Intellectual Disability Signs & Symptoms

Not everyone experiences intellectual disability disorder the same way. Understanding the signs, symptoms and effects of intellectual disability disorder is an important step toward recovery for your child.

Understanding Intellectual Disability

Learn about intellectual disability

Intellectual disability (ID) is a condition in which an individual experiences significant limitations to their intellectual functioning and within their ability to use every day social and practical skills. These cognitive and developmental deficits make it difficult for those with intellectual disability to excel academically, occupationally, or socially. More specifically, these children tend to meet developmental milestones slower than other children their own age. For example, they may start walking or talking later than others. However, it is not until school age that the signs and symptoms of intellectual disability become more noticeable as these children struggle to keep up with their peers.

While intellectual disability is a life-long condition, those individuals who get appropriate help and intervention at an early age are able to achieve a high quality of life. Despite their limitations, they are still capable of learning new skills and learning how to support themselves on a daily basis. It may just take them a little longer to master these skills.


Intellectual disability statistics

Multiple research studies have determined that intellectual disabilities affect about 6.5 million individuals throughout the United States. Of that population, approximately 85% have mild intellectual disability. Additionally, according to the American Psychiatric Association, severe intellectual disability is estimated to affect approximately six out of every 1,000 people.

Causes and Risk Factors

Causes and risk factors for intellectual disability

Researchers have determined that intellectual disability can be caused by a medical condition that interferes with the development of a person’s brain. However, while many causes for intellectual disability have been identified, in one third of individuals with intellectual disability the exact cause still remains unknown. Some of the most commonly accepted causes include:

Genetic: There are many genetic disorders that have been linked to the development of intellectual disability, which is the result of gene abnormalities that have been passed down from an individual’s parents. Additionally, any errors that occur when genes from each parents combine can also lead to the development of intellectual disability. One such gene disorder includes Fragile X syndrome.

Environmental: In addition to genetic factors, environmental factors have been known to play a large role in the development of an intellectual disability. Some of these environmental factors include things such as use of alcohol and/or drugs by the mother during pregnancy, low birth weight, lack of oxygen during birth, and the presence of a variety of childhood diseases such as whooping cough, or chicken pox.

Risk Factors:

  • Problems during pregnancy or birth
  • Exposure to extreme malnutrition, both prenatally and post-birth
  • Contacting certain illnesses or infections
  • Almost drowning
  • Poverty
  • Prenatal exposure to drugs and/or alcohol
  • Injuries to the head

Signs and Symptoms

Signs and symptoms of intellectual disability

The signs and symptoms of intellectual disability are going to vary based upon the level of disability that is present along with specific characteristics of each child. This wide variety of signs and symptoms may become apparent in infancy or may not present themselves until the child is school age. Examples of various signs and symptoms that may indicate the presence of intellectual disability can include:

  • Shows difficulty or delays in learning
  • Late to roll, sit up, or walk
  • Delayed speech
  • Difficulties problem-solving
  • Struggles with logical thinking
  • Memory difficulties
  • Has difficulty in mastering tasks such as potty-training, dressing oneself, and/or feeding oneself
  • Unable to connect actions with their consequences
  • Does not appear to understand or pick up on social cues
  • Presence of additional health problems such as motor handicaps, hearing and vision concerns, and seizures (in those with severe or profound ID)

Additionally, intellectual disability is typically grouped into four distinct categories depending upon severity of the symptoms, including mild, moderate, severe, and profound. The following includes descriptions of what can be expected at each level of severity:


  • IQ score between 50 and 70
  • Able to develop reading and math skills up to grades 3-6
  • Is able to conform socially, yet social interactions are typically immature when compared to peers
  • Has difficulties regulating emotions and behaviors in age-appropriate manners
  • Typically functions at an age-appropriate level in regards to self-care
  • Is able to acquire practical skills and daily task skills
  • Develops at a slower pace than is developmentally appropriate


  • IQ score between 35 and 49
  • Presence of unusual physical signs
  • Is capable of being taught simple self-care routines and can typically participate in them without assistance
  • Conceptual skills are markedly behind those of peers
  • Spoken language is primary social communication tool, but is much less complex than peers
  • Is capable of understanding elementary level health and safety skills


  • IQ score between 20 and 34
  • Attainment of conceptual skills is highly limited
  • The acquisition of skills requires long-term teaching, as well as ongoing, consistent support
  • Has little or no communication skills, however, is able to understand some speech and can provide some, however minimal responses
  • Typically requires support for all activities of daily living
  • Typically requires supervision at all times as they are not capable of making responsible decisions regarding the wellbeing of themselves or others


  • IQ score of less than 20
  • Presence of extreme cognitive abnormalities
  • Presence of motor impairments
  • Is dependent on others for all aspects of daily physical care, health, and safety
  • Conceptual skills are highly limited
  • Has extremely limited understanding of symbolic communication in speech or gesture
  • Presence of sensory and physical impairments


Effects of intellectual disability

With proper support and interventions these individuals will be able to live a happy and fulfilling life. However, each individual with intellectual disability is still going to face their own set of challenges.

  • Memory and attention problems
  • Needs support to solve daily problems
  • Difficulties interacting socially
  • Impaired or lowered self-esteem
  • Difficulties finding and maintain employment as adults
  • Being unable to live on one’s own due to required assistance and supervision
  • Presence of additional medical concerns
  • Suicidal thoughts and behaviors

Co-Occurring Disorders

Intellectual disability and co-occurring disorders

It is believed that children and adolescents who have an intellectual disability are 3 to 4 times more likely to have co-occurring mental health disorders. Some of the most commonly cited co-occurring disorders and conditions that exist alongside intellectual disability include:

  • Depressive disorders
  • Impulse control disorders
  • Attention-deficit/hyperactivity disorder
  • Autism spectrum disorder
  • Aggression
  • Self-harm
  • Mood disorders
  • Anxiety disorders

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– Former client