According to the definition provided by the American Association for Intellectual and Developmental Disabilities (AAIDD), intellectual disability is characterized by significantly below-average intellectual functioning during the developmental period (from pregnancy to the age of 18), accompanied by deficits in adaptive behavior. Individuals with intellectual disabilities demonstrate significantly slower progress compared to their peers in areas such as academic learning, daily life skills, understanding of their environment, and the ability to adapt to their surroundings.

These deficits may include challenges in:

• Communication
• Self-care
• Home life
• Social skills
• Community adaptation
• Self-direction
• Health and safety
• Functional academic abilities
• Leisure and recreation
• Work-related skills

There is a significant difference among people with intellectual disabilities, ranging from mild, moderate, severe, to extremely severe. Even within the same type of intellectual disability, there can be varying degrees of difference, resulting in different levels of educational and care needs. According to statistical definitions, the abilities of persons with various levels of disabilities are as follows:

1. Mild: IQ scores are between 55 and 69 points, with a mental age of 7 to 11 years old. Social and communication skills can be developed during the preschool stage (0-5 years old). While sensory and motor skills may be slightly delayed, there is no significant difference compared to normal children at this age. However, differences become more noticeable as they grow older.

   At the school age (6-20 years old), individuals can learn skills up to the sixth-grade level by the age of 18-19 and can receive guidance to meet social expectations. In adulthood (21 years and above), they can develop social and vocational skills sufficient to sustain independent living. However, in the face of social or economic difficulties, they may require counseling and support.

2. Moderate: IQ scores are between 40 and 54, with a mental age of 6 to 7 years old. In the preschool stage (0 to 5 years old), individuals can speak or learn to communicate, though their social perception is limited. Motor development is generally typical, and self-care skills are relatively easy to learn.

   At school age (6-20 years old), they can acquire basic social and vocational skills. However, learning skills and knowledge beyond the second-grade level is challenging. They may also learn to travel independently to familiar places.

   In adulthood (21 years and older), they can support themselves in protected semi-skilled or unskilled workplaces. However, when faced with social or economic difficulties, counseling and support may be required.

3. Severe: IQ scores are between 25 and 39 points, with a mental age of 3 to 5 years old. During the preschool stage (0-5 years old), motor development is poor, spoken language and communication skills show minimal development, and self-care skills are difficult to acquire.

   At school age (6-20 years old), individuals can learn to communicate or speak to some extent. With systematic training, they may acquire basic hygiene habits.

   In adulthood (21 years and older), they can achieve partial self-reliance under full supervision and may develop limited but useful self-protection skills in controlled environments.

4. Extremely Severe: IQ scores are below 25, with a mental age of less than 3 years old. During the preschool stage (0-5 years old), intellectual development is significantly delayed, sensory and motor skills are poor, and constant care is required.

   At school age (6-20 years old), individuals may develop some basic motor skills, but their response to self-care training is very limited.

   In adulthood (21 years and older), they may develop a few motor or spoken language skills, or acquire limited self-care abilities. However, ongoing care and supervision remain essential.

The degree of intellectual disability varies from person to person, which means that individuals have different needs in terms of education, daily support, and work skills.

Causes

1. Congenital Organic Factors

Many cases are idiopathic. Known possible pathogenic factors include genetic inheritance, chromosomal variations (e.g., Down syndrome, Fragile X syndrome), pre- and post-natal metabolic issues (e.g., hypothyroidism, phenylketonuria), infectious diseases (e.g., maternal rubella infection and syphilis), abnormal head development (e.g., hydrocephalus, microcephaly), poisoning and allergic reactions (e.g., maternal alcoholism, drug abuse), complications during pregnancy (e.g., premature delivery), and accidents during the delivery process. All of these are considered congenital causes of intellectual disability.

2. Acquired Environmental Factors

Children in poor environments may suffer from malnutrition, which can impact their physical energy and motivation. Other contributing factors include viral infections (e.g., encephalitis, meningitis), trauma and physical injuries (e.g., hypoxia, car accidents), or delayed intellectual development caused by a lack of medical care and untreated physical, visual, or auditory disorders.

How to take care of patients with intellectual disability

• Children with intellectual disability will inevitably bring psychological disappointment and harm to their parents. From shock and denial to acceptance, it is often a painful and tormenting journey. Parents' bad adaptation will bring more negative effects to their children. Therefore, early detection and professional assistance can minimize possible damage. Appropriate emotional processing and educational counseling of parents can provide better acquired environment and reduce the negative effects caused by environmental factors. Appropriate special education should be offered to avoid learning setbacks and peer pressure that affect self-esteem development and opportunities to learn professional skills
• Mental retardation is often accompanied by emotional disorders, behavioral disturbances and other mental illnesses; especially more serious cases complicated by other mental illnesses are as high as 50%. However, the cognitive impairment with insufficient intelligence and poor speech expression often make their performance different from that of people with normal intelligence, which is difficult to diagnose. It is advisable for pediatric psychiatrists to make detailed diagnosis and treatment, provide appropriate drug therapy, family and school counseling, psychotherapy, functional rehabilitation treatment, and deal with the combined physiological abnormalities in coordination with different specialties in the medical system.

Notes

1. When children exhibit clinical characteristics of intellectual disability, a handbook for physical and mental disabilities should be issued to facilitate access to medical, educational, and social resources.
2. Caregivers are advised to utilize the optimal treatment window before the age of 6 for early detection and intervention. They should actively cooperate with treatment plans and continue to practice at home to enhance treatment efficacy.
3. Caregivers are encouraged to train the child’s individual and group adaptability based on their learning characteristics. For example, if the child’s performance in motor tasks is stronger than their speech ability, caregivers should reduce verbal demands and incorporate more hands-on assignments. Emphasis should be placed on learning through "demonstration and imitation."
4. Caregivers are advised to gradually improve their children’s self-care abilities and adherence to group norms to facilitate their future performance in school and employment.

Conclusion

Caring for children with intellectual disabilities requires the same treatment as for other children: appropriate physical care, proper nutrition, love, and healthy interpersonal relationships. Expectations should be aligned with their abilities, providing adequate but not excessive assistance. They also need respect and support from siblings, classmates, and society, as well as appropriate use of medical, welfare, and educational resources.