Does Non-Suicidal Self-Injury Function Primarily as an Experientially Avoidant Behaviour within Aotearoa New Zealand?

Theoretical, empirical, and experiential attempts at disentangling the functions of Non-Suicidal Self-Injury (NSSI) have been driven by the desire to answer the complex question: Why do people engage in self-injurious behaviours? A recently developed behavioural model of NSSI—the Experiential Avoidance Model (EAM; Chapman, Gratz, & Brown, 2006)—proposes that self-injury functions primarily as a form of negatively reinforced, experiential avoidance and places particular emphasis on emotional avoidance. Experiential avoidance is conceptualised as a behavioural process whereby people are unwilling to tolerate distressing emotions, thoughts, memories, or physical sensations and engage in behaviours to change, avoid, or escape from these aversive, intrapersonal experiences (Hayes, Wilson, Gifford, Follette, & Strosahl, 1996). Although the results of international studies support the key assumptions of this model to varying degrees (Klonsky, 2007; Klonsky & Glenn, 2008; Nock & Prinstein, 2004), the EAM has never been empirically evaluated within Aotearoa New Zealand. To determine whether experiential avoidance is the primary function of NSSI for people living within Aotearoa New Zealand, I designed and conducted three studies. For my first study, I interviewed 24 people who had engaged in nonsuicidal self-injurious behaviours in the previous 12 months about the antecedents and consequences of their most recent episode of self-injury. The interviews were analysed using a framework based on behavioural principles, which I developed for the purpose of this research. This method of analysis, which I called Interpretative Functional Analysis, allowed me to identify, and then compare, the functions served by discrete self-injurious episodes. Results supported the EAM (Chapman et al., 2006) in that self-injury episodes functioned predominantly as attempts to avoid or escape from intense, negative emotional experiences. Cognitive avoidance, however, also played a significant role in the self-injury trajectory, which highlighted the importance of investigating unwanted thoughts in subsequent studies. The second study involved surveying 198 people across Aotearoa New Zealand who had self-injured in the previous 12 months to further test whether the key assumptions of the EAM (Chapman et al., 2006) apply to a New Zealand-based population. Quantitative findings supported the model and were consistent with extant international studies in that experientially avoidant, intrapersonal functions (i.e., affect regulation and self-punishment) were identified as primary to the reinforcement and maintenance of NSSI. Intrapersonal functions, in general, were more highly endorsed than interpersonal functions. Finally, both negative affect and cognitions decreased following episodes of self-injury, while joviality increased. The increase in positive emotions undermines the EAM's (Chapman et al., 2006) exclusive focus on negative reinforcement, suggesting that positive reinforcement also has an important role to play in the continued use of NSSI. Analyses of the open-ended, survey responses highlighted the impact of particular contextual factors (such as interpersonal conflict and community norms) on the incidence and maintenance of NSSI. Conducting a thematic analysis of the consequences of people's most recent episode of NSSI allowed me to identify two distinct themes within this data corpus. Specifically, through self-injury participants assumed two paradoxical roles, that of transgressor and helper. For my final study, I surveyed university students across two time-points (Time 1 N = 408, Time 2 N = 224) about their general intrapersonal experiences (i.e., emotions and thoughts) and dispositional coping styles (e.g., global experiential avoidance, thought suppression). Negative intrapersonal experiences and avoidant coping styles were found to vary as a function of NSSI history and recency. Negative automatic thoughts and guilt at Time 1 also predicted new episodes of self-injury at Time 2. Additionally, thought suppression, not global experiential avoidance, was identified as a partial mediator of Time 1 relationships between negative intrapersonal experiences and NSSI. To conclude, the findings from this thesis are situated within a global context, and implications for clinical practice and future research studies are discussed.