Issues concerning self-report data and population-based data sets involving people with intellectual disabilities.

Emerson et al. (2013) wrote a methods paper. They looked at three common data sources for people with intellectual disability.

The sources were self-report, proxy answers, and big public data sets. The team warned that each source has built-in flaws.

The paper does not give new numbers. It says you should doubt self-report and proxy data.

Always list the limits of your measures when you write reports.

Schmidt et al. (2010) and Spriggs et al. (2015) show the same worry. Staff and family usually rate quality of life lower than the adults with ID rate themselves.

Jackson et al. (2025) seems to disagree. Older adults with ID could report their psychotropic meds almost perfectly when checked against pharmacy records. The gap shrinks when the topic is clear and concrete.

Berástegui et al. (2021) adds that youth with ID and their proxies agree even less. The younger the person, the shakier the match.

You now have a rule of thumb. Use self-report for simple, factual questions like pill names. Use both self and proxy for fuzzy topics like feelings or life satisfaction. Always write the limits in your session note or assessment report so future readers know the score may be off.