What Causes Intellectual Disability?

What Causes Intellectual Disability?

Intellectual disability, sometimes referred to as an intellectual developmental disorder, is a condition characterized by limitations in intellectual function and adaptive behavior. An intellectual disability involves problems with general mental abilities and will generally affect functioning. Intellectual functioning is one area that can be affected by an intellectual disability – this can include difficulties with learning, problem solving, and judgment. An intellectual disability can also affect adaptive functioning. This can include difficulties with activities of daily life, such as communication skills and independent living. The intellectual and adaptive deficits will generally begin early in a child’s developmental period. Intellectual disability affects 1% of the population, and an estimated 85% of those that are affected have what is classified as a mild intellectual disability. Intellectual disabilities are far from rare, yet understanding what causes intellectual developmental disorders can be complex. The Special Olympics Arizona team is exploring the various factors that can lead to intellectual disability, the conditions associated with it, and its prevalence.

What Causes Intellectual Disability?

An intellectual disability can be caused by a number of underlying causes, many of which can occur during different stages of a person’s life. These causes can be broadly categorized into pre-birth causes, causes that can happen during birth, and causes that can occur during early childhood.

Pre-Birth Causes

Pre-birth causes of an intellectual disability are those that happen during fetal development, and sometimes there may be events that occur during their fetal development or genetic factors that influence their development. Genetic factors that cause intellectual disabilities are numerous, including chromosomal abnormalities and single-gene mutations. Chromosomal abnormalities cause conditions like Down syndrome, which is caused by an extra chromosome and can lead to an intellectual disability. Single gene mutations, like Fragile X syndrome, can also result in an intellectual disability. Some inherited disorders, such as phenylketonuria, or PKU, in which the body is unable to properly break down and use protein, can result in intellectual disabilities if not treated early. This condition can cause buildup in the brain.

In addition to genetic factors, there are environmental factors that can cause intellectual disability during pre-birth. Maternal exposure to harmful substances like alcohol, tobacco, or certain drugs during pregnancy can harm fetal brain development, leading to intellectual disability. Infections like rubella or cytomegalovirus (CMV) can increase the risk of intellectual disability if contracted during pregnancy, and other issues such as malnutrition or inadequate maternal nutrition during pregnancy can negatively impact fetal brain development.

Causes That Can Happen During Birth

Birth complications can sometimes occur and result in an intellectual disability. Hypoxia is an insufficient oxygen supply to the baby’s brain during birth, which can happen for a number of reasons and can lead to intellectual disability. Extremely premature infants are at a higher risk of intellectual disability due to underdeveloped brain structures.

Causes That Can Happen During Early Childhood

During early childhood, while your child’s brain is still developing, there are a number of things that could occur and cause an intellectual disability. Severe head injuries, generally referred to as traumatic brain injuries or TBI, during early childhood can result in intellectual disability. If your child is exposed to lead, they may suffer from lead poisoning, which can damage a developing brain. This most commonly occurs due to exposure to lead based paint. Some infections can lead to brain damage and ultimately cause an intellectual disability. Severe cases of bacterial meningitis can lead to brain damage and intellectual disability in children. Encephalitis, or inflammation of the brain, due to infections like the herpes simplex virus can result in cognitive impairments and lead to intellectual disability. Other metabolic disorders may also cause intellectual disability. As mentioned earlier, PKU is an inherited disorder that, if left untreated, can cause intellectual disability due to the accumulation of phenylalanine in the brain.

What Conditions Can Cause or Occur Alongside Intellectual Disability?

Intellectual disability can often be associated with other medical conditions or syndromes, including:

• Autism Spectrum Disorder (ASD): Many individuals with ASD also have intellectual disabilities.
• Cerebral Palsy: Intellectual disability can co-occur with cerebral palsy, a condition characterized by motor impairments.
• Epilepsy: Some forms of epilepsy can be associated with intellectual disability.
• Attention-Deficit/Hyperactivity Disorder (ADHD): ADHD and intellectual disability can sometimes coexist.
• Behavioral and Emotional Disorders: Individuals with intellectual disabilities may also experience behavioral and emotional challenges.

Understanding these comorbid conditions is crucial for providing comprehensive care and support to individuals with intellectual disabilities.

Intellectual Disability Risk Factors

Several factors can increase the risk of intellectual disability, including your family history, maternal age, low birth weight, premature birth, and maternal health. A family history of intellectual disabilities or genetic conditions can raise the risk of having a child with an intellectual disability. Speaking with a genetic counselor can help you determine the risks. Babies born to older mothers may have a slightly higher risk of intellectual disability, as may babies that are born extremely prematurely or babies that are born with a low birth weight. Maternal health conditions like diabetes, hypertension, or infections during pregnancy can contribute to the risk.

How Common Is Intellectual Disability?

Intellectual disability is not uncommon, and its prevalence varies depending on the underlying causes. It is estimated that approximately 1-3% of the global population has some form of intellectual disability. The severity of intellectual disability can also vary, with some individuals experiencing mild impairments that may not be immediately noticeable, while others have more significant challenges that require ongoing support and care.

Can Intellectual Disability Be Prevented?

Preventing intellectual disability often involves addressing its underlying causes and risk factors. While there is no way to prevent some forms of intellectual disability, the risk of others can be lowered to some extent. Receiving early and regular prenatal care is crucial to monitoring the health of both the mother and the developing fetus. Avoiding harmful substances like alcohol, tobacco, and certain drugs during pregnancy is essential, and receiving the proper care may help lower the risks. Families with a history of genetic conditions can benefit from genetic counseling to understand the risks and make informed decisions.