Reward processing in self-harm

Self-harm is a complex yet common behaviour, which can be learned instrumentally through positive and negative reinforcement. It is thought to be processed in part via the reward system. Evidence for this comes mainly from pain research and studies combining neuroimaging with pain application in populations with self-harm. However, relatively little is understood about how reward processes may sustain self-harm. It is also equally important to understand whether biases in how rewards are processed contribute to difficulties managing self-harm, for example self-reported escalation, loss of control and relapse. To address these gaps in our understanding, this thesis has systematically reviewed the literature on reward mechanisms involved in self-harm, and reward processing biases that may be associated with self-harm. It has experimentally investigated whether processes underpinned by the reward system, such as incentive salience and approach biases, are involved in motivation for self-harm using a Dot Probe task and an Incentive Delay task. Finally, it has experimentally investigated whether biases processing non-salient rewards (as opposed to self-harm a potentially 'salient' reward) are present in young people with self-harm using an Incentive Delay task and Probabilistic Reversal Learning task, with a particular focus on behavioural motivation, and reward learning as related to compulsivity. Evidence for incentive salience and approach biases towards self-harm was limited in this thesis. However, other findings showed that avoidance of self-harm stimuli may be associated with ambivalence towards self-harm in young people. There was limited evidence to support the role of compulsivity in repetitive self-harm measured using a PRL task, or that individuals with self-harm exhibit differences in reward sensitivity as compared with controls. However, reward processing biases associated with comorbid depression and borderline personality disorder may contribute to self-harm in these individuals. Areas for future research and the implications of these results are discussed.