Background Compared to other parts of the British Isles, until recently there has been little information on rates of self-harm in Northern Ireland.

Objectives To investigate the rates of self-harming among adolescents, help seeking behaviour among self-harmers, and risk factors associated with these behaviours in Northern Ireland.

Design Two large scale surveys based on the Northern Ireland adolescent population were undertaken that contained questions on self-harm: the 2006/07 Belfast Youth Development Study (BYDS), a school based longitudinal study of adolescents, and the 2008 Young Life and Times survey, a postal survey of 16-year olds using the Child Benefit Register to identify the target population. Both surveys included questions asked in the CASE (Child and Adolescent Self-harm in Europe) study. Logistic regression models were used to analyse the association of personal characteristics with the odds of reporting having self-harmed. We also assessed the association between these characteristics and help seeking behaviour for those participants who had self-harmed.

Setting/participants In total there were 3178 respondents. The 2249 (71%) BYDS respondents were 17 or 18 years of age at the time of the study. The 929 (29%) YLT respondents 16 years old when surveyed. Around 59% were female, 99% had used alcohol, 37% had used drugs, and 22% had mental health problems.

Results 333 (10.4%) respondents reported self-harm, with similar proportions in both surveys. Females were 84% more likely to self-harm than males (OR 2.31 95% CI 1.93 to 2.78), but were also 70% more likely to seek help before self-harming (OR 1.70 95% CI 1.12 to 2.57). Smoking, using illegal drugs, and poorer mental health were more likely to be associated with those reporting self-harm. People who reported having smoked (OR 3.41 95% CI 2.66 to 4.37) or having used illegal drugs (OR 2.40 95% CI 1.97 to 2.94) were more likely to self-harm than those who did not. Poor mental health was associated with a greater likelihood of seeking help before self-harming (OR 1.81 95% CI 1.11 to 2.93).

Conclusion The relative association of gender with self-harm was low compared to other countries. Males reported much higher relative rates of self-harm compared to other regions of the UK, suggesting there may be risk factors for poor adolescent mental health specific to Northern Ireland. Reasons for these differences should be further investigated.