Relationship between age and IQ among fragile X males: a multicenter study

Area of Science:

• Neuroscience
• Genetics
• Psychology

Background:

• Recent studies suggest a longitudinal decline in IQ among males with fragile X syndrome.
• Concerns exist regarding the impact of test-retest factors, such as interval duration and initial scores, on IQ measurements in this population.
• Understanding the stability of IQ scores in fragile X males is crucial for accurate assessment and intervention planning.

Purpose of the Study:

• To investigate the generality of IQ score changes in a cohort of fragile X males.
• To determine the influence of specific factors (intertest interval, initial IQ) on IQ score variations.
• To examine the reliability and patterns of IQ changes over time in fragile X males.

Main Methods:

• Analysis of IQ retest scores from 60 males with fragile X syndrome across six centers.
• Utilized Stanford-Binet and Wechsler intelligence scales to ensure high test-retest reliability (r = 0.85).
• Employed z-score analysis to quantify IQ differences and multiple regression to identify predictive factors.

Main Results:

• Test-retest reliability was robust and comparable to non-fragile X individuals with intellectual disability.
• IQ score differences showed a mean of 1 SD below expected, with 18 subjects exhibiting significant decreases and 6 significant increases.
• Initial IQ score was a significant predictor of score differences, indicating a regression-to-the-mean effect, while intertest interval had minimal impact.

Conclusions:

• Factors influencing IQ retest scores appear to have a lesser effect in fragile X males than previously assumed.
• While some IQ decline is observed, it is not solely attributable to testing artifacts.
• The findings suggest potential dynamic neurological processes underlying IQ changes in fragile X syndrome, warranting further investigation.