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What is Intellectual Disability?

intellectual disability

Intellectual disability, also known as intellectual developmental disorder, is a complex condition of deficits in general mental abilities and limitations in adaptive functioning. This condition usually appears at a young age and is diagnosed through a doctor’s assessment and some standardized testing. Generally, more severe cases will become apparent earlier in life.  Parents and doctors usually first notice something is off when these people consistently lag behind their peers in meeting developmental milestones in early childhood.

People with intellectual disability struggle with intellectual functions including reasoning, practical problem-solving, abstract thinking, and judgment. People with intellectual disability typically score in the bottom 2-3% of the general population on intelligence tests. This translates to an IQ range of about 65-75. However, numerous factors influence test scores, including communication, language, motor skills, and sensory functioning. A full assessment often involves a broad examination of each individual’s abilities, which is crucial for academic and vocational planning.

People with intellectual disability also experience difficulties related to social judgment, risk assessment, self-management, and motivation in educational or work environments. Unfortunately, this social gullibility often makes people susceptible to being influenced by others, exploited, and victimized. People are also at increased risk for co-occurring mental disorders, including suicidal thoughts and attempts.

Causes and Risk Factors


The rate of intellectual disability in the general population is roughly 1%. It is roughly 50% more common in men than in women.

Genetic causes

Intellectual disability can be caused by both inherited genetic factors and new mutations that occur spontaneously. Some of the most well-known disorders include Down syndrome, Fragile X syndrome, Lesch-Nyhan syndrome, and Rett syndrome. Many of these disorders have additional notable characteristics, like specific facial features or personality aspects.

Problems in the womb

Numerous problems during pregnancy can disrupt development and potentially cause intellectual disability. These factors include infections like toxoplasmosis and rubella and exposure to teratogens (substances like alcohol, tobacco, and certain medications that interfere with fetal development). Specific medical conditions in the mother, such as hypothyroidism, can also cause problems. Additionally, problems during birth, including prolonged lack of oxygen during difficult deliveries may contribute to intellectual disability.

Acquired causes

Intellectual disability can also come from various causes during early childhood. Injuries or accidents leading to brain damage, toxic exposures to substances like lead and mercury, infections affecting the nervous system like measles or meningitis, and brain tumors can contribute to intellectual disability. Additionally, medical conditions like seizures and certain forms of epilepsy can lead to brain damage and intellectual disability.

Co-occurring disorders

Conditions like ADHD, depressive and bipolar disorders, anxiety disorders, and autism spectrum disorder often appear alongside intellectual disability. Communication disorders and specific learning disorders can also co-occur with intellectual disability.

Diagnosing Intellectual Disability

Diagnosing it

Intellectual disability is a disorder that affects the development of functioning in a wide variety of areas. These include physical, cognitive, social and general functioning. This diagnosis involves two overarching themes. People struggle in intellectual areas, like thinking, learning, and problem-solving. They have trouble with the abilities to acquire, process, store, and use information.

Secondly, people with this disorder have problems with many practical areas of life as well. This negatively affects their abilities to engage in daily activities like communication, social interactions, and independent living.

Different severities

The levels of severity can vary widely between different people with intellectual disability. Mild conceptual disability appears as slow progression as people are noticeably behind their peers. They don’t advance academically and struggle socially. As adults they can do the more concrete activities of daily life but need support from others for those that require more planning and complex thought.

On the most severe end of the spectrum, people need significant support in all areas of life. They have trouble with understanding complex language and may have motor and coordination impairments.

Treating Intellectual Disability

There is no cure or medical treatment for intellectual disability. However, there are a wide variety of therapies and supportive services that will help people throughout their lives. In fact, early and continuous intervention can significantly improve functioning and help individuals thrive throughout their lifetime.

Starting early with special education

Early intervention is critical to improving the quality of life for children with intellectual disabilities. Special education is a customized set of educational guidelines and classes that are designed to meet the unique needs of different students with disabilities, including intellectual disability, learning disabilities, autism, ADHD, speech and language impairments, and emotional or behavioral disorders.

A central part of this is special education that includes individualized education plans (IEPs) tailored to each child’s unique needs. They are legally binding documents that outline the educational goals and specific services a student with a disability will receive. IEPs involve consistent collaboration between parents, educators, and mental health professionals. Federal law ensures that special education and related services are provided free of charge to every child with a disability like intellectual disability.

Transitioning to adulthood

Growing out of school age and transitioning to adulthood is a challenging phase for people with intellectual disability. Transitions involve shifts in the expectations surrounding an individual’s cognitive and adaptive capabilities. They are leaving a time where, for years, much of their time was spent in an extremely structured environment in school.  They are transitioning to a life where they (and the people caring for them) have to create their own structure. This can be in the form of jobs, sports, volunteering, or day programs. This not only changes what they spend their time doing but also how they find meaning and enjoyment in their time and activities.

Specialized transition guidelines help them and their families navigate this stage. Vocational programs, such as job coaching and skill learning, help people develop essential work-related skills that enable them to success on the job. Additionally, day programs offer structured environments for these people to socialize with their peers and give their caregivers some respite time. This socialization is very important as this time is one of the best opportunities for people with intellectual disability to connect with people similar to them. Day programs also often involve therapy and other supportive services where people practice skills that help them in day-to-day life.

Social services

Case managers play a crucial role in coordinating the diverse services that people with intellectual disability need. They ensure that these people receive the proper care and support to function at their best. This includes finding housing for people able to live on their own and helping people manage their money, healthcare, and transportation. Case managers also help people with intellectual disability find jobs that fall within their range of abilities to function.  Performing a job, either with or without support, gives people with intellectual disability  meaning, purpose, and fulfillment.

Managing Intellectual Disability

Family support

Families are the cornerstone of support for individuals with intellectual disabilities. They offer love, understanding, and care that form the foundation of the person’s life. Additionally, they help coordinate resources and advocate for their loved ones, working to ensure that they have access to appropriate services and opportunities.

Assistance with daily living

Many individuals with intellectual disabilities require assistance with daily activities such as grooming, meal preparation, and transportation. Families often take on these care giving roles, ensuring their loved ones can lead fulfilling lives while addressing their unique needs.

Supportive services

People with intellectual disability have a wide array of functional areas that can be impaired. However, special services can help people adapt. These include psychological or psychiatric services, speech and language pathology, audiology services, therapeutic recreation, and adaptive equipment or assistive technology.

Family support

Families of people with intellectual disability spend much of their free time helping them function. While this is incredibly noble and driven by love, it does mean that families need frequent rests to recharge. Support groups and community organizations offer respite services that allow caregivers to take a break while ensuring their loved ones continue to receive care and support.

Types of Developmental Disorders

Wondering about a possible disorder but not sure? Let’s explore your symptoms.

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