Non-suicidal self-injury (NSSI) is a dangerous and common behaviour, particularly among adolescents. Childhood trauma, insecure child-parent attachment, psychological distress, and impulsivity are some of the risk factors for NSSI that have been previously identified. However, the pathways from distal risk factors to NSSI and the ways in which these correlated risk factors interact with each other remains unclear. Identifying these pathways will provide valuable insight into the aetiology of NSSI and potentially highlight targets for treatment and intervention. In this dissertation I examine data from multiple large samples of young people, looking at multiple risk and protective factors together, and examining moderation and mediation pathways between risk factors. Using longitudinal data from 933 adolescents with no prior history of NSSI I demonstrated that the association between childhood family adversity before age 5 and new onset of NSSI between the ages of 14 and 17 was mediated by age 14 family functioning and possibly mental illness. Next, I validated a new measure of child perceptions of positive parenting, which I used to demonstrate the uni-directional prospective association between positive parenting and lower rates of NSSI amongst 1489 adolescents (ages 14-25). I then used this new measure of positive parenting to demonstrate that the prospective parenting-NSSI association was mediated by psychological distress. This is also one of the first prospective studies to show that impulsivity is independently predictive of NSSI. Using data I collected myself from a sample of 596 adolescents (ages 16-19) I validated a much needed measure of childhood trauma, with which I then demonstrated that the trauma-NSSI association was mediated by attachment and distress. Using data from this sample I was also able to reaffirm my previous findings that the attachment-NSSI association was mediated by psychological distress, and that impulsivity was uniquely associated with NSSI. Finally, using data from a sample of 559 Flemish 13 year-olds, I demonstrated that behavioural problems were more salient to NSSI than emotional problems among young adolescents, and that the attachment-NSSI association might be mediated by hyperactivity and conduct problems. Together, these findings reaffirm that childhood trauma, insecure child-parent attachment, psychological distress, and impulsivity are robust risk factors for NSSI and potential targets for treatment and intervention. Moreover, both distress and child-parent attachment may be viable targets for interventions aimed at attenuating the impact of early childhood trauma after it has occurred. Future research should use randomised controlled trails to test the efficacy of NSSI treatments aimed at these risk factors.

Adolescent self-harm is a growing epidemic in the United States with thousands of adolescent children being treated in hospitals every year. Despite awareness that self-harm impacts the family unit, little attention has been given to the full impact that self-harm has on parents. Due to this lack of knowledge, counselor educators and supervisors are not equipped to train counselors to work with parents of self-harming adolescent children leaving counselors feeling unprepared to work with parents. The purpose of this phenomenological study was to explore the lived experiences of parents who have self-harming adolescent children. Family systems theory was used to explore the concept that self-harm impacts the entire family system. The key research question for this study was: What are the lived experiences of parents of self-harming adolescent children? Six participants were interviewed using a semi structured design. The interviews were transcribed, coded, and analyzed using Pietkiweicz and Smith's 3 stage analysis process. Six main themes emerged from the data: (a) reaction to behavior, (b) change in self, (c) change in parenting style, (d) impact on relationships, (e) change in perception of mental health issues, and (f) support systems. The results of the study confirmed that parents have strong emotional responses to the self-harm and consequently adjusted their parenting styles. The outcomes of this study have the potential to impact positive social change by informing changes in counseling curriculum, training programs, and the level of support and services counselors provide when working with parents of a self-harming adolescent child.