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Sleep and Affect 201 © 2015 Elsevier Inc. All rights reserved.
http://dx.doi.org/10.1016/B978-0-12-417188-6.00010-4
CHAPTER
10
Sleep and Repetitive Thought:
The Role of Rumination and
Worry in Sleep Disturbance
Vivek Pillai and Christopher L. Drake
Sleep Disorders and Research Center, Henry Ford Health System,
Detroit, Michigan, USA
SLEEP AND REPETITIVE THOUGHT: THE ROLE OF
RUMINATION AND WORRY IN SLEEP DISTURBANCE
Negative affect is widely recognized as a common precipitant of both
subjective and objective sleep disturbance (Vandekerckhove & Cluydts,
2010). However, recent models of insomnia disorder attribute sleep distur-
bance more to the dysregulation of negative affect than to the mere emer-
gence of negative affective states (Espie, 2002). A burgeoning and reliable
body of research suggests that repetitive thought can preclude adaptive
emotion regulation and prolong negative affect states (for a review, see
Thomsen, 2006). Repetitive thought therefore represents a more critical
ingredient in the etiology of sleep disturbance than previously thought.
Broadly defined, repetitive thought is the process of recurrently focus-
ing attention on the self and on the environment (Segerstrom, Stanton,
Alden, & Shortridge, 2003). As such, repetitive thought may be construc-
tive or unconstructive, based on the function of the thought content and
the nature of underlying affect states. In the context of psychopathology
and hence this chapter, repetitive thought refers to the perseverative, in-
trusive activation of cognitive representations of stressful events or nega-
tively valenced affect. Although the literature is teeming with numerous
conceptualizations of unconstructive repetitive thought (for a review, see
Watkins, 2008), two conceptually distinct forms have garnered the most
research attention: worry and rumination.
202 10. SLEEP REPETITIVE THOUGHT
WORRY: PHENOMENOLOGY AND ASSESSMENT
A cardinal feature of anxiety disorders such as generalized anxiety dis-
order, worry involves recurrent, intrusive thoughts or images about the
potential negative outcomes signaled by a perceived threat (Borkovec,
Robinson, Pruzinsky, & DePree, 1983). Commonly reported functions of
worry include problem-solving, preparation for the worst, and determin-
ing ways to avoid feared stimuli (Borkovec & Roemer, 1995). However,
nearly 70% of reported worries involve fears of unlikely or implausi-
ble events. Thus, any perceived benefits are typically overshadowed
by the physiological and emotional costs of worrying (Borkovec, 1994).
Studies indicate that worrying is associated with various indices of au-
tonomic arousal such as increased skin conductance, increased skin
conductance variability, and a high cortisol awakening response (CAR)
(Schlotz, Hellhammer, Schulz, & Stone, 2004; Weise, Ong, Tesler, Kim, &
Roth, 2013). Notably, daily levels of worry are associated with elevated
heart rate and low heart rate variability (HRV) not only while waking,
but also during the following sleep period (Brosschot, Gerin, & Thayer,
2006; Brosschot, Van Dijk, & Thayer, 2007). Similarly, worry is predictive
of future anxiety and negative affect (Calmes & Roberts, 2007; Llera &
Newman, 2010; McLaughlin, Borkovec, & Sibrava, 2007). Thus, worry is
a perseverative thought mechanism by which cognitive manifestations of
perceived threats, as well as the associated physiological and emotional
arousal, are prolonged.
The Penn-State Worry Questionnaire (PSWQ; Meyer, Miller, Metzger, &
Borkovec, 1990) is presently the most widely used instrument for measur-
ing worry. This 16-item self-report questionnaire assesses the pervasive-
ness (e.g., “many situations worry me”), excessiveness (e.g., “I am always
worrying about something”), and uncontrollability of worry (“I know I
shouldn’t worry, but I just can’t help it”). The PSWQ has excellent inter-
nal consistency (α = 0.95) and high test-retest reliability over an 8-10-week
period (r = 0.92). Zero-order correlations between the PSWQ and sleep
disturbance measures, such as the Pittsburgh Sleep Quality Index (PSQI:
Buysse, Reynolds, Monk, & Berman, 1989), range from moderate (r = 0.43,
p < 0.01) to high (r = 0.67, p < 0.01) in clinical samples (Swanson, Pickett,
Flynn, & Armitage, 2011; Yook et al., 2008).
Another instrument, the Night-time Thoughts Questionnaire (NTQ),
assesses the extent to which (“not at all” to “a lot”) worrisome thoughts
occur during the night (Watts, Coyle, & East, 1994). The NTQ is composed
of six subscales: mental activity and rehearsal (e.g., “rehearsing import-
ant things I will do tomorrow”), thoughts about sleep (e.g., “wanting to
sleep,” “being tired tomorrow”), family and long-term concerns (“going
over and over the same thing”), positive concerns and plans (e.g., “things
I enjoy”), somatic preoccupations (e.g., “feeling too hot or too cold”), and
WORRY AND SLEEP 203
work and recent concerns (e.g., “concerns about work”). In a recent study,
participants categorized as “high worriers” based on the PSWQ scored
significantly higher than controls on all factors of the NTQ, including
the “thoughts about sleep” factor, implying an association between trait
worry and sleep-related worry (Omvik, Pallesen, Bjorvatn, Thayer, &
Nordhus, 2007).
Finally, based on clinical observation of insomnia patients, Tang and
Harvey (2004a) recently developed the Anxiety and Preoccupation about
Sleep Questionnaire (APSQ). The APSQ is a 10-item measure composed of
two collinear factors: worries about the consequences of poor sleep (e.g.,
“I worry about how the amount of sleep I get is going to affect my health”)
and worries about the uncontrollability of sleep (e.g., “my failure to rectify
my sleep problems troubles me a lot”). In two prior studies, the APSQ
achieved high internal consistency (α = 0.92-0.93), and it reliably distin-
guished between good and poor sleepers (Jansson-Fröjmark, Harvey,
Norell-Clarke, & Linton, 2012; Tang & Harvey, 2004a).
WORRY AND SLEEP
Evidence suggesting that cognitive factors may play a more central role
in the etiology of sleep disturbance than somatic arousal provided the ini-
tial impetus for the study of cognitive mechanisms in sleep disruption.
Now a landmark in the field, an early study indicated that individuals
with insomnia disorder were 10 times more likely to attribute their sleep
disturbance to cognitive factors, including worrying, planning, or diffi-
culty controlling thoughts, than to somatic complaints, such as sweating
or shifting in bed (Lichstein & Rosenthal, 1980). As theoretical and empir-
ical models of the worry were refined in the following decades, several
studies recognized its deleterious impact on sleep (Harvey, 2002b; Watts
et al., 1994). Today, nearly all insomnia models highlight worry as a pre-
cipitant of sleep disturbance (Espie, 2002; Harvey, 2005).
As Harvey (2005) observes, the bulk of prior research on sleep and worry
comes from three groups of studies: exploratory studies, which examine
the content of presleep cognition; correlational studies on the association
between sleep parameters and worry measures; and experimental studies,
which explore the impact of experimentally induced worry on sleep. Many
studies on the so-called worry and sleep rely on instruments that measure
diffuse cognitive activity that is not specific to worry; thus, these stud-
ies are beyond the scope of this chapter (for a review, see Harvey, 2005).
Exploratory thought-sampling studies that attempt to distinguish worry
from other forms of cognition point to generalized worrying, problem-
solving, and preoccupation with sleep as the most pervasive themes
in presleep cognitive activity (Fichten et al., 1998; Harvey, 2002a;
204 10. SLEEP REPETITIVE THOUGHT
Kuisk, Bertelson, & Walsh, 1989; Nelson & Harvey, 2003; Watts et al., 1994).
However, with one exception (Fichten et al., 1998), these studies focus on
individuals with insomnia disorder. Therefore, it is presently unclear how
generalizable these findings are to other patient populations, especially
those for whom sleep disturbance is not the primary presenting problem.
Correlational studies, on the other hand, have shown that university
students who endorse high levels of worry report significantly shorter ha-
bitual sleep durations (Kelly, 2002); that work-related worry is associated
with poor sleep quality (Rodríguez-Muñoz, Notelaers, & Moreno-Jiménez,
2011); and that worrying about sleeplessness is related to self-reported
sleep disturbances, including shorter total sleep time (TST), longer sleep
onset latency (SOL), and prolonged wake time after sleep onset (WASO)
among patients with long-term (>6 months) insomnia disorder (Jansson &
Linton, 2006). Similarly, in a nationally representative sample of over 2000
participants, individuals with insomnia disorder reported significantly
higher levels of worry than did a group of poor sleepers who reported at
least one insomnia symptom (onset/maintenance/daytime impairment)
but did not meet full diagnostic criteria (Jansson-Fröjmark et al., 2012).
Both groups reported significantly higher worry than normal sleepers,
however, implying a potential dose response relationship between worry
and the severity or chronicity of sleep disturbance. Together these studies
offer a coherent picture of the association between worry and sleep distur-
bance. Notably, with the exception of Jansson-Fröjmark et al. (2012) who
assessed worry using the APSQ, all aforesaid investigators developed
novel worry measures for their respective studies.
Because prior studies relied on trait measures of worry, they failed to
capture any within-person variance or temporal effects in the association
between worry and sleep. Specifically, common trait measures of worry,
such as the PSWQ (Meyer et al., 1990), assess one’s propensity for worry
and thus offer little insight into whether worrying actually occurred during
a particular sampling period. To the best of our knowledge, only one study
has directly addressed the covariation between state worry and sleep. Using
an ecological momentary assessment (EMA) design, Weise et al. (2013)
showed that presleep worry (on a three-item scale: “worrying,” “sweat-
ing,” and “heart racing or pounding”) was associated with self-reported
and actigraphy-based WASO, lower actigraphy-based sleep efficiency (SE),
and poor subjective sleep quality. Importantly, actigraphy-based WASO for
participants who worried prior to sleep (~47 min) was nearly twice that
for those who did not (~24 min). Though this study offers important and
timely support for the relationship between the act of worrying and sleep
disturbance, it suffers from a number of limitations, including the use of a
nonstandardized worry measure that conflates cognitive and physiological
correlates of worry. Furthermore, causality could not be inferred because
levels of presleep worry were not experimentally manipulated.
WORRY AND SLEEP 205
Despite widespread acceptance of the role of worry in sleep distur-
bance, few experimental studies have investigated the impact of worry
induction on sleep. Three of these studies (Hall, Buysse, Reynolds, Kupfer,
& Baum ,1996; Gross & Borkovec, 1982; Tang & Harvey, 2004b) employed
a speech threat paradigm in which participants were informed prior to
going to sleep that they would have to deliver a speech upon waking.
Presumably, the prospect of public speaking elicits worry that, in turn,
disrupts sleep. Data suggest that such a worry induction task is associ-
ated with longer polysomnography (PSG) and self-reported SOLs and
shorter PSG-based TST during an afternoon nap (Gross & Borkovec, 1982;
Tang & Harvey, 2004b), as well as longer PSG-based SOLs and more fre-
quent awakenings during the night (Hall, Buysse, Reynolds, Kupfer, &
Baum, 1996). Notably, worry-induced SOL was in the clinically significant
range (~54 min) in the Gross and Borkovec study. However, this study
did not involve a manipulation check, rendering it impossible to ascer-
tain whether participants engaged in worry in the presleep period (Gross
& Borkovec, 1982). Similarly, Hall and colleagues assessed presleep “in-
trusive thoughts” using the Impact of Event Scale, an instrument more
germane to rumination than worry (see the section on “Rumination:
Phenomenology and Assessment”). Finally, Tang and Harvey (2004b)
assessed task-induced cognition using the State Trait Anxiety Inventory-
State Scale, an empirically validated measure of state anxiety (Hedberg,
1972), and not worry per se (see the section on “Rumination and Worry:
Common and Distinguishing Features”). It is therefore unclear whether
any of the above studies captured presleep worry or another form of cog-
nitive activity.
Another classic study on “cognitive anxiety” and sleep followed a sim-
ilar paradigm and deserves mention here (Lichstein & Fanning, 1990, p.
49). In a study involving insomnia patients and healthy controls, exper-
imenters staged a PSG-equipment malfunction purported to potentially
shock participants during an overnight sleep study. The insomnia group
exhibited a significantly higher skin conductance response than did the
control group, presumably because the former were more likely to worry
about being accidentally shocked while going to bed. Furthermore, the
percentage of PSG epochs scored as sleep was significantly lower among
insomniacs than in controls. Once again, the protocol did not involve a
manipulation check to determine whether participants actually engaged
in presleep worry, however, and the impact of other forms of cognitive ac-
tivity cannot be ruled out. A recent study on the role of repetitive thought
forms in insomnia disorder aimed to address this particular limitation of
the sleep and worry literature.
Carney, Harris, Moss, and Edinger (2010) assessed trait rumination
and worry in a sample of 210 patients before monitoring their sleep via
electronic sleep diaries for a period of 2 weeks. Patients with higher trait
206 10. SLEEP REPETITIVE THOUGHT
rumination scores reported significant sleep disturbance in parameters
such as WASO and SE. Surprisingly, trait worry did not exert a main ef-
fect on sleep. As Carney and colleagues note, a troubling implication of
these findings is that previous studies may have mischaracterized the re-
petitive thought processes observed in insomnia disorder. In other words,
rumination and not worry may serve as the key etiological agent behind
wake-promoting cognitive activity. Arguably, some of this confusion is
attributable to the inherent similarities between rumination and worry,
because both involve abstract, negatively valenced, perseverative think-
ing. A close look at the phenomenology of rumination is warranted to
understand any conceptual and empirical differences between these two
repetitive thought forms.
RUMINATION: PHENOMENOLOGY AND ASSESSMENT
Nolen-Hoeksema (1990) originally proposed the construct of rumina-
tion as an explanation for the gender disparity in the prevalence of depres-
sion and as a mechanism by which depressive episodes are exacerbated.
Rumination refers to passively and repetitively focusing attention on the
self or on negative affect. Empirical data support three mechanisms by
which rumination prolongs negative affect: (1) intensifying negative affect
states by calling attention to negative traits and memories, (2) inhibiting
adaptive distraction from negative affect, and (3) interfering with problem-
solving by usurping attentional resources required for coping (Wisco &
Nolen-Hoeksema, 2008). As it was initially conceptualized, rumination in-
volves recurrent thoughts about mood symptoms and not about specific
life events or stressors (Nolen-Hoeksema, 1991). Indeed, in her initial de-
scription of this response style, Nolen-Hoeksema stressed that nonspecific
rumination was more insidious than rumination anchored to a specific
event. However, the concept of rumination has since been expanded be-
yond its roots in depression to capture recurrent, intrusive thoughts about
past events and stressors across a variety of disorders, including post-
traumatic stress disorder (PTSD) and insomnia disorder (Carney, Harris,
Falco, & Edinger, 2013; Echiverri, Jaeger, Chen, Moore, & Zoellner, 2011;
Watkins, 2008). This chapter adopts the latter, more transdiagnostic view
of rumination.
Not unlike worry, rumination can be conceptualized as both a trait- and
state-level construct. In an early study, 83% of a nonclinical sample of col-
lege students exhibited consistency in their “typical” cognitive response
style (rumination vs. distraction) over a 30-day period (Nolen-Hoeksema,
Morrow, & Fredrickson, 1993). Similarly, in a large sample of bereaved
adults, scores on a trait measure of rumination did not vary significantly
between a baseline assessment and a follow-up roughly 5 months later
RUMINATION: PHENOMENOLOGY AND ASSESSMENT 207
(Nolen-Hoeksema, Parker, & Larson, 1994). Together, these studies sug-
gest that a proportion of the population exhibits a trait disposition for
rumination. However, data from daily or experience sampling studies sug-
gest that the level of actual engagement in rumination varies significantly
from day to day, as a function of life events or stressors, even among trait
ruminators (Moberly & Watkins, 2008; Puterman, DeLongis, & Pomaki,
2010). Similar daily variations in levels of state rumination have also been
reported in community (Wood, Saltzberg, Neale, Stone, & Rachmiel, 1990)
and student samples (Lavallee & Campbell, 1995). A number of empiri-
cally validated measures of both state and trait ruminations are presently
available in the literature.
The original standardized measure of rumination is called the Response
Style Questionnaire, Rumination Scale (RRS: Nolen-Hoeksema & Morrow,
1991). The RRS consists of 22 items scored on a Likert-type scale that in-
dicates how often (“almost never” to “almost always”) one engages in ru-
minative thought. The RRS has shown high internal consistency (α = 0.88)
and acceptable test-retest reliability (r = 0.62) over a 26-week period
(Bagby, Rector, Bacchiochi, & McBride, 2004). A recent factor analysis of
the RRS by Treynor, Gonzalez, and Nolen-Hoeksema (2003) reveals three
underlying components: intropunitive brooding (e.g., “what am I doing
to deserve this”), reflective pondering about the causes of negative affect
(e.g., “go someplace alone to think about your feelings”), and focusing on
depressive symptoms (e.g., “think about how sad you feel”). Although
the depressive symptom-focused subscale is highly collinear with depres-
sion, the brooding and reflective pondering subscales, known together
as self-focused rumination, are less confounded and constitute the active
components of the rumination construct (Armey et al., 2009; Bagby &
Parker, 2001; Bagby et al., 2004).
For more stress-specific rumination, sleep studies (Thomsen, Mehlsen,
Christensen, & Zachariae, 2003; Zoccola, Dickerson, & Lam, 2009) have
turned to the Emotion Control Questionnaire-Rehearsal Scale (ECQ-R:
Roger & Najarian, 1989). The ECQ-R is composed of 14 true-or-false items
that assess whether or not one is generally likely to engage in persevera-
tive, intrusive ideation about prior events and stressors (e.g., “I get worked
up thinking about things that have upset me in the past”). Though concep-
tually congruent with rumination, we were unable to find any empirical
data on the convergent validity of this instrument with respect to the RRS.
Two other scales of life event- or trauma-related rumination have
emerged from the PTSD literature: the Revised Impact of Events Scale-
Intrusion subscale (IES-I: Weiss, 2007) and, more recently, the Event
Related Rumination Inventory (ERRI: Cann et al., 2011). The IES-I com-
prises eight items that measure the severity of recurrent, egodystonic ide-
ation in response to stressors (e.g., “I thought about it when I didn’t meant
to”; “other things kept making me think about it”). Notably, this scale also
208 10. SLEEP REPETITIVE THOUGHT
includes sleep-specific items (e.g., “I had dreams about it”; “I had trouble
falling asleep”) that may inflate its correlation with sleep measures. The
20-item ERRI is similar to the IES-I in its focus on event-related rumina-
tion, with the exception that it also probes for the frequency of more de-
liberate forms of rumination aimed at adaptive coping or posttraumatic
growth (e.g., “I thought about whether I have learned anything as a result
of my experience”). Owing to their novelty, these scales have yet to re-
ceive adequate research use. However, given the well-established associ-
ation between stress and sleep disturbance (Healey et al., 1981; LeBlanc
et al., 2009), instruments such as the IES-I and the ERRI may help elucidate
whether rumination mediates the association between stress exposure
and sleep disruption.
A final rumination scale that deserves mention is the Daytime Insomnia
Symptom Response Scale (DISRS). Developed and validated by Carney
et al. (2013) for the assessment of rumination specific to daytime insom-
nia disorder symptoms, the DISRS is a 20-item scale that targets rumina-
tion about three domains of insomnia disorder complaints: cognitive and
motivational problems (e.g., “think about how unmotivated you feel”;
“think about how everything requires more effort than usual”), negative
affect (e.g., “think about how irritable you feel”), and fatigue (e.g., “think
about how tired you feel”). The DISRS exhibits high internal consistency
(α = 0.93-0.94) and good convergent validity. In a sample of patients with
comorbid insomnia disorder and depression, the DISRS was significantly
related to insomnia severity, even after controlling for depressive symp-
toms and depressive rumination on the RRS.
RUMINATION AND SLEEP
Although research on worry and sleep disturbance has grown steadily
since the 1980s, rumination did not fall under the lens of sleep research-
ers until the past decade. Not surprisingly, we found only five studies on
rumination and sleep disturbance. In 2003, Thomsen et al. (2003) adminis-
tered self-report measures of trait rumination (ECQ-R), depressed mood,
and sleep quality to a nonclinical sample. Results indicated significant bi-
variate correlations between trait rumination and various sleep indices,
including SOL, such that higher levels of trait rumination were associated
with worse sleep outcomes. Furthermore, rumination was significantly
associated with overall sleep quality even after controlling for depressed
mood. More recently, a comparison of good and poor sleepers (global PSQI
scores > 6) revealed that the latter reported significantly higher scores on
the RRS (Carney, Edinger, Meyer, Lindman, & Istre, 2006). These studies
offer preliminary evidence that individuals with a ruminative response
style are more likely to experience sleep difficulties than are individuals
RUMINATION AND SLEEP 209
without such a cognitive vulnerability. However, due to the correlational
nature of these data, neither study was able to establish a causal or tem-
poral relationship between rumination and sleep disturbance. An equally
plausible alternative explanation is that the inability to fall asleep after
going to bed may trigger ruminative thinking. We are aware of only one
sleep study in which state rumination was experimentally induced.
Guastella and Moulds (2007) assessed the impact of presleep rumina-
tion and distraction inductions on sleep quality in a sample of college stu-
dents. Based on a median split of RRS scores, the sample was divided into
two groups: high and low trait ruminators. Analyses revealed that high
ruminators assigned to the rumination condition reported significantly
worse sleep quality than did high ruminators in the distraction condition
and low ruminators in either condition. In other words, ruminating prior
to bed impaired sleep only among those predisposed to a ruminative re-
sponse style. Guastella and Moulds reasoned that the low trait ruminators
likely reverted back to their default nonruminative cognitive style follow-
ing the rumination induction (2007; p. 1158). A more recent study on the
association between poststressor rumination and objective sleep disrup-
tion reported similar findings (Zoccola et al., 2009). In this study, partici-
pants reported levels of in-lab state rumination after delivering a speech
that was negatively evaluated by a panel of judges. The following night,
sleep was monitored via actigraphy in participants’ homes. Actiwatch
data indicated that trait rumination (assessed by the ECQ-R) was related
to significantly longer SOLs. On the other hand, though state rumination
was not significantly associated with any sleep parameter, there was a sig-
nificant interaction between trait and state rumination, such that high trait
ruminators who engaged in more state rumination experienced the lon-
gest SOLs. Neither trait nor state rumination was related to TST or WASO.
Finally, Pillai, Steenburg, Ciesla, Roth, and Drake (2014) examined the
effects of naturally occurring presleep rumination on self-reported and
actigraphy-based sleep. This study adopted a week-long, daily sampling
approach to overcome some of the limitations of prior studies, including
first-night effects and low ecological validity. A sample of high trait ru-
minators (>1.5 standard deviations on the RRS) completed a short ques-
tionnaire after waking each morning for a period of 7 days. Participants
reported the duration and quality of sleep they experienced the previous
night, as well as levels of engagement in presleep rumination. Sleep was
also assessed throughout this period in participants’ home environments
via wrist actigraphy. Analyses revealed that nightly levels of presleep ru-
mination were associated with significantly longer actigraphy- and diary-
based SOL. Notably, a 1-SD increase on the presleep rumination scale was
associated with an approximately 7-min increase in actigraphy-based
SOL, even after controlling for baseline sleep disturbance and depres-
sive symptomatology. Other sleep parameters such as SE and TST were
210 10. SLEEP REPETITIVE THOUGHT
unrelated to rumination. Consistent with prior experimental data, this
more naturalistic study suggests that individuals with a trait vulnerability
to rumination do engage in presleep rumination, further indicating that
this state phenomenon disrupts both actigraphy- and self-reported sleep.
In summary, though rumination is a reliable predictor of delayed sleep
onset, its association with sleep maintenance is less robust (Zoccola et al.,
2009; Pillai et al., 2014). With the exception of Carney et al. (2010), who
found a significant association between trait rumination and diary-based
SE and WASO, prior research has yet to establish an association between
rumination and sleep maintenance difficulties. Arguably, null effects may
simply reflect the methodological limitations of these studies. Three of
the five studies reviewed here relied on samples of university students, a
population notorious for erratic sleep schedules and poor sleep hygiene
(Gaultney, 2011). Laboratory studies with a controlled sleep window are
needed to test more definitively the association between rumination and
sleep maintenance.
RUMINATION AND WORRY: COMMON
AND DISTINGUISHING FEATURES
As alluded to earlier, rumination and worry emerged largely inde-
pendently as respective cognitive pathways to depression and anxiety.
However, the substantial comorbidity between depression and anxiety
(Clark & Watson, 1991) has prompted researchers to examine whether
rumination and worry are distinct or overlapping features of affective
disorders. By definition, rumination involves dwelling on the past to un-
derstand and, potentially, alleviate negative mood states (Lyubomirsky &
Nolen-Hoeksema, 1993), whereas worry is elicited by future threats and
uncertainties (Dugas, Buhr, & Ladouceur, 2004). Thus, although rumi-
nation and worry both involve negatively valenced, repetitive thoughts
(Brosschot et al., 2006; Watkins, 2008), they differ in terms of temporal
focus (past vs. future) and perceived motivation (mood alleviation vs. un-
certainty reduction). Empirical attempts to distinguish between rumina-
tion and worry within this conceptual framework have largely relied on
assessing the specificity of these repetitive thought forms for various affec-
tive disorders. Despite some inconsistent findings in the past (for review,
see Querstret & Cropley, 2013), the most robust thesis to emerge from this
literature is that rumination and worry are significantly correlated and
that each is uniquely associated (i.e., controlling for the other) with both
depression and anxiety (Chelminsky & Zimmerman, 2003; McEvoy &
Brans, 2013; McLaughlin et al., 2007).
A second group of studies has explored the factor structure of com-
monly used self-report measures of rumination and worry to identify
RUMINATION AND WORRY: COMMON AND DISTINGUISHING FEATURES 211
shared or unique higher-order constructs. Segerstrom et al. (2000), for
instance, used structural equation modeling to find a single repetitive
thought factor underlying both rumination and worry, thus implying con-
siderable overlap between these two mechanisms. In contrast, more recent
investigations in both clinical (Goring & Papageorgiou, 2008; McEvoy &
Brans, 2013) and nonclinical samples (Fresco, Frankel, Mennin, Turk, &
Heimberg, 2002) have yielded some evidence of structural divergence. For
instance, McEvoy et al. (2013) offer evidence for a four-factor model: reflec-
tive pondering, brooding, worrying, and general repetitive thought. This
factor-analytic solution is especially noteworthy because the investigators
removed disorder-specific items from the rumination and worry scales, in
addition to controlling for the method variance associated with these in-
struments. However, with the exception of the reflective pondering factor,
which was not predictive of anxiety, all other factors were significantly
related to both depression and anxiety symptoms. Together, these data
imply that, although rumination and worry may constitute phenomeno-
logically distinct cognitive mechanisms, this distinction is less clinically
meaningful in the context of affective disorders. Both forms of repetitive
thought are predictive of affective disorders and warrant assessment and
treatment in clinical settings. Not surprisingly, many recent reviews of this
literature subsume rumination and worry under a common rubric, known
variously as repetitive thought, repetitive negative thought, or persever-
ative thought (Mansell, Harvey, Watkins, & Shafran, 2008; Querstret &
Cropley, 2013; Watkins, 2008).
With respect to sleep disturbance, however, we presently lack evidence
to judge the respective merits of separating or combining the rumination
and worry constructs. We are aware of only two studies that have exam-
ined the impact of both rumination and worry on sleep. As noted earlier,
Carney et al. (2010) found that, although rumination was significantly re-
lated to sleep disturbance in insomnia patients, worry was not associated
with sleep. A similar study in a sample of undergraduate students yielded
nearly identical findings (Takano, Iijima, & Tanno, 2012). In this study,
baseline trait rumination scores were associated with reduced subjective
sleep quality at a 3-week follow-up, though no relationship between trait
worry and sleep was found. However, there was a significant interaction
between trait rumination and worry, such that rumination was associated
with poor sleep quality among high trait worriers but not among low trait
worriers. Thus, although worry did not exert a main effect on sleep, it
amplified the effects of rumination.
Carney and colleagues reason that a potential explanation for these
findings is that worry and sleep-related repetitive thought may be distinct
constructs (2010, 2013). In a recent study, they administered the PSWQ and
the DISRS to a nonclinical sample of college students. A factor-analysis of
pooled items from these scales yielded a two-factor solution, such that
212 10. SLEEP REPETITIVE THOUGHT
items from the PSWQ and DISRS loaded onto separate factors. Though
the authors cite this result as evidence for divergence between worry and
sleep-related rumination, this factor-analytic solution may simply reflect
the method variance in these scales (Harris & Bladen, 1994; McEvoy &
Brans, 2013). Furthermore, though the correlation between PSWQ and the
DISRS was not reported in this study, the correlation between the RRS and
the DISRS was high (r = 0.62, p < 0.01). Data from other studies show that
the RRS and the PSWQ are similarly correlated in both clinical (Carney
et al., 2010: r = 0.56, p < 0.01) and nonclinical samples (Segerstrom et al.,
2000: r = 0.52, p < 0.01; Takano et al., 2012: r = 0.52, p < 0.01). Finally, studies
that rely on single measures of rumination and worry may only address
the covariation between specific instruments and not the underlying con-
structs. Future studies must adopt multitrait-multimethod approaches
before they can satisfactorily explain the relationships between these con-
structs (Williams & Brown, 1994). State measures of rumination and worry
should also be emphasized to gain a more valid assay of the dynamic re-
lationship between repetitive thought and sleep.
RUMINATION, WORRY, AND SLEEP:
THEORETICAL MODELS
The inability to suppress mental activity while attempting to sleep
is considered its own form of arousal called cognitive arousal (Harvey,
Tang, & Browning, 2005). Therefore, the charge facing current research
is twofold: (1) to explain why repetitive thought processes persist and
(2) to show that these processes can override homeostatic and circadian
sleep regulation. With respect to the durability of repetitive thought,
transdiagnostic models suggest that repetitive thoughts are maintained
by two mechanisms: faulty or maladaptive metacognitions about repeti-
tive thought and ineffective strategies for suppressing repetitive thought
(Clark, 2002). Perceptions about the function and meaning of repetitive
thought vary. With respect to rumination, some data show that ruminators
consciously prolong the ruminative response because they believe that
rumination will help them gain insight into and eventually alleviate the
target distress (Lyubomirsky & Nolen-Hoeksema, 1993). Similarly, wor-
rying, as noted earlier, is often perceived as an adaptive coping strategy
for planning or problem solving (Borkovec & Roemer, 1995). On the other
hand, repetitive thoughts may be egodystonic and anxiety-provoking
when, for instance, their content is related to trauma- or fear- specific
schemas (Ehlers & Clark, 2000; Grisham & Williams, 2013). In such cases,
counterproductive efforts to suppress repetitive thoughts are triggered,
further prolonging repetitive thought processes (see the section on
“Treatment Implications”).
RUMINATION, WORRY, AND SLEEP: THEORETICAL MODELS 213
As for the interaction between repetitive thought and endogenous sleep
regulation, research suggests that the attentional resources usurped by re-
petitive thought processes are on par with the demands of an executive or
effortful cognitive task. Studies show that experimentally induced rumina-
tion degrades performance on effortful-attentional tasks such as random
number generation (Watkins & Brown, 2002). Thus, it is conceivable that
repetitive thought processes may be cognitively strenuous enough to pre-
clude the relatively automatic inhibition of wakefulness that occurs around
sleep onset (Borbely, 1982). However, none of the studies we reviewed as-
sessed the association between repetitive thought and alertness, though
such a relationship was typically inferred based on the association between
repetitive thought and nocturnal SOL. Nocturnal SOL is a poor measure of
arousal because considerable within- and between-person variability ex-
ists in this measure (Roehrs, Randall, Harris, Maan, & Roth, 2011).
The association between repetitive thought and other arousal indices,
such as heart rate (HR) and HRV, offer some insight into this phenome-
non. The cardiovascular health literature provides extensive and reliable
evidence that state worry is associated with increased HR and reduced
HRV (Aldao, Mennin, & McLaughlin, 2013; Hofmann et al., 2005). In
a recent EMA study, Weise et al. (2013) showed that presleep worry is
associated with increased skin conductance, elevated HR, and lower
HRV, both during the presleep period and in the following sleep episode.
Furthermore, these autonomic arousal indices were associated with sig-
nificantly higher actigraphy-based nocturnal awakenings and reduced SE.
Data on rumination and autonomic arousal are more equivocal. Although
some studies report an association between state rumination and blunted
HRV (Gerin, Davidson, Christenfeld, Goyal, & Schwartz, 2006; Key,
Campbell, Bacon, & Gerin, 2008; Ottaviani, Shapiro, Davydov, Goldstein,
& Mills, 2009), others report no association (Aldao et al., 2013). Further
research on the autonomic phenotypes of rumination using standardized
instruments is warranted to resolve these inconsistences.
Repetitive thought is also associated with markers of central nervous
system (CNS) hyperarousal, such as hypothalamic-pituitary-adrenal
axis (HPA) activity (Drake, Roehrs, & Roth, 2003; Rydstedt, Cropley, &
Devereux, 2011). According to the sustained activation theory, the failure
to downregulate physiological responses to stress exposure contributes
to morbidity (Ursin & Eriksen, 2010). As repetitive thoughts offer a me-
dium by which cognitive manifestations of stress endure, some research-
ers have examined whether repetitive thought inhibits CNS recovery.
Cropley, Rydstedt, Devereux, and Middleton (2013) assessed the associ-
ation between work-related rumination and salivary cortisol levels in a
nonclinical sample of adult school teachers. Salivary cortisol (SC) is an
easily procured measure of HPA activity, with empirically validated stress
responsivity (Clow, Hucklebridge, Stalder, Evans, & Thorn, 2010). SC also
214 10. SLEEP REPETITIVE THOUGHT
exhibits a reliable diurnal pattern in healthy adults, such that its levels
peak within a 30-45 min window of awakening, a phenomenon known as
the CAR. SC levels subsequently decline over the remainder of the day un-
til reaching a nadir late in the evening (Kudielka, Schommer, Hellhammer,
& Kirschbaum, 2004). Participants in this study provided SC assays im-
mediately before going to sleep, upon waking, and then 15, 30, and 45 min
after waking. Participants also reported state levels of rumination before
going to bed and again after waking in the morning. Analyses showed
that rumination was associated with significant sleep disturbance, higher
before-bed SC levels, and a blunted CAR in the morning. Notably, the as-
sociation between repetitive thought and CAR dropped to insignificance
when sleep disturbance was included in the model. The investigators spec-
ulated that sleep disturbance may have mediated the association between
repetitive thought and CAR, though no statistical mediation analyses were
performed. Other research groups report a similar association between
repetitive thought and a blunted CAR (Kuehner, Holzhauer, & Huffziger,
2007; Rydstedt et al., 2011). Individuals with insomnia exhibit a remark-
ably similar pattern of elevated evening cortisol levels and a blunted CAR
(Backhaus, Junghanns, & Hohagen, 2004; Vgontzas et al., 2001), implying
an association between repetitive thought and the sleep-disruptive hyper-
arousal seen in insomnia.
In summary, there is now considerable evidence that rumination and
worry are related to sleep disturbance, and several potential mechanisms
have been proposed. Most of these findings are preliminary, however, and
further investigation of the physiological correlates of cognitive arousal is
warranted. Similarly, more laboratory-based PSG studies are needed be-
cause the association between repetitive thought and sleep architecture
has not been examined. A recent study showed that a presleep negative
affect-induction task was predictive of an increased latency to slow-wave
sleep and an increased number of awakenings from rapid eye movement
(REM) sleep (Vandekerckhove et al., 2011). Given the significant collin-
earity between affect and repetitive thought, it is important to ascertain
whether repetitive thought is similarly related to sleep architecture. The
unique neurobiology of REM sleep—limbic and forebrain levels of ace-
tylcholine are significantly higher during REM sleep than during NREM
sleep and quiet waking—has salient implications for the consolidation
of emotional memories (for a review, see van der Helm & Walker, 2011).
Furthermore, studies show that, although sleep loss impairs the encoding
of neutral and positively valenced memories, negative memories appear
relatively refractory (Walker & Stickgold, 2006). Thus, sleep loss leads to
a selective disinhibition of negatively toned memories, which may then
act as fodder for ruminative perseveration. Presently, these neurochem-
ical mechanisms have largely been studied in the broad context of emo-
tion regulation and not rumination or worry per se. We believe that future
RUMINATION, WORRY, AND SLEEP: TREATMENT IMPLICATIONS 215
research along these lines, especially in diverse clinical samples, will fur-
ther elucidate these phenomena, because disorder-specific research may
only yield disorder-specific insight.
RUMINATION, WORRY, AND SLEEP: TREATMENT
IMPLICATIONS
Early clinical trials of mindfulness-based techniques, such as
mindfulness-based stress reduction and mindfulness-based cogni-
tive therapy, show promise for alleviating both rumination (Jain et al.,
2007; Kingston, Dooley, Bates, Lawlor, & Malone, 2007; Ramel, Goldin,
Carmona, & McQuaid, 2004) and worry (Delgado et al., 2010; Yook et al.,
2008). Rumination involves a perseverative analysis of discrepancies
between current and desired mood states, often leading to self-blame
(Lyubomirsky, Tucker, Caldwell, & Berg, 1999). Similarly, worry is trig-
gered by the emotional discomfort associated with fear and uncertainty
(Dugas et al., 2004). These aspects of repetitive thought are ideal targets
for mindfulness-based interventions that emphasize a nonjudgmental,
nonreactive acceptance of egodystonic thoughts and emotions. In a re-
cent survey study, a nonclinical sample of university students completed
the PSWQ and a trait measure of mindfulness (Fisak & von Lehe, 2012).
Analyses revealed a significant inverse association between PSWQ scores
and three factors of the mindfulness scale: nonreactivity to inner expe-
rience, nonjudgment of inner experience, and acting with awareness.
Furthermore, a review of 19 clinical trials (which included a variety of
treatment modalities, including cognitive behavior therapy, motiva-
tional interviewing, mindfulness-based meditation, etc.) concluded that
interventions aimed at regulating one’s emotional response to repetitive
thought using mindfulness-based techniques are efficacious in alleviating
rumination and worry (Querstret & Cropley, 2013).
Individuals with sleep difficulties typically engage in thought suppres-
sion to minimize the cognitive arousal triggered by rumination and worry
(Ansfield, Wegner, & Bowser, 1996). Most thought suppression techniques
are not only ineffective but are also associated with poor sleep outcomes,
however. Consistent with Wegner’s (1994) ironic process theory, engag-
ing in thought suppression prior to bed results in a paradoxical increase
in cognitive arousal (Harvey & Greenall, 2003). Thus, despite its intui-
tive appeal, thought suppression is not an effective antidote to repetitive
thought. On the other hand, given its focus on acceptance and nonreactiv-
ity, mindfulness may represent a more suitable treatment (see Chapter 16
on mindfulness and sleep for additional information). Notably, although
current treatments, such as cognitive behavior therapy for insomnia
(CBTI), are effective in restructuring dysfunctional attitudes about sleep
216 10. SLEEP REPETITIVE THOUGHT
(Roane, Dolan, Bramoweth, Rosenthal, & Taylor, 2012) and sleep-specific
worry (Sunnhed & Jansson-Frojmark, 2014), their effects on rumination
and more global, nonspecific worry have not been investigated. We there-
fore support recent efforts to supplement CBTI with mindfulness-based
interventions (Ong, Shapiro, & Manber, 2008).
RUMINATION, WORRY, AND SLEEP: OTHER
CLINICAL IMPLICATIONS
Though we emphasize the distinction between sleep disturbance and
insomnia disorder throughout this chapter, research on acute sleep dis-
turbance may nevertheless offer insight into premorbid vulnerabilities to
insomnia disorder. A subset of normal sleepers exhibits heightened stress-
related sleep disruption. Notably, this group exhibits this response in re-
lation to a variety of stressors or challenges to the sleep system, including
a first night in the sleep laboratory, caffeine administration, and circadian
phase shifts (Bonnet & Arand, 2003; Drake, Jefferson, Roehrs, & Roth, 2006).
Such sleep reactivity or the tendency to exhibit pronounced sleep distur-
bance in response to stress exposure has recently gained attention as a di-
athesis of insomnia disorder (Drake & Roth, 2006). The Ford Insomnia in
Response to Stress Test (FIRST: Drake, Richardson, Roehrs, Scofield, & Roth,
2004), a nine-item self-report measure of sleep reactivity, assesses the likeli-
hood of experiencing sleep disturbance in response to common psychoso-
cial stressors. Studies suggest that sleep reactivity, as assessed by the FIRST,
may constitute a trait vulnerability to insomnia disorder; it manifests pre-
morbidly, shows within-person stability, and is predictive of insomnia onset
(Drake, Roehrs, Richardson, & Roth, 2004; Drake, Scofield, & Roth, 2008).
Fernandez-Mendoza et al. (2010) found that trait rumination, as mea-
sured by the ECQ-R, was significantly associated with FIRST scores in a
sample of good sleepers (Global PSQI < 5), even after controlling for gender,
depression, and anxiety. This study offers preliminary evidence that sleep
reactivity and repetitive thought in the form of rumination are correlated
vulnerabilities to insomnia disorder. The above data are cross- sectional,
however, and the investigators did not rule out prior histories of insomnia
disorder in their participants. Similarly, there were no worry measures in
this study. To determine how trait repetitive thought relates to other vulner-
abilities to insomnia disorder, such as sleep reactivity, future studies should
assess levels of trait rumination and worry during the prodromal phase of
the disorder. This research can help integrate the presently disparate liter-
atures on cognitive and somatic/sleep-system vulnerabilities to insomnia.
The association between repetitive thought and sleep disturbance
may also shed light on the comorbidity between insomnia disorder and
depression. Studies suggest that 60-90% of individuals with depression
RUMINATION, WORRY, AND SLEEP: OTHER CLINICAL IMPLICATIONS 217
experience clinically significant levels of insomnia (Kloss & Szuba, 2003).
Clinical and basic science research has amassed a wealth of evidence for
shared etiological pathways to insomnia disorder and depression in re-
cent years, leading some to conclude that these disorders may represent
alternate manifestations of the same or related diatheses (Pillai, Kalmbach, &
Ciesla, 2011). For instance, neuroendocrinological studies suggest that the
mechanisms responsible for the negative-feedback inhibition of stress-
response systems, such as HPA activity, are impaired in both popula-
tions (Balbo, Leproult, & Van Cauter, 2010; Boyce & Ellis, 2005; McKay &
Zakzanis, 2010; Roth, Roehrs, & Pies, 2007). We propose that repetitive
thought may represent another common vulnerability to insomnia disor-
der and depression.
The depression literature suggests that individuals with depression are
significantly more likely to engage in rumination in response to stress, and
that this response style is associated with greater levels of depressive se-
verity and relapse (Calmes & Roberts, 2007). Levels of pathological worry
are similarly elevated in this population and are comparable to those
observed in anxiety disorders (Chelminsky & Zimmerman, 2003). Thus,
existing evidence suggests not only that repetitive thought characterizes
depression, but also that this cognitive style is associated with sleep dis-
turbance. Individuals with insomnia disorder also engage in repetitive
thought, though the focus of cognitive perseveration in this population is
typically on the daytime impairments caused by sleep loss (Carney et al.,
2013). Hence, it stands to reason that sleep-focused and mood-focused
repetitive thought may represent correlated vulnerabilities for insomnia
disorder and depression, respectively. Although sleep-specific repetitive
thought may trigger and maintain insomnia disorder, a more diffuse re-
petitive thought style will more likely precipitate depression or depres-
sion comorbid with insomnia disorder.
In a recent longitudinal study, a large community sample of adults
(n = 3496) with no depression at baseline completed self-report measures
of rumination and sleep disturbance (Batterham, Glozier, & Christensen,
2012). Follow-up data 4 years hence revealed that baseline sleep dis-
turbance was a significant predictor of risk for depression (OR = 1.34;
p < 0.01). This association was reduced to insignificance once rumination
was included in the model, however, such that rumination was signifi-
cantly associated with depression after controlling for sleep disturbance
(OR = 1.12; p < 0.01). Importantly, rumination was measured using a short-
ened version of the RRS, which included depression-focused items (e.g.,
“think about how sad you feel”). Thus, the association between rumina-
tion and depression may have been artificially inflated due to scale collin-
earity. Similarly, sleep was not assessed using a standardized instrument,
and there were no measures of worry. Despite these limitations, however,
this study alludes to the possibility that repetitive thought may underlie
218 10. SLEEP REPETITIVE THOUGHT
the covariation between mood and sleep disturbance. More longitudinal
studies of repetitive thought during the premorbid phase of depression
and insomnia disorder are needed to test this hypothesis.
CONCLUSION
Our review points to a growing literature that supports the association
between sleep disturbance and both rumination and worry. Presently, em-
pirical evidence indicates that trait worriers are significantly more likely
to experience sleep disturbance and that both experimentally induced and
naturally occurring worry can impair subsequent sleep onset and mainte-
nance. The rumination and sleep literature echoes these findings, with the
exception that the association between rumination and objective indices
of sleep maintenance has not been empirically substantiated. A number of
methodological limitations limit the scope of current findings, however,
including the use of single-night assays for sleep assessment, relying on
subjective measures of sleep disturbance, correlational and cross-sectional
designs, lack of standardization in the assessment of repetitive thought
constructs, and an emphasis on disorder-specific models of repetitive
thought and sleep. Consequently, there are several gaps in our current
understanding of this relationship: (1) the mechanisms by which rumi-
nation and worry disturb sleep are poorly understood, (2) it is unknown
whether repetitive thought has any impact on sleep architecture, and (3)
the debate about whether rumination and worry are functionally distinct
with respect to sleep remains unresolved. Targeting these neglected areas
in future research will help elucidate an important link in the pathophys-
iology of sleep disturbance.
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