Introduction
Posttraumatic stress symptoms are common in the immediate aftermath of traumatic experiences but only a minority of trauma survivors develops chronic psychological problems. It therefore appears important to investigate which variables
maintain posttraumatic stress symptoms (Ehlers & Steil,
1995; Schnurr, Lunney, & Sengupta,
2004). Ehlers and Clark (
2000) suggested that one important maintaining factor in posttraumatic stress disorder (PTSD) is rumination about the trauma and/or its consequences.
1 Whereas much of the earlier literature on PTSD subsumed rumination under the re-experiencing symptoms of PTSD (e.g., Greenberg,
1995; Holman & Silver,
1998), several theorists have recently argued that
remembering the trauma (re-experiencing) and repetitively
thinking about it (rumination) are phenomenologically and functionally different forms of intrusive cognitions in PTSD (Ehlers & Clark,
2000; Joseph, Williams, & Yule,
1997). Intrusive re-experiencing is thought to be due to characteristics of cognitive processing during the trauma and the resulting trauma memory (Brewin & Holmes,
2003; Ehlers, Hackmann, & Michael,
2004), whereas rumination is thought to be driven by problematic appraisals and can be regarded as an important cognitive strategy used by individuals with PTSD to control perceived threat (Ehlers & Clark,
2000; Joseph et al.,
1997).
Some preliminary phenomenological studies indeed supported a distinction between rumination and intrusive re-experiencing. Differences were found on a number of dimensions, including content (evaluative thoughts vs. memories), type of cognition (verbal thoughts vs. sensory impressions) and duration (minutes/hours vs. seconds) (Evans, Ehlers, Mezey, & Clark, in press; Hackmann, Ehlers, Speckens, & Clark,
2004; Michael, Ehlers, Halligan, & Clark,
2005; Speckens, Ehlers, Hackmann, Ruths, & Clark, submitted).
In line with the hypothesis that rumination maintains PTSD, there is preliminary evidence that repetitive and perseverative thinking about issues surrounding the trauma such as its causes, consequences and implications predicts PTSD symptom severity following traumatic events (Clohessy & Ehlers,
1999; Ehlers, Mayou, & Bryant,
1998; Michael, Halligan, Clark, & Ehlers, in press; Murray, Ehlers, & Mayou,
2002; Nolen-Hoeksema & Morrow,
1991; Steil & Ehlers,
2000). Prospective longitudinal studies further found that rumination explains PTSD symptom severity over and above other known predictors (Ehlers et al.,
1998), and over and above diagnostic status at initial assessment (Michael et al., in press).
Although past trauma research has largely focused on PTSD, traumatic experiences can also trigger other disorders, especially major depression (e.g., Mayou, Bryant, & Ehlers,
2001; O’Donnell, Creamer, Pattison, & Atkin,
2004). There is extensive evidence that rumination is involved in the development and maintenance of depression and is associated with a range of detrimental cognitive, emotional and social effects in dysphoric individuals (for a review see Lyubomirsky & Tkach,
2004). However, only one published study to date has investigated the role of rumination in the development of depressive symptoms following trauma. Nolen-Hoeksema and Morrow (
1991) assessed symptoms of depression in college students who had experienced the Loma Prieta earthquake. The students had filled in a trait measure of depressive rumination 2 weeks prior to the earthquake. The authors found that trait levels of a ruminative response style to sad mood assessed before the event significantly predicted post-event levels of depression, even when initial symptoms of depression were controlled for.
In the studies described above, PTSD and depressive symptoms were assessed by self-report measures so that it cannot be ruled out that response styles were partly responsible for the observed associations. The present studies tested whether the relationship between rumination and PTSD and depression after trauma can be replicated using structured diagnostic interviews.
Furthermore, the present studies were designed to explore a possible mechanism by which rumination may maintain PTSD. Theories regarding the role of recurrent negative thinking in emotional disorders need to explain two features. First, although recurrent negative thinking has been found to be associated with emotional disorders, repeatedly thinking about one’s problems or anticipating possible future threats can also be helpful in reaching one’s goals and successfully solving problems (King & Pennebaker,
1996; Martin & Tesser,
1996). It therefore appears important to specify how dysfunctional forms of recurrent thinking can be distinguished from functional ones (see also Harvey, Watkins, Mansell, & Shafran,
2004; Watkins,
2004). Second, rumination and worry are typically described as involuntary and difficult to control. Once ruminative or worrisome thoughts are triggered in individuals with emotional disorders, they tend to persevere for minutes or even hours (Borkovec,
1994; Speckens et al., submitted). It therefore appears necessary to understand the self-perpetuating properties of rumination in individuals with emotional disorders.
A number of different hypotheses have been developed to account for one or both of these features of recurrent negative thinking (e.g., Borkovec, Alcaine, & Behar,
2004; Papageorgiou & Wells,
2003; Startup & Davey,
2001; Wells,
1995). Several authors have argued that functional and dysfunctional forms of recurrent thinking can be distinguished on the basis of the mode in which information is processed. For example, Teasdale (
1999) and Watkins (
2004) suggested that the detrimental effects of ruminative self-focus are due to a conceptual-evaluative—as opposed to an experiential—mode of processing meaning. Similarly, Borkovec and colleagues described worry as a form of cognitive avoidance that is mainly based on verbal thinking and leads to the suppression of visual imagery as well as the attenuation of physiological and emotional responding to aversive stimuli, thereby inhibiting emotional processing (Borkovec,
1994; Borkovec et al.,
2004). Stöber further elaborated this idea in the
reduced concreteness hypothesis of worry (Stöber,
1998; Stöber & Borkovec,
2002). He proposed that worrying leads to reduced imagery because it mainly consists of
abstract thoughts that evoke less imagery and physiological and emotional responses than thoughts of more concrete content (see also Paivio,
1986). Although reduced concreteness might help to avoid aversive imagery or strong emotions in the short term, it is thought to maintain recurrent thinking because it is less likely than concrete thinking to produce a specific conclusion and a suitable problem solution, and because it inhibits emotional processing. The latter suggestion is in line with Foa and Kozak (
1986) who suggested that emotional processing requires the activation of the relevant emotional memory in order to enable the integration of new information. Thinking about a problem or feared situation in an abstract way may lead to an incomplete activation of the relevant emotional memory, and may thus interfere with emotional processing.
Evidence for the reduced concreteness hypothesis of worry comes from three studies. In two studies, participants were asked to describe problems or worries and their potential consequences, and their answers were rated for levels of concreteness. Stöber, Tepperwien, and Staak (
2002, Study 1) found that students’ elaborations of ‘high-worry’ topics were less concrete than those of topics that they did not worry much about. In a second study, patients with generalized anxiety disorder provided less concrete worry descriptions than controls (Stöber & Borkovec,
2002). With successful cognitive behavior therapy, the patients’ descriptions became more concrete.
In the third study, Stöber et al. (
2002, Study 2) used the ‘Catastrophizing Interview’ originally developed by Vasey and Borkovec (
1992). This interview assesses perseverative thinking about a worrisome topic in an iterative procedure by asking participants to elaborate their concerns repeatedly. The degree of perseverative thinking is operationalized as the number of steps completed in the interview. In addition, worry content can be assessed from the answers given in the interview. The interview has successfully been used by different researchers to test hypotheses regarding the process and content of worry (Davey, Jubb, & Cameron,
1996; Davey & Levy,
1998,
1999; Provencher, Freeston, Dugas, & Ladouceur,
2000; Startup & Davey,
2001,
2003), depressive rumination (Watkins & Mason,
2002) and perseverative thinking in insomnia (Harvey & Greenall,
2003). Stöber et al., (
2002) compared the concreteness of answers in the Catastrophizing Interview for topics that the student participants worried about to those that they did not worry about, and found lower concreteness for ‘high-worry’ topics.
These findings provide preliminary support for the hypothesis that worry is characterized by reduced concreteness. It is conceivable that trauma-related rumination in PTSD may similarly be characterized by reduced concreteness. If this is the case, low concreteness may be one mechanism by which rumination maintains PTSD. According to Ehlers and Clark (
2000), recovery from posttraumatic stress symptoms depends on an elaboration of the trauma memory and a modification of problematic appraisals. Both processes require the processing of information on very concrete levels, and thinking about the trauma in an abstract way is unlikely to produce changes in the trauma memory or appraisals.
The studies reported in this paper had two aims. First, we aimed to replicate earlier reports on the role of rumination in predicting PTSD and depression, using both self-reports of symptom severity and structured diagnostic interviews. It was expected that rumination is concurrently and prospectively related to the severity of PTSD and depressive symptoms and that it significantly predicts symptoms at follow-up over and above initial symptom levels. Second, we aimed to test whether the reduced concreteness hypothesis of perseverative thinking applies to rumination in trauma survivors. It was expected that (a) self-reported rumination is significantly related to reduced concreteness of answers in an iterative Rumination Interview that is based on the Catastrophizing Interview, (b) reduced concreteness is significantly related to the perseveration of negative thinking in the interview (i.e., the number of steps) and (c) reduced concreteness is significantly related to symptom levels of PTSD and depression.
Discussion
The first aim of this study was to replicate earlier findings regarding the role of rumination in the maintenance of PTSD and depression following trauma. In line with previous studies (e.g., Ehlers et al.,
1998; Murray et al.,
2002), self-reported rumination about the trauma was significantly and substantially correlated with the severity of PTSD symptoms. Rumination was not only related to concurrent PTSD symptoms, but also predicted subsequent symptoms at 6 months. Rumination predicted a substantial amount of the variance (between 36 and 50%) of PTSD symptom severity. The findings extended those of previous studies in that rumination not only predicted self-reported PTSD symptoms, but also a diagnosis of ASD at 2 weeks, and a diagnosis of PTSD at 6 months after the traumatic event. In addition, rumination predicted the severity of PTSD symptoms over and above what could be predicted from initial symptom levels. In sum, the results of the present studies clearly support the view that rumination is an important maintaining factor of PTSD following trauma, as suggested by recent theoretical accounts (Ehlers & Clark,
2000; Joseph et al.,
1997).
In an earlier study by Murray et al. (
2002), rumination assessed at 1-week posttrauma was found to predict PTSD symptom levels at the 6-month follow-up to a much lower degree than rumination assessed at 1 month after the event. In contrast to this earlier finding, the present study did not find differences in the predictive power of rumination assessed at 2 or 4 weeks. Both showed high correlations with PTSD severity at follow-up. This suggests that rumination is a powerful predictor from 2 weeks onwards.
This finding is of considerable interest for the early detection of people at risk for chronic PTSD. Research into early intervention following trauma has shown discouraging results for debriefing interventions that are offered to every trauma survivor, whereas a course of cognitive-behavioral interventions with individuals at high risk of chronic PTSD has been shown to be effective (for a review see McNally, Bryant, & Ehlers,
2003). The present study suggests that the assessment of rumination might help improve the early identification of trauma survivors in need of early intervention, given that rumination was highly predictive of PTSD at 6 months and that it predicted over and above initial symptom levels. This idea is further supported by the finding that the degree of trauma-related rumination remained high between 2 weeks and 1 month in participants with ASD whereas participants without the disorder showed a reduction in the frequency of ruminative thinking during this interval.
In the past, trauma-related rumination and re-experiencing symptoms have sometimes been treated as a unitary phenomenon (e.g., Greenberg,
1995; Holman & Silver,
1998). However, recent theoretical models of PTSD (Ehlers & Clark,
2000; Joseph et al.,
1997) as well as results from recent phenomenological studies (Evans et al., in press; Michael et al.,
2005, in press; Speckens et al., submitted) suggest that rumination and re-experiencing are conceptually and phenomenologically distinct. This view is supported by our findings that rumination still predicted the maintenance of PTSD when initial symptoms were statistically controlled for and that the size of the correlations did not change when PTSD symptom severity was calculated omitting the re-experiencing symptoms. Thus, the relationship between rumination and PTSD found in this study cannot be explained by a possible lack of discrimination between rumination and re-experiencing in the participants’ answers.
Although there is extensive evidence that rumination is involved in the development and maintenance of depression (see Lyubomirsky & Tkach,
2004 for a review), only one study to date has investigated the role of rumination in the development of depression following trauma (Nolen-Hoeksema & Morrow,
1991). In this study, depressive rumination assessed prior to the traumatic experience significantly predicted posttrauma symptoms of depression. The present results extend this finding by showing that levels of depressive rumination assessed after the trauma are also significantly associated with concurrent and subsequent levels of depression. In addition, it could be shown that rumination assessed shortly after the trauma predicts depression at follow-up over and above initial symptom levels and that rumination not only predicts self-reported levels of depressive symptoms but also a diagnosis of major depression.
Rumination has been identified as a maintaining factor in a number of emotional disorders and it remains unclear whether different types of perseverative thinking identified in different emotional disorders represent similar or different processes (Harvey et al.,
2004). The present results suggest a relationship between trauma-related rumination and depressive rumination. The RIQ and RSQ were moderately to highly correlated, and both measures predicted both PTSD and depression. These findings may have been influenced by the high comorbidity between PTSD and depression in the present samples, as nearly all participants with depression also met criteria for PTSD or subthreshold PTSD. The nature of the samples thus did not allow a direct comparison between rumination in trauma survivors who have PTSD, but no depression, and those who have depression, but no PTSD. However, partial correlations in the prospective study provided preliminary evidence for a specific association between trauma-related rumination and PTSD symptom severity on the one hand (controlling for depressive symptoms), and between depressive rumination and severity of depressive symptoms on the other hand (controlling for PTSD symptoms). It would be desirable in future studies to identify groups of trauma survivors that are more clearly separated by their diagnostic status, for example, by including mixed groups of trauma survivors who have suffered loss or threat to life.
Despite evidence that rumination is involved in the maintenance of emotional disorders following trauma, to our knowledge, no published study to date has investigated the process by which rumination might maintain posttraumatic stress symptoms. Self-report measures used to date mainly assess the frequency and content of rumination and therefore appear to be of limited use when studying the processes underlying perseverative thinking. The present studies therefore adapted the Catastrophizing Interview to investigate process characteristics of rumination in trauma survivors. The original paradigm has repeatedly been shown to be useful in studying factors underlying chronic worry (e.g., Davey et al.,
1996; Startup & Davey,
2001). In the studies reported here, the number of steps in the Rumination Interview was significantly related to self-reported rumination, providing initial evidence that perseveration in the interviews is indeed related to naturally occurring perseverative thinking. However, as in most earlier studies (e.g., Startup & Davey,
2001; Watkins & Mason,
2002), correlations were only modest.
The answers given in the Rumination Interview were analyzed to test the reduced concreteness theory of recurrent negative thinking in emotional disorders (Stöber,
1998) in the context of trauma-related PTSD and depression. Three different hypotheses were derived from the theory. First, it was expected that recurrent negative thinking is characterized by reduced concreteness. This hypothesis had found initial empirical support in studies of non-clinical worry and generalized anxiety disorder (Stöber & Borkovec,
2002; Stöber et al.,
2002). The present studies failed to show a relationship between self-reported rumination and level of concreteness in the Rumination Interview. Differences between the present results and Stöber et al.’s findings may be due to differences in methodology, or differences between worry about future events and rumination about a past event. As to methodological differences, Stöber et al.’s positive results with the Catastrophic Interview technique were based on within-subject comparisons showing that the (non-clinical) participants’ thinking about topics that they worried about was less concrete than their thinking about non-worry topics. The present studies used between-subject and correlational analyses of rumination about the same topic, which may have less power than a within-subject comparison. Furthermore, in contrast to Stöber et al.’s study (
2002), all participants were interviewed about a recent very upsetting event, and this may have led to a reduced range in concreteness ratings compared to the range of concreteness for worry and non-worry topics in Stöber et al.’s study.
The results may also point to possible differences between worry and rumination. Worry and rumination have so far mainly been distinguished on the basis of their content, in that rumination is typically associated with thinking about the past, whereas worry represents anxious thoughts about future events (Fresco, Frankel, Mennin, Turk, & Heimberg,
2002; Segerstrom, Tsao, Alden, & Craske,
2000). The anticipation of future events (as in worry) may lend itself to a greater range of levels of concreteness than thoughts about past experiences that have already happened (as in rumination), which are by definition more concrete than future events. The investigation of concreteness vs. abstractness of thinking about the past might therefore need a more fine-grained analysis than reflected by the concreteness rating scale developed by Stöber and colleagues. This may apply especially when looking at concerns related to a trauma, which is a specific event with sometimes very concrete worrying consequences such as physical injuries and the need for further operations.
A second hypothesis derived from the reduced concreteness theory was that reduced concreteness is involved in the perseveration of negative thinking in individuals suffering from emotional disorders. In line with this idea, Study 1 showed a significant relationship between the number of steps generated in the Rumination Interview and concreteness ratings. However, Study 2 did not replicate this result. It is conceivable that the observed relationship with reduced concreteness only applies to chronic forms of rumination, as the negative findings in Study 2 were obtained only 2 weeks after the event, when the event may have been very prominent on all participants’ minds. Thus, the findings of Study 1 need replication before further conclusions can be drawn.
Finally, we hypothesized that if functional and dysfunctional ways of recurrent thinking about problems or negative experiences differ in concreteness, then reduced concreteness should predict the severity of psychological problems after trauma. This hypothesis received some, but overall weak support in Study 2, which found significant group differences in concreteness between participants with and without major depression at 2 weeks after the accident, and correlations between low concreteness at 2 weeks and severity of depressive symptoms at 3 and 6 months. There were also some correlations between low concreteness and PTSD symptom severity. Overall, the correlations were small. The hypothesis received some further support as multiple regression analyses showed that PTSD symptoms at 6 months were better predicted by the combination of the frequency of trauma-related rumination and reduced concreteness of ruminative thinking at initial assessment than by rumination frequency alone. Overall, the results were disappointing and only showed weak support for the view that reduced concreteness of thinking about the trauma is associated with the maintenance of depression and PTSD following trauma. The results need to be interpreted with great caution as correlations and group differences were non-significant for some of the time points and concreteness in the rumination task did not correlate with self-reported rumination. More research is needed before any firm conclusions regarding the role of reduced concreteness in trauma-related rumination can be drawn. Future studies should especially aim to improve the assessment of concreteness. The measure used in this study might have lacked sensitivity as some of the problems that participants worried about were by definition concrete (physical and financial problems), and the measure only consisted of one global rating. Thus, a refined assessment of concreteness may show stronger relationships with self-reported rumination and with psychopathology. In addition, alternative hypotheses regarding the processes by which rumination maintains PTSD should be developed and tested.
In sum, results from the present studies replicated and extended earlier findings regarding the role of rumination in the maintenance of emotional disorders following trauma. Rumination at 2 weeks and 1 month after the trauma appears to be an important predictor of PTSD. In addition, there was very preliminary support for a role of the style or mode of ruminative thinking. However, the hypotheses that frequent rumination and perseveration in the Rumination Interviews are associated with reduced concreteness were only partially supported. More research is needed to replicate and extend these results as well as clarify the disparate findings between the two studies.
A number of limitations of the studies are noteworthy. First, although a prospective longitudinal design was used in Study 2, the results remain correlational. Future studies are needed that manipulate rumination and its characteristics such as concreteness experimentally and test the effect of these manipulations on symptom severities. Second, the high comorbidity between PTSD and depression in the samples studied did not allow a direct comparison between rumination in different diagnostic groups. Future studies comparing clearly distinct diagnostic groups are needed to investigate similarities and differences between different types of perseverative thinking in PTSD and depression. Third, other measures of concreteness may have shown stronger relationships with self-reported rumination and symptom measures. Finally, it remains unclear whether low concreteness is an important dimension underlying dysfunctional forms of recurrent negative thinking. Alternative approaches suggest that functional and dysfunctional ways of thinking about problems or negative experiences can rather be distinguished by the amount of imagery vs. verbal processes involved (Borkovec,
1994; Borkovec et al.,
2004) or the degree of conceptual-evaluative vs. experiential self-focus (Teasdale,
1999; Watkins,
2004). Although these views appear to be related, future theoretical as well as empirical work is needed to clarify the relationship between these processes and isolate the most relevant dimensions involved in the maintenance of PTSD and depression after trauma. Such research may point toward possible ways of directly targeting dysfunctional rumination in treatment.