Identifying Individuals With Intellectual Disability Within a Population Study.

The picture vocabulary score may not be equivalent across cultures, and young people with reduced educational opportunities may score lower than those with better opportunities. Add Health had a limited range of variables available to assess intellectual and adaptive functioning. The method may miss some people with intellectual disability because 1,048 adolescents and young adults with a low picture vocabulary score but no adaptive limitation were excluded. Self-report may be difficult for young people with significant intellectual disability and may reflect reluctance to report disability. Learning disability and physical disability features can risk invalid intellectual disability classification if taken alone. ADL questions in Wave 1 were skipped unless extremity or physical limitation was reported, so adaptive limitations from intellectual disability alone may have been missed.

The authors report no conflicts of interest. The article metadata lists NIH extramural and non-U.S. government research support, but the text does not say the funder designed or wrote the study.

Do not treat the 441 adolescents and young adults as clinically diagnosed with intellectual disability. The method used proxy scores and reports to identify a research subsample, and the authors note the picture vocabulary test may not be equivalent across cultures or educational opportunities.