1: Overview: defining developmental disorders


Overview: defining developmental disorders

H. Barry Waldman, DDS, MPH, PhD and
Steven P. Perlman, DDS, MScD, DHL (Hon)

It was not that long ago when children with developmental disabilities and adults with a range of disorders did not exist. We never saw them in our schools, movies, or communities. President Roosevelt may have had an attack of poliomyelitis, but everyone knew he had no problem standing and walking. At least it all seemed that way.

It took a long time to find out that tens of millions of youngsters and the not so young with a vast range of disabilities were concealed out of sight in institutions or in family homes. Somehow it was disgraceful, shameful, embarrassing, and a reflection on other family members to have a relative with some type of developmental or intellectual disability—except maybe a 95-year-old great-grandmother. Only later did we find out that the press and just about everyone in Washington was involved in the cover-up to ensure that the president of the country did not appear weak during the years of the Depression and World War II.

But that was the middle and the final decades of the twentieth century. In this second decade of the twenty-first century, we have learned that there are more than half a billion people in the world who are disabled as a consequence of mental, physical, and sensory impairment (United Nations 2010). “Disability is a complex phenomenon, reflecting an interaction between features of a person’s body and features of the society in which he or she lives” (World Health Organization 2008). In the United States, there are more than fifty million individuals with developmental disabilities, complex medical problems, significant physical limitations, and a vast array of other conditions under the rubric of “disabilities” who live in local communities; many as a result of deinstitutionalization and mainstreaming them into community housing, education, and employment (U.S. Census Bureau 2010a).

The U.S. Census Bureau reported for 2006, among the total population:

  • 5 years and over—6.8% had one disability. 8.3% had two or more disabilities.
  • Five–15 years—536,400 had a sensory disability, almost 500,000 had a physical disability, and 2.8 million had an intellectual disability.
  • Adults—37 million had a hearing disability, 21 million had a vision disability, and 15 million had a physical functioning disability. Specifically for seniors, 14.6 million had one or more disabilities (U.S. Census Bureau 2010a).

Among the non-institutionalized U.S. population 5 years and older:

  • A larger number of females than males had physical, mental, and self-care disabilities—particularly in the older years, reflecting the greater longevity of females.
  • A larger number of males than females had sensory disabilities (Table 1.1).

The number of persons with disabilities is projected to increase dramatically as the population 65 years and over reaches 1 in 5 residents during the next 2 decades (U.S. Census Bureau 2010b, 2010c). Media reports abound with references to the increasing numbers of older individuals with disabilities and government efforts to control the potential costs to service their mounting needs. By contrast, attention to the costs for youngsters with disabilities generally is centered on supportive education programs. Health financial issues, particularly during the years when youngsters enter adulthood, tend to be underreported.

It is estimated that the lifetime costs for all people with intellectual disabilities who were born in the United States in 2000 will total $51.2 billion (in 2003 dollars). These costs include both direct and indirect costs. Direct medical costs, including physician visits, prescription drugs, and inpatient hospital stays, account for 14% of these costs. Direct nonmedical expenses, such as home modifications and special education, make up 10% of the costs. Indirect costs, which include the value of lost wages when a person dies early, cannot work, or is limited in the amount or type of work that can be done, make up 70% of costs. These estimates do not include expenses such as hospital outpatient visits, emergency room visits, residential care, and family out-of-pocket expenses. The actual economic costs of intellectual disabilities are, therefore, even higher (CDC 2010e). Specifically, the average per capita society lifetime cost for individuals with autism through 66 years of age is $3.1 million (Ganz 2007).

Table 1.1 Non-institutionalized U.S. residents (in thousands) with disabilities by gender and age: 2006 (U.S. Census Bureau 2010a).

Male Female
Sensory disabilities:
  5–15 yrs 292 229
  16–20 155 126
  21–64 2,926 2,215
  65–74 1,028 835
  75+ 1,674 2,347
  Total 6,075 5,752
Physical disabilities:
  5–15 yrs 289 218
  16–20 172 179
  21–64 6,346 7,433
  65–74 1,828 2,515
  75+ 2,346 4,453
  Total 10,981 14,798
Mental disabilities:
  5–15 yrs 1,529 758
  16–20 626 388
  21–64 4,033 4,186
  65–74 654 783
  75+ 1,053 1,915
  Total 7,895 8,030
Self-care disabilities:
  5–15 yrs 240 148
  16–20 89 66
  21–64 1,835 2,197
  65–74 455 677
  75+ 807 1,780
  Total 3,426 4,868


This chapter will describe the more common developmental disorders in the literature today. However, it is important to note that there are literally hundreds that exist and hundreds that are yet to be identified.

Autism spectrum disorders

Autism spectrum disorders (ASDs), also known as pervasive developmental disorders, are a group of developmental disorders defined by a significant impairment in social interaction and communication and by the presence of unusual behaviors and interests. Many individuals with ASD have atypical ways of learning, paying attention, or reacting to different sensations and stimuli. The assessment and learning abilities of youngsters and adults with ASD can vary from gifted to severely challenged. ASDs usually are diagnosed before age 3 and last throughout a person’s life. ASDs occur in all racial, ethnic, and socioeconomic groups and are 4 times more likely to occur in boys than girls (CDC 2010a). “If 4 million children are born in the United States every year, approximately 24,000 of these children will eventually be diagnosed with ASD” (CDC 2010b).

The Centers for Disease Control and Prevention (CDC) conducts two nationally representative surveys in which parents are asked whether their child has ever received a diagnosis of autism. Estimates from these studies suggest that, as of 2003–2004, autism had been diagnosed in at least three hundred thousand children aged 4–17 years (CDC 2010d). “CDC estimates 1 in 88 children in United States has been identified as having an autism spectrum disorder” (CDC 2012).

Based upon these national studies and other CDC local studies, it is estimated that up to five hundred thousand individuals between the ages of 0 and 21 years have an autism spectrum disorder (Yeargin-Allsopp et al. 2003; Bertrand et al. 2005) (Table 1.2). A CDC study found that the rate among young children (3–10 years) was lower than the rate for intellectual disabilities but higher than the rates for cerebral palsy, hearing loss, and vision impairment.

Table 1.2 Prevalence of parent-reported autism among non-institutionalized children age 4–17 years (per 1,000 children) by selected demographic characteristics 2003–2004 (U.S. Census Bureau 2010a).

  Male 8.8 8.5
  Female 2.4 2.3
Age (yrs):
  4–5 4.8 4.4
  6–8 7.5 7.6
  9–11 7.2 5.8
  12–14 4.6 4.3
  15–17 4.2 4.1
  Hispanic 2.9 3.2
  White, non-Hispanic 7.0 6.2
  Black, non-Hispanic 5.2 5.8
Highest level of education achieved by family member:
  ≤ High school grad. 4.0 4.1
  > High school grad. 6.6 6.0
Family income:
  < 200% poverty level 5.7 5.6
  ≥ 200% poverty level   7.1

*NHIS – National Health Interview Survey

NSCH – National Survey of Children’s Health

More children are being classified as having an autism spectrum disorder, but it is unclear how much of this increase is due to changes in how one identifies and classifies people with ASDs or whether it is a true increase in prevalence (Shieve et al. 2006). By current standards, “the ASDs are the second most common serious developmental disability after mental retardation/intellectual impairment” (CDC 2010c).

The total number of children (3–22 years of age) with ASDs in a state is, to a great extent, a reflection of the variation in state populations. As of 2003, there were almost 25,000 youngsters with ASDs in California, almost 12,000 in Texas, and approximately 9,500 in New York. In addition, there were between 5,000 and more than 7,000 children with ASDs in 9 states, and between 1,000 and more than 4,000 children with ASDs in 21 states (Statemaster.com 2010).

Whether because of (1) better diagnosis, (2) a broader definition of autism, (3) a marked enlargement in the population of a particular state (e.g., Nevada), or (4) an actual increase in the numbers of individuals with ASDs, nationally between 1992 and 2003 there has been about a 2,560% increase in reported cases. These increases range from 23,300% in Ohio, 17,700% in Nevada, 16,200% in Wisconsin, 12,500% in Maryland, and 11,600% in New Hampshire, to between 1,000% and 5,000% in twenty-one states and less than 500% in eight states. There was a 1,086% increase in California (Table 1.3).

Table 1.3 Cumulative growth of autism cases in children (ages 6–22 years) by state: 1992–2003 (Statemaster.com 2010).

  % increase
Ohio 23,291
Nevada 17,720
Wisconsin 16,195
Maryland 12,529
New Hampshire 11,600
Between 1,000% and 5,000% increase (in decreasing order):
  Colorado, Arkansas, Minnesota, Illinois, Mississippi, Vermont, Nebraska, Montana, Kentucky, New Mexico, Idaho, Connecticut, Rhode Island, Alaska, Georgia, California, Oklahoma, Iowa, North Dakota, Guam, Maine, Kansas
Between 500% and 980% increase (in decreasing order):
  Wyoming, New Jersey, Utah, South Dakota, Arizona, Pennsylvania, Missouri, Texas, Alabama, South Carolina, Florida, Oregon, Hawaii, District of Columbia, Massachusetts, Virgina, Indiana
Between 40% and 472% increase (in decreasing order):
  Washington, Michigan, West Virginia, American Samoa, Northern Mariana Islands, North Carolina, Louisiana, Puerto Rico, Tennessee, New York, Delaware, U.S. Virgin Islands
  National average = 2,560% increase

The number of children ages 3–22 with ASDs per 10,000 population in Oregon and Minnesota is about 4–5 times greater than the proportions in West Virginia, Montana, Oklahoma, Mississippi, New Mexico, and Colorado, as well as the Northern Mariana Islands, Puerto Rico, the U.S. Virgin Islands, and American Samoa (Statemaster.com 2010).

Types of autism spectrum disorders

1. Asperger syndrome: characterized by a greater or lesser degree of impairment in language and communication skills, as well as repetitive or restrictive patterns of thought and behavior. The most distinguishing symptom of Asperger syndrome is a child’s obsessive interest in a single object or topic to the exclusion of any other. Unlike children with other types of autism, children with Asperger syndrome retain their early language skills (National Institute of Neurological Disorders and Stroke 2010c).
2. Rett syndrome: characterized by normal early development followed by loss of purposeful use of the hands, distinctive body movements, slowed brain and head growth, gait abnormalities, seizures, and intellectual disabilities. It affects females almost exclusively (National Institute of Neurological Disorders and Stroke 2010b).
3. Pervasive developmental disorder, not otherwise specified (PDD-NOS): encompasses cases where there is marked impairment of social interaction, communication, and/or stereotyped behavior patterns or interest (Yale Developmental Disabilities Clinic 2010b).
4. Childhood disintegrative disorder: a rare condition that resembles autism but only after a relatively prolonged period (usually 2–4 years) of clearly normal development. Typically language, interest in the social environment, and often toileting and self-care abilities are lost, and there may be a general loss of interest in the environment (Yale Developmental Disabilities Clinic 2010a).
5. Fragile X syndrome: a genetic condition involved in changes in part of the X chromosome. It is the most common form of inherited intellectual disability in males and a significant cause of intellectual disability in females. Fragile X syndrome is caused by a change in the FMR1 gene. A small section of the gene code (three letters only—CGG) is repeated on the fragile bottom area of the X chromosome. (The name “fragile X” was derived from the appearance of the X chromosome in a specialized tissue culture, because it looked like the end of the chromosome was broken.) The more repeats in the gene code, the more likely there is to be a problem. Normally, the FMR1 gene makes a protein needed for normal brain development. As a result of a defect in this gene, too little or none at all of the protein is produced. A male and female can both be affected, but because males have only one X chromosome, a fragile X is likely to affect them more severely (MedlinePlus 2010). Men pass the mutation only to their daughters. Their sons receive a Y chromosome, which does not include the FMR1 gene. Fragile X syndrome occurs in approximately 1 in 4,000 males and 1 in 8,000 females (Genetics Home Reference 2010).
  When the gene shuts down in people with fragile X syndrome, the result is that brain cells do not communicate normally and cause a form of hyperactive brain activity, a form common in many autism spectrum disorders. Compounds exist that dampen these effects. Studies are under way using lithium to intervene with autism and fragile X syndrome symptoms (Fraxa Research Foundation 2010).
6. Savant syndrome: not a recognized medical diagnosis. It is a rare condition in which people with developmental disorders have one or more areas of expertise, ability, or brilliance that are in contrast with the individual’s overall limitations. About half of persons with savant syndrome have autistic disorder, while the others have another developmental disability, intellectual disability, brain injury, or disease. Savant syndrome is 6 times more frequent in males than females (Savant syndrome 2010).

Down syndrome

Down syndrome is a set of mental and physical symptoms that result from having an extra copy of chromosome 21 (called trisomy 21), which affects brain and body development. While individuals with Down syndrome may have some physical and mental features in common, the signs can range from mild to severe. Usually mental and physical developments are slower than in those individuals without the condition. IQs range in the mild to profound range of intellectual disability. Language and physical motor development may be delayed or slow. Common physical signs include:

  • Flat face with an upward slant to the eyes, short neck, and abnormally shaped ears.
  • Deep crease in the palm of the hand.
  • White spots on the iris of the eye.
  • Poor muscle tone, loose ligaments.
  • Small hands and feet.

There are a variety of other health conditions that often are seen, including:

  • Congenital heart disease—30–50% have heart defects at birth.
  • Hearing loss and eye problems (mostly due to cataracts). These changes tend to occur 20–30 years before other persons in the general population.
  • Intestinal problems, such as blocked small bowel or esophagus—8–12% have gastrointestinal tract abnormalities at birth.
  • Celiac disease.
  • Thyroid dysfunction.
  • Skeletal problems.
  • Dementia—similar to Alzheimer’s disease (National Institute of Child Health and Human Development 2010; National Down Syndrome Congress 2010).

Down syndrome is the most commonly inherited form of learning disability. In developed countries it accounts for 12–15% of the population with learning disabilities (Bittles & Glasson 2004). The chance of having a baby with Down syndrome increases as a woman gets older—from about 1 in 1,250 for a woman who becomes pregnant at age 25, to about 1 in 100 for a woman who becomes pregnan/>

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Jan 5, 2015 | Posted by in General Dentistry | Comments Off on 1: Overview: defining developmental disorders
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