Emotion regulation processes in adolescent non-suicidal self-injury (NSSI): the roles of cognitive reapprasal, expressive suppression, and rumination

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Poor emotion regulation has been implicated in the occurrence of non-suicidal self-injury (NSSI), yet how this affects adolescent self-injury is not well understood, particularly in light of changes in emotion regulation during adolescence. The set of three empirical studies reported in this thesis aimed broadly to examine the roles of three emotion regulation processes (cognitive reappraisal, expressive suppression and rumination) in NSSI among adolescents. Together, these studies investigated how the emotion regulation processes of interest were related to NSSI, and in particular, to its onset and on-going severity as assessed by frequency, duration and medical seriousness of methods used. Method: Data from 3,143 predominantly female high school students (aged 12-18 years), recruited from Australian secondary schools, were analysed. Of these, 555 indicated they had a history of NSSI. Mean age of onset ranged from 12-14 years, with most participants reporting they had engaged in NSSI in the twelve months preceding data collection. Reported frequency of NSSI ranged from one to 300 times. Cutting and hitting oneself were the most common forms of NSSI although a range of methods and multiple methods were reported. Results: Adolescents who engaged in NSSI were more likely, compared to their non-self-injuring peers, to use emotion regulation processes which tend to heighten negative emotional states (i.e. expressive suppression and rumination) rather than those which can potentially reduce these emotions (i.e. cognitive reappraisal). Nonsignificant differences in the trajectories of these processes across the study period suggest similar developmental patterns between groups. However, self-injurers were more likely to have experienced more adverse life events. Taken together, these findings suggest adolescents who self-injure are more vulnerable and less prepared to respond effectively to the emotional challenges they experience. This observation is especially pertinent in NSSI onset where acute life stressors increased risk of engaging in NSSI for the first time (but were not related to NSSI severity) and echoes the general consensus that adolescent self-injury is associated with deficits in emotion-focused coping and difficulties with emotion regulation when faced with adversity. A hypothesised model that specified the relationships between adverse life events, psychological distress and NSSI were each moderated by the emotion regulation processes of interest was only minimally supported. While this indicated direct effects were more pertinent, only cognitive reappraisal emerged as a significant predictor of future NSSI. Reappraisal was protective of first episode NSSI occurring 12-months from baseline but not at 24-months. Increasing use of cognitive reappraisal was also related to decreasing NSSI severity (i.e. frequency, duration, medical severity) over a two-year period. Findings on the contribution of reappraisal in NSSI onset and its escalation over time hint at the influence of developmental changes in these relationships. Conclusion: Results emphasised different processes are implicated in engaging in NSSI for the first time, and in the overall severity of the behaviour. Adolescents may engage in NSSI as a response to emotional distress, however behavioural contingencies are likely more relevant in the maintenance and escalation of the behaviour. In both instances, addressing adolescents’ appraisals of stressful situations and life events, including the meanings they attribute to them, is likely to be beneficial. Implications for interventions addressing adolescent NSSI across the spectrum of prevention and treatment are discussed.