Multiple: Developmental Disability

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Multiple: Developmental Disability

Causes and Symptoms
The Future
For more information


Developmental disability is a term applied to a group of chronic disorders caused by physical and/or mental impairments that occur before age twenty-two and typically last for a lifetime. These disorders affect a person's ability to learn, speak effectively, take care of themselves, hold a job, and live independently.

Developmental disabilities are defined as mild, moderate, severe, or profound on the basis of how much social support the person needs. A person with mild developmental disabilities, for example, may be able to benefit from special education programs, finish high school or a vocational training program, work in certain types of jobs, and live with their family or in the community. Those with profound disabilities, on the other hand, may require twenty-four-hour care in a group home or institution.


Developmental disabilities can be described as falling into one of several types:

  • Disabilities involving the brain, spinal cord, and nervous system. These developmental disabilities include mental retardation (Down syndrome, fragile X syndrome) and autism spectrum disorders.
  • Disabilities related to hearing or vision loss.
  • Disabilities related to metabolic disorders. Metabolism refers to the sum total of the chemical changes in the body that are needed to provide energy and repair or grow tissues. Metabolic disorders that affect children's development include thyroid diseases and phenylketonuria.
  • Disabilities related to degenerative disorders. Degenerative disorders are those in which a child appears normal at birth and reaches some developmental milestones but then starts to lose the abilities they have attained.

Developmental disabilities have been recognized for centuries even though people did not always understand their causes. Before the eighteenth century, people suffering from mental retardation and other disabilities were often cared for by their families or in religious institutions like monasteries. After the Industrial Revolution in the nineteenth century, people with developmental disabilities were more likely to be taken from their families in childhood and placed in large asylums—some containing as many as several thousand people. Some of these institutions provided an elementary education as well as food, shelter, and clothing, but most met only the basic needs of the children and adults in their care. It was not until the 1960s that doctors and teachers began to question the effectiveness of placing people with disabilities in large institutions.

Developmental Milestones in Children

Here are some of the physical characteristics or abilities that doctors look for in evaluating a child's development during the preschool years:

  • Three months: Baby smiles when smiled at, grasps rattle, turns head toward lights or voices.
  • Six months: Baby can sit in a high chair, imitate parent's hand movements, laugh, and make sing-song noises.
  • Twelve months: Baby can eat finger food, crawl, walk holding parent's hand, respond to music, say first word.
  • Eighteen months: Toddler can walk without help, identify an object in a picture book, say eight to ten different words, ask for something by pointing.
  • Two years: Child can open boxes, drink from a straw, have a vocabulary of several hundred words, hum or try to sing, play with other children.
  • Four years: Child can eat or drink without spilling; draw simple objects; undress without help; use the toilet alone; tell the difference between the real world and imaginary worlds; speak in complete sentences with good grammar.
  • Five years: Child can count to ten; has an understanding of time; can hop, climb, skip, and turn somersaults.

Between the 1960s and the 1990s, the United States and other developed countries moved toward individualized education and social support for people with developmental disabilities. Instead of separating these persons from the wider community, doctors and teachers now focus on each individual's gifts and talents as well as their needs, and try to place them in classroom and work settings where they can interact with others. In 2000 the U.S. Congress passed the Developmental Disabilities Assistance and Bill of Rights Act, which funds four grant

programs to assist people with developmental disabilities and their families.

There are still several challenges to teaching and treating or supporting people with developmental disabilities. One is that these children and adults are vulnerable to abuse by others. They also have a higher than normal rate of mental health issues, not only because they are often hurt or abused but also because they frequently become dependent on drugs or alcohol. Third, people with developmental disabilities sometimes behave in ways that are upsetting or dangerous to others, such as hitting, screaming, kicking, being sexually inappropriate, stealing or throwing objects, or injuring themselves. Treatment of people with developmental disabilities often has to include medications or psychotherapy to help them control problem behaviors.


According to the U.S. Administration on Developmental Disabilities (ADD), there were about 4.5 million children and adults in the United States with developmental disorders as of 2008. Some statistics for specific disorders are as follows:

  • Autism: 560,000 persons between the ages of one and twenty-one years.
  • Cerebral palsy: 800,000 children and adults.
  • Hearing loss: 72,000 children between the ages of six and twenty-one.
  • Mental retardation: 2 million children and adults between the ages of six and sixty-four.

Causes and Symptoms

Developmental disabilities can be caused by a number of different factors:

  • Injury to the baby's brain before birth or during the birth process.
  • Mother's lifestyle. Heavy drinking, drug use, or smoking can lead to fetal alcohol syndrome or other forms of brain damage.
  • Rubella or other infectious diseases.
  • Extreme prematurity.
  • Child abuse.
  • Genetic disorders. Down syndrome, phenylketonuria, fragile X syndrome, and some degenerative disorders are all caused by genetic mutations or an extra copy of a chromosome.
  • Poor diet and health care.

Developmental disabilities are defined by the U.S. government as disabilities that affect the individual's functioning in three or more of the following areas:

  • The ability to live on one's own
  • The ability to support oneself financially
  • The ability to learn in school
  • The ability to get around on one's own, by walking, driving, or using public transportation
  • The ability to use and understand spoken language
  • The ability to take care of one's personal needs (dressing, eating, washing, using the toilet, doing laundry)
  • Self-direction (the ability to make decisions, evaluate situations, and generally be in charge of one's life)


The diagnosis of developmental disabilities is made at different points before or after the child's birth, depending on the specific disorder. Some genetic disorders, like Down syndrome, can be diagnosed before the baby is born. Metabolic disorders like phenylketonuria can be detected by a blood test used to screen babies shortly after birth.

In other cases, developmental disabilities may be identified by the baby's doctor during periodic checkups. The doctor can observe how the child interacts with its caregiver; can test his or her vision and hearing; and see whether the child has attained specific developmental milestones. Parents who have noticed that their child does not seem to be walking, talking, or responding to them at the age at which these abilities usually appear will often consult a specialist in child development for an evaluation of the child. Some learning disabilities may not become evident until after the child starts school and may be first noticed by a teacher.


There is no cure for developmental disabilities. Treatment of developmental disabilities is tailored to the individual child and his or her

specific type of disability. It may include one or more of the following types of treatment or care:

  • Medications or surgery for specific physical or emotional problems.
  • Special education programs.
  • Vocational training for future employment.
  • Speech and language therapy.
  • Physical therapy.
  • Psychotherapy and counseling for behavioral problems.
  • Support services for people who are profoundly disabled. These may include nursing care as well as assistance with housekeeping, personal cleanliness, shopping, and handling money.

Although many people with developmental disabilities cannot be completely self-sufficient in all aspects of daily life, treatment is aimed at helping them achieve as much independence as possible.


The prognosis for children with developmental disabilities depends on the severity of the child's specific disability; whether it is progressive (gets worse over time); and the extent to which it affects his or her ability to get along with other people, finish school or train for a job, and live independently. In general, developmental disabilities shorten a person's life expectancy by about twenty years, although improvements in technology as well as medicine are helping people with disabilities have a better quality of life as well as live longer.


Not all developmental disabilities can be prevented. Some measures that people can take, however, to lower their risk of having a child with developmental disabilities include:

  • Genetic screening for both parents, particularly if either father or mother comes from a family with a history of genetic disorders
  • Proper nutrition and health care for the mother during pregnancy
  • Avoidance of drinking, smoking, and drug use during pregnancy
  • Vaccination against rubella before pregnancy if the mother has not been exposed to it

The Future

Developmental disabilities are likely to become a serious concern for caregivers and health care professionals in the years ahead. One reason is that some developmental disabilities, such as autism and hearing loss, are becoming more rather than less common. Another reason is that people with developmental disabilities are living longer, which means that they will require treatment and support services for many more years than was the case in the 1960s. The needs of adults over fifty with developmental disabilities are presently being studied by policy makers as well as medical researchers.

Another rapidly expanding area of research is finding better screening instruments to identify children with developmental disabilities as early as possible. The available evidence indicates that the earlier these children are diagnosed and treated, the more likely they are to develop their full potential as they grow older.

SEE ALSO Asperger syndrome; Autism; Cerebral palsy; Child abuse; Down syndrome; Fetal alcohol syndrome; Fragile X syndrome; Hearing loss; Phenylketonuria; Prematurity; Rubella; Seizure disorder; Shaken baby syndrome; Spina bifida


Chronic: Long-term.

Degenerative disorder: A type of disorder in which a child gradually loses certain abilities that he or she had acquired at an earlier age.

Metabolism: The sum total of the chemical changes in living cells that are necessary to maintain life.

Milestone: A physical development or accomplishment that most children reach within a specific age range.

Progressive: Referring to a disease or disorder that gets worse over time.

For more information


Greenbaum, Judith. Life Planning for Adults with Developmental Disabilities: A Guide for Parents and Family Members. Oakland, CA: New Harbinger Publications, 2007.

Ochiari, Midori. Different Croaks for Different Folks: All about Children with Special Learning Needs. Translated by Esther Sanders, with notes on

developmental differences by Shinya Miyamoto. Philadelphia: Jessica Kingsley Publishers, 2006. This is a book for children intended to help them understand others with developmental disabilities.

Taulbee, Jack. Understanding Children of Special Needs: What Every Parent Needs to Know. Monrovia, CA: Wayne Publishing, 2005.


Administration on Developmental Disabilities (ADD). ADD Fact Sheet. Available online at (updated July 22, 2008; accessed on October 3, 2008). The ADD is a sub-department of the U.S. Department of Health and Human Services; it is the Federal agency responsible for carrying out the Developmental Disabilities Assistance and Bill of Rights Act of 2000 (DD Act).

Centers for Disease Control and Prevention (CDC). Developmental Disabilities: Topic Home Page. Available online at (updated September 20, 2005; accessed on October 3, 2008).

Centers for Disease Control and Prevention (CDC). Baby Steps: Learn the Signs; Act Early. Available online at (posted September 22, 2008; accessed on October 3, 2008). This is a four-and-a-half minute video to help parents recognize the early signs of developmental disabilities in their child.

National Institute of Child Health and Human Development. Birth Defects and Developmental Disabilities. Available online at (updated September 18, 2006; accessed on October 3, 2008).

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Multiple: Developmental Disability

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