Intellectual Disability: Degrees, Characteristics, and Available Treatments

People with intellectual disabilities have varying degrees of impairment. In this article, we'll explain the main symptoms and available treatments.
Intellectual Disability: Degrees, Characteristics, and Available Treatments
Elena Sanz

Written and verified by the psychologist Elena Sanz.

Last update: 25 July, 2022

Many names have been used over time to describe intellectual disability. This is a neurodevelopmental disorder that manifests with below-average cognitive functioning. It also affects other areas, such as sociability and the ability to function in an environment.

There are different levels of intellectual disability. For this reason, what determines its real impact on a person’s life are the difficulties carrying out basic adaptive skills, such as reading, writing, organization, relating to others, and taking care of themselves on a day-to-day basis.

How professionals measure a person’s intellectual capacity

A child listening to music.
Deviations below the mean (IQ of 100) indicate an intellectual disability.

Intellectual ability is generally measured through standardized tests, such as the Wechsler Intelligence Scale for Children Fifth Edition (WISC-V). These tests generate a score that indicates a person’s IQ. In other words, the ratio of mental age to chronological (physical) age.

Experts estimate the population average to be around 100, meaning that two standard deviations below the mean (IQ below 70) indicate an intellectual disability.

However, although intellectual disability is present from birth or early childhood, many children don’t manifest obvious symptoms until preschool age. In this regard, prenatal and developmental screening tests pediatricians routinely perform help ensure an early diagnosis.

Other symptoms besides IQ characterize intellectual disability. These are the signs that can indicate an inappropriate child development:

  • Firstly, difficulties reaching major development milestones. For example, the child may take longer than others to sit up, crawl, or walk.
  • Language acquisition and verbal expression delays.
  • Thirdly, Memory problems
  • Inability to perceive the consequences of their actions.
  • Learning, logical thinking, and problem-solving difficulties.
  • Difficulty understanding social rules and relating to others.
  • Finally, inability to completely function independently on a day-to-day basis.

Main causes

Although intellectual disability has many possible causes, the exact origin of this condition is found in only about 25% of cases. The main factors include chromosomal abnormalities (Down syndrome, for example) and inherited disorders.

Problems during pregnancy, such as pre-eclampsia or maternal use of alcohol or drugs, can also cause it. Similarly, infections, maternal or infant malnutrition, severe head injuries, or severe emotional neglect of the baby can increase the risk.

Keep reading to learn more: A Mother’s Microbiota Impacts Fetal Brain Development

Levels of intellectual disability

As we mentioned above, this condition can manifest in several levels. Experts have established four levels of intellectual disability, according to the affected person’s IQ and autonomy:


Most people with intellectual disabilities are in this range. Their IQ scores are between 50 and 70.

Although their cognitive and learning abilities are somewhat limited, they usually manage to adapt to the educational system and engage in a professional activity. Most have appropriate social skills and only need occasional help to function in their environment.


With an IQ between 35 and 50, these people have greater cognitive difficulties, especially when it comes to processing complex concepts. They can train their skills and do supervised low-skilled jobs.

Similarly, they’re capable of establishing social relationships, even though their communication skills are limited. In fact, they can even travel alone in familiar places but could require help in social situations.


With an IQ between 20 and 35, people with severe intellectual disabilities often require constant supervision and support. Their language acquisition is delayed and limited.

They can learn to read certain words and understand simple social communication. In addition, they can do simple tasks with help and vigilance. However, they aren’t very independent.


Profound intellectual disability only accounts for 1-2% of cases. These people usually have severe cognitive, social, and practical difficulties and other associated disabilities. However, they can have relationships with people they know and navigate their everyday life, as long as they have a lot of support.

Available treatments

A child with Down syndrome playing the guitar.
Specialists create a tailored plan to help a person with an intellectual disability reach their full potential.

Treatment is mostly based on helping the affected person reach their full educational, social, and practical potential.
A multidisciplinary team of different professionals, including doctors, psychologists, speech therapists, and occupational therapists, create an individualized program. It’s based on both strengths and weaknesses and addresses the needs of both the patient and their family.

How to reduce the chance of intellectual disability

Prevention should begin even before pregnancy, with adequate prenatal care, including folic acid intake and appropriate vaccination. Pregnant women need to avoid malnutrition, alcohol and tobacco consumption, and exposure to toxic environmental agents.

Similarly, proper medical care during labor helps reduce the risk of complications. After birth, the baby should be properly cared for, meaning that their physical and emotional needs should be met. But you should know that it isn’t possible to eliminate the risk.

The importance of family and professional accompaniment

Intellectual disability is disabling not because of the person’s low IQ, but due to lack of support. For this reason, drugs, therapies, or curricular adaptations are important to help the patient develop and enjoy a better quality of life.

In addition, family support is essential so that these people can relate appropriately to their environment. It’s important to provide them with practical and functional tools that help them reach their full potential and for their family to support them as much as they can.

All cited sources were thoroughly reviewed by our team to ensure their quality, reliability, currency, and validity. The bibliography of this article was considered reliable and of academic or scientific accuracy.

  • Alonso, I. G. (2005). Concepto actual de discapacidad intelectual. Psychosocial intervention14(3), 255-276.
  • Ke, X., & Liu, J. (2017). Discapacidad intelectual. En Manual de Salud Mental Infantil y Adolescente de la IACAPAP, 1-28.
  • Giné, C. (2004). Servicios y calidad de vida para las personas con discapacidad intelectual. Siglo Cero35(2), 1-13.

This text is provided for informational purposes only and does not replace consultation with a professional. If in doubt, consult your specialist.