An Overview of Intellectual Disability: Definition, Diagnosis, Classification, and Systems of Supports (12th ed.)

AAIDD recommends a correction of 0.3 points per year since test norms were collected to Full Scale IQ when diagnosing intellectual disability with aged norms.

“Current best practice guidelines recommend that in cases in which an IQ test with aged norms is used as part of a diagnosis of ID, a correction of the full-scale IQ score of 0.3 points per year since the test norms were collected is warranted”

The 1.2 IQ points per decade is lower than the 3 points per decade identified from meta-analyses and sanctioned by AAIDD for ID diagnosis.

“strikingly lower than the 3 points per decade identified from meta-analyses (Pietschnig and Voracek 2015; Trahan et al. 2014) and sanctioned as an adjustment to be made for Wechsler FSIQs in ID diagnosis by AAIDD (Schalock et al. 2021), especially in capital punishment court cases.”

The Flynn effect is incorporated into diagnostic criteria for intellectual disabilities by AAIDD and DSM-5-TR, and in capital punishment cases.

“The FE is incorporated into the diagnostic criteria for intellectual disabilities by the American Association on Intellectual and Developmental Disabilities (AAIDD), by DSM-5-TR, and in capital punishment cases.”

The AAIDD diagnostic manual and DSM-5-TR require examiners to take practice effects fully into account when diagnosing ID.

“Nonetheless, both the AAIDD diagnostic manual (Schalock et al. 2021) and DSM-5-TR (American Psychiatric Association 2022) make it imperative that examiners take practice effects fully into account when diagnosing ID.”