Developmental Disabilities

The 9 months that precedes the birth of every child involves an amazing process. From the moment an egg is fertilized to the birth of an infant, so many complicated steps have occurred. In each step, there are many chances for errors to happen. Yet the surprise is not the number of children born with birth defects, but  the  number  of  children  who  are  born  healthy.

A number of events that consequently affect a child’s development can go wrong, including genetic abnormality, cell division, growth before birth, maternal nutrition, congenital malformation, infections, and teratogens (any agent that causes a defect in the fetus, such as radiation and drugs).

Developmental  disabilities  are  a  diverse  group of physical, cognitive, psychological, sensory, and speech impairments that begin anytime during the development up to 18–22 years of age (depending on various state and federal definitions). In most instances, the cause of disability is not known.


The definition used by federal agencies of developmental disabilities is severe, chronic, or unending disabilities of a person that (1) are attributable to a mental or physical impairment or combination of mental and physical impairments; (2) are apparent before the person attains the age of 22; (3) are likely to continue indefinitely; (4) result in substantial functional limitations in three or more of the following areas of major life activity— (a) self-care, (b) receptive and expressive language, (c) mobility, (d) self-direction, (e) capacity of independent living, and (f) economic self-sufficiency—and (5) reflect the person’s need for a combination and sequence of special, interdisciplinary, or generic care, treatment, or other services that are of lifelong or extended duration and are individually planned and coordinated.

Developmental Diagnoses

Attention Deficit Disorder with or Without Hyperactivity

The core symptoms of attention deficit/hyperactivity disorder are developmentally inappropriate levels of inattention, hyperactivity, and impulsivity. These problems are persistent and usually cause difficulties in one or more major life areas: home, school, work, or social relationships.

Autism, Pervasive Developmental Disorders

A diagnosis of autistic disorder is made when an individual displays 6 or more of 12 symptoms listed across three major areas: social interaction, communication, and behavior. When children display similar behaviors but do not meet the criteria for autistic disorder, they may receive a diagnosis of pervasive developmental disorder, not otherwise specified.

Cerebral Palsy

Cerebral palsy (CP) is a condition caused by injury to the parts of the brain that control our ability to use our muscles and bodies. Cerebral means having to do with the brain. Palsy means weakness or problems with using the muscles. Often the injury happens before birth, sometimes during delivery. CP can be mild, moderate, or severe. Mild CP may mean a child is clumsy. Moderate CP may mean the child walks with a limp. He or she may need a special leg brace or a cane. More severe CP can affect all parts of a child’s physical abilities. Usually, the greater the injury to the brain, the more severe the CP. However, CP does not get worse over time, and most children with CP have a normal life span.

Deafness/Hearing Impairments

Sound is measured by its loudness or intensity (measured in units called decibels, dB) and its frequency or pitch (measured in units called hertz, or Hz). Impairments in hearing can occur in either or both areas and may exist in only one ear or in both ears. Hearing loss is generally described as slight, mild, moderate,  severe,  or  profound,  depending  on  how well a person can hear the intensities or frequencies most greatly associated with speech.

Down Syndrome

Down syndrome is the most common and readily identifiable chromosomal condition associated with mental retardation. It is caused by a chromosomal abnormality, an accident in cell development that results in 47 instead of the usual 46 chromosomes. This extra chromosome changes the orderly development of the body and brain.

Emotional Disorders

Many terms are used to describe emotional, behavioral, or mental disorders. Children are said to have emotional disorders when their lives and education are significantly adversely affected by (a) an inability to learn that cannot be explained by intellectual, sensory, or health factors; (b) an inability to build or maintain satisfactory interpersonal relationships with peers and teachers; (c) inappropriate types of behavior or feelings under normal circumstances; (d) a general pervasive mood of unhappiness or depression; or (e) a tendency to develop physical symptoms or fears associated with personal or school problems.


Epilepsy is a physical condition that occurs when there is a sudden, brief change in how the brain works. When brain cells are not working properly, a person’s consciousness, movement, or actions may be altered for a short time. These physical changes are called epileptic seizures. Epilepsy is therefore sometimes called a seizure disorder. Epilepsy affects people in all nations and of all races. Some people can experience a seizure and not have epilepsy (e.g., febrile convulsion). A single seizure does not mean that the person has epilepsy.

Learning Disabilities

Learning disability is a general term that describes specific kinds of learning problems. A learning disability can cause a person to have trouble learning and using certain skills. The skills most often affected are reading, writing, listening, speaking, reasoning, and doing math.

Mental Retardation

Mental retardation is a term used when a person has certain limitations in mental functioning and in skills such as communicating, taking care of himself or herself, and social skills. These limitations will cause a child to learn and develop more slowly than a typical child. Mental retardation is diagnosed by looking at two main things: (a) the ability of a person’s brain to learn, think, solve problems, and make sense of the world (called IQ or intellectual functioning); and (b) whether the person has the skills he or she needs to live independently (called adaptive behavior or adaptive functioning).

Speech/Language Impairments

Speech and language disorders refer to problems in communication and related areas such as oral motor function.  These  delays  and  disorders  range  from simple sound substitutions to the inability to understand or use language or use the oral-motor mechanism for functional speech and feeding. Some causes of speech and language disorders include hearing loss, neurological disorders, brain injury, mental retardation, drug abuse, physical impairments such as cleft lip or palate, and vocal abuse or misuse. Frequently, however, the cause is unknown.

Spina Bifida

Spina bifida means “cleft spine,” which is an incomplete closure in the spinal column. In general, the three types of spina bifida (from mild to severe) are (a) spina bifida occulta, (b) spina bifida meningocele, and (c) myelomeningocele. The effects of spina bifida may include muscle weakness or paralysis below the area of the spine where the incomplete closure (or cleft) occurs, loss of sensation below the cleft, and loss of bowel and bladder control. In addition, fluid may build up and cause an accumulation of fluid in the brain (a condition known as hydrocephalus).

Traumatic Brain  Injury

Traumatic brain injury (TBI) is an injury to the brain caused by the head being hit by something or by being shaken violently. This injury can change how the person acts, moves, and thinks. A traumatic brain injury can also change how a student learns and acts in school. The term TBI is not used for a person who is born with a brain injury. It also is not used for brain injuries that happen during birth.

Visual  Impairments

The terms partially sighted, low vision, legally blind, and totally blind are used in the educational context to describe students with visual impairments. Visual impairment is the consequence of a functional loss of vision, rather than the eye disorder itself. Eye disorders that can lead to visual impairments can include retinal degeneration, albinism, cataracts, glaucoma, muscular problems that result in visual disturbances, corneal disorders, diabetic retinopathy, congenital disorders, and infection.


Developmental disabilities affect the lives of nearly 4  million Americans.  Developmental  disabilities  are severe, chronic disabilities attributable to mental, physical, sensory, and speech impairment that begin before ages 18 to 22. Significant limitations in three or more areas result from developmental disabilities: self-care, receptive and expressive language, learning, mobility, self-direction, capacity for independent living, and economic self-sufficiency, as well as the continuous need for individually planned and coordinated services.


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  2. American Academy of Child and Adolescent Psychiatry,
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