| Summary: | Inconclusive previous research has hinted at the significance of social support in cancer-related outcomes. Some recent studies have also attempted to show the role of proangiogenic cytokines as the possible underlying mechanisms in this relationship between social support and cancer progression. This thesis aimed to further investigate these pathways by investigating the association between social support, loneliness and disease markers in colorectal cancer. This thesis systematically reviewed the longitudinal prospective findings (N =27) on the relationship between social support and cancer progression, and found that the evidence from methodologically sound studies (n = 16) was strong for breast cancer (67%) but not for other types of cancer (0%) and mixed cancers (50%). It also suggested that disease-related variables should be considered when assessing the role ofpsychosocial factors in cancer-related outcomes. Due to the issues associated with the self-reported assessment of social support and loneliness, this thesis aimed to use an implicit measure ofloneliness, in addition to the conventional explicit measures of social support and loneliness. Therefore, Study 1 adapted and validated an Implicit Association Test ofloneliness (IAT-L). This IAT-L showed low internal consistency, and weak construct and criterion-related validity in this study on 50 healthy volunteers (mean age = 24.1 years). In order to overcome these weaknesses, Study 2 used a modified IAT-L and investigated the relationship between implicit loneliness, social support, and cardiovascular reactivity to stress, to establish its predictive validity in another sample of23 healthy female volunteers (mean age =22.1 years). Results yielded satisfactory internal consistency ofthe modified tool (IAT-L (M), and implicit loneliness was found to be more strongly correlated with cardiovascular reactivity to stress than the explicit measures of social support and loneliness. Finally, Study 3 used the IAT-L (M) to investigate whether implicit loneliness was related with the in situ levels of four important biological markers (three cytokines and oxytocin) along with explicit measures of social support and loneliness in 51 colorectal cancer patients (mean age =68.3 years). Results showed that implicit loneliness explained significant variance in vascular endothelial growth factor (VEGF), extending previous findings with an implicit test. No significant relations were found for other biological markers. Social support and loneliness indices did not show any significant relationship with disease severity markers including stage and tumour size. Overall, this research attempted to make a unique contribution to the fields ofhealth psychology and psychoneuroimmunology. Implications are discussed in terms ofimplicit testing of loneliness with reference to physiological outcomes, and devising targeted psychosocial and immunotherapeutic interventions for cancer patients with low social support.
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