harmed without suicidal intent during the past year at age 21 years. Thirdly, we cannot rule out the possibility of reverse causation for associations with GCSE qualifications, as these school examinations are generally taken at age 16 years, when self harm was also measured, and the age at onset of self harm was not known. There is also the possibility of residual confounding, whereby associations may be accounted for by an additional unmeasured variable. A final limitation concerns the difficulty inherent in establishing suicidal intent accompanying an episode of self harm. In the present study, determination of suicidal intent was based on self report and may include bias; for example, adolescents may be ambivalent or fluctuate in their intent to die and reports may be influenced by current mood state or change over time. This may result in some individuals being classified as having self harmed with suicidal intent who did not truly intend to end their life. However, our approach is in line with previous research,15 where individuals are classified as having a history of suicidal self harm if they report any “non-zero” level of self reported suicidal intent.
