This research dissertation examines factors that may influence the subjective well-being of students. Students have been reported to show a greater level of stress and psychological distress than the general population (Roberts et al., 2000; Stewart-Brown et al., 2000). For example Bayran and Bilgel (2008), in a sample of University students, identified that 27.1% reported moderate depression, 47.1% reported anxiety, and 27.1% reported stress. The degree of psychological distress found in student populations has been identified as a cause for concern (Adlaf, Gliksman, Demers, & NewtonTaylor, 2001; Bewick, Gill, Mulhearn, Barkham, & Hill, 2008; Cotton, Dollard, & De Jonge, 2002; Jessop, Herberts, & Solomon, 2005; Monk, 1999; Rosal et al., 1997; Stewart-Brown et al., 2000). One such study by Chen, Wong, Ran and Gilson (2009), investigated the relationship between university stress and subjective well-being, and found a negative relationship between the two. Subjective wellbeing is an umbrella term used to describe the level of well-being people experience according to their subjective evaluations of their lives (Diener & Ryan, 2009). It is considered to be a dynamic state in which people appraise how fulfilled their lives are, through their interactions with their circumstances, activities and psychological resources (Aked, Marks, Cordon, & Thompson, 2009). This complex concept relates to optimal experience and functioning (Ryan & Deci, 2001). In the light of these findings, investigating what factors might promote and enhance the subjective well-being of students is an urgent priority. Boosting student subjective well-being may have a protective function which may in turn reduce psychological distress in these at-risk populations. This thesis will consider both the literature on the use of mindfulness based interventions (MBIs) in student populations and report the findings of an empirical study investigating two relevant aspects of cognitive functioning in a group of medical students- a student population at especial risk of increased levels of stress compared to other student groups. Chapter one is a systematic literature review which examines whether mindfulness based interventions (MBIs) can improve student subjective well-being. The specific question, and inclusion and exclusion criteria, of this literature review were designed to assess robust reliable evidence that used specific subjective well-being measures to investigate the effectiveness of MBI studies on student subjective well-being. The review only included randomised controlled trails (RCTs). The review recognised that student populations are reported to experience a higher degree of stress than the general population samples (see above) and that there is a large volume of research that has investigated mindfulness based therapies. However the majority of studies report changes in rates of psychopathology and extrapolate this to an impact on subjective well-being (Bränström, Kvillemo, Brandberg, & Moskowitz, 2010; Cusens, Duggan, Thorne, & Burch, 2010; Frank, Reibel, Broderick, Cantrell, & Metz, 2015; Kingston, Chadwick, Meron, & Skinner, 2007). Subjective well-being is not the same as nor equivalent to a reduction or absence of psychiatric symptoms (Bech, Olsen, Kjoller, & Rasmussen, 2003). Therefore the review included only studies that employed a specific subjective well-being measure to investigate the efficacy of MBIs in student populations. The review identified nine RCTs. The data from these studies were extracted, quality assessed and reviewed. The findings are discussed in detail and suggestions made for future research. This review found that although many of the studies reported findings in the same direction - an increase in the subjective well-being of female students, the quality of the studies was poor. Most studies recruited mainly female students and few reported treatment effect sizes. Mindfulness as a concept is not easily defined and there is no clear widely accepted definition. A recent article identified 33 different definitions extracted from a pool of 308 articles (Nilsson and Kazemi, 2016). For the purposes of this thesis several definitions will be provided to give a sense of the concept. Baer et al (2009, p191): "Mindfulness [. . .] is generally defined to include focusing one's attention in a non-judgmental or accepting way on the experience occurring in the present moment [and] can be contrasted with states of mind in which attention is focused elsewhere, including preoccupation with memories, fantasies, plans, or worries, and behaving automatically without awareness of one's actions." Rosch (2007, p.259): "A simple mental factor that can be present or absent in a moment of consciousness. It means to adhere, in that moment, to object of consciousness with a clear mental focus." Mindfulness has also been defined as the quality of conscious experience or awareness which comes about through intentionally attending to present moment experience in an accepting and nonjudgemental way (Kabat-Zinn, 2004). Through the process of maintaining this focused and intentional awareness a person practices through formal meditations and informal exercises, the ability to identify when their mind has wandered and learns to non-judgementally bring their attention back to the intended object (e.g. their breath). This process of identifying thoughts, disengaging from them and then focusing on a desired object may provide a form of training that aids in the process of disengaging from one cognitive process and increases another one. These processes are perseverative negative thinking (e.g. rumination and worry) and attention control (the ability to be aware of and choose to control attention) (Chambers, Lo, & Allen, 2008; Englert & Bertrams, 2015). Mindfulness meditation has been reported to be particularly effective at reducing repetitive and persistent thinking (Jain et al., 2007). In this way, mindfulness may help people disengage from perseverative thinking and increase their ability to control the focus of their attention. Chapter two is an empirical study examining whether these two processes - perseverative negative thinking and attention control - have an impact on the relationship between threatening experiences and subjective well-being (SWB). Research has identified that the greater the frequency and severity of threatening experiences, the lower the reported experience of SWB in the following months (Suh, Diener, & Fujita, 1996). This quantitative study investigated whether perseverative negative thinking and attention control mediate and moderate respectively the relationship between threatening life experiences and subjective well-being. The findings suggest firstly that the effect of threatening experiences (using the List of Threatening Experiences Scale (LTE)) (Brugha & Cragg, 1990) on subjective well-being (as measured by the Modified BBC Subjective Well-Being Scale (BBC-SWB) (Pontin, Schwannauer, Tai, & Kinderman, 2013) is partially mediated by perseverating negative thinking (Perseverative Thinking Questionnaire (PTQ)) (Ehring et al., 2011); and secondly that attention control (Attention Control Scale (ACS)) (Derryberry & Reed, 2002) moderates the relationship between threatening experiences and subjective well-being. These relationships imply that the effects of threatening experiences on subjective well-being could be decreased by reducing perseverative negative thinking and increasing attention control. Investigating whether interventions designed to modify these thinking processes can reduce the detrimental impact on subjective wellbeing from threatening experiences, could potentially benefit both students and wider populations.