An IQ below 70 is considered mildly mentally retarded.

1. Mild mental retardation

People with an IQ between 50 and 69 are considered mildly mentally retarded. They can reach the mental age of 9 to 12 years old in adulthood and can show symptoms in early childhood. Children of the same age have slow intellectual development and have learning difficulties after primary school.

Able to communicate in daily language, but have poor ability to understand and use language. Through vocational training, they can engage in simple unskilled work and have the ability to make a living and do housework.

2. Moderate mental retardation

People with IQs between 35 and 49 are moderately mentally retarded. After adulthood, they can reach the mental age of 6 to 9 years old. They can complete simple labor, but the efficiency is low. Low, poor quality. Through corresponding guidance and help, you can learn to take care of yourself and live a simple life.

3. Severe mental retardation

People with IQs between 20 and 34 are severely mentally retarded. They can reach the mental age of 3 to 6 years old after adulthood. They can only learn simple sentences, but cannot carry out tasks. Effective language communication, unable to learn, count, or work, often requires care from others in daily life, and has no ability for social behavior.

4. Extremely severely mentally retarded

People with intelligence below 20 are extremely mentally retarded. After adulthood, they can reach the mental age of less than 3 years old. They have no language ability at all, cannot avoid danger, and cannot Recognize loved ones and the surrounding environment, and express needs with primitive emotions. Unable to take care of himself, with urinary and fecal incontinence.

Extended information:

Causes of mental retardation

1. Perinatal injury

Severe malnutrition or illness in pregnant women, low Blood sugar, kernicterus, sepsis. Compression and injury inside and outside the uterus of the mother during pregnancy, ectopic placenta, injury during delivery, asphyxia, intracranial hemorrhage, premature infants, trauma in infancy and early childhood, radiation damage, etc. can all cause mental retardation.

2. Pathogenic factors during mother’s pregnancy

The 8-12 weeks in the early pregnancy is a critical period for the formation and development of the fetus’s brain in the mother’s body. Various physical and chemical poisons, public hazards Radiation, tobacco and alcohol, and viral infections are all causative factors that cause fetal brain dysplasia. Secondly, pregnant women have abdominal trauma, drug abuse, severe mental and psychological stimulation, and incomplete blood types of the fetus and mother, which can all cause obstacles to fetal development. Make children mentally retarded.

3. Genetic factors

For example, parents with mental retardation, parents with consanguineous marriages or parents with contagious abnormalities, parents with certain metabolic diseases, such as phenylketonuria, Congenital intellectual defects can be passed on from generation to generation, resulting in children with mental retardation. If one parent has mental retardation or both parents have mental retardation, the incidence of mental retardation among their children is as high as 77-96%.

4. Brain injury

Children’s intellectual disability caused by brain injury may be caused by brain damage (such as car accidents) or stimulation by external things. caused.

5. Incestuous marriage

Incestuous marriage is not only one of the causes of fetal malformations, stillbirths, and diseases, but it is also an important factor in children's mental retardation. Among the mentally retarded children analyzed, 22.22 were whose parents were consanguineous, while only 7.94 were whose parents were not consanguineous. Children born from incest marriages are three times more likely to be mentally retarded than those from non-consanguineous marriages.

Baidu Encyclopedia - Mentally Retarded