Childhood Disorder: Mental Retardation

Mental Retardation is present when a child or adolescent has a level of intellectual functioning (generally referred to as IQ or IQ equivalent) that is measurably and significantly below average. In addition, a child with mental retardation demonstrates an inability to adapt to the demands of everyday functioning.

According to the DSM criteria for Mental Retardation (MR), children or adolescents under the age of 18 must have an IQ score that is no higher than 70 (as demonstrated by performance on a standard intelligence test described below), and they must have delays in at least two (out of a possible ten) areas of functioning. IQ scores are constructed in such a way that the average score is always 100 and the standard deviation is always 15. A score of 70 or below is a rare event, occurs only 2.5% of the time. Individuals with MR may have impairments in communication, self-care, home living, social/interpersonal, using community resources, self-direction, academic, work, leisure, health, and/or safety skills.

Functional impairment is a crucial piece of the Mental Retardation diagnosis. A child with an IQ below 70 who does not demonstrate difficulties in any of these aspects of everyday functioning would not be diagnosed as mentally retarded. So, clinically speaking, below average intelligence is different than mental retardation.

The DSM-IV-TR further divides the diagnosis of Mental Retardation into four levels: mild, moderate, severe, and profound. These levels are distinguished not only by varying degrees of intelligence, but also by differing abilities in adaptive functioning. The IQ scores that distinguish the varying levels of Mental Retardation are:

The DSM also has a category called "Mental Retardation, Severity Unspecified", for situations where there is strong evidence of Mental Retardation, but the person's intelligence is untestable by standard measurements (e.g., they are unable to sit through a traditional IQ test).

Mental Retardation is not actually an illness-rather, it is an intellectual and behavioral consequence of an illness or injury causing brain damage, or one that derails brain development. It can have genetic causes, or it can be caused by trauma sustained in an otherwise healthy child.