MENTAL RETARDATION
Mental retardation is a term for a pattern of persistently slow learning of basic motor and language skills ("milestones") during childhood, and a significantly below-normal global intellectual capacity as an adult. One common criterion for diagnosis of mental retardation is a tested intelligence quotient (IQ) of 70 or below and deficits in adaptive functioning.
People with mental retardation may be described as having developmental disabilities, global developmental delay, or learning difficulties.
Signs
There are many signs. For example, children with developmental disabilities may learn to sit up, to crawl, or to walk later than other children, or they may learn to talk later. Both adults and children with intellectual disabilities may also
• have trouble speaking
• find it hard to remember things
• have trouble understanding social rules
• have trouble discerning cause and effect
• have trouble solving problems
• have trouble thinking logically.
• persistence of infantile behaviour.

In early childhood mild disability (IQ 60–70) may not be obvious, and may not be diagnosed until children begin school. Even when poor academic performance is recognized, it may take expert assessment to distinguish mild mental disability from learning disability or behavior problems. As they become adults, many people can live independently and may be considered by others in their community as "slow" rather than retarded.
Moderate disability (IQ 50–60) is nearly always obvious within the first years of life. These people will encounter difficulty in school, at home, and in the community. In many cases they will need to join special, usually separate, classes in school, but they can still progress to become functioning members of society. 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.
Among people with intellectual disabilities, only about one in eight will score below 50 on IQ tests. A person with a more severe disability will need more intensive support and supervision his or her entire life.
The limitations of cognitive function will cause a child to learn and develop more slowly than a typical child. Children may take longer to learn to speak, walk, and take care of their personal needs such as dressing or eating. Learning will take them longer, require more repetition, and there may be some things they cannot learn. The extent of the limits of learning is a function of the severity of the disability.
Nevertheless, virtually every child is able to learn, develop, and grow to some extent.
Diagnosis
According to the latest edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV), there are three criteria before a person is considered to have a developmental disability: an IQ below 70, significant limitations in two or more areas of adaptive behavior (i.e., ability to function at age level in an ordinary environment), and evidence that the limitations became apparent in childhood.
It is formally diagnosed by professional assessment of intelligence and adaptive behavior.
IQ below 70
IQ tests were created as an attempt to measure a person's abilities in several areas, including language, numeracy and problem-solving. The average score is 100. People with a score below 75 will often, but not always, have difficulties with daily living skills. Since factors other than mental ability (depression, anxiety, etc.) can yield low IQ scores, it is important for the evaluator to rule them out prior to concluding that measured IQ is "significantly below average".

The following ranges, based on the Wechsler Adult Intelligence Scale (WAIS), are in standard use today:
Class IQ
Profound mental retardation Below 20
Severe mental retardation 20–34
Moderate mental retardation 35–49
Mild mental retardation 50–69
Borderline mental retardation 70–79
Significant limitations in two or more areas of adaptive behavior
Adaptive behavior, or adaptive functioning, refers to the skills needed to live independently (or at the minimally acceptable level for age). To assess adaptive behavior, professionals compare the functional abilities of a child to those of other children of similar age. To measure adaptive behavior, professionals use structured interviews, with which they systematically elicit information about the person's functioning in the community from someone who knows them well. There are many adaptive behavior scales, and accurate assessment of the quality of someone's adaptive behavior requires clinical judgment as well. Certain skills are important to adaptive behavior, such as:
• daily living skills, such as getting dressed, using the bathroom, and feeding oneself;
• communication skills, such as understanding what is said and being able to answer;
• social skills with peers, family members, spouses, adults, and others.
Evidence that the limitations became apparent in childhood
This third condition is used to distinguish it from dementing conditions such as Alzheimer's disease or is due to traumatic injuries that damaged the brain.
Causes
Down syndrome, fetal alcohol syndrome and Fragile X syndrome are the three most common inborn causes. However, doctors have found many other causes. The most common are:
• Genetic conditions. Sometimes disability is caused by abnormal genes inherited from parents, errors when genes combine, or other reasons. Examples of genetic conditions include Down syndrome, Fragile X syndrome, Phelan-McDermid syndrome (22q13del), Mowat-Wilson syndrome and phenylketonuria (PKU).
• Problems during pregnancy. Mental disability can result when the fetus does not develop inside the mother properly. For example, there may be a problem with the way the fetus's cells divide as it grows. A woman who drinks alcohol (see fetal alcohol syndrome) or gets an infection like rubella during pregnancy may also have a baby with mental disability.
• Problems at birth. If a baby has problems during labor and birth, such as not getting enough oxygen, he or she may have developmental disability due to brain damage.
• Health problems. Diseases like whooping cough, measles, or meningitis can cause mental disability. It can also be caused by not getting enough medical care, or by being exposed to poisons like lead or mercury.
• Iodine deficiency, affecting approximately 2 billion people worldwide, is the leading preventable cause of mental 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 cretinism, as retardation caused by severe iodine deficiency is called, is mild impairment of intelligence. Certain areas of the world due to natural deficiency and governmental inaction are severely affected. India is the most outstanding, with 500 million suffering from deficiency, 54 million from goiter, and 2 million from cretinism. Among other nations affected by iodine deficiency, China and Kazakhstan have begun taking action, whereas Russia has not.
• Malnutrition is a common cause of reduced intelligence in parts of the world affected by famine, such as Ethiopia.
• The use of forceps during birth can lead to mental retardation in an otherwise normal child. They can fracture the skull and cause brain damage.
• Institutionalisation at a young age can cause mental retardation in normal children.
• Sensory deprivation in the form of severe environmental restrictions (such as being locked in a basement or under a staircase), prolonged isolation, or severe atypical parent-child interactions.
Treatment and assistance
By most definitions mental retardation is more accurately considered a disability rather than a disease. MR can be distinguished in many ways from mental illness, such as schizophrenia or depression. Currently, there is no "cure" for an established disability, though with appropriate support and teaching, most individuals can learn to do many things.
There are thousands of agencies in the United States that provide assistance for people with developmental disabilities. They include state-run, for-profit, and non-profit, privately run agencies. Within one agency there could be departments that include fully staffed residential homes, day habilitation programs that approximate schools, workshops wherein people with disabilities can obtain jobs, programs that assist people with developmental disabilities in obtaining jobs in the community, programs that provide support for people with developmental disabilities who have their own apartments, programs that assist them with raising their children, and many more. The Burton Blatt Institute at Syracuse University works to advance the civic, economic, and social participation of people with disabilities. There are also many agencies and programs for parents of children with developmental disabilities.
Although there is no specific medication for "mental retardation", many people with developmental disabilities have further medical complications and may take several medications. Beyond that there are specific programs that people with developmental disabilities can take part in wherein they learn basic life skills. These "goals" may take a much longer amount of time for them to accomplish, but the ultimate goal is independence. This may be anything from independence in tooth brushing to an independent residence. People with developmental disabilities learn throughout their lives and can obtain many new skills even late in life with the help of their families, caregivers, clinicians and the people who coordinate the efforts of all of these people.
Traditional terms
Several traditional terms denoting varying degrees of mental deficiency long predate psychiatry, but have since been subject to the euphemism treadmill. In common usage they are simple forms of abuse. Their now-obsolete use as psychiatric technical definitions is of purely historical interest. They are often encountered in old documents such as books, academic papers, and census forms (for example, the British census of 1901 has a column heading including the terms imbecile and feeble-minded).
There have been some efforts made among mental health professionals to discourage use of these terms. Nevertheless their use persists. In addition to the terms below, the abbreviation retard or tard is still used as a generic insult, especially among children and teens. (The F-word has been added to "tard" to make fucktard, which is also an insult.) A BBC survey in 2003 ranked retard as the most offensive disability-related word, ahead of terms such as spastic (not considered offensive in America) and mong.
• Cretin is the oldest and probably comes from an old French word for Christian. The implication was that people with significant intellectual or developmental disabilities were "still human" (or "still Christian") and deserved to be treated with basic human dignity. This term has not been used in any serious or scientific endeavor since the middle of the 20th century and is now always considered a term of abuse: notably, in the 1964 movie Becket (film), King Henry II calls his son and heir a "cretin." "Cretinism" is also used as an obsolescent term to refer to the condition of congenital hypothyroidism, in which there is some degree of mental retardation.
• Idiot indicated the greatest degree of intellectual disability, where the mental age is two years or less, and the person cannot guard himself or herself against common physical dangers. The term was gradually replaced by the term profound mental retardation.
• Imbecile indicated an intellectual disability less extreme than idiocy and not necessarily inherited. It is now usually subdivided into two categories, known as severe mental retardation and moderate mental retardation.
• Moron was defined by the American Association for the Study of the Feeble-minded in 1910, following work by Henry H. Goddard, as the term for an adult with a mental age between eight and twelve; mild mental retardation is now the term for this condition..