Childhood trauma is experienced by a third of young people in the United Kingdom (UK) and is defined as the experience of traumatic, or negative, life events during childhood; including emotional abuse, emotional neglect, physical abuse, physical neglect, and sexual abuse. Importantly, childhood trauma is a key variable in the aetiology of poorer health outcomes, including suicidal behaviour. Of concern, suicidal behaviour, a term capturing both suicidal ideation and suicide attempts, is a major cause of death worldwide, responsible for 1.5% of all mortality, with an estimated 700,000 individuals that die each year by suicide. Moreover, childhood trauma has been implicated in increasing suicide risk, however, the specific pathways through which it influences suicidal behaviour remain unclear. Nonetheless, there is empirical research indicating a clear relationship between distal and proximal risk factors with suicidal behaviour: individuals with pre-existing vulnerabilities, such as childhood trauma and greater impulsive behaviours, are more likely to experience stressful life events and react to them with emotional and cognitive dysregulation which in turn is associated with greater suicidal ideation and suicide attempts.
There is a series of theoretical models mapping the pathways from childhood trauma to suicidal behaviour. Two dominant models being: 1) Lovallo’s model, postulating childhood trauma to be associated with reduced stress reactivity, altered cognitive abilities and greater impulsive behaviours which in turn contribute to greater risk of experiencing poorer health behaviours, and 2) the Integrated Motivational-Volitional (IMV) model of suicidal behaviour, proposing three distinct phases in the transition to suicide attempts, highlighting a series of psychological vulnerability factors such as defeat, entrapment, stress and impulsivity that contribute to an increased risk of suicidal ideation and later suicide attempts. Informed by these models, the primary aim of this thesis was to address the evidence gap in understanding how childhood trauma increases the risk of later suicidal behaviour, by examining the role of risk and protective factors and to improve understanding of the nature of these associations.
The current research found childhood trauma and suicide significantly predicted greater impulsivity, poorer executive functioning and greater self-reported stress in a large cross-sectional survey of adults in the UK (chapter 2; study 1). In a longitudinal analysis, individuals with a history of suicidal behaviour appeared to have experienced poorer executive functioning, greater impulsivity and COVID-related stress in the initial phase of the Coronavirus 2019 (COVID-19) pandemic (chapter 3; study 2). This evidence is corroborated by an ecological momentary assessment (EMA) study where childhood trauma was associated with greater daily stress and daily indicators of suicide risk. The research also uncovered key pathways whereby trauma had indirect effects on reasons for living, optimism, daily thoughts of suicide, defeat and entrapment through executive functioning, impulsivity, sleep quality and stress (chapter 4; study 3). Lastly, evidence was synthesised in a meta-analysis from 58 studies to assess the effectiveness of psychological interventions at improving cortisol levels, finding medium sized effects in positively influencing cortisol levels (chapter 5; study 4).
The findings from this thesis expand upon existing theoretical models and incorporate novel methodological approaches to highlight the complexity of childhood trauma and subsequent potential pathways which can lead to damaging impacts on stress-related vulnerability factors and poorer health outcomes. Greater understanding of pathways by which trauma may impact later health outcomes is essential for development of interventions. Future work is needed to elucidate the precise causal mechanisms between these factors and to determine effectiveness of interventions that can attenuate the relationship between childhood trauma and suicidal behaviour.
