Psychiatry - Theses
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ItemA prospective study of the relationship between stress, coping and the onset of psychosis in a high risk group( 2005-06)The experience of stress and associated coping responses are often described as playing an important role in the onset of schizophrenia and other psychotic disorders. Despite widespread acceptance of this model, there is little empirical evidence to support such a relationship. This is partly due to a lack of well-designed prospective studies of the onset of psychotic disorders that incorporate different aspects of the stress and coping process. The relatively recent development of validated and reliable criteria for identifying young people at high-risk (UHR) of developing psychosis has enabled the process of onset of psychotic illnesses to be studied more closely than was previously possible. It has also opened the way to the development and evaluation of preventive interventions. This longitudinal study aimed to compare the experiences of stress and coping between a UHR cohort (N = 143) and a group of young people without mental health concerns (HC group, N = 32). In addition, the contribution of stress and coping in the development of acute psychosis in a subgroup of the UHR cohort (UHR-P, n = 18) was also investigated.
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ItemThe effects of catecholamine depletion and acute psychosocial stress on neurocognition( 2012)Extensive research has clearly established that neurocognition is negatively impacted by various stressors. While the extant research has focused on the effects of cortisol on declarative memory, little attention has been given to the role of the catecholamines in the deterioration of neurocognitive performance following psychosocial stress. Forty healthy male (n = 21) and female (n = 19) volunteers aged between 18-47 years who had been screened for eligibility participated in the study. Heart rate, blood pressure and salivary cortisol were measured at baseline, pre-stress, post stress (immediate) and after one hour of rest (post stress recovery). Neurocognitive assessment included immediate and delayed verbal recall, spatial learning and strategy, attention and working memory (spatial and non-spatial) at the same four phases. Participants randomly received an L-tyrosine and L-phenylalanine depleted (DEP) or a nutritionally balanced (BAL) amino acid drink in a randomised, double blind, placebo-controlled parallel group design 5 hrs before exposure to the Trier Social Stress Test (TSST). The ratio of L-tyrosine and L-phenylalanine to the sum of other large neutral amino acids (ΣLNAAs) in plasma were both significantly reduced by -80% at the post-ingestion period (5 h) compared to baseline. Exposure to the TSST for both ATPD and balanced-treated participants resulted in the robust stimulation of the sympathomedullary (SAM) and hypothalamic-pituitary adrenocortical (HPA) axes. This was demonstrated by significant increases in heart rate and blood pressure immediately after stress exposure compared to baseline in both ATPD and balanced conditions. Salivary cortisol levels significantly increased immediately after the completion of the TSST compared to pre-stress levels. There were a limited number of effects of the TSST combined with ATPD on measures of neuropsychological performance. These outcomes suggest that neurocognition is not severely impacted by acute social stress under conditions of catecholamine depletion.