Characteristics of Cognitive Development

Up to 80% of males with fragile X syndrome are described as cognitively delayed. In the older studies of males with fragile X, almost all of the boys and men were described as having moderate or severe mental retardation.  However, many of these studies were based upon institutionalized males. With increased awareness of fragile X, more persons who have the syndrome are being properly diagnosed, and 10-15% of the boys tested may have IQs in the borderline or mild mental retardation range.

Many boys, and some girls, are described as mentally retarded. Mental retardation is defined as a non progressive disorder evident during childhood, with disabilities in adapting to the environment, and a score on an IQ test below 70.  The average score on an IQ test is 100, with scores of 85-115 being seen as the average range. The borderline range is usually applied to those with scores of 70-84. Scores in the mentally retarded range may be in the mild range (55-69 IQ), moderate (40-54), severe (25-39) or profound (less than 25). Non progressive means that the disorder is not degenerative. Children with fragile X syndrome move forward, not backward, but at a slower pace and with a lower end result, than do normally developing children. Disabilities in adapting to the environment refer to delays in life skills, not just academics.

A number of girls and women with the full mutation are described as learning disabled. Having a specific learning disability (LD) means that overall intelligence is at least in the low average range, but that there are specific strengths and weaknesses in learning patterns that cause problems. Achievement in some areas is not at the level expected, based upon aptitude, or overall ability. Thus, girls who have difficulties in math or various spatial tasks may have good reading and overall language levels and average IQs. About 30% of girls with the full mutation score above 85 on an IQ test, with the other 70% mostly in the borderline or mild mental retardation range.

Persons may be called both mentally retarded and learning disabled, meaning that their overall IQ is lower than average, but that they have strengths and weaknesses on various skills.  Children and adults with fragile X syndrome often have these "up and down" patterns.

Cognition is also affected by such issues as attention deficit hyperactivity disorder (ADHD), seizure disorders, anxiety, speech and language disorders, sensory motor problems, and other issues that may impact both test taking and learning. Many children and adults with fragile X achieve more than would be expected based upon an IQ score.

What patterns of strengths and weaknesses in cognition are seen in boys with fragile X syndrome?

What patterns of strengths and weaknesses in cognition are seen in girls with fragile X syndrome?

What changes may occur in intelligence quotients (IQ) over time?

Gail Harris-Schmidt, Ph.D., CCC-SLP