An intellectual disability can be described as an impairment to cognitive functioning. Intellectual disabilities, which originate before age 18 and are the most common type of developmental disability, may be mild to severe and are characterized by limitations in intellectual functioning and adaptive behavior (social and practical skills).

A child diagnosed with an intellectual disability is likely to develop and learn at a slower pace than a child who does not have an intellectual disability, and it may take the child longer to learn language, self-care skills, and social skills. Children with an intellectual disability are often still able to learn and achieve some level of function, especially with the help and support of a trained professional.

Understanding Intellectual Disabilities

Between 1% and 3% of the population has some type of intellectual disability. An intellectual disability may be diagnosed if an individual demonstrates cognitive limitations (often determined by an IQ test score that falls between 70 and 75) and experiences limitations to adaptive behavior. Adaptive behavior can be described as the conceptual, social, and practical skills that are essential to daily life—following rules and obeying laws; having an understanding of time, money, and other number concepts; being able to care for oneself; being able to safely travel from one place to another; and so on. 

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Those who are diagnosed with this condition will typically experience some difficulty with general learning and may take longer to develop the skills necessary for everyday function. Although there may be some life skills that an individual with an intellectual disability may be unable to learn, individuals diagnosed with an intellectual disability are still often able to attend school, obtain an education, and learn how attend to their personal needs. General learning typically takes longer and requires more repetition, but many individuals are able to learn the life skills necessary to live independently, such as find and maintain employment. 

In the past, the term mental retardation was used widely to refer to this condition, but in 2010, President Obama signed Rosa's Law, a bill that required any instances of "mental retardation" to be gradually replaced with "intellectual disability" and "individual with an intellectual disability" in all federal policy. Many other agencies followed suit, changing their terminology in response to requests from advocacy organizations that rejected the term "mental retardation" for its negative connotations, potential to generate misunderstanding about an individual's particular condition, and general offensiveness. The term has now fallen out of general useBy 2013, the Social Security Administration had replaced the term in the Listing of Impairments with the term "intellectual disability." 

The fifth edition of the Diagnostic and Statistical Manual (2013) also reflected the updated terminology. In the DSM, intellectual disability, or intellectual developmental disorder, is described as a condition that is marked by deficits in intellectual and adaptive functioning, the onset of which occurs during the developmental period, or before age 18. 

Signs and Symptoms of Intellectual Disability 

A child who has an intellectual disability may reach certain milestones of development later than children who are not similarly affected. For example, a child may stand and walk later than other children of the same age, be unable to see the consequences of actions, lack curiosity, display infant-like behavior past the age of infancy, and have difficulty in school. 

A young girl and her mother smiling at each other

Other indicators of intellectual disability may include: 

  • Deficits in memory skills
  • Delays in oral language development
  • Delays in developing adaptive behaviors such as self-care or self-help
  • Difficulty learning social rules
  • Difficulty with problem-solving skills
  • A lack of social inhibitors

Potential Causes of Intellectual Disability

Not all causes of intellectual disability are known. In about 75% of all cases diagnosed, doctors are not able to find a specific reason for the disability. Some known causes include:

  • Lack of oxygen at birth, infections or other problems during labor and birth.
  • Fetal infection or fetal developmental issues.
  • Exposure to toxins such as lead, mercury, and drugs. Fetal alcohol syndrome, which results from intrauterine exposure to alcohol, can also cause intellectual disability. 
  • Diseases such as whooping cough, meningitis, and measles.
  • Chromosomal abnormalities. Down syndrome and fragile X syndrome both result from inherited abnormal genes. 
  • Iodine deficiency and malnutrition.
  • Trauma to the developing fetus.
  • Trauma sustained in infancy or childhood. 

Therapy and Support 

Individuals challenged with an intellectual disability often have a variety of options for help and support available to them. While intellectual disabilities cannot be cured and there are no specific medications to treat their effects, special education programs and training can begin assisting a child even early in life through early intervention programs. The first step, once a condition has been diagnosed and evaluated by a specialist, is typically an Individualized Family Services Plan (IFSP), which outlines the needs of the child and the services that child should receive.

Once the child reaches school age, an Individualized Education Plan (IEP) will be developed by school staff and the parents of the child. Special education programs and related services are available at no cost to every child who has a disability, and these programs are often able to help children access and develop their potential fully. Behavioral counseling may also be recommended in some cases. As a child grows older, age-specific adaptive skills are included in instruction, and IEPs generally begin to include information on transition planning by or before age 16. 

Research shows individuals who have an intellectual disability have a higher risk of mental health concerns, including depression and suicidal ideation. At least 33% of individuals with an intellectual disability also face some type of mental health challenge, but this estimate is thought to be a conservative one. Because some individuals with cognitive limitations may find it difficult to explain their emotions and experiences, it can be challenging for mental health care providers to identify and diagnosis conditions when they are present, and many professionals are unaware of the frequency of the comorbidity of these conditions. When these conditions are identified, however, counseling and some forms of therapy can often help. 

Intervention methods are typically tailored to the individual, and in some cases, small changes in lifestyle or care arrangements may lead to improvement. In others, more specialized health care, counseling, or therapy may be more effective. Psychotropic medications may also be prescribed in some cases. 

Other services that can be of benefit to people with intellectual disabilities include residential homes, day rehabilitation programs, and workshops that can help individuals obtain jobs and homes and connect with members of the community. Specific psychotherapeutic programs also provide a way for those challenged with intellectual disabilities to learn basic life skills and set and achieve life goals while learning to obtain independence.

The Americans with Disabilities Act protects all individuals with intellectual or other disabilities. This act prevents discrimination in employment and housing, requires reasonable accommodations from employers and educational institutions, and mandates that public facilities be made accessible to all individuals. 

Case Example

  • Martina, 32, has an intellectual disability that is believed to be the result of trauma before birth. Although she experiences some cognitive impairment, she has achieved a significant level of independence. She lives with a roommate and has a part-time job cleaning cages and feeding animals at the animal shelter. Martina's older sister checks in on her once a week, and Martina always reports that she is happy and "doing just fine." However, one week, her sister visits to find Martina has stopped showering, dressing herself, or going to work. Martina cannot explain to her sister why she has stopped doing these things, she simply says she did not "feel like it." Martina's sister encourages Martina to call her case worker, who helps Martina make an appointment with a therapist. In the therapy session, the therapist discovers Martina has recently found out that some of the animals at the shelter are put down and not adopted. She previously believed they were all being adopted, and her discovery has led her to experience significant sadness and a low mood. Martina breaks down into tears, telling the therapist and her sister (who is present for the session at Martina's request) she does not want the animals to go away anymore. The therapist asks Martina whether she might like to try working at another type of job, and Martina agrees. Her sister helps her find a job at a grooming salon, where she can work with animals in a more positive environment, and Martina's mood improves once more. 


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