Aim: To add to knowledge about the health of the ‘hidden majority’ of adults with mild intellectual disabilities (ID) who do not use ID services.

Method: Secondary analysis of data from Understanding Society. We identified 299 participants aged 16 to 49 years (1.1% of the unweighted age-restricted sample) as having ID, and 22,927 as not having ID. Multivariate logistic regression was used to investigate between-group differences adjusting for potential confounding personal characteristics.

Results: British adults with ID have markedly poorer health than their non-disabled peers on the majority of indicators investigated including self-rated health, multiple morbidity, arthritis, cancer, diabetes, obesity, measured grip strength, measured lung function and polypharmacy. Adjusting for between-group differences in socio-economic disadvantage and neighbourhood quality had a marked impact on risk estimates with the number of statistically significant differences reducing from 13 to 8 and statistically significant attenuation of risk on three indicators.

Conclusions: The ‘hidden majority’ of adults with primarily mild ID have significantly poorer health than their non-disabled peers. This may, in part, reflect their increased risk of exposure to well established ‘social determinants’ of poorer health.