The present study aims at replicating earlier findings regarding the link between childhood trauma and young adults' health risk behaviours and extends previous work by examining potential moderating effects of demographic and trait characteristics. Specifically, the current study enables to disentangle individual differences in response to trauma and separate the effect of trauma on health risk behaviours from possible confounders known to be associated with health risk behaviours. Data were used from a large British sample of young adults (N = 236,755, age 18–35) who participated in an online survey. Young adults who had experienced the sudden death of a loved one, violence, or non-sexual abuse in childhood, scored higher on a range of health risk behaviours. There was a cumulative effect; the more traumatic events an individual experienced, the more health risk behaviours they reported. Some support was found for individual differences in health risk behaviour after trauma. All moderating effects were, however, very small. The findings confirm and extend prior work on childhood trauma and young adult outcomes by providing evidence for long-term correlates, and highlight the value of big data studies to increase our understanding of the subtle individual differences in adverse outcomes after trauma.