What is an Intellectual Disability?

Before diving deep into what is an intellectual disability, it is best to explain what it is not. Intellectual disabilities are not mental illnesses, like depression, there is no cure for intellectual disabilities and it is not contagious. An intellectual disability (ID) is a disability that limitations an individual’s cognitive functions. It affects many different elements and areas of an individual’s life. Here are some of the common questions people have concerning IDs.   

So if someone has a learning difficulty, do they have an intellectual disability?

Not every person who has learning difficulties has an intellectual disability (ID). For someone to be diagnosed with an intellectual disability, they must fulfill the following 3 requirements: 

  1. Have an IQ below 70, but some literature sets qualifying IQ scores between 70-75. 
  2. They have a significant limitation in two or more adaptive areas.
  3. The condition is discovered before the age of 18. 

Intellectual disabilities affect more than just learning, while learning difficulties mainly impact learning. People with learning difficulties usually have normal development in all other areas. A person with an ID often has developmental delays or difficulties that also impact their engagement in other areas of life. This is why therapy for people with ID is a combination of different kinds of activities to help the person participate in important areas of life. 

What causes an intellectual disability?

There is no set process that has to happen for someone to develop an intellectual disability. Intellectual disabilities can occur due to numerous factors that occur during the prenatal, perinatal, and postnatal stages of development. Factors such as genetics,  exposure to disease or toxin while in utero, complications during pregnancy and/or problems during birth are examples of prenatal and perinatal influences. Some examples of postnatal influences are severe head trauma, infection, stroke, and seizure disorders. It is important to know that it has been discovered that genetics does play a key factor in at least 45% of cases (Batshaw, Roizen, & Lotrecchiano, 2013).

If someone has an intellectual disability, is that the only disability that they have?

No. Intellectual disability only covers the cognitive part of an individual’s diagnosis. It is common to see an individual with an ID also have developmental, adaptive, and communication disabilities as well. 

Developmental disabilities are chronic, meaning that they are lifelong. They can range from larger physical issues such as cerebral palsy or epilepsy, or minor ones such as poor vision or hearing. Because these disabilities are often co-occurring, professionals and caregivers need to have an understanding of them.

Adaptive disabilities are the lack to perform basic life activities such as brushing teeth and showering. According to the DSM-5 (APA, 2013), these adaptive skill difficulties cross over the conceptual domain, social domain, practical domain. An individual with an ID may be delayed in reaching normal life milestones. This does not mean that the life milestone will not be achieved, rather that the child may achieve the milestone later than other children without an ID.

Communication skills use numerous different functions of the brain to operate. Cognitive functions such as memory, executive function, and processing speed are needed for effective communication. Communication uses the muscles in the mouth to articulate what the brain has processed in response to the world around someone. This is why it is common to find communication difficulties in individuals with an ID. Each individual with an ID will have different types of communication styles that work for them. Some may use normal speech languages, while others might use nonsymbolic (gestures, vocalization, etc.) and/or symbolic (signs, pictures, etc.). There is no set solution to improve a person’s communication style, but many do see therapy to strengthen these skills in regards to the way that the person receiving therapy communicates. 

Are there any common signs or symptoms?

Every intellectual disability expresses itself differently. There is one set sign or set of symptoms that present when a child has an intellectual disability. The signs do not always present at the same developmental stage as well. Often they go unnoticeable until the child reaches school age. Individuals with ID often have deficits in the following intellectual areas (APA 2013): Language development, reasoning, problem-solving, planning, abstract thinking, judgment, academic learning, learning from experiences to name a few. It is also common for them to have deficits in adaptive functions.

How does an Individual get diagnosed with an ID?

Comprehensive assessments and screenings are critical when diagnosing an individual. Trained clinicians and experts will collaboratively work together to give a parent a comprehensive assessment. ASHA, an organization for speech-language pathologists and audiologists does a great job of explaining the comprehensiveness of the assessment that an individual would undertake.  

What does a diagnosis of an ID mean for patients and family members?

Having an intellectual disability just means an individual is wired a little differently. They may use different communication methods and need help understanding what is occurring around them.  Just because a person with an ID may experience life a little differently than individuals without an ID, it does not mean they are less deserving of respect than anyone else. Individuals with intellectual disabilities still have personalities, feelings, and basic needs like any other person.

Just like any diagnosis, ID is just a description of what may or may not be a challenge a person will encounter. Not every diagnosis of an ID can and will be treated the same. The best thing a person can do to help a person with an ID develop an understanding of what a person needs and how you can be a source of support in their lives. This is important for therapists, family members, and other people who are a part of an individual’s life. 


American Psychiatric Association. (2013). Diagnostic and statistical manual of mental disorders (5th ed.). Washington, DC: Author.

Batshaw, M. L., Roizen, N. J., & Lotrecchiano, G. R. (2013). Children with disabilities: A medical primer (7th ed.). Baltimore, MD: Brookes. 

Christine Campbell

Christine is HappyNeuron Pro’s Marketing Specialist. People with intellectual disabilities have a special place in her heart. Growing up with a sibling with an autism diagnosis and intellectual disability influenced the way she views life. She is passionate about educating people about health and sharing cognitive tips.

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