BackgroundPrevious studies and reports have highlighted the effect of caregiving responsibilities on caregivers. However, the predominance of older caregivers and the exponential increased risk of death with age has led to the under-representation of young carers. This study aimed to investigate the association between caregiving and physical or mental health, and mortality risk among young carers compared with both their non-caregiving peers and older caregivers. MethodsThis was a census-based record linkage study of data on all residents enumerated in the 2011 Northern Ireland Census (providing self-reported assessment of chronic physical and mental health conditions) with subsequently registered mortality information until the end of 2015. The sample consisted of 433 328 individuals aged 5–24 years, with about 19 621 of the cohort (4·5%) reporting that they were providers of informal care. Logistic regression models adjusted for demography (age, sex, ethnicity), household (tenure, care availability), and area variables (urbanicity, deprivation). Cox regression further adjusted for physical and mental health. FindingsIntense caregiving was associated with worse physical health among caregivers aged 5–17 years (odds ratio 1·61, 95% CI 1·16–2·23), but better physical health among those aged 18 or older (0·86, 0·69–1·08). A positive and dose-response association was observed between caregiving status and mental ill-health, with the effect being more evident among 5–17 year-olds than 18–24 year-olds. There is sufficient evidence to suggest that young caregivers differ from older care givers in terms of mortality risk (p<0·0001). In contrast to the association at older ages, caregiving in younger people was associated with an increased mortality risk (adjusted hazard ratio 1·54, 95% CI 1·10–2·14). InterpretationThis population-based study shows that caregiving among young people, in contrast to their older peers, is associated with an increased mortality risk. A cross-sectional association with poor mental health is also demonstrated. FundingNone.