Mental retardation, now more commonly referred to as intellectual disability, is a neurodevelopmental condition characterized by significant limitations in both intellectual functioning and adaptive behavior. These limitations must be present before the age of 18.

Intellectual disability signifies markedly below average general intellectual capacity, accompanied by related deficits in adaptive behavior, which become apparent during the developmental period.

Individuals with intellectual disability exhibit lower than average mental abilities and struggle with skills essential for daily living. While learning is possible, they typically acquire new skills at a slower pace compared to their neurotypical peers.

Key Characteristics of Intellectual Disability:

People with intellectual disability demonstrate limitations in two primary areas:

• Intellectual Functioning (Intelligence Quotient – IQ):

  • This refers to an individual’s capacity for reasoning, learning, problem-solving, and decision-making.

  • IQ is assessed through standardized tests, with an average score of 100. An IQ score below 70 is a significant indicator of intellectual disability.

• Adaptive Behaviors:

  • These encompass the extent to which an individual can meet age and culturally expected standards of personal independence and social responsibility.

  • Adaptive behaviors include essential everyday skills such as effective communication, social interaction, and self-care abilities.

Classification of Intellectual Disability

Historically, intellectual disability was classified based on Intelligence Quotient (IQ) scores, which represent the ratio of Mental Age (MA) to Chronological Age (CA), multiplied by 100. Chronological age is based on birth date, while mental age is derived from intelligence tests. The classifications are:

• Mild Intellectual Disability

• Moderate Intellectual Disability

• Severe Intellectual Disability

• Profound Intellectual Disability

Levels of Intellectual Disability (and previous terms):

• Mild Intellectual Disability (Educable):

  • IQ Range: 50-69

  • Often undiagnosed until school age.

  • May exhibit slight delays in early development like talking, walking, and self-feeding.

  • Capable of learning practical and domestic skills, including basic reading and math.

  • Can achieve considerable independence in self-care activities like eating, dressing, and hygiene.

  • Able to develop social and vocational skills and may live independently.

• Moderate Intellectual Disability (Trainable):

  • IQ Range: 35-49

  • Show noticeable delays in speech and motor skill development from an early age.

  • Unlikely to attain significant academic proficiency, but can learn basic communication, health and safety routines, and simple practical skills.

  • Reading and mathematical abilities are typically very limited.

  • Adults require ongoing supervision and cannot live fully independently, but can perform simple tasks and navigate familiar environments independently.

• Severe Intellectual Disability (Dependent):

  • IQ Range: 20-34

  • Often diagnosed at or shortly after birth.

  • Exhibit significant delays in motor development and have minimal communication skills by preschool age.

  • With consistent training, can acquire basic self-help skills such as feeding and bathing.

  • May learn to walk and develop a rudimentary understanding of speech as they age.

  • Adults require substantial supervision to follow daily routines and need a protected living environment.

• Profound Intellectual Disability (Life Support):

  • IQ Range: Below 20

  • This is the least common and most severe form.

  • Diagnosis is typically made at birth and often associated with other significant medical conditions requiring intensive care.

  • Exhibit delays across all developmental domains.

  • Often immobile with limited comprehension, unable to perform self-care, and frequently have neurological and physical disabilities, as well as impairments in vision and hearing, and other associated conditions.

Etiology of Intellectual Disability

Intellectual disability is a multifaceted condition resulting from a combination of factors. In approximately 75% of cases, the exact cause remains unidentified.

• Genetic Factors:

  • Heredity: Increased risk if one or both parents have intellectual disability.

  • Chromosomal Abnormalities: Conditions such as Down syndrome, where individuals inherit an extra chromosome.

• Prenatal Factors (Problems During Pregnancy):

  • Maternal Infections: TORCH infections (Toxoplasmosis, Rubella, Cytomegalovirus, Syphilis, Herpes Simplex) during pregnancy.

  • Alcohol Exposure: Fetal Alcohol Syndrome (FAS) resulting from maternal alcohol consumption during pregnancy.

  • Placental Issues: Placental dysfunction such as pre-eclampsia (toxemia of pregnancy), placenta previa, and umbilical cord prolapse.

  • Substance Abuse: Maternal drug use, such as cocaine.

  • Maternal Malnutrition: Inadequate nutrition during pregnancy.

  • Radiation Exposure: Exposure to ionizing radiation during pregnancy.

• Perinatal Factors (Problems During Birth):

  • Premature birth

  • Very low birth weight

  • Instrumental deliveries (forceps, vacuum)

  • Prolonged labor

  • Kernicterus (severe jaundice)

  • Birth asphyxia (oxygen deprivation during birth)

• Postnatal Factors (Problems After Birth):

  • Heavy metal poisoning (lead, mercury)

  • Severe malnutrition in infancy/early childhood

  • Traumatic brain injuries from accidents

  • Infections of the central nervous system (meningitis, encephalitis)

  • Untreated hypothyroidism (cretinism)

  • Brain tumors

  • Epilepsy

• Environmental Factors:

  • Cultural deprivation

  • Low socioeconomic status

  • Inadequate or neglectful caregiving

  • Child abuse and neglect

Signs and Symptoms of Intellectual Disability

The presentation of intellectual disability is diverse and varies depending on the severity level. Common indicators include:

• IQ Score below 70

• Failure to achieve developmental milestones at expected ages.

• Delayed language development.

• Memory deficits.

  • Difficulty learning social norms and roles.

  • Challenges with problem-solving skills.

  • Reduced learning capacity or inability to meet academic demands.

  • Limited motor and communication abilities.

  • Potential visual and hearing impairments.

  • Increased prevalence of epilepsy.

  • Need for consistent supervision.

  • Increased likelihood of neurological disorders.

  • Some individuals may also experience co-occurring psychotic or behavioral disorders.

  • Difficulties with self-care skills.

Diagnosis of Intellectual Disability

Diagnosis involves a multi-faceted approach:

1. IQ Testing: Using standardized intelligence tests to calculate IQ (MA/CA x 100).

2. Developmental History: Gathering detailed history from parents or caregivers about developmental milestones.

3. Biochemical Tests: Screening for metabolic disorders.

4. Physical Examination: Comprehensive physical assessment.

5. Neurological Examination: Assessing neurological function.

6. Developmental Milestone Assessment: Evaluating progress against expected developmental norms.

7. Investigations:

   • Urine and blood tests for metabolic screening.

   • Cultures for biochemical analysis.

   • Amniocentesis for prenatal diagnosis of chromosomal disorders.

   • Chorionic villus sampling (CVS) for prenatal genetic testing.

   • Hearing and speech evaluations.

   • Neuroimaging: CT scan or MRI of the brain.

   • Thyroid function tests (if hypothyroidism/cretinism is suspected).

8. Radiological Studies: X-rays as indicated.

Management of Intellectual Disability

Care for individuals with intellectual disability is primarily community-based, with home care being the most common setting. Hospitalization or institutionalization is typically reserved for situations involving parental incapacity, severe behavioral issues, or significant stigma.

Management Goals:

1. Maximize Potential: To enable the individual to reach their highest possible level of functioning and independence.

2. Ensure Safety: To provide a safe and supportive environment.

Management strategies involve:

• Specialized Education and Training: Placement in specialized schools or institutions offering tailored education and training programs appropriate to their abilities.

• Therapeutic Interventions: Incorporating physical therapy, recreational therapy, and social activities into the treatment plan.

• Nurturing Environment: Providing love, attention, and consistent care.

• Communication Strategies: Utilizing written, verbal, and visual communication methods, as well as gestures and demonstrations, to enhance understanding and treatment adherence.

• Comprehensive Skill Development Programs: Implementing programs aimed at improving speech, language, cognitive, psychomotor, social, self-care, and vocational skills.

• Multidisciplinary Team Approach: Developing a comprehensive management plan involving special educators, speech and language therapists, behavioral therapists, occupational therapists, and community service providers.

• Psychiatric Comorbidity Management: Ongoing assessment and management of co-occurring psychiatric disorders like depression, bipolar disorder, and ADHD.

• Pharmacological Interventions: Neuroleptic medications, such as haloperidol, may be used for managing psychotic behaviors. Analgesics may be needed for pain management, particularly in severe cases.

• Family Therapy: Providing family therapy to assist parents in developing coping mechanisms and addressing feelings of guilt and anger.

• Early Intervention Programs: Implementing early intervention programs for children under 3 years of age with intellectual disability.

• Day Schooling: Providing day schooling to teach basic self-care and life skills, such as bathing and feeding.

• Vocational Training: Offering vocational training programs to enhance employability and independence.

Prevention of Intellectual Disability

Prevention strategies are crucial and span preconception, prenatal, perinatal, and postnatal periods:

• Preconception:

  • Genetic counseling for families with a history of intellectual disability.

  • Maternal rubella immunization prior to pregnancy.

  • Ensuring adequate maternal nutrition before conception.

  • Family planning to promote healthy pregnancies and spacing.

• During Gestation (Prenatal):

  • Maintaining adequate maternal nutrition throughout pregnancy.

  • Regular fetal monitoring during pregnancy.

  • Protecting the mother from infections.

  • Avoiding teratogenic substances like alcohol and minimizing radiation exposure.

• At Delivery (Perinatal):

  • Ensuring delivery takes place in a hospital setting with skilled birth attendants.

  • Performing Apgar scoring at 1 and 5 minutes after birth to assess newborn health.

  • Close monitoring of both mother and newborn in the immediate postpartum period.

• Childhood (Postnatal):

  • Improving general healthcare access and quality for children.

  • Ensuring adequate nutrition for infants and children.

  • Providing prompt and appropriate treatment for childhood infections.

  • Implementing comprehensive childhood immunization programs as per recommended schedules.