Intellectual disability (ID), also known as general learning disability and formerly mental retardation, is a generalized neurodevelopmental disorder characterized by significantly impaired intellectual and adaptive functioning. It is defined by an IQ under 70, in addition to deficits in two or more adaptive behaviors that affect everyday, general living.

Intellectual functions are defined under DSM-V as reasoning, problem‑solving, planning, abstract thinking, judgment, academic learning, and learning from instruction and experience, and practical understanding confirmed by both clinical assessment and standardized tests.

Adaptive behavior is defined in terms of conceptual, social, and practical skills involving tasks performed by people in their everyday lives.

Intellectual disability is subdivided into

  • Syndromic intellectual disability, in which intellectual deficits associated with other medical and behavioral signs and symptoms are present, and
  • Non-syndromic intellectual disability, in which intellectual deficits appear without other abnormalities. Down syndrome and fragile X syndrome are examples of syndromic intellectual disabilities.

Intellectual disability affects about 2 to 3% of the general population. Seventy-five to ninety percent of the affected people have mild intellectual disability. Non-syndromic, or idiopathic cases account for 30 to 50% of these cases. About a quarter of cases are caused by a genetic disorder, and about 5% of cases are inherited. Cases of unknown cause affect about 95 million people as of 2013.


Intellectual disability (ID) becomes apparent during childhood and involves deficits in mental abilities, social skills, and core activities of daily living (ADLs) when compared to same-aged peers. There often are no physical signs of mild forms of ID, although there may be characteristic physical traits when it is associated with a genetic disorder (e.g., Down syndrome).

The level of impairment ranges in severity for each person. Some of the early signs can include:

  • Delays in reaching, or failure to achieve milestones in motor skills development (sitting, crawling, walking)
  • Slowness learning to talk, or continued difficulties with speech and language skills after starting to talk
  • Difficulty with self-help and self-care skills (e.g., getting dressed, washing, and feeding themselves)
  • Poor planning or problem-solving abilities
  • Behavioral and social problems
  • Failure to grow intellectually, or continued infant childlike behavior
  • Problems keeping up in school
  • Failure to adapt or adjust to new situations
  • Difficulty understanding and following social rules

In early childhood, mild ID (IQ 50–69) may not be obvious or identified until children begin school.  Even when poor academic performance is recognized, it may take expert assessment to distinguish mild intellectual disability from specific learning disability or emotional/behavioral disorders. People with mild ID are capable of learning reading and mathematics skills to approximately the level of a typical child aged nine to twelve. They can learn self-care and practical skills, such as cooking or using the local mass transit system. As individuals with intellectual disability reach adulthood, many learn to live independently and maintain gainful employment. About 85% of persons with ID are likely to have mild ID.


Moderate ID (IQ 35–49) is nearly always apparent within the first years of life. Speech delays are particularly common signs of moderate ID. People with moderate intellectual disabilities need considerable supports in school, at home, and in the community in order to fully participate. While their academic potential is limited, they can learn simple health and safety skills and to participate in simple activities. As adults, they may live with their parents, in a supportive group home, or even semi-independently with significant supportive services to help them, for example, manage their finances. As adults, they may work in a sheltered workshop. About 10% of persons with ID are likely to have moderate ID.

 People with Severe ID (IQ 20–34), accounting for 3.5% of persons with ID, or Profound ID (IQ 19 or below), accounting for 1.5% of persons with ID, need more intensive support and supervision for their entire lives. They may learn some ADLs, but an intellectual disability is considered severe or profound when individuals are unable to independently care for themselves without ongoing significant assistance from a caregiver throughout adulthood. Individuals with profound ID are completely dependent on others for all ADLs and to maintain their physical health and safety. They may be able to learn to participate in some of these activities to a limited degree.


Among children, the cause of intellectual disability is unknown for one-third to one-half of cases. About 5% of cases are inherited. Genetic defects that cause intellectual disability, but are not inherited, can be caused by accidents or mutations in genetic development. The most common are:

Genetic conditions. The most prevalent genetic conditions include

  • Down syndrome,
  • Klinefelter syndrome,
  • Fragile X syndrome (common among boys),
  • neurofibromatosis,
  • congenital hypothyroidism,
  • Williams syndrome,
  • phenylketonuria (PKU), and
  • Prader–Willi syndrome.
  • Other genetic conditions include
  • Phelan-McDermid syndrome (22q13del),
  • Mowat–Wilson syndrome,
  • genetic ciliopathy, and
  • Siderius type X-linked intellectual disability

Problems during pregnancy. Intellectual disability can result when the fetus does not develop properly. A pregnant woman who drinks alcohol i.e., fetal alcohol spectrum disorder or gets an infection like rubella during pregnancy may also have a baby with an intellectual disability.

Problems at birth. If a baby has problems during labor and birth, such as not getting enough oxygen, they may have a developmental disability due to brain damage.

Exposure to certain types of disease or toxins. Diseases like whooping cough, measles, or meningitis can cause intellectual disability if medical care is delayed or inadequate. Exposure to poisons like lead or mercury may also affect mental ability.

Iodine deficiency, affecting approximately 2 billion people worldwide, is the leading preventable cause of intellectual disability in areas of the developing world where iodine deficiency is endemic. Iodine deficiency also causes goiter, an enlargement of the thyroid gland. More common than full-fledged congenital iodine deficiency syndrome (formerly cretinism), as intellectual disability caused by severe iodine deficiency is called, is mild impairment of intelligence.

Malnutrition is a common cause of reduced intelligence in parts of the world affected by famine, such as Ethiopia and nations struggling with extended periods of warfare that disrupt agriculture production and distribution.

Absence of the arcuate fasciculus.


Diagnostic and Statistical Manual of Mental Disorders (DSM-IV), three criteria must be met for a diagnosis of intellectual disability:

  • significant limitation in general mental abilities (intellectual functioning),
  • significant limitations in one or more areas of adaptive behavior across multiple environments (as measured by an adaptive behavior rating scale, i.e. communication, self-help skills, interpersonal skills, and more), and
  • evidence that the limitations became apparent in childhood or adolescence. In general, people with intellectual disabilities have an IQ below 70, but clinical discretion may be necessary for individuals who have a somewhat higher IQ but severe impairment in adaptive functioning.

It is formally diagnosed by an assessment of IQ and adaptive behavior. A third condition requiring onset during the developmental period is used to distinguish intellectual disability from other conditions, such as traumatic brain injuries and dementias (including Alzheimer's disease).


There are four broad areas of intervention that allow for active participation from caregivers, community members, clinicians, and of course, the individual(s) with an intellectual disability. These include psychosocial treatments, behavioral treatments, cognitive-behavioral treatments, and family-oriented strategies.

 Psychosocial treatments are intended primarily for children before and during the preschool years as this is the optimum time for intervention. This early intervention should include encouragement of exploration, mentoring in basic skills, celebration of developmental advances, guided rehearsal and extension of newly acquired skills, protection from harmful displays of disapproval, teasing, or punishment, and exposure to a rich and responsive language environment

Behavioral treatments core components include language and social skills acquisition. Typically, one-to-one training is offered in which a therapist uses a shaping procedure in combination with positive reinforcements to help the child pronounce syllables until words are completed. Sometimes involving pictures and visual aids, therapists aim at improving speech capacity so that short sentences about important daily tasks (e.g. bathroom use, eating, etc.) can be effectively communicated by the child. In a similar fashion, older children benefit from this type of training as they learn to sharpen their social skills such as sharing, taking turns, following instruction, and smiling. At the same time, a movement known as social inclusion attempts to increase valuable interactions between children with an intellectual disability and their non-disabled peers.

Cognitive-behavioral treatments, a combination of the previous two treatment types, involves a strategical-metastrategical learning technique that teaches children math, language, and other basic skills pertaining to memory and learning. The first goal of the training is to teach the child to be a strategical thinker through making cognitive connections and plans. Then, the therapist teaches the child to be metastrategical by teaching them to discriminate among different tasks and determine which plan or strategy suits each task.

Finally, family-oriented strategies delve into empowering the family with the skill set they need to support and encourage their child or children with an intellectual disability. In general, this includes teaching assertiveness skills or behavior management techniques as well as how to ask for help from neighbors, extended family, or day-care staff. As the child ages, parents are then taught how to approach topics such as housing/residential care, employment, and relationships. The ultimate goal for every intervention or technique is to give the child autonomy and a sense of independence using the acquired skills they have.


  • Learn the specifics about the child’s intellectual disability, including their limitations, strengths, needs, and other individual factors.
  • Connect with other parents who have children with intellectual disability.
  • Encourage activities that support independence and responsibility, such as chores, dressing, feeding, or bathing.
  • Seek support from community, medical, or other supportive services.
  • Be patient, kind, hopeful, and understanding.
  • Get involved with social, recreation, sports, or other activities.
  • Try to avoid negative thinking, projections, or words.
  • Work with early intervention services to develop an Individualized Family Services Plan that focuses on the child’s and family’s needs.
  • Contact local school systems or elementary schools to get access to special education and related services.
  • Practice social and communication skills.
  • Recognize that parents and caregivers can help improve the functioning of someone with intellectual disability.
  • Be as clear as possible, using demonstrations such as a picture or hands-on materials rather than verbal directions.
  • Break longer and new tasks into simpler steps.
  • Work with teachers and academic support workers to assess the child’s progress at school and at home.
  • Work with adolescent or child psychiatrists to set appropriate expectations for the individual.


Food plays an important role in development of human beings. Following food may be of help-

  • Omega-3 fatty acids- Deficiency in proper intake of omega- 3 fatty acids may lead to speech development delay in children. It can also affect speech quality. Include fish like salmon, flaxseeds, walnuts, soybeans, tofu etc for ample supply of omega -3 fatty acids.
  • Vitamin D- It is important for brain development in foetus. Hence during pregnancy consume more of fish, eggs, liver etc. Expose to early morning sunshine.
  • Folic Acid- Foods rich in folic acid or Vitamin B9 helps in prevention of nerve defects. Include leafy dark green vegetables and food fortified with folic acids like breads, wheat flour in your diet.
  • Vitamin E- This acts as antioxidants and kills free radicals which can damage our nerves resulting in speech problems. Include more fruits, vegetables, nuts, sunflower seeds, pumpkin seeds, etc in diet.
  • Include food containing zinc, phosphorus, magnesiumin diet for better overall development of child. Include dairy foods, fish, rice, nuts, chocolates, spinach, tomatoes, ginger, cumin, cloves, eggs, beans, peas, yogurt etc.
  • Avoid foods that cause allergies to you since allergic reactions are an important cause of hearing loss which can simultaneously contribute to speech disorders.
  • Avoid food preservatives, canned foods, additives in artificial foods, glutamates, excess coffee and alcohol.
  • Avoid smoking and alcohol during pregnancy.


Few of the homoeopathic listed below are helpful to prevent blindness or to treat intellectual disability with favourable result, if taken according to the totality of symptoms. They are:

BARYTA CARB: Specially indicated in infancy and old age. This remedy brings aid to scrofulous children, especially if they are backward mentally and physically, are dwarfish, do not grow and develop, have scrofulous ophthalmia, swollen abdomen, take cold easily, and then always have swollen tonsils. The child is timid, cowardly, and hides behind the furniture and keeps the hands over the face, peeping through the fingers. The child also have dullness of the mind. The child has trouble in concentrating.

AETHUSA CYNAPIUM: Idiotic children who cannot assimilate due to mental repletion. Idiocy may alternate with furor and irritability. Awkwardness. Attention deficit. Confused, cannot retain what he has been taught.

LYCOPODIUM CLAVATUM : Children having weak memory , and confused thoughts. The child spells or writes wrong words and syllables. The child cannot read what he writes. His speech is indistinct and stammers out the last word. He is unable to learn languages and often makes mistakes. Brain fag after influenza. The child does not like to take up new tasks or do new things. The child has trouble paying attention during a conversation.

MERCURIUS SOLUBILIS : Profound reading disorder and disturbed speech. Child has poor self confidence, memory weak, forgets everything. Loss of will power and slow in answering. Profuse salivation from mouth.

STRAMONIUM -Stramonium is used for mental retardation where the person calls things by wrong names.

CANNABIS SATIVA : Repeats words while writing. The child is very forgetful cannot finish the sentence. There is vanishing of thoughts and want of words. Ideas seems to stand still , he stares in front of him is absorbed in higher thoughts , but is unconscious of them. The child has trouble in recalling what he has just done.