Adolescent Self-Harm and Suicidal Ideation

Questions about self-harm and suicidal thoughts were included in a self-completion postal questionnaire, sent to study participants when they were aged 16 years (see Additional file 2: Appendix B for the full list of self-harm questions asked). Participants were asked “have you ever hurt yourself on purpose in any way (e.g. by taking an overdose of pills or by cutting yourself)?”, wording which was used in the Childhood Interview for DSM-IV Borderline Personality Disorder (CI-BDP) [17 ], asked during clinic interviews with the ALSPAC sample aged 11. Those who answered yes were asked further closed response questions regarding frequency (once, 2–5 times. 6–10 times, >10 times), what they did the last time they hurt themselves on purpose (4 response categories) and why they did it that time (6 response categories) - response options were a modified version of those in the CASE questionnaire [18 (link)]. Participants were also asked whether they sought medical help and how they felt following the most recent time, and whether they had ever seriously wanted to kill themselves when self-harming. The whole sample were then asked whether they had ever felt life was not worth living, wished they were dead and away from it all, thought of killing themselves, or made plans to kill themselves; questions which were drawn from a study of suicidal feelings in the USA [19 (link)].
Those who selected ‘other’ for what they did when they self-harmed and why they did it were invited to give further details (see Additional file 2: Appendix B). These free text responses were independently coded by JK and DG, based on the themes emerging from the data [20 ], for example ‘head butting a wall’ and ‘pulling hair’ were classified into the theme ‘self-battery’ for what was done, and ‘because I was grieving and it made me feel better’ was classified as ‘response to difficulty’ for why it was done. Where appropriate, themes arising from our data were classified using the categories from Hawton et al. in their coding of open responses [15 ]. Where more than one code applied, the response was given as many codes as needed. If the raters did not deem a described action to be self-harm then it was given a code of ‘not self-harm’. All cases that had received discrepant codes were examined and a consensus reached for each. Initial inter-rater agreement was 88% for ‘what they did’ and 72% for ‘why they did it’, but consensus was easily reached once the final coding frame was agreed. The coding frames and discrepant cases were then discussed with JE and GL, and a final coding frame and codes for each case agreed. All categories that emerged in our study had equivalents in Hawton et al’s study [15 ]; there were no discrepancies. In total nine out of 147 free text responses concerning method/reason for self-harm were excluded from the self-harm group following this process (this included six responses that referred to not eating).