Intellectual disability begins in childhood. People with intellectual disability have limits in their mental functioning seen in below-average intelligence (IQ) tests and in their ability to communicate, socialize, and take care of their everyday needs. The degree of disability can vary from person to person. It can be categorized as mild, moderate, severe, or profound.
Several hundred causes of intellectual disability have been discovered, but many are still unknown. The most common ones are:
Biomedical causes resulting from:
Abnormal genes inherited from parents
Errors when genes combine, such as
Fragile X syndromeNutritional deficiencies
Metabolic conditions, such as
Developmental brain abnormality, such as
and brain malformation
Infections during pregnancy, such as:
Cytomegalovirus (CMV) infection
Behavioral issues during pregnancy, such as:
that affect the developing fetus
MalnutritionContraction of certain illnesses or infections while pregnant
Problems at birth, such as:
delivery or low birth weight
Baby doesn’t get enough oxygen during birthBaby is injured during birth
Factors during childhood, such as:
Illnesses or infections that affect the brain, including
whooping cough, and
mercury, and other toxins
near drowningSocial factors, such as child stimulation and adult responsivenessEducational deficiencies
Head Injury in Child
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A child could be at higher risk for intellectual disability due to any of the causes listed above, or due to intellectual disability in other family members. If you are concerned that your child is at risk, tell your child's doctor.
Symptoms appear before a child reaches age 18. Symptoms vary depending on the degree of the intellectual disability. If you think your child has any of these symptoms, do not assume it is due to intellectual disability. These symptoms may be caused by other, less serious health conditions.
Symptoms include: Learning and developing more slowly than other children of the same ageDifficulty communicating or socializing with othersLower than average scores on IQ testsTrouble learning in schoolInability to do everyday things like getting dressed or using the bathroom without helpDifficulty hearing, seeing, walking, or talkingInability to think logically
The following categories are often used to describe the level of intellectual disability:
IQ 50-70Slower than normal in all areasNo unusual physical signsCan learn practical skillsReading and math skills up to grades 3-6Can conform sociallyCan learn daily task skillsFunctions in society
IQ 35-49Noticeable delays, particularly speechMay have unusual physical signsCan learn simple communicationCan learn elementary health and safety skillsCan participate in simple activities and self-careCan perform supervised tasksCan travel alone to familiar places
IQ 20-34Significant delays in some areas; may walk lateLittle or no communication skills, but some understanding of speech with some responseCan be taught daily routines and repetitive activitiesMay be trained in simple self-careNeeds direction and supervision socially
IQ <20Significant delays in all areasCongenital abnormalities presentNeeds close supervisionRequires attendant careMay respond to regular physical and social activityNot capable of self-care
If you suspect your child is not developing skills on time, tell the doctor as soon as possible. You will be asked about your child’s symptoms and medical history. A physical exam will be done. Standardized tests may be given that measure: Intelligence—IQ tests measure a person’s ability to do things such as think abstractly, learn, and solve problems. A child may have intellectual disability if IQ test results are 70 or below.
Adaptive behavior—These are skills needed to function in everyday life, including:
Conceptual skills like reading and writingSocial skills like responsibility and self-esteemPractical skills like the ability to eat, use the bathroom, and get dressed
Children with intellectual disability have a higher risk for other disabilities such as
hearing impairment, visual problems,
attention deficit hyperactivity disorder, or orthopaedic conditions. Additional testing may be needed to check for other conditions.
Talk with your doctor about the best treatment plan for your child. Treatment is most helpful if it begins as early as possible. Treatment includes: Early intervention programming for infants and toddlers up to age 3Family counselingHuman development training, including emotional skills and hand-eye coordinationSpecial education programsLife skills training, such as preparing food and bathingJob coachingSocial opportunitiesHousing services
To help reduce your child’s chance of becoming intellectually disabled, take the following steps:
If you smoke,
talk to your doctor about ways to
Don’t drink alcohol or use drugs.
healthful diet—one that is low in saturated fat and rich in whole grains, fruits, and vegetables.
to your diet.
See your doctor regularly.
Have your newborn screened for conditions that may produce intellectual disability.
Have your child properly
Schedule regular visits to the pediatrician.Use child safety seats and bicycle helmets.Remove lead-based paint from your home. Have your child tested for lead levels in the blood.Keep poisonous household products out of reach.
Aspirin is not recommended for children or teens with a current or
recent viral infection. This is because of the risk of
syndrome, which can cause neurological problems. Ask your doctor which medications are safe for your child.
Causes and prevention of intellectual disabilities. The Arc website. Available at:
http://www.thearc.org/page.aspx?pid=2453. Updated March 1, 2011. Accessed November 18, 2015.
Daily D, Ardinger H, et al. Identification and evaluation of mental retardation.
Am Fam Physician. 2000;61(4):1059-1067.
Facts about intellectual disability. The Centers for Disease Control and Prevention website. Available at:
http://www.cdc.gov/ncbddd/actearly/pdf/parents_pdfs/IntellectualDisability.pdf. Accessed November 18, 2015.
Questions and answers about persons with intellectual disabilities in the workplace. US Equal Employment Opportunities Commission website. Available at:
http://www.eeoc.gov/laws/types/intellectual_disabilities.cfm. Accessed November 18, 2015.
Last reviewed November 2015 by Rimas Lukas, MD
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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