Worry : a questionnaire and psychophysiological study/

It has been proposed that worry is a form of cognitive fear avoidance (Borkovec, Shadick, & Hopkins, 1991). That is, individuals faced with actual or potential threat avoid unpleasant physiological arousal by increasing their thought-based mental activity: worry. Worry is maintained by this avoidance of arousal and in some individuals becomes a common response to threat. The proposed mechanism by which cognitive fear avoidance operates has been termed autonomic rigidity. Autonomic rigidity refers to the suppression of the sympathetic nervous system that results in the restriction of heart rate and skin conductance responses to stress observed in patients with generalised anxiety disorder (Hoehn-Saric, McLeod, & Zimmerli, 1989). The empirical part of this thesis consists of two sections. The first is the collection of questionnaire data relating to worry in the Tasmanian university population. The second section describes a series of three experiments that investigate the autonomic rigidity hypothesis in female participants. The first experiment aimed to investigate the autonomic rigidity hypothesis using a worry period of one hour prior to a speaking task. Worriers (N=15) did not differ from non-worriers (N=15) in their physiological response to this task. A possible explanation for this result was that both groups may have engaged in productive cognitive activity (thought) before the speaking task and therefore the physiological response of the groups was similar. Despite these results subjective reports indicated a difference in worry activity between the groups. Studies published after the first experiment was completed indicated that there may be differences in both parasympathetic and sympathetic nervous system activity in chronic worriers (Lyonfields, Borkovec, & Thayer, 1995; Thayer, Fiedman, & Borkovec, 1996). Parasympathetic activity is indexed by measuring heart period variability. The second experimental study compared average heart rate, heart rate variability and skin conductance of worriers (N=32) and non-worriers (N --32) during verbal and non-verbal thinking task and worry. Contrary to predictions, the results were that worriers had more heart rate variability and tended to have lower average heart rates than non-worriers. There was no evidence of a restriction in heart rate variability for worriers. However, subjective differences in worry activity were found as predicted. The third experiment aimed to establish conditions similar to those where autonomic rigidity was found in worriers. The average heart rate and heart period variability of worriers (N=31) and non-worriers (N=31) were compared while they engaged in relaxation, worry, and-aversive imagery. No difference was found in the pattern of response to the tasks for worriers and non-worriers. However, relaxation resulted in more heart period variability than worry or imagery. Subjective differences in worry and relaxation were found as predicted. The conclusions of this thesis were that, firstly, survey data reveals that there are marked gender differences in the amount of worry in the University of Tasmania population with women reporting more worry than men across a number of topics. Secondly, the results of the three experiments demonstrate that autonomic rigidity is not always found in worriers. Although differences in experimental conditions and population may explain the findings, the phenomenon is harder to establish than earlier findings imply.