Mental Retardation: Levels, Causes, and Outlook
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What causes mental retardation? 17 possible conditions

If your child has an intellectual disability (ID), their brain doesn’t develop properly. Their brain may also not function within the normal range of both intellectual and adaptive functioning. In the past, medical professionals called this condition... Read more

See a list of possible causes in order from the most common to the least.


Down Syndrome

Down syndrome (sometimes spelled "Down's syndrome") is a genetic abnormality. It is the most common single cause of birth defects in the United States.

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Hydrocephalus is a condition that occurs when fluid builds up in the skull and causes the brain to swell. The name literally means "water on the brain."

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Cerebral Palsy

Cerebral palsy is a group of disorders that affect muscle movement and coordination. Learn about the causes, types, symptoms, and treatment of cerebral palsy.

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Lead Poisoning

Lead is a toxic metal and a very strong poison. Lead poisoning is serious and sometimes fatal. Discover the causes, treatments, and tips for prevention.

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Fanconi Anemia

Fanconi anemia causes bone marrow failure. Your bone marrow is responsible for making three different types of blood cells in your body.

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Find information on phenylketonuria causes, symptoms, diagnosis, and treatment.

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Muscular Dystrophies

Muscular dystrophies are a group of inherited diseases that damage and weaken your muscles over time. This damage and weakness is due to the lack of a protein.

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Homocystinuria is an inherited disorder that keeps the body from processing the essential amino acid methionine. Amino acids are the building blocks of protein.

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Tuberous Sclerosis

Tuberous sclerosis is a rare genetic condition that causes noncancerous tumors in your brain, other organs, and skin. Learn how it's treated.

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Ito Syndrome (Incontinentia Pigementi Achromians)

Ito syndrome (IS) is a rare condition that researchers believe iscaused by genetic irregularities. The conditionis not inherited, however,and a family history of IS is rare. IS is characterized by loss of skin color o...

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Genetic changes that occur while the fetus is growing can cause disorders that are present at birth. These are sometimes referred to as "congenital disorders." Acrodysostosis is one such condition, albeit a rare one...

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Huntington's Disease

Huntington's disease is a hereditary condition in which your brain's nerve cells gradually break down. It can cause physical and psychological symptoms.

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Aarskog Syndrome

Aarskog syndrome is a very rare genetic disorder that can affect a person's stature, facial features, genitalia, muscles, and bones.

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Aicardi Syndrome

Aicardi syndrome is a rare disorder that interferes with the formation of the corpus callosum. Learn about its symptoms, causes, and diagnosis.

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Tay-Sachs Disease

Tay-Sachs disease is a neurodegenerative disorder most commonly found in infants. Learn more about this rare disease.

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As Rare as it Gets: Chediak Higashi Syndrome

Chediak-Higashi Syndrome is a rare type of albinism that causes problems with your vision. Learn about the different types and possible symptoms.

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Basal Cell Nevus Syndrome

Basal cell nevus syndrome is a group of defects caused by a rare genetic condition. Learn about the symptoms and treatments for basal cell nevus syndrome.

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This feature is for informational purposes only and should not be used to diagnose.
Please consult a healthcare professional if you have health concerns.