The effects of rumination and worry on nightly sleep

In collaboration with J. Brinker 

  • Sleep difficulties can have detrimental effects of varying severity on physical and psychological health.
  • Separate research has shown rumination and worry can impact negatively on sleep.
  • There is debate surrounding whether rumination and worry are different constructs, or if they are the same thing.

This project is uses an outcome (impact on sleep) as a tool for distinguishing between two constructs largely characterized by their temporal thought orientation.

This study drew from my honours thesis, written in 2012.

Click here to see the talk slides for: Walsh, E. & Brinker, J.K. (2012) The impact of rumination and worry on nightly sleep - a trait and state approach Poster, 47th Annual Australian Psychological Society Conference (Perth, 27th - 30th September)

 

Introduction

Objective: Sleep difficulties can have detrimental effects of varying severity on physical and psychological health. Rumination and worry are recurrent, repetitive and intrusive thoughts, both of which are associated with changes in sleep. They may be differentiated by their temporal orientation; rumination is past-focussed, while worry is future-focussed. This study investigated the distinction between rumination and worry by exploring their impact on nightly sleep. This distinction is theoretically meaningful, as there is debate surrounding whether rumination and worry are discrete constructs, and has practical applications in insomnia treatment, which currently only addresses worry. It was hypothesised that rumination and worry would have overlapping, yet distinct, impacts on sleep.

Methods: Rumination, worry, mood, stress, and sleep were measured at baseline by self-report inventories and daily utilizing a novel repeated measures SMS daily diary framework, in a sample of 120 undergraduate students.

Results: The hypothesis was supported. Baseline rumination was associated with poorer sleep at baseline, and baseline and daily rumination were independently associated with less nightly sleep.  Baseline worry relied on variance shared with baseline rumination to predict baseline sleep, and moderated the relationship between daily worry and sleep. Daily worry was associated with more hours slept nightly.

Conclusions: Rumination and worry have theoretically and practically meaningful distinct impacts upon sleep.

Rumination and worry are closely related constructs characterised by recurrent, repetitive and intrusive thoughts. Some researchers distinguish them via cognitive focus (Raes, 2010), however the traditional delineation of rumination being depression-focussed and worry anxiety-focussed is challenged by evidence that depressive mood, anxiety and stress have complex associations with both rumination and worry (DeJong-Meyer, Beck, & Riede, 2009; McLaughlin, Borkovec, & Sibrava, 2007; Leahy, 2002; Brosschot, Gerin, & Thayer, 2006; Cropley, Dijk, & Stanley, 2006).  The nature of rumination and its relationship with negative thought is obfuscated by a widespread definition explicitly including negative thinking (Brinker & Dozios, 2009). Conceptualisation of worry is similarly unclear, defined by some according to the focus of repetitive thoughts (i.e. Raes, 2010), and by others as repetitive thought with a cognitive problem solving component (i.e. Szabò & Lovibond, 2002).  A temporal orientation definition bypasses these issues by including all repetitive thought regardless of content. McLaughlin et al. (2007) define rumination as past-focussed, while worry is future-focussed. This broad definition encompasses a variety of content, including the problem-solving component of worry explored in Szabò and Lovibond (2002).

The tendency to ruminate is stable across time (Puterman, DeLongis, & Pomaki, 2010), but the act of ruminating can be transitory and linked with events as they are experienced (Riley, 2010). These trait and state behaviours can be distinguished by differing physiological impacts, such as sleep onset latency (Zoccola, Dickerson, & Lam, 2009). Worry can also be divided into independent trait and state predictors of physiological outcomes (Brosschot, Van Dijk, & Thayer, 2007).

Sleep difficulties can have detrimental, sometimes fatal, effects on physical and psychological health (Barnett & Cooper, 2008; Taylor & Bramoweth, 2011). Worry has been linked with shorter sleep duration in a correlational context (Kelly, 2002). Current insomnia therapies address only worry (Carney, Harris, Moss, & Edinger, 2010), however given the possible distinction between rumination and worry, this limited focus is remiss. Findings that rumination is generally associated with poorer sleep (Guastella & Moulds, 2007), and that experimentally induced rumination impacts negatively on sleep duration (Zoccola, Dickerson & Lam, 2009) add weight to the argument that exploration of the distinction between rumination and worry in terms of their impact on sleep has practical significance.

Mood and stress have a complicated interrelationship with rumination and worry, and also have direct impacts upon sleep (Berset, Elfering, Luthy, Luthi, & Semmer, 2010). It has been proposed that the prolonging of the physiological effects of mood and stress is the mechanism by which rumination and worry affect sleep (Cropley et al., 2006). As it is beyond the scope of the current paper to fully disentangle the true nature of the roles of mood and stress in potentially moderating the effect of rumination and worry on sleep, their contribution will be noted but statistically removed from analysis. The current study hypothesised that rumination and worry would have overlapping yet distinct impacts on sleep.

 

Method

Participants

One hundred and twenty Australian National University undergraduate students (70% female) aged 17-54 (M=20) participated as part of a larger study. They were given course credit for their participation.

Materials and Procedure

Participants completed an online battery of baseline questionnaires including the Ruminative Thought Style Questionnaire (RTS; Brinker & Dozios, 2009), the Penn State Worry Questionnaire (Meyer et al., 1990), the Pittsburgh Sleep Quality Index (PSQI; Buysse, Reynolds, Monk, Berman, & Kupfer, 1989), the Positive Affect Negative Affect Schedule (Watson, Clark & Tellegen, 1988), and the Perceived Stress Scale (Cohen, Karmarck & Mermelstein, 1983). For the diary portion, participants were issued SMS response keys consisting of nine questions about sleep length and disruption, napping, time spent ruminating daily, time spent worrying daily, and daily mood and stress levels. SMS prompts for responses to all nine questions were sent at 7:00pm nightly for a week, beginning on a Monday, during a teaching period.

 

Results

PSQI, RTS and daily rumination and worry scores were transformed to correct for skewness. 63 participants completed the diary portion of the study. T-tests revealed no significant differences between SMS completers and non-completers. When mood and stress were controlled for, baseline rumination was significantly associated with poorer baseline sleep. Baseline worry was only significantly associated with baseline sleep when rumination was included in the model, however it was in an unexpected direction, with worry related to better sleep (Table 1). To explore this overlap in variance, the non-overlapping portions of rumination and worry were isolated by regressing baseline worry on rumination and vice versa, and using the residuals to predict PSQI score. Neither residuals were significantly associated PSQI score, indicating that the impact of rumination and worry on sleep is contingent on their shared variance.

 

Predictor
ΔR
β
SE
t
p
Regression onea
         
Step 1
.306*
       
      Covariatesc
         
Step 2
.027*
       
      Baseline rumination
 
.195
 
2.155*
.033
Step 3
.470*
       
      Baseline worry
 
-.228
.004
-2.921*
.004
Regression twoa
         
Step 1
.306*
       
      Covariatesc
         
Step 2
.022
       
      Baseline worry
 
-.107
.004
-.195
.055
Step 3
.052*
       
      Baseline rumination
 
.286
 
3.074*
.004
Step 4
.006
       
      Baseline rumination
      and worry interaction
 
-1.665E-06
2.134e-06
-.780
.436
Regression threeb
         
Step 1
.306*
       
      Covariatesc
         
Step 2
.064*
       
      Rumination residuals
 
.158
 
1.484
.141
      Worry residuals
 
-.161
.006
-1.442
.152

Daily responses were nested by participant in multilevel linear models. All model comparison were evaluated at α=.05. Only daily stress (χ2=16.6) and sleep disturbance (χ2 =4.2) significantly improved upon null model fit, thus were retained as covariates. Baseline and daily rumination were significantly and independently associated with fewer hours slept nightly (χ2 =40, B=-5.59e-05 and  χ2=56, B=-.589 respectively). Baseline worry was significantly associated with more hours slept nightly (χ2 =49.4, B=1.90e-04), and interacted significantly with daily worry such that it too predicted more hours slept nightly (χ2=8.4, B=-2.15), indicating moderation was taking place. Baseline and daily worry scores were centred. The farther below average baseline worry, the greater its impact on the now positive relationship between daily worry and nightly sleep; B=8.99 at 1 SD below mean baseline worry, B=8.44 at mean baseline worry, and B=7.89 1SD above mean baseline worry. 

Discussion

The hypothesis that rumination and worry would have distinct impacts on sleep was supported. There was overlap between the constructs, as neither were significantly related to sleep when their overlapping variance was removed from analysis. There were also points of distinction. Baseline and daily rumination were independently associated with sleep, while baseline worry moderated the relationship between daily worry and sleep.

Results reaffirmed that rumination has a negative impact on sleep (Zoccola et al., 2009). Congruent with the literature, rumination was associated with poorer sleep quality as operationalised by the PSQI (Guastella & Moulds, 2007) and shorter sleep duration (Groeger et al., 2004). As the current study operationalised rumination broadly to include non-depressive thought, this suggests that a ruminative thought style in general can have a negative impact upon sleep. The current study extended  Zoccola, Dickerson and Lam (2009) by supporting the link between rumination and shorter sleep duration in a naturalistic, rather than experimental, setting. Taken together, these factors support the conception that rumination has an impact on sleep that is meaningful in an insomnia treatment context.

Interestingly, contrary to previous research (Kelly, 2002), worry had a positive impact on sleep. The unexpected positive relationship between worry and nightly sleep may be explained by the theoretical differences between rumination and worry. Unlike rumination, worry has a protective, problem-solving component (Szabò & Lovibond, 2002) which could mitigate the physiological impact of negative thought content  (as in Van Der Heiden & Broeke, 2009). Thus,  worrying may protect the participant from the sleep disturbances caused by negative mood and stress.  As the measures used by this study preclude worry and rumination occuring concurrently,  worry may protect sleep by preventing rumination, which lacks this problem solving component.

The incongruence of this suggestion with the current literature may be explained by the  methodological approach of the current study. The choice to control for stress, as stress may be a necessary component of the physiological mechanism by which worry impacts upon sleep (Cropley et al., 2006). Alternatively, the use of a broad, temporally-oriented definition may underlie the discrepancy with the literature. Carney et al. (2010) proposed that unclear definitions of worry may have led to past worry research conflating the concepts of rumination and worry, thus the unintentional capture of rumination rather than worry, or a combination of both rumination and worry. Thus, the detrimental effect of rumination upon sleep could have been misattributed to worry.

Future research could explore these potential explanations in more depth, and see whether the positive impact of worry holds in both clinical and non-clinical populations. The current study highlights the need to re-evaluate and broaden the current clinical focus on worry and sleep pathology to include the association between rumination and sleep.

 

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