There was strong evidence of an association (p < 0.001) between self-harm and both gender and current negative mood (see Table 2). Females were at almost 3.5 times more likely to report self-harm than males and individuals with negative mood symptoms were more than 5 times greater risk. The risk of self-harm was also somewhat higher amongst among respondents whose mother scored 13+ on the EPDS five years earlier (OR = 1.48 [1.17, 1.86], p = 0.001), those whose mothers were of manual social class (OR = 1.46 [1.12, 1.90], p = 0.005) and those achieving grades A*-C in less than five GCSE/GNVQ exams (1.20 [1.03, 1.34], p = 0.025). Finally there was no strong evidence of an association between self-harm and either maternal education or the young person’s ethnicity. Comparison of these results showed good agreement across the two imputation samples considered and we were confident that the estimates were not being overly impacted by noise due to imputation of the outcome (see Additional file 3).
