The prevalence of self-harm in ALSPAC is higher than that reported in the only other community-based study in England of similar size (13.2%) [4]. This may be partially explained by a number of methodological differences. Our sample was approximately one year older, and we had a higher proportion of girls (58.9% compared to 42.7% [7]), although this has been adjusted for in the imputation models, with little change to prevalence. Further, we used the term ‘hurt yourself on purpose’ – to remain consistent with questions asked of the ALSPAC sample aged 11 during clinic interviews - whereas Hawton et al. used ‘harm yourself’ which may have implied more serious self-harm and led to inclusion of fewer episodes. The earlier study collected data through schools which may have led to greater concerns about confidentiality and higher levels of under reporting, and also to an underestimation of prevalence due to absent pupils [4]. However, the increase in prevalence may also reflect a genuine rise in self-harm rates over time as the data were collected approximately eight years apart. There is some evidence
