Introduction: Extensive theoretical evidence has emphasized the benefits of social support for health, by attenuating the negative effects of stress; however, the empirical research is characterised by inconsistent and contradictory findings. Though scholars have begun to incorporate attachment theory to account for individual differences among the effects of support on health, this literature is still in its infancy, and specific gaps are yet to be addressed. To address these gaps, firstly, this thesis builds on the support literature to focus on the source and quality of social relationships by examining variations in attachment bonds across different relationship figures (i.e., parents, peers, and partners). Secondly, it explores the impact of relationships on both psychological and physiological health, paying particular attention to cardiovascular reactivity (CVR); an area not examined in research integrating support and attachment. Thirdly, it incorporates methodological advancements in attachment research by including traditional, discrete, categorisations (i.e., anxious, avoidant, and secure styles) of attachment, and a continuous, multi-dimensional approach. Finally, it focuses on transitional stages of development where individuals may be particularly vulnerable to stress, and where changes in relationship networks are most likely to occur. Methods: Three empirical studies are reported. Using a nationally representative sample of 7525 13-year-olds, Study 1 examined the quality of adolescents’ relationships with their parents and their peers as potential mediators explaining the association between stressful life events (SLEs) and psychological well-being. To build on the source and quality of relationships in Study 2 (N = 138), and moving towards physiological health, the association between attachment bonds to key relationship figures (mother, father, partner and best friend) and CVR were examined, with social support explored as a mediator. Finally, to experimentally test the interaction between attachment and social support on CVR, Study 3 (N = 138) manipulated the provision of support across individuals with secure, anxious and avoidant attachment styles. In both Study 2 and 3, young adults were subject to a standardized stress testing protocol where cardiovascular indices (systolic and diastolic blood pressure (SBP; DBP) and heart rate (HR)) were continuously monitored. Results: Study 1 showed that the negative association between SLEs and the psychological well-being of adolescents is mediated by peer relationship quality, but only for girls (i.e., more SLEs were associated with poorer quality relationships with peers, which in turn, was linked to lower levels of psychological well-being). Results from Study 2 showed that insecure attachment bonds was associated with lower CVR, with perceived support mediating this association (i.e., insecure attachment was linked to lower levels of perceived social support, which in turn, was associated with lower CVR). Interestingly, for anxious attachment, this was only noted for mother, father and best friend relationships, and only father and partner relationships, for avoidant attachment. Finally, in Study 3, contrary to our expectations, results from a factorial ANOVA showed no significant interaction between support and attachment on any CVR parameter (SBP, DBP, HR) or any main effect of attachment, or support. Conclusion: This research sets a foundation for recognising attachment as a potential ‘driving force’ behind the perceptions of support, and provides a valuable insight into the effectiveness of support as a protective factor for health. While we cannot conclusively determine which attachment style may benefit from, or is damaged by support, we point to future directions integrating the attachment and social support literatures which can provide further insights into the effects of social relationships for health.</p
