Understanding Neurodevelopmental Disorders

Intellectual Disability (Intellectual Developmental Disorder)

Diagnostic criteria for intellectual disability (intellectual developmental disorder) emphasize the need for an assessment of both cognitive capacity (IQ) and adaptive functioning. Severity is determined by adaptive functioning rather than IQ score. The term mental retardation was used in DSM-IV. However, intellectual disability is the term that has come into common use over the past two decades among medical, educational, and other professionals, and by the lay public and advocacy groups. Moreover, a federal statue in the United States (Public Law 111-256, Rosa’s Law) replaces the term “mental retardation with intellectual disability. Despite the name change, the deficits in cognitive capacity beginningin the developmental period, with the accompanying diagnostic criteria, are considered to constitute a mental disorder. The term intellectual developmental disorder was placed in parentheses to reflect the World Health Organization’s classification system, which lists “disorders” in the International Classification of Diseases (ICD; ICD-11 to be released in 2015) and bases all “disabilities” on the International.

Classification of Functioning, Disability, and Health (ICF). Because the ICD-11 will not be adopted for several years, intellectual disability was chosen as the current preferred term with the bridge term for the future in parentheses.

The DSM-5 communication disorders include language disorder (which combines DSM-IV expressive and mixed receptive-expressive language disorders), speech sound disorder (a new name for phono logical disorder), and childhood-onset fluency disorder (a new name for stuttering). Also included is social (pragmatic) communication disorder, a new condition for persistent difficulties in the social uses of verbal and nonverbal communication. Because social communication deficits are one component of autism spectrum disorder (ASD), it is important to note that social (pragmatic) communication disorder cannot be diagnosed in the presence of restricted repetitive behaviors, interests, and activities (the other component of ASD). The symptoms of some patients diagnosed with DSM-IV pervasive developmental disorder not otherwise specified may meet the DSM-5 criteria for social communication disorder.

Autism spectrum disorder is a new DSM-5 name that reflects a scientific consensus that four previously separate disorders are actually a single condition with different levels of symptom severity in two core domains. ASD now encompasses the previous DSM-IV autistic disorder (autism), Asperger’s disorder, childhood disintegrative disorder, and pervasive developmental disorder not otherwise specified. ASD is characterized by

1) deficits in social communication and social interaction and

2) restricted repetitive behaviors, interests, and activities (RRBs). Because both components are required for diagnosis of ASD, social communication disorder is diagnosed if no RRBs are present. Attention-Deficit/Hyperactivity Disorder The diagnostic criteria for attention-deficit/hyperactivity disorder (ADHD) in DSM-5 are similar to those in DSM-IV. The same 18 symptoms are used as in DSM-IV, and continue to be divided into two symptom domains (inattention and hyperactivity/impulsivity), of which at least six symptoms in one domain are required for diagnosis. However, several changes have been made in DSM-5:

1) examples have been added to the criterion items to facilitate application across the life span;

2) the cross-situational requirement has been strengthened to “several” symptoms in each setting;

3) the onset criterion has been changed from “symptoms that caused impairment were present before age 7 years” to “several inattentive or hyperactive-impulsive symptoms were present prior to age 12”;

4) subtypes have been replaced with presentation specifiers that map directly to the prior subtypes;

5) a comorbid diagnosis with autism spectrum disorder is now allowed; and

6) a symptom threshold change has been made for adults, to reflect their substantial evidence of clinically significant ADHD impairment, with the cutoff for ADHD of five symptoms, instead of six required for younger persons, both for inattention and for hyperactivity and impulsivity. Finally, ADHD was placed in the neurodevelopmental disorders chapter to reflect brain developmental correlates with ADHD and the DSM-5 decision to eliminate the DSM-IV chapter that includes all diagnoses usually first made in infancy, childhood, or adolescence.

Specific learning disorder combines the DSM-IV diagnoses of reading disorder, mathematics disorder, disorder of written expression, and learning disorder not otherwise specified. Because learning deficitsin the areas of reading, written expression, and mathematics commonly occur together, coded specifiers for the deficit types in each area are included. The text acknowledges that specific types of reading deficits are described internationally in various ways as dyslexia and specific types of mathematicsdeficits as dyscalculia.

The following motor disorders are included in the DSM-5 neurodevelopmental disorders chapter: developmental coordination disorder, stereotypic movement disorder, Tourette’s disorder, persistent (chronic) motor or vocal tic disorder, provisional tic disorder, other specified tic disorder, and unspecified tic disorder. The tic criteria have been standardized across all of these disorders in this chapter. Stereotypic movement disorder has been more clearly differentiated from body-focused repetitive behavior disorders that are in the DSM-5 obsessive-compulsive disorder chapter.