability (intellectual developmental disorder) (Box 8-3). The choice of which category to use is determined in large part by the strength or clarity of the evidence that criteria are met.

NOTICE. Criteria set above contains only the diagnostic criteria and specifiers; refer to DSM-5 for the full criteria set, including specifier descriptions and coding and reporting procedures.

Clinical Description

Intellectual disability (previously termed mental retardation in DSM-IV-TR [American Psychiatric Association 2000] and also referred to as intellectual disability by the American Association on Intellectual and Developmental Disabilities [AAIDD]) is a developmental disorder defined by deficits in both intellectual functioning and adaptive functioning relative to peers of the same chronological age and gender and of the same linguistic and sociocultural group. It was necessary that the name of this disorder be changed in DSM-5 because the term mental retardation, which was used in DSM-IV-TR, is no longer in use internationally or in U.S. federal legislation.

The criteria used to establish a diagnosis of intellectual disability in DSM-5 and the changes made in regard to how severity is specified are consistent with the field's emphasis on the interaction of a person with his or her environment rather than solely on IQ. In DSM-5, a diagnosis of intellectual disability requires that three criteria be met, which is consistent with the previous criteria used in DSM-IV-TR to establish a diagnosis of mental retardation.

In a change from DSM-IV-TR, DSM-5 no longer includes subtypes of intellectual disability (i.e., mild, moderate, severe, profound); instead, an innovation of DSM-5, for all disorders, is the inclusion of "specifiers" that describe, in a more dimensional fashion, interindividual differences. In the case of intellectual disability, the specifiers reflect severity of affectedness (i.e., mild, moderate, severe, profound). The criteria for establishing severity level in DSM-5 are focused on the individual's ability to cope with the demands of the environment and establish the levels of personal independence and social responsibility expected based on chronological age, sociocultural background, and community setting. In DSM-IV-TR, in contrast, degree of severity was based solely on the individual's level of intellectual functioning. This change in DSM-5 was necessary to reflect the current understanding that intelligence is not a monolithic construct and that an IQ score does not always provide a valid measure of how a person navigates the demands of daily living. Instead of utilizing a range of IQ scores, DSM-5 provides descriptions of severity for three domains of adaptive functioning: 1) conceptual, 2) social, and 3) practical. In situations in which an individual demonstrates differing levels of severity across the different domains, the clinician is to assign the level that best fits the individual on average. Inclusion of this severity guide for the clinician acknowledges that many individuals with intellectual disability demonstrate a pattern of strengths and weaknesses across domains of functioning.

It is important to point out that because intellectual disability is a heterogeneous condition with multiple causes, the resulting clinical picture is quite complex. In addition to the features essential to a diagnosis of intellectual disability, many problems and additional behavioral characteristics are commonly observed in individuals with intellectual disability. For example, challenging behaviors are frequently observed, often due to limitations in communicative and behavioral regulation abilities. Although the presence of challenging behaviors is not a part of the intellectual disability diagnostic criteria, the presence of these behaviors may impede the process of assessing the individual's overall intellectual functioning and adaptive function to determine the appropriateness of an intellectual disability diagnosis (Abbeduto and McDuffie 2010).

Furthermore, research on the behavioral characteristics of individuals who have intellectual disability resulting from a neurogenetic syndrome indicates that many of these syndromes are associated with a particular behavioral phenotype—that is, an increased probability of demonstrating certain behavioral and developmental characteristics relative to those individuals without the syndrome. For example, individuals with fragile X syndrome are at increased risk for social anxiety (Cordeiro et al. 2011), as well as verbal perseveration and atypical language behaviors (Abbeduto et al. 2007); individuals with Lesch-Nyhan syndrome are at increased risk for compulsive self-injurious behavior (Hall et al. 2001); and individuals with chromosome 22q11.2 deletion syndrome are at increased risk of demonstrating symptoms consistent with adolescent-onset psychosis (Drew et al. 2011). Such differences in the behavioral presentations of individuals with intellectual disability can complicate the process of assessing the presence of intellectual disability.

More generally, intellectual disability is a complex disorder, and the lives of individuals who have or are suspected of having intellectual disability are complex. Disentangling this intricate picture requires careful consideration of the interaction between the external physical and social environments, the individual's pattern of strengths and weaknesses in intellectual and adaptive functioning abilities, genetic predispositions, and any secondary behavioral characteristics present (e.g., challenging behaviors, psychopathology, medical issues) from a developmental learning perspective.

Epidemiology/Prevalence

Current estimates of the prevalence of intellectual disability vary as a function of operational definition, chronological age, sex, and socioeconomic status. The latest prevalence rates released by the Centers for Disease Control and Prevention (CDC) show that approximately 7.1 in every 1,000 children in the United States have an intellectual disability (Boyle et al. 2011). Furthermore, the results reported by the CDC demonstrate increased risk of intellectual disability for males, with a 1.24:1.00 male-to-female risk ratio, and for individuals whose family income is below the federal poverty level (Boyle et al. 2011).

It is important to note that prevalence rates are impacted by the methods used to define the disorder. For example, based on the Gaussian function, or normal distribution model, approximately 2.5% of the population are expected to have an IQ score 2+ standard deviations from the mean (an IQ score of 70+5 points or lower, which includes a margin for measurement error). Although this benchmark (an overall IQ of 65-75 or lower) is used as the criterion for demonstrating a deficit in overall cognitive abilities indicative of intellectual disability (DSM-5 Criterion A), it is important to note that not all of these individuals will also present with the adaptive functioning impairments (Criterion B) necessary to warrant a formal diagnosis of intellectual disability. In addition, some have argued that there are more individuals with IQ scores within the intellectual disability range than would be expected based on the Gaussian function due to the cases of intellectual disability resulting from biomedical factors, such as genetic anomalies (Zigler 1967).

Etiology

DSM-5 presents two categories of risk and prognostic factors associated with intellectual disability: genetic/physiological and environmental. However, the DSM-5 description of the development and course of intellectual disability highlights the current view that intellectual disability is a multifactorial construct that reflects a complex interaction involving biomedical factors (e.g., nutrition, genetic predisposition), the environment (e.g., social and learning), environmental insults (e.g., illness, toxin exposure), and developmental timing (American Association on Intellectual and Developmental Disabilities 2010). Additionally, because the development of the complex systems that contribute to intellectual development and adaptive functioning occurs antenatally, through infancy, and into childhood, the factors that can contribute to the presence of intellectual disability are varied in their nature and timing.

Diagnostic Evaluation

Intellectual Disability (Intellectual Developmental Disorder)

DSM-5 Criterion A states that the diagnosis of intellectual disability should be based on both clinical assessment and the results of standardized intelligence testing. Overall level of intelligence or functioning is typically assessed using a standardized test, such as the Wechsler Intelligence Scale for Children—Fourth Edition (Wechsler 2003), Stanford-Binet Intelligence Scales—Fifth Edition (e.g., Roid 2003), or Differential Ability Scales—II (Elliott 2007), each of which yields an overall IQ score. On a standard IQ test, the criterion for a deficit in overall intellectual functioning is typically considered to be an IQ approximately two standard deviations below the mean for the general population. This level of impairment, given a measurement error of ~5 points on each side, equates to an IQ score from 65 to 75 or lower. Assessment of intellectual functioning must take into account other factors that may limit performance, such as sociocultural background, native language, associated communication or language disorder, and motor or sensory difficulties. Moreover, in cases where there is significant variability across subtest scores, the overall IQ is not considered a valid reflection of overall level of intellectual functioning. In these instances, experienced clinical judgment is required to interpret the profile of strengths and weaknesses across each subscale to determine the appropriateness of a diagnosis of intellectual disability. Research to date has demonstrated that many individuals with a variety of neurodevelopmental disorders (e.g., autism spectrum disorder, Down syndrome, fragile X syndrome, Williams syndrome) present with significant differences in their profiles of scores across subscales.

Adaptive functioning, which is the focus of Criterion B for intellectual disability, refers to how well an individual copes with the common tasks of everyday life and how well the individual meets the standards of personal independence and social responsibility expected for someone of similar chronological age, sociocultural background, and community setting. Typically, assessment of adaptive functioning is based on both clinical assessment and standardized testing. Evidence of adaptive functioning should be gathered from the individual, if able to self-report, as well as from reliable informants familiar with the individual (e.g., parent/care-giver, teacher, group home staff). Interpretation of standardized assessments of adaptive functioning must take into account sociocultural background, education, motivation/cooperation of the informant, and associated communication, motor, or sensory difficulties.

Finally, a comprehensive evaluation includes pre- and perinatal medical histories, family pedigree, genetic evaluation (e.g., chromosome analysis), evaluation for associated medical conditions, and evaluation for co-occurring challenging behaviors and/or psychopathology. Whenever possible, comprehensive evaluations should be conducted when assessing individuals for a diagnosis of intellectual disability, because understanding the etiology and associated medical and behavioral conditions can have a potentially significant impact on prevention and treatment.

Global Developmental Delay or Unspecified Intellectual Disability

The diagnosis of global developmental delay (see Box 8-2) or unspecified intellectual disability (see Box 8-3) is to be used when patients demonstrate clear evidence of a significant overall intellectual or developmental delay but do not fully meet criteria for another specific disorder (e.g., intellectual disability). Such a diagnosis is made most often in situations in which 1) the patient is under age 5 years, 2) symptoms of cognitive and adaptive functioning impairments are evident but psychometric test data are not available or are considered invalid, or 3) cognitive and adaptive functioning impairments are suggestive of intellectual disability but there is insufficient information about age at onset. In a substantial proportion of cases, the diagnosis of global developmental delay or unspecified intellectual disability is replaced by the diagnosis of intellectual disability at a later point in development.

Comorbid Psychiatric Disorders

A diagnosis of intellectual disability, global developmental delay, or unspecified intellectual disability does not preclude the diagnosis of other psychiatric disorders, including both learning disorders and communication disorders, which was not the case in the previous edition of DSM. Co-occurring psychiatric diagnoses are frequently observed in individuals with intellectual disability, with prevalence rates of many psychiatric disorders higher than what is observed for the general population. Although it is possible for an individual with intellectual disability to also present with the full range of psychiatric disorders, assessment procedures may require modification to take into account the severity of the cognitive deficit and associated conditions. In addition, it is frequently necessary to rely on other informants who are familiar with the individual being assessed to complete the assessment process or to report on symptoms in question.

Disorders frequently observed in conjunction with intellectual disability include attention-deficit/hyperactivity disorder (ADHD), anxiety disorders, autism spectrum disorder (ASD), stereotypic movement disorder, and impulse-control disorders. Major depressive disorder may also be diagnosed in patients with intellectual disability, regardless of severity level.

Developmental Course and Prognosis

The specific chronological age and features present at onset of intellectual disability vary as a function of both etiology and severity. Individuals who present with more severe forms of intellectual disability tend to be identified earlier in development, especially in instances in which the individual has a syndrome associated with a specific physical phenotype that can be identified at birth (e.g., Down syndrome). In contrast, individuals who are less severely affected and do not have a congenital genetic syndrome associated with recognizable physical characteristics are often not identified until later in development. The course of intellectual disability is impacted by the course of underlying general medical conditions and by environmental factors (e.g., educational and other opportunities, environmental stimulation, appropriateness of management). It is important to note that intellectual disability is not necessarily a lifelong disorder. Individuals diagnosed with intellectual disability at a young age may develop good adaptive skills in other domains such that they do not meet the criteria necessary for a diagnosis of intellectual disability at an older age.

Treatment

Treatment varies with chronological age and severity, as well as with the profile of strengths and weaknesses that the individual presents. In general, early behavioral interventions help to optimize outcomes, as do various accommodations during the school years. Vocational training during the high school years is effective for preparing many individuals with intellectual disability for some type of employment. Many individuals, especially those with more severe impairments, however, require intensive supports throughout life. Historically, pharmacological treatments have been used to treat comorbid symptoms such as anxiety and hyperactivity in individuals with intellectual disability. More recently, pharmaceutical treatments have been introduced that target core features of genetic syndromes associated with intellectual disability, such as fragile X syndrome (Berry-Kravis et al. 2011).

Communication Disorders

Clinical Description

The DSM-5 subclass of communication disorders (a heading retained from the nomenclature of DSM-IV-TR) refers to a group of impairments that impact the ability to receive, send, process, and/or comprehend the verbal, nonverbal, and graphic symbol systems that are shared within a community of individuals. Psychological and linguistic theories propose that communicative competence is the result of achievements in a number of conceptually distinct but interrelated subdomains, all of which interact synergistically to enable a given individual to communicate successfully. The first sub-domain of communicative competence is phonology, which refers to knowledge of how words are pronounced. Morphology is the subdomain that refers to the internal structure of a word and includes word endings (e.g., -'s, -ing, -ed, -est) that determine how words in a sentence relate to one another. Syntax is the subdomain that refers to grammar or the internal structure of sentences. The meanings of words are represented by the communicative subdomain of semantics. Finally, knowledge of how to use language within the context of ongoing social discourse is reflected in the pragmatic sub-domain of communication. A disorder may affect any or all of these subdomains of communication. A communication disorder may be considered a primary disability or may be secondary to another condition (e.g., hearing impairment, cerebral palsy, ASD).

DSM-5 specifies the following subcategories of communication disorders: language disorder, speech sound disorder, childhood-onset fluency disorder (stuttering), social (pragmatic) communication disorder, and other specified and unspecified communication disorder. The category of language disorder has replaced the previous DSM-IV-TR categories of expressive language disorder and mixed receptive-expressive language disorder. The category of speech sound disorder has replaced the previous DSM-IV-TR category of phonological disorder, and the category of childhood-onset fluency disorder has replaced the previous category of stuttering. Social (pragmatic) communication disorder is new to DSM-5.

Language Disorder

A language disorder is diagnosed when a child has difficulty in understanding or using his or her native language (DSM-5 diagnostic criteria for language disorder are presented in Box 8-4). Although children show great individual variability in the emergence of spoken language skills, most children are using adult-like morphology and syntax and have a vocabulary size of up to 5,000 words by the end of the preschool years. Children in this age range are able to easily understand what is said to them, answer simple questions, and talk about objects and events that are not actually present. Prevalence studies suggest that 13%-18% of 1.5- to 3-year-old children present with expressive language delays. These children are often termed "late talkers" because as many as half will outgrow their delays by age 4 years.

An additional group of children may demonstrate delays in comprehension and/or the production of age-appropriate language skills in the absence of hearing impairment, general developmental delay (i.e., normal nonverbal ability), or other diagnosable conditions (e.g., ASD). This group of children has come to be identified as having "specific" language impairment (SLI). Numerous theories have been developed to account for the linguistic deficits observed in children with SLI. Most theories propose that these children have core deficits in grammatical knowledge or deficits in underlying cognitive processes that are either domain general (e.g., speech perception, auditory working memory) or domain specific (e.g., attention, processing speed) with regard to language abilities.

Current measures used to screen children for the presence of a language disorder do not reliably predict which children will continue to experience language delays. Factors associated with early language delays include cognitive ability, family history, low socioeconomic status, and the quantity and quality of verbal language stimulation that caregivers provide to their children. Language disorders in children should be addressed in a timely fashion given the demonstrated relationship between early language disorders and later academic, behavioral, and socioemotional challenges. For example, studies have confirmed that preschoolers with language impairments are at risk for developing reading disabilities. Additionally, even children whose early language delays appear to resolve in later childhood, such that standardized tests no longer reveal a significant delay in scores, remain at higher risk for developing reading problems that may not emerge until later in the elementary years (Scarborough 2005).

Speech Sound Disorder

Speech sound production describes the clear articulation of the individual sounds of a spoken language, known as phonemes, and requires both the knowledge of the speech sounds and the ability to coordinate the movements of the tongue, lips, and jaw with breathing and vocalizing. Full mastery of the speech sounds of one's native language should occur by age 8 years; however, the speech of a young child should be fully intelligible by age 4 years. About 75% of preschool children with a speech sound disorder will go on to meet developmental norms for speech production by age 6 years (Shriberg 1997). A small proportion of children will continue to exhibit residual speech errors involving the later-emerging phonemes/s/,/r/, and/l/. According to the DSM-5 criteria (Box 8-5), a speech sound disorder cannot be diagnosed when the observed deficits can be attributed to physical, structural, neurological, or hearing impairment.

Despite individual differences in the age of speech-sound acquisitions, there is a consistent order of mastery of basic types of sounds (e.g., nasals, stops, and glides are mastered early and before fricatives, affricates, and consonant clusters). This order of emergence may be used by clinicians in determining which sounds should be targeted in treatment. Disorders of speech-sound production are frequent among preschoolers and may coexist with language disorders or appear independently. These disorders may involve phonological knowledge, neuromotor control, or articulatory skill.

Childhood-Onset FluencyDisorder (Stuttering)

The category of childhood-onset fluency disorder describes a condition, often termed "stuttering," involving a clinically significant impairment in the production of fluent speech, such that the timing of the speech stream is disrupted. Disfluencies most often take the form of repetitions of words or parts of words, pauses in the production of connected speech, circumlocutions (changing around the order of words or avoiding certain words), or the prolongation of speech sounds. Speech also may become completely blocked in that the mouth is positioned to say a sound, but little or no sound is produced. Interjections such as "um" or "like" also can occur and maybe repeated ("um-um-um") or prolonged ("ummmm") as the individual struggles to resume speaking. DSM-5 criteria for childhood-onset fluency disorder (stuttering) are presented in Box 8-6.

Although a developmental period of disfluency is not unusual, such problems typically resolve by age 4 years. Thus, fluency disorders are usually considered to emerge around ages 4-5 years and are estimated to occur in approximately 1% of school-age children. The onset of a fluency disorder is almost always prior to age 10 years. Although all young children are sometimes disfluent, individuals who are considered to have a fluency disorder experience disfluencies that are frequent and/or severe enough to impair intelligibility and to cause disruption of social discourse and/or academic or occupational performance. The likelihood that a fluency disorder will persist past childhood is increased in relation to a family history of the disorder, continuation of the disorder for more than 6 months, presence of a comorbid speech-sound or language disorder, and/or presence of strong fears about the disorder on the part of the individual or family.

Social (Pragmatic) Communication Disorder

Social (pragmatic) communication disorder is a new category in DSM-5 and refers to children who have a primary difficulty with the pragmatic aspects of language (Bishop 2000). Social communication disorder can affect both comprehension and production of spoken language, with particular difficulty in the comprehension of narrative texts and ongoing conversation that contains idiomatic and nonliteral language (Box 8-7). Individuals with a social communication disorder may have difficulties following rules for conversation and storytelling, such as taking turns in Conversation, rephrasing when misunderstood, and knowing how to use verbal and nonverbal signals to regulate interactions. The presence of a social (pragmatic) communication disorder is unexpected given a child's relatively intact vocabulary, grammar, and speech-sound production abilities (Tomblin et al. 2004).

According to DSM-5, ADHD, behavioral problems, and specific learning disorders commonly co-occur with social (pragmatic) communication disorder. The primary alternate diagnostic possibility for individuals suspected of having a social communication disorder is autism spectrum disorder. As described in the DSM-5 section addressing differential diagnosis, the two disorders can be differentiated by the absence in social communication disorder of a current presentation or past history of restricted/repetitive patterns of behaviors, interests, or activities.

Unspecified Communication Disorder

The "unspecified" diagnostic category (Box 8-8) may be used when the clinician chooses not to specify the reason that the individual does not meet the full criteria for a communication disorder or one of the other neurodevelopmental disorders or when there is inadequate information to make a more specific diagnosis.

Epidemiology/Prevalence

In the fall of 2011, almost 5.8 million school-age children in the United States were receiving special education services under Part B of the Individuals with Disabilities Education Act (IDEA). More than 1 million of these children, or 19%, were classified as having a speech or language disorder (U.S. Department of Education, Office of Special Education Programs, Data Analysis System [DANS] 2012). For this same time period, 46% of children ages 3-5 years receiving Part B services were classified as having a speech or language impairment. These prevalence estimates do not include children who have speech and language disorders secondary to other conditions such as hearing impairment, ASD, or intellectual disability. Although productive speech should be fully intelligible by age 8 years, moderate to severe speech sound disorders affect 2%-3% of school-age children. Fluency disorders typically emerge prior to age 10 years and affect approximately 1% of the school-age population. Figures are not yet available for the prevalence of social (pragmatic) communication disorder. In all cases, communication disorders are more prevalent in boys than girls.

Etiology

Environmental factors that can contribute to the presence of a communication disorder include prematurity, prenatal exposure to drugs or alcohol, environmental deprivation, and frequent middle ear infections. Additionally, speech and language disorders have been shown to cluster in families, suggesting a genetic basis, although the molecular etiology of these disorders is just beginning to be understood. Most studies conducting whole-genome screenings have yet to reveal substantial overlap of the chromosomal regions linked to the presence of speech and language disorders of different individuals, suggesting that multiple genes are likely to contribute to a variety of functions and that this genetic background interacts with the child's environment in determining the emergence of a communication disorder. It is also likely, however, that the genes that provide the biological substrate for communication disorders also will be found to be implicated in the presence of other disorders, such as reading disabilities and ASD (Grigorenko 2009).

Diagnostic Evaluation

An assessment for determining the presence of a communication disorder should be conducted by a speech-language clinician who is certified by the American Speech-Language-Hearing Association or other international agency that regulates the credentialing of professionals who have received the educational training to diagnose and treat communication disorders. In conducting an assessment, clinicians should consider data from multiple sources (i.e., a developmental history, individualized and culturally appropriate standardized psychometric assessments, naturalistic language samples), in addition to applying clinical judgment in determining which children are delayed or at risk for different categories of communication disorder. A regional, social, or cultural/ethnic variation (e.g., dialect) of language is not a communication disorder.

Comorbid Psychiatric Disorders

Psychiatric comorbidity is common in children with communication disorders. A common etiology has been proposed between communication disorders and ADHD and between communication disorders and reading disorders. Disruptive behavior disorders and social anxiety disorders are also common in those with communication disorders, although the direction of causality in these relationships is unclear.

Developmental Course and Prognosis

Most young children with communication disorders go on to develop communication abilities that are within the normal range by late elementary school. However, even those children with resolved early language disorders may be at risk for language-based learning disorders. Several prospective studies have revealed that children with a history of early communication disorders show poorer adult outcomes across several domains, including the continued presence of communication disorders, as well as lower levels of educational achievement and occupational status. These outcomes are differentially predicted by multiple risk factors, including low socioeconomic status, poor reading skills, and child behavior problems.

Treatment

Support in the form of a behavioral intervention or environmental modifications for an individual with a language disorder should be provided based on a comprehensive assessment that integrates multiple sources of information regarding the individual's ability to learn and use language in a variety of contexts. Behavioral support for a language disorder can be provided in the form of a naturalistic intervention or one that adheres to analog principles. Additionally, treatment can range from guided practice to address a specific aspect of the language disorder to the provision of augmentative and alternative communication, such as picture communication systems, sign language, and speech-generating devices.

For the treatment of speech sound disorders, it has been suggested that treatment goals are more important than treatment approaches (Gierut 2005). Additionally, vocabulary development is considered to drive phonological learning; thus, some experts suggest that the primary focus of remediation efforts for speech sound disorders should be at the level of word acquisition rather than the production of individual sounds (Kamhi 2006).

For preschoolers who are disfluent, indirect therapy maybe used to create a fluency-enhancing environment, by teaching parents to slow their rate of speech, avoid interrupting, reframe responses, and modify questions to reduce demands on the child. Other therapists may use verbal contingencies to praise "smooth speech" and to acknowledge or correct unambiguous stuttering. Different treatment options are available for older children and adolescents who have a fluency disorder. Techniques that have the greatest efficacy for reducing the disfluencies in these individuals are those that change the timing of speech (e.g., slowing down, stretching out sounds) or reduce physical tension during speaking (e.g., using gentle onsets of speech movement).

Autism Spectrum Disorder

Clinical Description

ASD is defined by core impairments in social communication behaviors and the presence of repetitive and stereotyped behaviors. Kanner's (1943) initial account of autism and the earliest diagnostic criteria described the most classic and severe features of the disorder, whereas newer conceptualizations recognize the spectrum nature of the condition and encompass milder symptom manifestations. Diagnostic criteria have both broadened and changed with each version of DSM. The changes in DSM-5 are perhaps the most extensive in the history of the diagnostic manual. In brief, the DSM-5 revisions include the following:

• The diagnostic category name has been changed from pervasive developmental disorders to autism spectrum disorder.
• A single disorder, ASD, is diagnosed rather than one of the five individual DSM-IV (American Psychiatric Association 1994) disorders. More specifically, autistic disorder, Asperger's disorder, childhood disintegrative disorder, and pervasive developmental disorder not otherwise specified (PDD NOS) are subsumed under one label (i.e., ASD). In addition, Rett's disorder has been eliminated because its molecular basis is now known (and DSM focuses on disorders without a molecular or biological test that must instead be defined behaviorally).
• Dimensional "severity" criteria have been added to capture the spectrum nature of the disorder and interindividual variations in symptom intensity and degree of impairment.
• Inclusion of the new social (pragmatic) communication disorder (outside the autism spectrum) within the broader diagnostic class of neurodevelopmental disorders will provide diagnostic coverage to children who present with only social-communication problems and do not display the repetitive and stereotyped behaviors of ASD.
• The number of symptoms used to establish the diagnosis of ASD has been streamlined from 12 to 7 by merging criteria that were overlapping or described similar behaviors and eliminating symptoms that are not specific to ASD (e.g., delayed development of language).
• Three symptom domains (social, communication, and repetitive behavior) have become two (social communication and repetitive behaviors).

The DSM-5 diagnostic criteria for autism spectrum disorder are listed in Box 8-9. Several associated features are not part of the diagnostic criteria but are commonly seen in individuals with ASD, including intellectual disability, uneven profiles of cognitive strengths and weaknesses, emotional dysregulation, motor deficits (e.g., clumsiness, odd gait), epilepsy, and disruptions in sleep and feeding.

NOTICE. Criteria set above contains only the diagnostic criteria and specifiers; refer to DSM-5 for the full criteria set, including specifier descriptions and coding and reporting procedures.

The DSM-5 changes are well supported empirically (Ozonoff 2012). There are multiple scientific rationales for using one diagnostic label rather than many. The subtypes of PDD appear genetically similar, as evidenced by the fact that different subtypes run in families and can even be found among monozygotic twins. Additionally, the majority of studies have failed to find empirical differences among DSM-IV PDD subtypes (summarized in Frith 2004; Macintosh and Dissanayake 2004). To the extent that differences between subtypes have been found, they have been quantitative (e.g., variations in degree of impairment, severity of symptoms, or level of cognitive function) rather than qualitative (Prior et al. 1998). Moreover, multiple studies have demonstrated that most children with an Asperger-like clinical presentation actually met DSM-IV criteria for autistic disorder (Gilchrist et al. 2001; Williams et al. 2008). There is a striking lack of consistency in how these labels have been used in both community and research settings (Lord et al. 2011; Williams et al. 2008). The change in the name of the category from PDD to ASD was actually proposed over 20 years ago (Happé and Frith 1991). Thus, although the proposed DSM-5 criteria have been controversial and contested (e.g., Ghaziuddin 2011), they reflect the current scientific landscape.

An innovation in DSM-5, for all disorders, is the inclusion of specifiers that describe, in a more dimensional fashion, interindividual differences. The specifiers for the ASD category are

• Severity (record level of support required);
• With or without accompanying intellectual impairment;
• With or without accompanying language impairment;
• Associated with a known medical or genetic condition or environmental factor;
• Associated with another neurodevelopmental, mental, or behavioral disorder; and
• With catatonia.

Epidemiology/Prevalence

When autism was initially described, it was considered a very rare condition. In the mid-1970s, its prevalence in the United Kingdom, Denmark, and United States was estimated at 5/10,000 children (Wing et al. 1976). Reported prevalence has been increasing rapidly since then (Fombonne 2002). The most recent estimated prevalence of ASD in the United States is 1/88 (Centers for Disease Control and Prevention 2012). Prevalence rates vary considerably worldwide (Elsabbagh et al. 2012); however, in all countries in which multiple studies have been conducted over time, there is a pattern of increasing prevalence. Clearly, some of the increase is attributable to better detection, increased awareness, and use of broader diagnostic criteria, although these factors do not appear to fully explain the dramatic rise in ASD (Hertz-Picciotto and Delwiche 2009). ASD affects individuals of all socioeconomic levels, races, and ethnicities, with a 4:1 male-to-female ratio.

Etiology

ASD is a biologically based condition with multifactorial etiology. Genetic factors play a strong role, although few specific genes accounting for any substantial percentage of cases have been discovered. ASD is highly heritable, with studies estimating the proportion of risk attributable to genetic factors at 80% or higher (Ronald and Hoekstra 2011). A large, multisite study of infants with an older sibling with ASD reported a recurrence rate of 18.7% (Ozonoff et al. 2011). Although genetic causes, such as chromosomal abnormalities and de novo copy number variations (Glessner et al. 2009), are implicated in some cases of ASD, no single genetic etiology accounts for more than l%-2% of cases (Abrahams and Geschwind 2008).

Genetic susceptibility may be modulated by environmental factors (Hertz-Picciotto et al. 2006; Schmidt et al. 2011). Established environmental influences include prenatal exposure to rubella, thalidomide, and valproic acid. Other potential nongenetic risk factors include prematurity, low birth weight (Pinto-Martin et al. 2011), and parental age (Sandin et al. 2012). Although some individuals with ASD have dysfunctional immune responses (Onore et al. 2012), numerous epidemiological studies have not supported a causal link between immunization and ASD (Gerber and Offit 2009).

Diagnostic Evaluation

Practice parameters for the assessment of ASD have been published by the American Academy of Neurology (Filipek et al. 2000), the American Academy of Pediatrics (Johnson and Myers 2007), and the American Academy of Child and Adolescent Psychiatry (Volkmar et al. 1999). In general, there are two levels of evaluation: Level 1 screening involves routine developmental surveillance by primary care physicians for young children, and Level 2 evaluations involve a diagnostic assessment by experienced clinicians for children who fail an initial screening. The Level 2 assessment involves 1) review of developmental history and presenting problems with parents, 2) review of available records (e.g., medical, school, previous testing, intervention reports), and 3) direct observation of, and interaction with, the child. Assessment of intellectual, language, and adaptive functioning usually rounds out the core assessment. More comprehensive evaluations may also include examination of neuropsychological functioning (e.g., attention, memory, and executive function), academic abilities, motor function, and psychiatric comorbidities.

Multiple measures are available for assessment of children suspected of ASD; each measure has its own strengths and weaknesses (see Ozonoff et al. 2005a for a more complete discussion). The current gold standard diagnostic tool for direct assessment of symptoms is the Autism Diagnostic Observation Schedule (Lord et al. 2012), which involves a 40-minute semistructured interaction, formatted into multiple modules that are developmentally appropriate from infancy through adulthood and across the range of functioning levels. The current gold standard diagnostic tool used in research to collect information from parents is the Autism Diagnostic Interview—Revised (ADI-R; Rutter et al. 2003b). The authors of the ADI-R have also developed a briefer version, the Social Communication Questionnaire (SCQ; Berument et al. 1999; Rutter et al. 2003a), which was derived from the ADI-R and consists of 40 items, administered as a parent questionnaire, that collect information about both current and lifetime symptoms.

A critical part of the process of case formulation is differential diagnosis to determine whether presenting symptoms are due to ASD, a different condition, or the presence of co-occurring disorders (Mazefsky et al. 2012). For example, poor eye contact and low social initiative may be indicative of ASD but also of depression. Examining the developmental history for the consistency of symptoms over time and pervasiveness across situations will help the clinician with differential diagnosis. The package of social and communication limitations, combined with odd or repetitive behaviors, expressed consistently throughout the lifetime, should alert the clinician that ASD must be part of the differential diagnosis. If additional problems not encompassed by the ASD criteria are present, or if changes from baseline indicate onset of new difficulties, or if the individual is not responding as expected to treatment, comorbidity should be considered (Lainhart 1999).

Comorbid Psychiatric Disorders

ASD can co-occur with a variety of additional disorders (Deprey and Ozonoff 2009). Common comorbid psychiatric conditions in the ASD population are anxiety disorders and depressed mood, with rates of these disorders higher than in the general population (Simonoff et al. 2008; White et al. 2009). Attention and activity level disturbances are also common comorbid features (Goldstein and Schwebach 2004). DSM-IV did not permit the diagnosis of ADHD in individuals with ASD, but this exclusion has been dropped in DSM-5.

Developmental Course and Prognosis

The onset of ASD usually occurs before age 3, at two peak periods. The majority of children (approximately two-thirds) display developmental abnormalities within the first 2 years of life. Often, onset, parental recognition, and clinical diagnosis do not coincide. Parents often begin to be concerned when language fails to develop as expected (De Giacomo and Fombonne 1998). However, several other behavioral differences may precede the language delays that parents report at the time of recognition, such as less looking at faces and infrequent responding to name, pointing, and sharing of enjoyment and interests with others (Lord 1995; Nadig et al. 2007; Wetherby et al. 2004).

A smaller group of children with autism display a period of typical or mostly typical development, followed by a loss of communication and social skills and onset of autism. The average age of regression across studies is between 14 and 24 months (Fombonne and Chakrabarti 2001). Regression typically progresses gradually, although onset can be sudden in a minority of cases. Loss of language is the most commonly described and most salient manifestation of regression (Goldberg et al. 2003). Virtually all children who lose language also lose social behaviors, such as eye contact and social interest (Hansen et al. 2008; Ozonoff et al. 2005b). It may be difficult to distinguish regression from a third onset pattern, developmental plateau (Jones and Campbell 2010; Kalb et al. 2010), in which children fail to progress and gain new skills as expected, but do not lose previously acquired skills.

ASD is a lifelong condition, but there is usually improvement in symptoms with age, and often periods of waxing or waning of particular symptoms. Existing literature suggests that the vast majority of children, once diagnosed with ASD, will retain this diagnosis into adulthood (Howlin et al. 2004; Piven et al. 1996), although this could change in another generation, given advances in intervention science and practice. Even now, there are children who progress sufficiently and no longer meet criteria for an ASD diagnosis (Lovaas 1987; Perry et al. 1995), although they may continue to have difficulties in other areas (Fein et al. 2005).

Later functional and adaptive outcomes are highly related to overall cognitive ability. The most powerful predictors of outcome continue to be IQ scores and verbal ability at age 5 (Gillberg 1984; Lotter 1974). Most individuals with ASD studied longitudinally present with functional impairment throughout life (Billstedt et al. 2005; Howlin et al. 2004). Educational, vocational, economic, community, and family supports play an important role in promoting positive adaptation and may be important factors in explaining variability in outcome. In addition, the availability of high-quality intensive early intervention for an increasing number of young children may change the frequency of what are considered the so-called best outcomes for ASD.

Treatment

Medical interventions are used primarily to treat associated or comorbid symptoms, rather than core symptoms of ASD. Studies have provided support for using risperidone and aripiprazole to treat aggression, irritability, and repetitive behaviors (summarized in McPheeters et al. 2011), although there are significant adverse effects, including somnolence and weight gain. A randomized, placebo-controlled, crossover trial of methylphenidate found clinical benefit (reductions in hyperactivity) at three dosing levels, although parents reported higher withdrawal/lethargy at the highest dose (Research Units on Pediatric Psychopharmacology Autism Network 2005). A small randomized trial of atomoxetine in ASD produced significant improvement in hyperactivity and was well tolerated, suggesting the need for further trials (Arnold et al. 2006). The use of serotonin reuptake inhibitors and stimulant medications lacks sufficient strength of evidence to evaluate benefit-risk profiles (McPheeters et al. 2011), although the medications are used clinically for repetitive behaviors and anxiety.

Behavioral interventions are the most effective and widely used treatments for core symptoms of ASD (for systematic reviews, see Vismara and Rogers 2010; Warren et al. 2011). It is, therefore, imperative that initial diagnosis is followed by the provision of validated behavioral treatments as soon as possible. Two treatment approaches stand out in terms of their evidence base: Lovaas's Early Intensive Behavioral Intervention (EIBI; Lovaas 1987) and the Early Start Denver Model (ESDM; Rogers and Dawson 2010). The EIBI approach is based on principles of operant conditioning (reinforce-merit and negative consequences) and applied behavior analysis. EIBI involves several years of one-to-one intervention for 35-40 hours per week, carried out in the home (and occasionally community settings). The ESDM approach incorporates similar behavioral principles but is more developmentally based and focuses on dyadic interactions, joint play, and activity routines between adult and child, in which teaching opportunities are embedded in the play. Outcome studies for both approaches demonstrate large and significant gains in IQ and language compared to control conditions (Dawson et al. 2010; McEachin et al. 1993).

Attention-Deficit/Hyperactivity Disorder

Clinical Description

ADHD is characterized by developmentally inappropriate, persistent problems in inattention and/or excessive motor restlessness and/or impulsivity that significantly interfere with functioning (DSM-5 criteria for attention-deficit/hyperactivity disorder are presented in Box 8-10). The inattentive symptoms may manifest as difficulty maintaining sufficient attention toward on-task stimuli and situations, excessive distractibility, disorganization, poor planning and follow-through, or forgetfulness. The ability to maintain attention may vary dramatically depending on the situation. For instance, novel situations, one-to-one interactions, and engagement in activities with a high rate of feedback may reduce inattention. The hyperactivity symptoms in young children can manifest as a high rate of physical activity, jumping from one activity to the next, or having difficulty sitting still in contexts where sitting still is expected (e.g., "circle time"). During earlier adolescence, overt hyperactivity typically declines and other forms of hyperactivity may be more prominent, such as frequent talking, fidgeting, or internal feelings of restlessness. The impulsive symptoms associated with ADHD are often characterized by a disproportionate influence of short-term rewards on behavior to the neglect of longer-term rewards, and often to the detriment of the individual. Impulsivity also refers to a lack of reflection in the decision-making process. The impulsive behavior can manifest as impatience, interrupting others, answering questions before knowing the full instructions, responding too quickly, spending money without considering one's financial assets, not heeding warning signs, and potentially engaging in high-risk behavior.

NOTICE. Criteria set above contains only the diagnostic criteria and specifiers; refer to DSM-5 for the full criteria set, including specifier descriptions and coding and reporting procedures.

The symptoms of the disorder must occur across settings for diagnostic purposes. The symptoms should be evident at home and school in children and at home and work in adults, although there can be situational differences, with certain settings more likely to be associated with more severe symptom presentation. A change in DSM-5 relative to DSM-IV is that symptom onset no longer needs to have occurred by age 7 years. The new criteria state that several inattentive or hyperactive-impulsive symptoms should be evident by age 12 years. For adults, manifestation of the symptoms should have occurred during childhood rather than representing an acute onset.

Associated features of ADHD include problems in maintaining positive relationships (e.g., with friends and coworkers), problems achieving persistent academic and occupational success, and poor frustration tolerance. Commonly co-occurring disorders include learning, substance abuse, mood, anxiety, oppositional defiant, and conduct disorders. Females with ADHD have a higher rate of suicide attempts than the general population (Hinshaw et al. 2012). Cognitive deficits associated with ADHD include increased within-person variability in response times, cognitive control impairments, problems with working memory and planning, and a steeper discounting of the value of delayed rewards. Task measures of these cognitive deficits, however, do not demonstrate diagnostic utility.

Subtypes and Specifiers

DSM-IV included three subtypes of ADHD: inattentive, hyperactive-impulsive, and combined. In DSM-5, there are now "presentation types" rather than "subtypes." The use of presentations rather than subtypes reflects a more dimensional rather than categorical approach to evaluating symptoms in ADHD. This includes an acknowledgment that there is some fluidity in symptom presentation and that the types of symptoms displayed can change within an individual. DSM-5 continues to include a partial remission specifier requiring fewer than six symptoms of inattention and/or hyperactivity-impulsivity currently, but the individual must have met criteria in the past and continue to experience significant impairment to qualify for the diagnosis. DSM-5 now includes three functioning severity specifiers: mild, moderate, and severe.

DSM-5 now includes an other specified ADHD category for symptom presentations characteristic of ADHD that cause clinically significant distress or impairment but do not meet full criteria for ADHD. This category is used when the clinician wishes to communicate the reason that the presentation does not meet the full criteria for ADHD or another neurodevelopmental disorder. Another category, unspecified ADHD, applies to presentations similar to those described for other specified ADHD, but it is used when the clinician chooses not to specify the reason why criteria for ADHD or another neurodevelopmental disorder are not met and includes situations in where there is too little information to develop a specific diagnosis.

Another important change from DSM-IV-TR to DSM-5 is moving ADHD from the Attention-Deficit and Disruptive Behavior Disorders section to the Neurodevelopmental Disorders chapter. This switch acknowledges that children with ADHD are not necessarily disruptive.

Epidemiology/Prevalence

In a recent meta-analysis of 86 studies of children and adolescents (N=163,688), Willcutt (2012) found that when DSM-IV criteria are applied, 5.9%-7.1% of children meet criteria for ADHD diagnosis using best estimate diagnostic procedures, parent ratings, or teacher ratings. Based on 11 studies of adults (N=14,112), using primarily self-report ratings, the authors found that 5.0% of adults met criteria for ADHD based on DSM-IV symptom thresholds.

The prevalence of ADHD subtypes varies depending on diagnostic procedures and age (Willcutt 2012). Based on ratings by parents, teachers, or the individuals themselves, the inattentive sub-type is the most common. Employing best-estimate diagnostic procedures, however, results in the combined subtype being the most frequently diagnosed in studies. The prevalence of the hyperactive-impulsive subtype of ADHD is lower than the prevalence of either the inattentive or the combined subtype. Prevalence rates are most stable between ages 5 and 9 years for the overall diagnosis of ADHD. The hyperactive-impulsive subtype is most common during preschool age, but prevalence gradually declines with age. Prevalence of the combined subtype increases from preschool age to elementary school age, but progressively declines during adolescence and adulthood. Prevalence rates for the predominantly inattentive subtype show a linear increase from preschool to adulthood. Adults are most likely to receive a diagnosis of inattentive type. Regardless of subtype, males are more likely to receive the diagnosis.

Etiology

The etiology of ADHD is multifactorial. Genetic factors are involved in ADHD, as demonstrated in family pedigree, twin, and adoption studies (Gizer et al. 2009). Several genes associated with monoamine and serotonin synthesis and metabolism pathways appear to contribute to the ADHD phenotype, although the effects for each appear to be relatively small.

Although the disorder is highly heritable, environmental contributions are likely as well. Very low birth weight, preterm births (Halmøy et al. 2012), lead exposure, and exposure to endocrine-disrupting chemicals can lead to increased risk for ADHD (de Cock et al. 2012). Parental smoking is also implicated; however, the smoking may more likely reflect genetic risk rather than an environmental exposure issue.

Studies of brain structure and function in ADHD consistently show significant differences between children and adults with ADHD and typically developing individuals in frontal, anterior cingulate, basal ganglia, and cerebellar regions. Children with ADHD display impaired functional connectivity between anterior and posterior brain regions, decreased connectivity within dorsal attention and default-mode networks, and increased functional connectivity within a reward-related network (e.g., Tomasi and Volkow 2012). There is evidence of impaired dopamine receptor and transporter availability in ADHD (Volkow et al. 2009). Norepinephrine functioning is also likely to be impaired in ADHD.

Diagnostic Evaluation

The evaluation of ADHD typically includes a parent and child clinical interview in conjunction with parent and teacher standardized rating scales assessing ADHD symptoms and related behaviors. In addition to reviewing the presence of ADHD symptoms, the clinician should consider other psychiatric conditions that may be contributing to the functioning or mimicking ADHD and attentional problems. Thus, it is best to use a rating scale that is primarily focused on ADHD, supplemented by evaluation procedures that review a broad perspective of other Axis I psychiatric disorders. Adult evaluations should include a clinical interview and standardized rating scales completed by the adult patient; when possible, parents and/or other respondents such as spouses, roommates, or supervisors should also rate the extent and duration of ADHD symptoms. Young adults may not provide the most accurate portrayals of their current functioning for a variety of reasons. Similarly, adults may have difficulty accurately recalling their childhood functioning. Thus, obtaining ratings and other information from multiple sources is strongly recommended. Corroborative evidence, such as old report cards, also can be highly informative. A physical examination and medical history should be gathered within the previous year to rule out any physical symptoms that may be contributing to the presentation. Neuroimaging (single-photon emission computed tomography, magnetic resonance imaging, functional magnetic resonance imaging) or electroencephalographic tests are not recommended for diagnosing ADHD.

A differential diagnosis should consider oppositional defiant and conduct disorder, intermittent explosive disorder, reactive attachment disorder, learning disorders, bipolar and other mood disorders, anxiety disorders, substance abuse, and ASD. Other nonpsychiatric factors—such as stress, a chaotic living situation, or unrealistic developmental expectations—and their impact on symptom presentation should be considered. In older adults, symptoms of dementia may mimic symptoms of ADHD. Intellectual or achievement functioning tests should be administered only if there is concern that either intellectual status or the presence of a learning disability is contributing to the presentation. It should be noted that academic functioning is often affected by ADHD.

Comorbid Psychiatric Disorders

There are many disorders that co-occur with ADHD, including oppositional defiant, learning, mood, and anxiety disorders. Speech and language disorders and motor disorders also occur at a higher rate with ADHD than at chance rate. In DSM-5, an individual can be diagnosed with both ASD and ADHD. Half or more of individuals with ASD also will likely qualify for the ADHD diagnosis. Adolescents and adults also are likely to experience higher rates of conduct disorders and substance abuse, which can lead to additional complications. The presence of these disorders should be considered during the evaluation.

Developmental Course and Prognosis

Although ADHD can be present during the preschool years, it may be difficult to distinguish from typical preschool behaviors. The disorder becomes easier to detect during the early elementary school- years when children are expected to complete more paperwork and sit at their desks. Overt symptoms of hyperactivity diminish but may be present in a less observable form. Inattention becomes more prominent during adolescence and through adulthood. The change from DSM-IV to DSM-5 requiring adult patients to evidence only five rather than six symptoms reflects the reduction of significant overt symptoms in adulthood. Engagement in high-risk behaviors or behaviors with potential to cause long-term negative consequences (e.g., traffic accidents, substance abuse, earlier sexual initiation) emerges during adolescence. Roughly one-third of individuals appear to no longer exhibit symptoms of ADHD during adulthood.

Treatment

There is strong empirical support for the use of pharmacological interventions for children and adults with ADHD (Table 8-1). Stimulants such as methylphenidate and amphetamine salts are the two major categories of pharmacological treatment for ADHD and are considered the first-line medication treatments for the disorder. Second-line medication interventions include the nonstimulant atomoxetine. Clonidine or guanfacine may be considered if the patient has failed to respond to two stimulant trials or experiences intolerable side effects from the stimulant medication, or if there are concerns regarding substance abuse, which may result in greater side effects (e.g., sedation).

Behavioral interventions, including behavioral classroom interventions, parent training, organizational skills training for adolescents, and cognitive-behavioral therapy for adults (Solanto et al. 2008), demonstrate some efficacy in addressing associated symptoms of ADHD and co-morbid disorders, as well as parent-child relationships (Chronis et al. 2006). The use of preventive interventions for ADHD in at-risk preschoolers was recently proposed, and there is some preliminary evidence of efficacy (Halperin et al. 2012). Cognitive training has also been tested for treating ADHD symptoms and demonstrates limited support; however, those studies are preliminary and need to be replicated on a wider scale using more placebo-controlled studies (see Rutledge et al. 2012 for review).

Specific Learning Disorder

Clinical Description

The category of specific learning disorder (SLD) was not listed in DSM-IV; instead, DSM-IV included the category of learning disorder not otherwise specified. A diagnosis of SLD requires persistent difficulties in reading, writing, or arithmetic/mathematical reasoning that emerge during the developmental period and have significant negative effects on academic performance, occupational functioning, or the activities of daily life (DSM-5 criteria for SLD are shown in Box 8-11). Moreover, these difficulties have some specificity in that they cannot be attributable to lower intelligence (i.e., intellectual disability or global developmental delay) or to an identified neurological, sensory, or motor disorder (Compton et al. 2012). Specifiers identify the domain affected (i.e., reading, written expression, or mathematics) and the severity of impairment (i.e., mild, moderate, or severe). Importantly, the difficulties leading to the diagnosis are defined in terms of performance that is well below normative expectations; however, no explicit psychometric criteria are specified in terms of level of achievement or discrepancy between achievement and age expectations or IQ. SLD includes a variety of conditions, including those labeled as developmental learning disabilities, specific learning disabilities, developmental dyslexia, dyslexia, dyscalculia, dysgraphia, and language learning difficulties. Some subtypes of this disorder remain controversial, such as nonverbal learning disorders (e.g., Spreen 2011), reinforcing the decision not to specify subtypes in DSM-5.

NOTICE. Criteria set above contains only the diagnostic criteria and specifiers; refer to DSM-5 for the full criteria set, including specifier descriptions and coding and reporting procedures.

Epidemiology/Prevalence

Prevalence is estimated at 3%-9% for school-age populations, but with considerable variability across languages, cultures, races, ethnicities, and socioeconomic conditions studied to date (Goswami et al. 2011). SLD prevalence during adulthood is estimated at 4%, but this estimate should be viewed cautiously given limited epidemiological data. Twice as many males as females are diagnosed with SLD (Leckliter and Enriquez 2013), and students who are learning English as a second language are also at elevated risk (Shifrer et al. 2011). Socioeconomic factors are particularly important in identification and likely outweigh race and ethnicity as risk factors (Shifrer et al. 2011).

Etiology

Twin and other kinship studies suggest moderate genetic influences for arithmetic and reading difficulties, although the specific genetic mechanisms involved remain elusive in the vast majority of cases (Miller and McCardle 2011). Low birth weight is also associated with an increased risk of SLD. Environmental factors, such as prenatal exposure to nicotine, are also risk factors. It has been suggested that similar genetic factors may underlie SLD, ADHD, ASD, and other neurodevelopmental disorders. Working memory impairments appear to contribute to many of the impairments associated with the disorder (Berninger and May 2011; Mammarella and Pazzaglia 2010; Toll et al. 2011).

Diagnostic Evaluation

Although SLD occurs in all languages and cultures, its manifestations and course vary as a function of educational and cultural practices and the language and orthographic systems involved. Consequently, the diagnosis should be informed by data on the relevance of such factors for the individual being assessed. It is especially important to ascertain whether there has been limited educational opportunity in individual cases.

Comorbid Psychiatric Conditions

SLDs often co-occur with other neurodevelopmental disorders as well as with other psychiatric disorders. These other disorders do not preclude the attribution of a SLD but they do complicate the assessment and diagnostic process. Individuals with SLD who do not meet criteria for another diagnosis nevertheless often experience difficulties in other domains, such as anxiety (Nelson and Harwood 2011). Oral language problems are especially common.

Developmental Course and Prognosis

In Western culture, SLD is typically diagnosed after age 6 or 7 years, which is when literacy and number-related demands are systematically encountered in school; however, earlier delays in reaching language milestones are often indicative of later literacy problems. The symptoms of the disorder vary with the demands of academic tasks and, thus, age (e.g., as difficulties in counting in kindergarten and first grade but as difficulty mastering arithmetic procedures and facts in second and third grades). The symptoms of SLD, and their functional impairments in daily life, often continue in adulthood (Gerber 2012).

Treatment

U.S. schools typically provide accommodations via special education services to students classified as having SLDs; however, these accommodations at best prevent worsening of impairments rather than their alleviation (Leckliter and Enriquez 2013). Several specially designed curricula focusing on alleviating impairments in the early school years, particularly in the area of literacy, have had some success (Bernlnger and May 2011), although the data concerning factors predicting response (and nonresponse) to intervention are poorly understood (Leckliter and Enriquez 2013). Pharmacological treatments, for the most part, are focused on treatment of comorbid symptoms (e.g., anxiety) rather than core learning problems (Leckliter and Enriquez 2013).

Motor Disorders

Clinical Description

The subclass of motor disorders includes a rather heterogeneous collection of disorders defined by significant delays in reaching developmental motor milestones and/or persistent and unusual patterns of motor behavior, with each disorder having an onset during childhood and a meaningful impact. Changes have been made in DSM-5 relative to DSM-IV in each of the disorders included in this subclass, with most of the changes reflecting an elimination of diagnostic requirements not supported by the accumulating empirical evidence on course, cause, and tractability to treatment. In most disorders in this subclass, the criteria include explicit requirements that the motor delays or unusual motor patterns result in significant functional impairments in terms of daily living activities or academics and are not the direct result of a general medical condition (e.g., Huntington's disease). The criteria for inclusion or exclusion also include reference to whether the symptoms of concern are a direct result of exposure to a substance, such as cocaine.

The disorders within this subclass are quite varied in presentation, course, causes, comorbid conditions, and tractability to treatment.

Developmental Coordination Disorder

Developmental coordination disorder (Box 8-12) is a condition characterized by motor performance below expectations for age and experience, with its manifestations including poor coordination, balance problems, clumsiness, or substantial delays in acquiring basic motor skills or meeting developmental milestones.

Stereotypic Movement Disorder

Stereotypic movement disorder (Box 8-13) is a condition characterized by repetitive motor behavior that appears to be both driven and without purpose and that is associated with significant distress and impairment of functioning. The behavior may also result in self-injury.

NOTICE. Criteria set above contains only the diagnostic criteria and specifiers; refer to DSM-5 for the full criteria set, including specifier descriptions and coding and reporting procedures.

Tic Disorders

The tic disorders (Box 8-14) comprise several diagnostic categories, all characterized by the presence of motor and/or vocal tics (sudden, rapid, recurrent, and nonrhythmic movements or vocalizations). Persistent (chronic) motor or vocal tic disorder is distinguished from Tourette's disorder by the fact that the former can be defined by a single tic whereas the latter must include multiple motor tics and at least a single vocal tic. In contrast to Tourette's syndrome and persistent (chronic) motor or vocal tic disorder, a provisional tic disorder is diagnosed when the tics have occurred for less than 1 year. The diagnostic categories other specified tic disorder (Box 8-15) and unspecified tic disorder (Box 8-16) are reserved for tic symptom presentations not fitting other tic disorder criteria. The former includes a clinician-stated reason that the presentation does not meet criteria for another tic disorder or neurodevelopmental disorder, whereas the clinician specifies no such reason in the latter condition.

Epidem iology/Prevalence

Prevalence varies considerably across the different types of motor disorders (Gunther and Sharp 2013). Prevalence has been estimated as less than 1% for Tourette's syndrome but as high as 3.7% for chronic tics (persistent [chronic] motor or vocal tic disorder in DSM-5) and 5%-6% for developmental coordination disorder (Stefanoff et al. 2008). Variation in prevalence is also observed with individual characteristics (Gunther and Sharp 2013). For example, although Tourette's syndrome occurs in all races and ethnicities (McNaught and Mink 2011), prevalence rates for Tourette's disorder are higher for non-Hispanic whites than for non-His-panic blacks (Centers for Disease Control and Prevention 2009). Higher rates of developmental coordination disorder, Tourette's syndrome, and other tic disorders have been seen in males than in females (Knight et al. 2012).

Etiology

Genetic contributions to tic disorders have been well documented. Studies of kinship relations, including comparisons of dizygotic and monozygotic twins, have documented a heritable component to Tourette's disorder (Gunther and Sharp 2013). More than 10 different chromosomes have been implicated in Tourette's syndrome (O'Rourke et al. 2009). Several candidate genes have been proposed, including several dopamine-related genes (O'Rourke et al. 2009) and genes that also are implicated in other disorders, including ADHD (Gunther et al. 2012). Studies of alternative splicing offer new insights into genetic mechanisms of a number of neurodevelopmental disorders, suggesting, for example, atypical exon expression in Tourette's syndrome (Tian et al. 2011). Genetic contributions to developmental coordination disorder are less clear.

Environmental contributions to motor disorders also have been identified. Maternal prenatal factors, such as stress and infection, and early postnatal strep infection have been proposed as risk factors for Tourette's syndrome and other tic disorders (Gunther and Sharp 2013); immune dysfunction may mediate these effects (Landau et al. 2012). Prenatal alcohol exposure and prematurity have been found to be risk factors for development coordination disorder.

Diagnostic Evaluation

Diagnosis of tic disorders is based on careful clinical observation, including a neurological examination, and a thorough developmental history (e.g., to determine age at onset and course). Several self- and informant-report measures have been used in the diagnostic process, most notably the Movement Assessment Battery for Children—Second Edition (Henderson et al. 2007) in the case of developmental coordination disorder and the Yale Global Tic Severity Scale (Storch et al. 2005) in the case of tic disorders. Clinical observation is especially important in differentiating movement disorders from other conditions that might represent a more appropriate primary diagnosis (e.g., obsessive-compulsive disorder) or to identify comorbid conditions (Gunther and Sharp 2013).

Comorbid Psychiatric Conditions

Motor disorders are often accompanied by a variety of comorbid conditions and symptoms (Kraft et al. 2012). In the case of Tourette's syndrome, for example, more than three-fourths of affected individuals also have a diagnosed mental health condition (Centers for Disease Control and Prevention 2009), including ADHD, which may be the most prevalent and appears to often precede tic onset, as well as obsessive-compulsive disorder, anxiety, depression, and learning disabilities (Gunther and Sharp 2013). ASD also co-occurs in up to 13% of individuals with Tourette's syndrome (Mejia and Jankovic 2005). Other behavior disturbances frequently observed in Tourette's syndrome are sleep problems, self-injurious behavior, and aggression (Gunther and Sharp 2013). Developmental coordination disorder is often associated with ASD and ADHD, with worse outcomes in general for individuals with these comorbidities (Rasmussen and Gillberg 2000).

Developmental Course and Prognosis

The motor disorders are not typically diagnosed until between ages 4 and 6 years, with the subsequent developmental course being variable across individuals, but with improvement being observed in a subset of individuals. In individuals with developmental coordination disorder, for example, there is often an abatement of symptoms with age; however, nearly two-thirds of affected individuals continue to show delays in adolescence (Cantell et al. 2003) and many are at risk for poor physical fitness in adulthood (Osika and Montgomery 2008). In Tourette's syndrome, simple tics emerge first, followed by the appearance of vocal tics and complex motor tics, with a peak in severity during adolescence (Leckman et al. 2010). As the affected individual becomes more self-reflective, typically during adolescence, premonitory urges are often reported as powerful sensations that the tic is imminent, much like a sneeze (Ganos et al. 2012). Nonetheless, one-third of individuals with Tourette's or another tic disorder experience remission of tics during early adolescence (Kraft et al. 2012).

Treatment

Tourette's disorder and other tic disorders typically require a combination of behaviorally or cognitively based interventions and pharmacological treatments, with more severe cases, such as those that involve self-harm, requiring deep brain stimulation or other invasive procedures (Gunther and Sharp 2013). Psychopharmacological interventions are often suggested for comorbid conditions, such as ADHD, and these frequently lead to improvements in tics as well (Eddy et al. 2011; Leckman et al. 2010). Indeed, some medications (e.g., clonidine) are more efficacious in individuals with comorbidities, such as Tourette's syndrome and ADHD (Waldon et al. 2013). Behavioral interventions with evidence of efficacy include habit reversal training and Comprehensive Behavioral Intervention for Tics, each of which involves replacing tics with more adaptive motor behaviors (Gunther and Sharp 2013; Wilhem et al. 2012). More invasive therapies include botulinum injections or implantation of electrodes (e.g., in the thalamic region) as in the case of deep brain stimulation (Eddy et al. 2011; Leckman et al. 2010). Moderators of treatment efficacy are poorly understood in tic disorders (Wenzel et al. 2012).

Other Neurodevelopmental Disorders

Two final conditions are included in the category of neurodevelopmental disorders. Other specified neurodevelopmental disorder (Box 8-17) is to be used for cases in which the symptom presentation fails to meet the full criteria for any specific neurodevelopmental disorder and the clinician chooses to provide an explanation as to why criteria are not met, as would be the case if the clinician arrived at a designation of neurodevelopmental disorder associated with prenatal alcohol exposure. The category unspecified neurodevelopmental disorder (Box 8-18) is to be used for cases in which the symptom presentation fails to meet the full criteria for any specific neurodevelopmental disorder and the clinician is not able to or chooses not to explain why the full criteria are not met.

Conclusion

The disorders described in this chapter are quite different in their symptom presentations. Nevertheless, they share a developmental course that includes an emergence during the childhood or adolescent period and a significant impact on the individual's functioning in the important contexts of daily life. For the clinician, deciding on a diagnosis requires access to information on 1) the emergence and stability of symptoms over development, 2) the individual's status in multiple domains of functioning, and 3) the impact of the impairment(s) as reported by the individual or by the parents or other caregivers. Treatment options include behavioral and educational programs as well as pharmacological agents. Although "cures" do not yet exist for any neurodevelopmental disorder, available treatment options do lead to improvements, including in some cases "moving out of" the diagnosis.

Key Clinical Points

• Neurodevelopmental disorders begin during the developmental period and are typically lifelong conditions.
• These disorders are defined by significant impairments in one or more domains of functioning (e.g., cognition, language, motor behaviors) and limit success in many of the contexts critical for full participation in one's culture and community.
• Impairments can include delays and lower final levels of achievement in skill acquisition or the presentation of atypical behaviors.
• These disorders often are associated with comorbid problems in other domains, which further limit successful negotiation of important life tasks.
• Early diagnosis provides the opportunity for treatments and support that can optimize development of the individual and ease the stresses experienced by families.
• Although cures are not imminent, the combination of new targeted pharmaceuticals and evidence-based intensive behavioral and educational interventions has created an unprecedented sense of optimism for the field and for families.

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Suggested Readings

Burack JA, Hodapp RM, Iarocci G, et al (eds): Oxford Handbook of Intellectual Disability and Development. New York, Oxford University Press, 2011

Hansen RL, Rogers SJ (eds): Autism and Other Neurodevelopmental Disorders. Washington, DC, American Psychiatric Publishing, 2013

Lord C, Jones RM: Annual research review: rethinking the classification of autism spectrum disorders. J Child Psychol Psychiatry 53:490-509, 2012

Schwartz R (ed): Handbook of Child Language Disorders. New York, Psychology Press, 2009

Online Resources

American Association on Intellectual and Developmental Disabilities: www.aaidd.org

American Speech-Language-Hearing Association: www.asha.org

Autism Speaks: www.autismspeaks.org