Background: Suicide represents a substantial problem, with significant societal and personal impact. The identification of factors influencing suicide risk is an important step in preventing self-harming behaviour. In this article the authors explore whether emotional instability increases risk of suicide, beyond that of mood intensity.

Method: This article provides a summary of existing theory and indirect evidence in support of an association between emotional instability and suicidality. A systematic literature search (Embase, Medline, PsychInfo) was carried out on literature conducted up to October, 2011. Meta-analysis was used to assess the strength of the proposed association.

Results: The systematic search identified 20 journal articles meeting the inclusion criteria, including retrospective questionnaire design studies and research conducted across several time-points. Meta-analysis revealed a moderate association, which remained statistically significant even when only including studies conducted over multiple time-points. This effect was attenuated, but remained significant, when controlling for study selection bias.

Limitations: Retrospective questionnaire studies failed to adequately control for mood level. Little is still currently understood about the types of emotional instability (e.g., dysoria, anxiety) most associated with suicidality.

Conclusions: Future avenues of investigation include micro- to macro-longitudinal research and the differentiation of emotion subtypes and instability metrics. Momentary assessment techniques may help to detect subtle fluctuations in mood leading to more effective and immediate intervention. Psychosocial intervention strategies for treating unstable emotions are discussed. (C) 2012 Elsevier B.V. All rights reserved.