Background Poor mental health is a risk factor for death by suicide, but not all individuals who die by suicide have poor mental health. Suicide itself is not a mental illness, but a behaviour, and the predictors for poor mental health and for suicide risk may vary. These associations are complex given the mediating effect of mental health on suicide risk. This study asks do self-reports of chronic poor mental health relate to subsequent suicide risk and do the social and demographic predictors of suicide and of poor mental health differ?

Methods Record linkage study utilising the Northern Ireland Mortality Study (NIMS), comprising census returns for the whole enumerated population (March 2011) and subsequently registered deaths (currently 2011–2014). The presence of chronic poor mental health was assessed by a Census question asking about “an emotional, psychological or mental health condition”. The outcome of interest was death by suicide.

Results Of the 1.22 million individuals aged 16–74 years enumerated in the 2011 Census, 7.5% identified as having chronic poor mental health. A total of 658 individuals completed suicide before December 2014, of which only 31% self-reported poor mental health. Cox regression models determined that individuals with poor mental health were 5 times more likely to die by suicide compared to those with no mental health problems (OR 5.59; 95% CI 4.72, 6.61). The cohort was stratified by mental health status; male gender was still a significant predictor of suicide risk in those who identified as having poor mental health (OR 2.75; 95% CI 2.03, 3.72). Middle age (35–44 years), poor physical health and high socio-economic status were also associated with increased risk of suicide in the poor mental health group but these associations failed to reach significance. Whereas in those individuals who did not identify as having chronic poor mental health the biggest predictors of suicide were male gender (OR 4.06; 95% CI 3.21, 5.13), never being married or separated/divorced (OR 1.94; 95% CI 1.48, 2.56 and OR 2.15; 95% CI 1.55, 2.99), physical illness (OR 1.87; 95% CI 1.25, 2.78), and low socio-economic status (OR 1.92; 95% CI 1.39, 2.65).

Discussion Relationship status, physical health and socio-economic position predict suicide risk in those with good mental health whereas male gender is the biggest predictor of suicide in those with poor mental health. Comparison work on the risk factors for poor mental health and suicide is underway along with further exploration of interactions to be presented at the conference.