تاثیر نشخوار فکری بر روی کیفیت خواب پس از یک عامل استرس زای زندگی

Previous research suggests an association between rumination and poor sleep quality. This study sought to clarify the direction of this association by inducing rumination about a negative event in the pre-sleep period and assessing self-reported sleep quality. On the evening following a stressful event (a mid-session exam), high (N = 59) and low (N = 55) trait ruminator undergraduate students were assigned to a pre-sleep rumination or distraction condition. Participants completed ratings of pre-sleep intrusive thoughts about the mid-session exam and sleep quality. As expected, high-trait ruminators experienced more pre-sleep intrusive thoughts and poorer sleep quality. Results confirmed that the instruction to ruminate had a particularly detrimental effect on sleep quality for high-trait ruminators compared to low-trait ruminators. Our findings confirm that rumination in the pre-sleep period following a stressful event has a negative impact on sleep quality for individuals with a trait tendency to ruminate. Suggestions are made for future research to investigate the interplay of rumination and stressful life events.

A substantial body of literature has established the deleterious impact of pre-sleep cognitive activity, such as worry, on subsequent sleep quality (Harvey, Tang, & Browning, 2005). Evidence drawn from correlational studies has suggested an association between pre-sleep worrisome thoughts and delayed sleep onset (see Harvey, 2005, for review). Experimental studies that have manipulated cognitive processing in the pre-sleep period have confirmed this link (e.g., Gross and Borkovec, 1982 and Tang and Harvey, 2004). Related to this, experiments that have employed cognitive inductions with the goal of disrupting pre-sleep worry have successfully reduced sleep onset latency (e.g., Harvey & Payne, 2002). Taken together, the existing evidence highlights the important role played by pre-sleep worry in the persistence of sleep difficulties. Rumination is a core cognitive process that has been implicated in the maintenance of a range of clinical disorders including posttraumatic stress disorder (Ehlers & Clark, 2000), social phobia (Clark & Wells, 1995) and depression (Nolen-Hoeksema, 1991). The majority of research on rumination has been conducted in the context of the Response Styles Theory of depression (Just and Alloy, 1997, Nolen-Hoeksema, 1991 and Nolen-Hoeksema, 2004). This model holds that the duration, severity and course of depressive illness are a consequence of the manner in which one appraises their depression symptoms. Specifically, the model predicts that possessing a ruminative response style (i.e., focusing on the causes, meanings, implications of symptoms) will increase the likelihood of developing depression, predict the persistence of depression symptoms, and contribute to the maintenance of depression-related deficits such as poor problem solving. Convergent evidence from longitudinal and experimental studies provides support for this account (see Nolen-Hoeksema, 2004 for review). The experimental literature in the field of rumination has predominantly explored the contribution of depressive rumination (i.e., rumination about depression symptoms) to the onset and course of depression. Thomsen, Mehlsen, Christensen, and Zachariae (2003) have recently argued for a broadening of the conceptualization of rumination to include ‘repetitive thoughts focusing on problematic situations or events as well as the emotions and symptoms these evoke and the possible consequences’ (Thomsen et al., 2003, p. 1294). Negative and/or stressful life events are an example of one such problematic event. Although some studies have investigated the association between rumination and adjustment to stressful life events (e.g., Nolen-Hoeksema and Morrow, 1991, Robinson and Alloy, 2003 and Young and Nolen-Hoeksema, 2001), in general this interrelationship has been less well explored. Worry and rumination have traditionally been distinguished in terms of their temporal focus (i.e., worry is typically about future events, while rumination focuses on events from the past). Interestingly, recent evidence suggests that worry and rumination are characterised by overlapping features (Fresco et al., 2002, Segerstrom et al., 2000 and Watkins et al., 2005), and share common appraisals and management strategies (Watkins, 2004a). On the basis of similarities between these two cognitive processes, and evidence of the negative impact of worry on sleep, it is plausible that rumination might similarly function as a source of pre-sleep cognitive arousal that maintains sleep-related difficulties. However, the role of rumination as a potential maintaining factor in insomnia has received limited research attention. This is surprising in view of the fact that leading commentators in the insomnia field have called for such investigations (Harvey, 2005 and Harvey et al., 2005). There is preliminary evidence that pre-sleep rumination may be linked to insomnia. Thomsen et al. (2003) examined the relationship between rumination, negative mood and sleep quality, and found a significant correlation between rumination and sleep quality after depression was partialled out. While promising, the correlational nature of these findings precludes a causal understanding of this relationship, thus it cannot be concluded that rumination leads to poor sleep quality. Further research is needed to clarify the temporal associations between these variables. Accordingly, our first objective was to clarify the direction of the association between rumination and sleep by manipulating cognitive processing about a negative event in the pre-sleep period, and to examine the impact of different styles of processing (e.g., rumination, distraction) on sleep quality. Our second objective was to examine the impact of rumination on the frequency of intrusions about a negative event in the pre-sleep period. To our knowledge, no study to date has experimentally manipulated rumination to determine its impact on sleep quality. We therefore allocated high- and low-trait ruminator undergraduate students to a rumination or distraction condition, and indexed pre-sleep intrusive thoughts about a stressful event (i.e., mid-session exam) on the evening of the exam. We selected the mid-session exam as the index negative event, as it was uniformly experienced by all participants in the study. In addition, it was felt that rumination may be more easily elicited under such stressful conditions. We predicted that high-trait ruminators assigned to a rumination induction would report: (i) poorer sleep quality, and (ii) more intrusive thoughts about the exam than high-trait ruminators in the distraction condition, or low-trait ruminators in either experimental condition.