Suicidal behaviour (SB) is a major public health issue, which encompasses both suicide attempts and suicide completions. Suicide tragically accounts for up to almost one million deaths across the world every year. So far, suicide prediction models have focused on the so-called classic risk factors (male gender, depression, alcohol-related problems, and so on). However, suicide is, thankfully, a very rare outcome. As a result, these suicide predictive models have performed very poorly due to the high number of false positives to pick up suicides.However, a history previous suicide attempts has been consistently reported to be the strongest predictor of a future SB. Hence, suicide prevention strategies may prioritise high-risk groups such as those who reattempt/repeat suicide. More specifically, an alternative to the classic 'clinical' risk assessment approach, which is based on rating 'clinical' risk factors, may be to identify biomarkers, which may increase the specificity and sensitivity of the aforementioned suicide prediction models, thus helping clinicians to predict future SB.Within this context, this chapter provides an up-to-date literature review literature on biomarkers of repeated SB. Three main conclusions can be drawn from our review. First, there is a paucity of studies on the role of biomarkers in repeated suicide attempts to date. Second, the vast majority of these studies focused on two biomarkers, which have been also more comprehensively researched in SB, namely, the serotonin system abnormalities and the HPA axis dysfunction. Finally, 'it seems to be unlikely that there is a single biomarker of (repeated) SB'. Rather, future research should look at the complex dynamic interaction of a wide range of biological, clinical and neuropsychological contributing risk factors leading up to SB.
Keywords: Biomarker; Clinical factor; Suicide reattempt.