CDBC/BCAAN Research Bite: Originally emailed December 15, 2023
Understanding long-term stability of IQ scores is essential, especially when we are making decisions about diagnoses expected to be stable over time (into adulthood). Watkins et al., (2022) found that with an approximately 2 ½ year interval, only the VCI, VSI and FSIQ were stable enough for normative comparisons, while unusual differences between subtests or index scores were unlikely to be repeated at retest. Previous research has shown stability in IQ scores for those with intellectual disabilities (Whitaker et al., 2008). Eichelberger and colleagues (2023) showed that those with lower-end IQ scores (below 100) were less likely to be stable over time. This suggests we need to be particularly cautious about diagnosing intellectual developmental disorder in preschool children with “borderline” type profiles. There is also evidence that IQ scores are more dynamic in individuals with autism (Prigge et al., 2022).
References
Watkins, M. W., Canivez, G. L., Dombrowski, S. C., McGill, R. J., Pritchard, A. E., Holingue, C. B., & Jacobson, L. A. (2022). Long-term stability of Wechsler Intelligence Scale for Children-fifth edition scores in a clinical sample. Applied neuropsychology. Child, 11(3), 422–428.
https://doi.org/10.1080/21622965.2021.1875827
Whitaker, S. (2008). The Stability of IQ in People With Low Intellectual Ability : An Analysis of the Literature. Intellectual and Developmental Disabilities, 46(2), 120–128. http://eprints.hud.ac.uk/id/eprint/4283/1/stability_of_IQ_%282008%29.pdf
Eichelberger, D. A., Latal, B., Kakebeeke, T. H., Caflisch, J. A., Jenni, O. G., & Wehrle, F. M. (2023). The influence of preschool IQ on the individual-order stability of intelligence into adulthood. Acta Paediatrica, 112(10), 2161–2163. https://doi.org/10.1111/apa.16925
Prigge, M. B. D., Bigler, E. D., Lange, N., Morgan, J., Froehlich, A., Freeman, A., Kellett, K., Kane, K. L., King, C. K., Taylor, J., Dean, D. C., King, J. B., Anderson, J. S., Zielinski, B. A., Alexander, A. L., & Lainhart, J. E. (2022). Longitudinal Stability of Intellectual Functioning in Autism Spectrum Disorder: From Age 3 Through Mid-adulthood. Journal of Autism and Developmental Disorders, 52(10), 4490–4504. https://doi.org/10.1007/s10803-021-05227-x