Postgraduate Trainee of Psychiatry
Silchar Medical College and Hospital
Mental retardation is a term that was once commonly used to describe someone who learns and develops more slowly than other kids. But it’s not used as much anymore because it hurts people’s feelings. Instead, you might hear terms like “intellectual disability” or “developmental delay.” But all these words mean basically the same thing. Someone who has this kind of problem will have trouble learning and functioning in everyday life. This person could be ten years old, but might not talk or write as well as a typical 10-year-old. He or she also is usually slower to learn other skills, like how to get dressed or how to act around other people. But having an intellectual disability doesn’t mean a person can’t learn. Ask anyone who knows and loves a person with an intellectual disability! Some kids with autism, Down syndrome, or cerebral palsy may be described as having an intellectual disability, yet they often have a great capacity to learn and become quite capable kids. Just like other health problems, an intellectual disability can be mild (smaller) or major (bigger). The bigger the disability the more trouble someone will have learning and becoming an independent person.
Mental retardation refers to substantial limitation in present functioning characterised by significant sub-average intellectual functioning existing concurrently with related impaired limitation in two or more of the following applicable skills areas: communication, healthcare, home living, social skills, community use, self direction, health and safety, functional, academic leisure and work, manifest before the age of 18 years.
Although mental retardation is classified as an axis II disorder in text revision of the fourth edition of the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders (DSM-IV-TR), it is not considered a mental illness as such, with its own unique signs and symptoms. It is a system of identifying groups of people who need social support and special educational services to carry out tasks of everyday living.
The causes of mental retardation can be grouped from most to least common as follows:
• Alterations in embryonic development, such as those caused by chromosomal abnormalities or fetal exposure to drugs or toxins;
• Environmental deprivation and other mental disorders, such as autism;
• Problems of pregnancy and the perinatal period, such as fetal malnutrition, hypoxia, infection, trauma, or prematurity;
• Hereditary abnormalities, such as inborn errors of metabolism or chromosomal aberrations;
• Medical conditions of infancy or childhood, such as central nervous system (CNS) infection or trauma, or lead poisoning.
Physical causes are evident in most cases of moderate-to-profound retardation. A disadvantaged environment is more likely in mild retardation.
The following ranges, based on Standard Scores of intelligence tests, reflect the categories of the American Association of Mental Retardation, the DSM-IV-TR, and the 10th Revision of the International Statistical Classification of Diseases and Related Health Problems (ICD-10):
Types Intelligence quotient (IQ)
Profound mental retardation Below 20
Severe mental retardation 20-34
Moderate mental retardation 35-49
Mild mental retardation 50-69
Borderline intellectual functioning 70-79
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