Mental Retardation: Diagnosis

Andrea Barkoukis, M.A., Natalie Staats Reiss, Ph.D., and Mark Dombeck, Ph.D.


If you believe your child might have symptoms of Mental Retardation, discuss your concerns with your pediatrician.  Ask for the name of a recommended child psychologist, if necessary, who can properly assess your child (this clinician should have expertise in testing children).  Assessment should include an evaluation of your child’s cognitive/intellectual and adaptive (every day) functioning, associated behavior and mood problems (if any exist), and an evaluation of home and school environments.

Clinicians use a variety of different assessment tools to determine whether a diagnosis of Mental Retardation is appropriate.  Specific test selection is determined by a particular clinician, however any tests utilized should measure a person’s intelligence levels as well as levels of adaptive functioning.

Weschsler-Intelligence Scale for Children (WISC-IV)

The WISC-IV is an intelligence test designed for use with children between 6 and 16 years of age.  The WISC consists of a combination of verbal (e.g., measuring language comprehension) and performance (e.g., assessing speed on problem solving tasks such as putting together puzzles or recreating patterns with blocks) tasks.  This test provides an IQ score (quotient), that allows a clinician to compare the child’s performance to other children his or her age.  An average IQ score is 100.  A different version of this test (the WPSSI) can be used with preschoolers.

Bayley Scales of Infant Development

The Bayley Scales of Infant Development are used to measure a child’s sensory and motor development. These scales measure various abilities such as sensation and perception, memory, learning, problem solving, abstract thinking, and motor movement (e.g., coordination of large and fine muscles in the hands and fingers).  Despite the test’s name, it is not only intended for infants; rather, it can be used to test children between 0 and 42 months, or roughly until age three and a half.

Vineland Adaptive Behavior Scales

The Vineland  is the most commonly used measure of adaptive, or everyday functioning.  The Vineland is a semi-structured interview, meaning that the clinician asks a caregiver a specified list of questions regarding various activities that their child may or may not be able to do.  The caregiver is then able to respond accordingly without having to “stick to” a list of example answers.  The Vineland measures Communication Skills (receptive, expressive, and written), Daily Living Skills (personal, domestic, and community), Socialization (interpersonal relationships, play and leisure time, coping skills), and Motor Skills (both gross and fine).

When diagnosing a child or adolescent with MR, it is important to be aware of the differences between the term “mental retardation” and “developmental delay”. A diagnosis of MR should only be made when both cognitive ability and every day functioning is significantly less than average. The term “developmental delay” indicates that children demonstrate difficulties with one or more adaptive functioning skills; however, they do not necessarily have significantly impaired cognitive functioning. In other words, although individuals with mental retardation are also affected by developmental delays, not all developmentally delayed individuals are mentally retarded.



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