• Do haemodynamic responses to mental stress tests predict future blood pressure one year later? Prospective studies in the United Kingdom and Thailand

      Sheffield, David; Baker, Ian S.; Maratos, Frances A.; Yuenyongchaiwat, Kornanong (University of Derby, 2013-08-21)
      This thesis explored whether haemodynamic responses to psychological stress test predict future blood pressure (BP) levels: the Reactivity Hypothesis. The research included a systematic review and two prospective cohort studies in the UK and Thai samples. In addition, the Blunted Reactivity Hypothesis, which posits that cardiovascular reactivity is inversely related to symptoms of anxiety and depression, was examined in cross-sectional analyses. A systematic review with meta-analysis and meta-regression with 41 prospective cohort studies (from 1950 to 2012) examined whether cardiovascular responses to psychological stress tests predict future BP levels, hypertension status, preclinical coronary heart disease (CHD) and cardiac events. Three possible moderators were included in analyses: type of task (active versus passive coping), age group (children versus adults), and duration of follow-up (short versus long-term follow-up). The review found that systolic BP reactions to psychological stress tests predict future systolic BP levels and that there was better prediction in child samples with shorter follow-up periods. Similarly, diastolic BP reactions to psychological stress predicted future diastolic BP levels. Cardiovascular reactions to psychological stress tests did not predict hypertension, preclinical CHD, or cardiac events. Cross-sectional analysis of two studies conducted in the UK and Thailand provided some evidence that anxiety and depressive symptoms were negatively associated with cardiovascular reactivity: these findings supported the Blunted Cardiovascular Hypothesis. However, these relationships were observed in the UK sample, but not in the Thai sample. Further, Thai participants responded to psychological stress task with large cardiovascular reactions, of a similar magnitude to the UK participants and observed in previous studies of Europeans and North Americans. Finally, prospective analyses revealed that systolic BP responses to mental arithmetic predict future systolic BP levels after one year of follow-up in both UK and Thai individuals, after controlling for baseline cardiovascular activity and traditional risk factors. In contrast, haemodynamic responses did not predict future BP. These results provide support for the “Reactivity Hypothesis” although the effect sizes were relatively small. However, responses to only one of the three stressors, mental arithmetic, predicted future BP implicating beta-adrenergically mediated cardiovascular responses. However, there was no physiologic evidence (i.e., cardiac output responses) that suggested beta-adrenergic mechanisms. Accordingly, future studies should examine alternate mechanisms (e.g., platelet aggregation and endothelial function) and cardiovascular responses in larger samples with a longer follow-up to further clarify the predictive value of reactivity in the development of hypertension, along with potential mechanisms.
    • The effects of anxiety on visual attention for emotive stimuli in primary school children

      Maratos, Frances A.; Lipka, Sigrid; Kelly, Lauren (University of Derby, 2014-02-24)
      Anxiety can be advantageous in terms of survival and well-being, yet atypically high levels may be maladaptive and result in the clinical diagnosis of an anxiety disorder. Several risk factors have been implicated in the manifestation of clinical anxiety, including cognitive biases. In recent years, a plethora of research has emerged demonstrating that anxious adults exhibit biases of attention for threatening stimuli, especially that which is biologically relevant (e.g., facial expressions). Specific components of attentional bias have also been identified, namely facilitated engagement, impaired disengagement, and avoidance. However, the majority of studies have focused on the spatial domain of attention. Furthermore, the area is under-researched in children, despite research demonstrating that symptoms relating to clinical and non-clinical anxiety follow a stable course from childhood through to adolescence and adulthood. Consequently, the aim of this thesis was to investigate how anxiety affects children’s visual attention for emotive, particularly angry, faces. In order to provide a more comprehensive understanding, the current research involved examining the role of temporal and spatial attention utilising rapid serial visual presentation with the attentional blink, and the visual probe paradigm, respectively. The main hypothesis was that high state and/or trait anxiety would be associated with an attentional bias for angry, relative to positive or neutral faces in both the temporal and spatial domains. In relation to the temporal domain, key findings demonstrated that high levels of trait anxiety were associated with facilitated engagement towards both angry and neutral faces. It was further found that all children rapidly disengaged attention away from angry faces. Findings related to the processing of angry faces accorded with the main hypothesis stated in this thesis, as well as research and theory in the area. The finding that anxious children preferentially processed neutral faces in an attentional blink investigation was unexpected. This was argued to potentially reflect this stimulus type being interpreted as threatening. Key findings regarding the spatial domain were that high trait anxious children displayed an early covert bias of attention away from happy faces and a later, overt bias of attention away from angry faces. The finding that high trait anxiety was linked to an attentional bias away from happy faces in a visual probe task was also unexpected. This was argued to potentially reflect smiling faces being interpreted as signifying social dominance, thus resulting in the viewer experiencing feelings of subordination and becoming avoidant and/or submissive. To conclude, this thesis has enhanced current knowledge of attentional bias in both the temporal and spatial domains for emotive stimuli in anxious children. It has demonstrated that higher levels of trait anxiety moderate children’s allocation of attentional resources to different stimulus types, whether these are threatening, positive, or neutral. This has important implications for evaluating past research in adults and children, and for further developing theoretical models of attentional bias and anxiety. It also offers important clinical implications, since attending towards or away from specific stimuli may affect the development and maintenance of anxiety disorders. Recently, a treatment that aims to modify attentional bias in anxious individuals has begun to be developed. In light of the present findings, it may be necessary to review this treatment so that anxious children are re-trained in the specific biases of attention demonstrated here.