Every year, approximately 800,000 people die by suicide, with an estimated 20 times this figure making a suicide attempt. Developing an understanding of variables associated with suicide risk is important in improving clinical intervention and contributing to prevention. This thesis aims to enhance understanding of suicide by exploring psychological factors associated with suicide ideation and behaviour, including attachment and emotion regulation. Paper one is a systematic review of quantitative empirical research findings, exploring the relationship between emotion dysregulation and suicide ideation and behaviour in adults. Nineteen papers were identified through a systematic search. Results indicated that there was a positive association between emotion dysregulation and suicide ideation and behaviour. However, this was not always present when controlling for other psychological variables. Studies were critically evaluated and a narrative description of findings was presented. Clinical implications and recommendations for future research were discussed. Paper two is an empirical study exploring the relationship between attachment insecurity and suicide ideation and behaviour. Emotion regulation was considered as a potential mediator and betrayal trauma as part of a moderated mediation model. Sixty-seven participants completed self-report questionnaires measuring adult attachment, emotion regulation, suicide ideation, betrayal trauma, depression and hopelessness. Avoidant attachment was associated with suicide ideation. Emotion regulation did not mediate the relationship between attachment insecurity and suicide ideation and behaviour. Findings were considered in light of limitations. Clinical implications and directions for future research were discussed. Paper three is a critical appraisal of papers one and two. Reflections on the research process were provided, including further discussion regarding implications, as well as evaluation and justification of key decisions.