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Developmental Disabilities: What to Know

Developmental Disabilities: What to Know

Developmental disabilities are conditions due to a learning, language, behavior, or physical impairment. These conditions begin during the developmental period (any time before a child turns 18) and can last throughout a person’s lifetime. Some examples include ADHD, cerebral palsy, down syndrome, fetal alcohol syndrome, and autism spectrum disorders. One in six children is diagnosed with some kind of developmental disability or delay. There are four categories of developmental disabilities and many different subsets nestled under the following four main groups.


A metabolic disability affects the way the body builds up, breaks down, and otherwise processes materials. These disorders can affect how your body uses materials for energy and growth. Problems with these processes can create too much or too little of something in your body, upsetting the balance of materials and disrupting bodily functions. Some examples include:

  • Congenital Hypothyroidism results from an absent or under-developed thyroid gland. The lack of this hormone can cause symptoms like jaundice, weak muscle tone, and slow growth.
  • Phenylketonuria is caused by the PAH gene not breaking up the phenylalanine amino acid in the body. This build-up in the blood and brain causes brain damage.

Nervous System

These developmental disabilities are birth defects that affect the brain, spinal cord, and nervous system function. These conditions influence intelligence and learning, as well as behavior, speech, and language. A few conditions in this category include:

  • Autism Spectrum Disorder can have a range of symptoms affecting communication skills, social skills, and intelligence.
  • Down Syndrome occurs when there is an extra copy of chromosome 21. This additional genetic material causes a specific set of mental, medical, and physical characteristics. A few common traits include low muscle tone and an upward slant to the eyes.
  • Fragile X Syndrome is caused by the FMR1 gene telling the body to produce little to none of the FMRP protein. It causes delays in talking, anxiety, and hyperactive behavior, as well as seizures in some cases. Physical features include a long face, flat feet, and large ears.


Sensory-related disabilities are birth defects that affect how the body senses the world around it. People with this disability struggle to use and process sensory information like sights, smells, sounds, touch, and taste. The most common issues are presented as vision and hearing problems.


Children born with degenerative disorders may appear normal at birth and even initially meet development milestones, but then slowly lose abilities or functions due to the disorder. These disorders can cause mental, physical, and/or sensory problems. Rett Syndrome is an example of a rare degenerative disorder that leads to severe impairments, including losing coordination, speech, and use of the hands.

What causes developmental disabilities?

In many cases, the direct cause of a developmental disability is unknown. Some known causes include:

  • Abuse and neglect
  • Accidents during childhood that cause brain trauma
  • Drug or alcohol abuse during pregnancy
  • Genetic disorders
  • Infectious diseases
  • Malnutrition

The Milestone Tracker App will help you monitor your child’s skills and abilities to ensure they are meeting typical developmental milestones, or skills that most children reach by a certain age in learning, moving, behaving, and speaking. For more information about developmental disabilities, visit the Center for Disease Control website.

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