Shame and non-suicidal self-injury: Conceptualisation and test of a novel developmental model

This thesis comprises an in-depth study into the role of shame, and shame-related functioning, in the development and maintenance of non-suicidal self-injury (NSSI) amongst adolescents and emerging adults. In the initial chapters of this thesis, I review the literature on NSSI, shame, and adolescent and emerging adult development and mental health outcomes through a developmental psychopathology approach, concluding with the presentation of a novel model linking shame to NSSI. Briefly, I posit that adverse experiences with caregivers in prior development, such as child maltreatment and invalidation, are linked to NSSI during adolescence and emerging adulthood, through an increased sensitivity and immediacy in experiencing shame (i.e. shame-proneness) and maladaptive styles of coping with shame. I also posit that these aspects of shame are responsible for the relationship between NSSI and various proximal risk factors of NSSI such as low body esteem, increased loneliness, and heightened psychological distress during these periods of development. I further explain how these aspects of shame are also functionally related to NSSI and how the model is consistent with both self-punishment and affect regulation pathways to NSSI.
   
   The two studies in this thesis were conceptualised to probe various aspects of this model. The aim of the first study was to test whether shame-proneness and an internalising manner of shame-coping could account for the relationships between adverse experiences with caregivers in prior development (i.e. child maltreatment, parental invalidation), proximal identity and interpersonal stressors (i.e. body esteem and loneliness respectively), heightened psychological distress and the likelihood and severity of engaging in NSSI amongst emerging adults. The aim of the second study was to test whether shame-proneness and an internalising manner of coping with shame could account for the long established relationships between parental invalidation, proximal psychological distress and the use of NSSI to regulate internal cognitive and affective states (i.e. self-targeted functions) amongst emerging adults.
   
   Cross-sectional data from both studies were obtained from a single sample of 748 emerging adults (age in years: M = 20.8, SD = 2.21, 71.7% female, NSSI history: n= 395) recruited throughout Australia who completed an online questionnaire assessing the constructs of interest across both studies. Structural equation modelling analyses findings in both studies suggested that the data from this sample was a good fit with the models tested in both studies. Specifically, the findings from the first study indicated that shame-proneness and internalising shame-coping styles significantly link adverse attachment experiences in earlier development to history of NSSI and NSSI severity in emerging adulthood. Further, current developmental identity and interpersonal stressors link shame-proneness to psychological distress, which is, in turn, linked to history and severity of NSSI through internalising shame-coping. In the second study, hypothesised indirect effects of parental invalidation and proximal psychological distress on NSSI through shame-proneness and internalised shame-coping were supported for five common self-targeting NSSI functions.
   
   Together, the findings from both studies established that the direct and indirect effects through shame on NSSI proposed in the thesis’ overarching theoretical model were present in the recruited sample, providing a case for further research to test the role of shame as a mediatory mechanism of NSSI amongst young people. The theory and research findings presented in this thesis contribute to a deeper developmental understanding of NSSI, highlight crucial pathways between adverse early caregiving experiences and NSSI, and illuminate important shame-based mechanisms that may be appropriate therapeutic targets for individuals at risk. Future research directions and clinical recommendations are discussed.