Signs & Symptoms of Intellectual Disabilities

Learn about the side effects, causes, signs and symptoms of intellectual disabilities. Millcreek of Magee Treatment Center offers the best residential treatment and home-based programs for children & adolescents struggling with intellectual disabilities.

Understanding Intellectual Disabilities

Learn more about intellectual disabilities

Intellectual disability (ID), previously known as mental retardation, is a term that is used when an individual has below-average intelligence or mental ability. Lack of skill necessary for day-to-day living are also commonly associated with this type of disorder. When it comes to intellectual disability, there are varying degrees ranging from mild to severe. While children and adolescents with intellectual disability are able to learn new skills, they do so at a slower rate than others. These children often have a hard time communicating their specific wants and needs, and usually struggle with taking care of themselves. In most cases, these individuals need assistance with speaking, walking, dressing, and eating.

Usually delays in motor functioning, language abilities, and social milestones can be identified within the first two years of a child’s life if he or she has more severe intellectual disabilities. However, mild intellectual disability may not be identifiable until the child reaches school-age, when challenges with academic learning become present. While it typically occurs during the developmental periods, it is also possible for intellectually disability to develop later as the result of illness or brain injury.

Intellectual disability is not a disease and cannot be cured, however early diagnosis and ongoing interventions can improve adaptive functioning throughout one’s childhood and into adulthood. With ongoing support and interventions, children with intellectual disability can learn to do many things.


Intellectual disabilities statistics

Researchers in the field believe that intellectual disabilities affect about 6.5 million people in the United States. Of those affected, about 85% have mild intellectual disability. The prevalence of severe intellectual disability is estimated by the American Psychiatric Association to be approximately 6 per 1,000 people.

Causes and Risk Factors

Causes and risk factors for intellectual disabilities

Anytime something occurs that interferes with a person’s normal brain development there is the risk for the development of intellectual disability. More specifically, intellectual disability can be caused by a problem that starts any time before the age of 18 as a result of injury, disease, or abnormality in the brain. However, the exact cause can only be determined about a third of the time. The most common causes and risk factors include:

Genetic:  Sometimes it is possible for intellectual disability to be caused by abnormal genes that have been inherited or from errors that occur when genes combine. Some examples of these genetic conditions include Down syndrome and fragile X syndrome.

Physical: The presence of some diseases and infections such as whooping cough, the measles, or meningitis can lead to intellectual disability. Additionally, intellectual disability can be caused by extreme malnutrition, not getting enough medical care, or exposure to poisons like lead or mercury.

Environmental: Problems during pregnancy that interfere with the fetal brain being able to develop properly can result in intellectual disability. Some of these interferences can include drug or alcohol use, maternal malnutrition, preeclampsia, and infections during pregnancy. Also, problems during childbirth, including extreme prematurity and oxygen deprivation increase the risk for intellectual disabilities. Finally, traumatic brain injuries, extreme malnutrition, and near-drowning have the potential to cause the onset of intellectual disabilities.

Risk Factors:

  • Malnutrition
  • Low parental IQ
  • Prenatal alcohol or drug exposure
  • Contraction of illnesses or infections while in utero
  • Deprivation of oxygen during birth
  • Brain injury

Signs and Symptoms

Signs and symptoms of intellectual disabilities

There are many different signs and symptoms of intellectual disability that can exist in children and will vary depending upon specific characteristics. These signs and symptoms may first become apparent in infancy or in some cases may not be noticeable until the child reaches school age. Some of the most common symptoms can include:

  • Learning and developing more slowly than other children same age
  • Rolling over, sitting up, crawling, or walking much later than developmentally appropriate
  • Difficulty communicating or socializing with others
  • Lower than average scores on IQ tests
  • Difficulties talking or talking late
  • Having problems remembering things
  • Inability to connect actions with consequences
  • Difficulty with problem-solving or logical thinking
  • Trouble learning in school
  • Inability to do everyday tasks like getting dressed or using the restroom without help

For those children with severe intellectual disabilities, additional health problems may exist including seizures, vision problems, hearing problems, and mental disorders. Additionally, the following categories are often used to describe each level of intellectual disability from mild to profound. This will give you a more specific idea of what this disorder looks like on each level.


  • IQ 50-70
  • Slower than normal in all areas
  • Can conform socially
  • Can acquire daily task skills
  • Integrated in society
  • No unusual physical signs
  • Can acquire practical skills
  • Reading and math skills up to grades 3-6


  • IQ 35-49
  • Can participate in simple activities and self-care
  • Can perform supervised tasks
  • Can travel alone to familiar places
  • Noticeable delays, particularly speech
  • May have unusual physical signs
  • Can learn simple communication
  • Can learn elementary health and safety skills


  • IQ 20-34
  • Significant delays in some areas; may walk late
  • May be trained in simple self-care
  • Need direction and supervision socially
  • Little or no communication skills, but some understanding of speech with some response
  • Can be taught daily routines and repetitive activities


  • IQ <20
  • Significant delays in all areas
  • May respond to regular physical and social activity
  • Not capable of self-care
  • Cognitive abnormalities present
  • Needs close supervision
  • Requires attendant care


The effects of intellectual disabilities

Every person who has intellectual disability is a unique individual and as such they are going to face different challenges. Some common effects include:

  • Requires special teaching and training to be able to learn
  • Needs support to solve everyday problems
  • Inability to establish interpersonal relationships
  • Difficulties finding and maintaining gainful employment
  • Difficulties functioning on a daily basis
  • Not being able to live on their own
  • Suicidal thoughts and behaviors

Co-Occurring Disorders

Intellectual disabilities and co-occurring disorders

There are a number of disorders that can co-occur in those who have intellectual disabilities. The most common of these disorders include:

  • Bipolar disorder
  • Autism spectrum disorders (ASDs)
  • Stereotypic movement disorder
  • Impulse control disorders
  • Major neurocognitive disorder
  • Attention-deficit/hyperactivity disorder (ADHD)
  • Depressive disorders
  • Anxiety disorders
  • Aggression
  • Self-injury