Multiple sclerosis (MS) is a chronic disease of the central nervous system. It is a progressive, neurodegenerative, incurable, autoimmune inflammatory disorder, characterised by deterioration of the myelin sheath, which causes a variety of symptoms including loss of motor, cognitive, affective, and sensory function. While MS is not classified as a terminal illness, people living with MS (PLwMS) have a shorter life expectancy compared to the general population. In addition, evidence has indicated PLwMS are at a greater risk of suicide compared to the general population. A better understanding of the relationship between MS and suicide can help to avoid this outcome through targeted intervention and development of preventative measures. This thesis aimed to establish possible risk factors for suicide amongst PLwMS and to better understand the psychological mechanisms that may contribute to the development of suicidal ideation and suicidal behaviours in this population. Part one of the portfolio presents a systematic review of factors associated with suicide in PLwMS. The findings of this review suggest there is a lack of studies consulting psychological theory and investigating psychological factors contributing to the development of suicidal ideation and behaviour amongst PLwMS. Part two presents an empirical paper that explored the experiences of PLwMS and their perspectives on death, dying, and suicide, using the Integrated-Motivational Volitional model of suicide as a conceptual guide to better understand what factors may contribute to the development of suicidal ideation and behaviour. The findings highlighted a particular trigger point for vulnerability to the development of suicidal ideation in participant’s ‘journey to diagnosis’. In addition, narratives suggest a role for illness perceptions in the pathways to suicide.