Attention, Memory, Intrusive Thoughts, and Acceptance in PTSD: An Update on the Empirical Literature for Clinicians

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Cognitive and Behavioral Practice 15 (2008) 349–363 www.elsevier.com/locate/cabp

Attention, Memory, Intrusive Thoughts, and Acceptance in PTSD: An Update on the Empirical Literature for Clinicians Jillian C. Shipherd and Kristalyn Salters-Pedneault VA Boston Healthcare System, National Center for PTSD, and Boston University School of Medicine Information processing theory suggests that cognitive changes following trauma are common and hypothesized to have an impact on attention, memory, and intrusive thoughts. There is an ever-expanding empirical literature where cognitive features of posttraumatic stress disorder (PTSD) are being explored. However, it can sometimes be difficult for front-line clinicians to stay abreast of this literature and how it impacts the treatment s/he provides. The goal of this paper is to provide an overview of some recent basic and applied research on information processing in PTSD and the implications of these findings for cognitive-behavioral clinicians. In particular, we explore recent findings regarding attention, memory, intrusive thoughts/thought suppression, and acceptance as they relate to clinical work in patients with PTSD.

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estimated 50% to 60% of individuals in the United States will experience at least one traumatic event in their lifetime (e.g., Kessler, Sonnega, Bromet, Hughes, & Nelson, 1995; Ozer, Best, Lipsey, & Weiss, 2003). In the immediate aftermath of a trauma, symptoms of posttraumatic stress disorder (PTSD), including reexperiencing of the trauma (e.g., intrusive thoughts, nightmares, flashbacks), emotional numbing (e.g., feelings of detachment, disinterest, and restricted range of affect), avoidance of trauma cues, and symptoms of excessive arousal (American Psychiatric Association [APA], 2000) are quite common. However, these symptoms tend to decline naturally in the first 3 to 6 months following the event (Blanchard et al., 1995; Delahanty et al., 1997; Ehlers, Mayou, & Bryant, 1998; Rothbaum, Foa, Riggs, Murdock, & Walsh, 1992; Valentiner, Foa, Riggs, & Gershuny, 1996), with some survivors of trauma even making positive changes in their lives (e.g., Linley & Joseph, 2004). Unfortunately, not all survivors follow a trajectory of recovery and/or growth after the event, with between 5% and 30% going on to develop chronic PTSD (e.g., Breslau et al., 1998; Kessler et al., 1995; Ozer et al., 2003). As a whole, cognitive behavioral therapy (CBT) for PTSD has been recommended by the International Society for Traumatic Stress Studies (Foa, Keane, & Friedman, 2000), the APA (Ursano et al., 2004), the National Institute for Clinical Excellence (Bisson et al., 2005), and the Departments of Veterans Affairs and N

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Defense (2003) as the standard of care for PTSD. Further, large treatment effect sizes are noted with CBT for PTSD in meta-analytic reviews (e.g., Butler, Chapman, Forman, & Beck, 2006). However, even with PTSD being considered a treatable disorder (e.g., Bradley, Greene, Russ, Dutra, & Westen, 2005), chronic PTSD can be persistent (e.g., Rothbaum et al., 1992; Zlotnick et al., 1999) and resistant to treatment relative to other anxiety disorders (e.g., Foa, 2000). Clearly, more research is needed to finetune and improve the efficacy of CBT for PTSD. Information processing theories (e.g., Foa & Kozak, 1986; Litz & Keane, 1989; Mathews & MacLeod, 1994) provide one framework for hypothesis-driven, basic research with relevance for CBT clinicians. Most readers will be familiar with this conceptualization,1 which argues that traumatic memories are constructed of a network of information about the trauma, including cues (e.g., discrete physical cues and contextual reminders of the trauma), internal responses (e.g., emotional and physiological responses), and meaning-making elements (e.g., trauma-related beliefs or assumptions). These theories further propose that trauma memories are stored in an 1 The reader less familiar with information processing theory is directed to Buckley, Blanchard, and Neill (2000) for a more comprehensive review of information processing in PTSD, and Barlow (2002) for a book-length review of information processing theory and cognitive features of anxiety in general. For readers seeking additional information regarding CBT for PTSD, Brewin and Holmes (2003) provide a review of the dominant cognitive behavioral theories of PTSD. In addition, Follette and Ruzek (2006) provide a book-length description of the application of cognitive-behavioral therapies, including case examples.

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excessively fragmented, disorganized network, isolated from other information networks, relative to “normal” memories. Hypothetically, the atypical storage and retrieval of trauma memories may result in attentional problems, memory disruption, and intrusive thoughts (Brewin, 2001; Ehlers & Clark, 2000; Foa & Kozak, 1985; Foa & Riggs, 1993; van der Kolk et al., 1994). Thus, the features of PTSD reviewed in this paper are believed to be a by-product of the unusual circumstances in which traumatic memories are formed and stored. The basic and translational information processing literature has direct implications for the applied treatment setting. Theoretically, it is believed that approachbased treatment techniques assist in the habituation to the emotions (generally fear) associated with the traumarelated thoughts (Horowitz, 1986; Lang, 1977; Rachman, 1971). From a behavioral perspective, a process of extinction learning is hypothesized to take place. Specifically, through approach of the trauma-related material, new learning occurs which specifies that this material (e.g., thoughts, emotions, and images related to the event) is not dangerous and that the fear reaction need not be activated when these reminders are encountered (see Keane, Zimering, & Caddell, 1985). From an information processing standpoint, the incorporation of new information into the trauma memory network (e.g., information that specifies when a particular trauma cue is no longer dangerous and does not need to be avoided), and the formation of new beliefs such as qthis is only a memory and what happened is in the past and cannot harm meq are important to recovery (Foa, Steketee, & Rothbaum, 1989). Thus, the new learning often involves a cognitive element where the individual develops more adaptive ways of reacting to thoughts and feelings. However, for this process of habituation and/or new learning to take place, a trauma survivor must be willing to face feared stimuli, including trauma memories, rather than avoid feared stimuli. In this paper, we review some recent findings from the basic, translational, and applied information processing literatures that have implications for CBT practice. In particular, exciting new research in the areas of attention, memory, intrusive thoughts, and thought suppression/ acceptance may help clinicians to refine their practice for patients with PTSD.

Attention Attention is fundamental to perception and encoding of new information. As such, attention is a necessary component for taking in new information such as psychoeducation, therapeutic strategies, and coping skills. Most therapists are aware that attention is affected in PTSD. Indeed, there is a large literature suggesting that individuals with PTSD show attentional biases toward

threat-related information, primarily when tested using the modified Stroop paradigm (Stroop, 1935). The modified Stroop paradigm has been used to study cognitive disinhibition of trauma-related material in trauma survivors by comparing participants’ latency to name the color of words related to their trauma (e.g., COMBAT: correct answer is “black”), to their latency to name the color of neutral words. The trauma-related Stroop delay has been demonstrated in a variety of populations, including sexual assault survivors (Cassiday, McNally, & Zeitlin, 1992; Foa, Feske, Murdock, Kozak, & McCarthy, 1991), childhood sexual abuse survivors (Bremner et al., 2004; Field et al., 2001), war veterans (Litz et al., 1996; McNally, English, & Lipke, 1993; McNally, Kaspi, Riemann, & Zeitlin, 1990), survivors of a ferry disaster (Thrasher, Dalgleish, & Yule, 1994), and motor vehicle accident survivors (Beck, Freeman, Shipherd, Hamblen, & Lackner, 2001; Bryant & Harvey, 1995). Trauma-related delays on Stroop tasks have also been demonstrated in child and adolescent trauma survivors (Freeman & Beck, 2000; Moradi, Taghavi, Neshat Doost, Yule, & Dalgleish, 1999). It is clear from the Stroop literature that there is some type of attentional problem with patients who have PTSD, perhaps due to the activation of the trauma memory and/or associated fear. However, without a better understanding of the specific qualities of these attentional problems, this research literature has been difficult to apply in clinical practice. Fortunately, more recent studies parsing the particular types of attentional difficulties in PTSD may better inform CBT strategies for addressing these problems. Facilitation Versus Interference A problem in the attention literature is that the methods employed (e.g., the Stroop task) do not elucidate whether individuals are demonstrating attentional biases due to enhanced detection (facilitation) of or difficulties disengaging from (interference) threatening stimuli (e.g., Derryberry & Reed, 2002). Differentiating between these two types of attentional biases is clearly important for informing treatment and understanding the exact nature of attentional biases in PTSD. More recently, studies using paradigms that disambiguate facilitation from interference effects have found support for attention interference but not for facilitation in PTSD (Pineles, Shipherd, Yovel, & Welch, 2007; Pollack & Tolley- Schell, 2003). Although this literature is new and requires replication, it seems that patients with PTSD tend to “get stuck” on trauma stimuli, rather than having attention drawn quickly to the stimuli. Attentional interference can affect concentration, interfere with task-performance, and lead to an overvaluation of threat-relevant information. Trauma-related cues can include both internal (e.g., thoughts) and external (e.g.,

Empirical Studies of PTSD angry person) stimuli. In daily life, attention interference can be problematic when attention should be redirected to new stimuli (e.g., a question from boss, traffic light turning red). Patients will sometimes describe this as a “lapse of concentration” when it is more accurately termed attentional interference. Notably, the participants in these studies were trying to perform well, yet were slower in redirecting attention, even with effort. Providing psychoeducation about attention can be important when trying to normalize a patient’s experiences with PTSD. This information can be important to some trauma survivors who may fear that they are “not trying hard enough” to pay attention. It is equally important to recognize that trauma survivors without PTSD did not demonstrate these delays, which can provide additional motivation for treating PTSD in some patients, as discussed below. What is perhaps even more interesting than the presence of attentional interference is the absence of facilitation (attention drawn quickly to stimuli) with PTSD patients in experimental settings. For many years, it has been assumed that hypervigilance in PTSD was due to attentional facilitation, based on the theoretical assumption that resources are easily drawn to trauma-related stimuli (e.g., Foa et al., 1989), but no support has been found for facilitation in the laboratory setting. Anecdotally, patients often report a reluctance to reduce hypervigilance symptoms due to the belief that attention biases are adaptive and lead to increased safety. For example, this belief is commonly held by combat veterans with PTSD, who may view PTSD-related hypervigilance as an extension of their increased vigilance in the war zone, a phenomenon that may well have been adaptive in that setting. Indeed, if hypervigilance could provide an increased ability to detect actual threat (facilitation) and respond accordingly, it would be adaptive. However, there is little empirical support for this notion, and this growing line of research suggests that patients with PTSD appear unable to redirect attention appropriately, a characteristic that is more likely to reduce safety than increase it. In contrast, trauma survivors without PTSD appear able to shift their attention in response to the demands of the environment, which is essential to responding to actual, present-moment threat. Thus, the experimental literature can be utilized by clinicians to assist patients in becoming motivated for treatment when they inaccurately believe that attentional biases associated with PTSD are adaptive. Another important implication of these findings for clinical work is the recognition that attentional interference is likely present during therapy sessions. Delivery of PTSD treatment inherently involves raising traumarelated cues, which can decrease the ability of the patient to redirect attention away from trauma-stimuli (e.g., intrusive thought) toward the session content (e.g., psychoeducation, coping skills). It should be assumed

that patients with PTSD will be slow to focus on the information being presented and will experience repeated attentional problems throughout treatment. Perceptual level problems (such as attentional interference) often occur outside the patient’s awareness or ability to report on the occurrence of the phenomenon. Thus, repeated attentional interference during CBT for PTSD should be assumed. Multiple presentations of information increase the likelihood of attention being on the relevant stimuli during the session. Additionally, all materials should be provided to the patient in a format that is easily accessible for repeated presentations outside the session (e.g., written handouts, audiotaped sessions). In sum, attentional biases must be acknowledged and attended to in the course of traditional CBT for PTSD. Attentional Retraining Another interesting possibility emerging from the empirical literature on attention in anxiety is the prospect that information processing biases (e.g., attentional bias towards threat) being directly manipulated through cognitive training techniques, thereby decreasing anxiety (see Mohlman, 2004, for a review). These attention and cognitive training techniques are outside of those employed in typical psychotherapeutic intervention. The methods of cognitive and attention retraining often involve adapted versions of experimental cognitive paradigms, which could be a challenge for therapists for whom the experimental paradigms are new. For example, an attentional retraining session may involve the patient engaging in a modified dot probe paradigm. In the dot probe task, the patient is seated in front of a computer screen and asked to gaze at a fixation point that appears on the center of the screen. Next, two stimuli appear briefly on either side of the screen; one neutral and one threat or trauma-related. Once these stimuli are withdrawn, a dot appears on the screen where one of the stimuli had been, and the participant is asked to respond with a key indicating which side of the screen the dot had appeared. In an experimental setting, participants are given no instructions as to which stimulus to attend to, and the latency to responding to the dot is measured as an index of attentional bias. However, in an attentional retraining context, patients would be instructed to repeatedly practice orienting and attending to the neutral stimuli while disengaging from threatrelevant stimuli throughout the procedure. In this way, it is hoped that the patient is provided with sufficient practice learning new patterns of attention allocation that are more flexible and adaptive. There is very preliminary evidence of the effectiveness of such techniques in the translational research literature (e.g., Rutherford, MacLeod, & Campbell, 2002, as cited in Yiend & Mathews, 2005). To date, however, there are no published

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randomized controlled trials supporting the efficacy of the techniques as they relate to anxiety disorder symptoms generally or PTSD specifically, so more work is needed before these types of techniques can be used confidently in conjunction with traditional CBT methods.

Memory For decades, information processing theories of PTSD have attended to the effects of trauma and PTSD on memory. Researchers have examined the impact of PTSD on memory in general, and on the specific qualities of the trauma memory, along with the implications of these qualities for the alteration of trauma memories in treatment (e.g., Isaac, Cushway, & Jones, 2006; Moore & Zoellner, 2007; Schonfeld & Ehlers, 2006; Schonfeld, Ehlers, Bollinghaus, & Rief, 2007). The literature suggests that for PTSD patients, trauma memories are different from other nontraumatic memories (Brewin, 2007). As an example, patients with PTSD recount trauma memories that are more sensory-laden as compared with trauma survivors without PTSD, where other elements such as thoughts and emotions are also included (e.g., Jones, Harvey, & Brewin, 2007; Meiser-Stedman, Dalgleish, Smith, Yule, & Glucksman, 2007). Further, recent findings are beginning to shed light on the formation of trauma memories and ways that these memories may be emended in therapy as described below. Peritraumatic Experiences and Memories An emerging finding from the basic research literature is that excessive disorganization/fragmentation of the trauma memory may be particularly likely when trauma survivors experienced strong reactions at the time of the trauma, termed peritraumatic responses (Ozer et al., 2003). As an example, perception of life threat during the traumatic event had a larger effect size in meta-analytic review when predicting later PTSD than prior traumas or mental health treatment (Ozer et al., 2003). This finding is notable, as prior traumas and treatment history are commonly accepted as important predictors of posttrauma functioning. Another strong peritraumatic reaction, dissociation, has also been linked to PTSD. A prospective longitudinal study of trauma recovery documented that peritraumatic dissociation predicted PTSD symptoms later, as did memory fragmentation, a related phenomenon (Murray, Ehlers, & Mayou, 2002). The authors of this study noted that persistent dissociation (as assessed 4 weeks posttrauma) was even more strongly associated with ongoing PTSD symptoms at 6 months. It was hypothesized that peritraumatic dissociation is a risk factor that can be overcome with post-event processing of the event, a process that is disrupted by persistent dissociation (Murray et al., 2002). Similarly, peritraumatic dissociation was strongly associated with PTSD across an

additional 16 studies (medium effect size across 16 studies; Ozer et al., 2003). Although, it is important to note that peritraumatic dissociation is not always associated with PTSD symptoms, especially if persistent dissociation is included in the analyses (e.g., Briere, Scott, & Weathers, 2005; Geraerts et al., 2007). The association between peritraumatic dissociation and PTSD has implications for memory given that disruptions in encoding of an event will occur with dissociation, and may affect the quality and coherence of trauma-related memories. Prospective experimental examinations of trauma narratives completed soon after an event demonstrate that less cohesive and more disorganized narratives are related to PTSD symptoms at 3 and 6 months post-event (Halligan, Michael, Clark, & Ehlers, 2003; Jones et al., 2007). Across all participants, narratives do become more cohesive across time (Jones et al., 2007). Interestingly, repeated narratives that become more cohesive are related to PTSD symptom improvement in treatment-based studies (van Minnen, Wessel, Dijkstra, & Roelofs, 2002), but not in the experimental setting (Jones et al.). The most parsimonious explanation for these findings is that there may be “dose effects” related to the number of repetitions of the narrative required in treatment versus the few assessments in experimental settings. While studies of peritraumatic responses may seem unrelated to the practice of CBT clinicians in traditional tertiary prevention contexts (other than in terms of assessment and prognosis), these findings are informative in several key ways. First, these findings suggest that the use of trauma narratives (particularly repeated trauma narratives) to improve the cohesion of the trauma memory may be useful. Second, the findings suggest that, wherever possible, secondary prevention of PTSD to alter dissociative responses as soon as possible after the trauma may be indicated in some cases. These two possibilities are discussed further below. Finally, these findings suggest that for populations that are likely to be exposed to trauma (e.g., combat servicepersons, emergency response personnel), trainings or primary prevention programs that reduce peritraumatic dissociation may be indicated. Learning, Extinction, and the Trauma Memory A key element of any CBT for PTSD is the approach of trauma-related information, either in the form of exposure, cognitive restructuring, or other techniques in which the trauma memory is accessed. From both behavioral and information processing standpoints, these techniques are intended to impact the retrieval of the trauma memory that formed at the time of the event, including the conditioned association between the trauma (and fear response) and previously neutral cues

Empirical Studies of PTSD (e.g., objects, people, and contexts). In the past, theorists described the process of learning in exposure-based therapies as an eradication of the original trauma memory, either through erasure of the original association between the fear-producing event stimulus and previously neutral cues (extinction, e.g., Keane et al., 1985), or through habituation and dismantling of the trauma memory network (e.g., Foa & Kozak, 1986). The structure of current exposure-based CBT for PTSD (e.g., Foa, Hembree, & Rothbaum, 2007) is based on these underlying theoretical assumptions. However, the latest learning and memory research suggests that neither of these explanations is sufficient (see also Mineka & Thomas, 1999); this literature has substantial implications for the day-to-day practice of CBT with PTSD. One of the central weaknesses of the early conditioning and information processing accounts of the alteration of the original trauma memory is that these explanations did not account for the return of fear that is often seen after treatment. In lab studies, return of fear after extinction has been demonstrated with the passage of time (spontaneous recovery; e.g., Bouton, 1993), a change in context (renewal; e.g., Bouton, 1993), or a reexposure to a stressor (reinstatement; e.g., Rescorla & Heth, 1975). Based on this basic research literature, behavioral theorists now propose that following exposurebased learning, the original fear associations remain intact (e.g., Bouton, 1994). Extinction is now conceptualized as new learning regarding the situations or contexts in which the fear response should be inhibited (Bouton, 1994). Thus, the original memory is not erased, but new competing and more adaptive information is added to the store of information that guides behavior. Unfortunately, unlike the original fear associations, this new extinction learning does not appear to be particularly robust. Instead, it is highly dependent on the context in which the extinction takes place (e.g., Bouton & Bolles, 1979; Bouton & King, 1983; Bouton & Peck, 1989). Bouton’s (1994) work suggests that many clinical failures to extinguish fear may be related to the variety of background contextual variables that operate in extinction learning. For example, changes in physical context or internal state (e.g., Bouton, Kenney, & Rosengard, 1990) or a variation in the passage of time (Bouton & GarcíaGutiérrez, 2006) have been shown to lead to a return of fear. Interestingly, laboratory findings regarding the properties of conditioned fear and extinction learning are consistent with a recent information processing account of memory retrieval. The “new theory of disuse” (Bjork & Bjork, 1992) posits that memories are subject to both storage strength and retrieval strength. Storage strength refers to how well the memory has been learned, whereas retrieval strength refers the accessibility of the memory.

Bjork and Bjork (1992) note that while storage strength is unlimited and permanent, retrieval strength is highly dependent on current context and cues. Lang, Craske, and Bjork (1999) applied this theory to the learning and memory aspects of CBT for emotional disorders, noting that the new theory of disuse also predicts the return of fear following CBT. They propose that while CBT creates a new, nonfearful response to anxiety-producing cues, the storage strength of the original memory of the cues and fear response is unaltered, and with the right contextual cues and/or passage of time, will reemerge as the dominant response. Thus, both these lines of inquiry raise concerns about the way that CBT for PTSD is currently being delivered. The learning promoted by therapy typically occurs only in one or two contexts during treatment. For example, imaginal exposure is generally conducted only in the therapist’s office and at the patient’s home, which may not provide enough contexts for the generalization of new learning. Furthermore, the duration of treatment is generally short-lived in comparison to the duration of the individual’s rehearsal of the original fear response, typically for many years before entering therapy. In addition, other aspects of the context may be narrow in CBT because clients are likely to select the timing of homework (e.g., schedule exposure homework at the same time every day) or the internal context (e.g., avoiding exposure when upset). Thus, when the experimental literature is taken in context, it is not difficult to see how CBT for chronic PTSD could fail. Fortunately, basic research also indicates ways that the extinction learning during the course of CBT may be strengthened. For example, Bouton’s work suggests that if the current context is reminiscent in some way of the therapy context, then fear is less likely to return (Brooks & Bouton, 1993, 1994). This is consistent with Lang and colleagues’ (1999) framework for applying the new theory of disuse to anxiety disorders. Simple changes in the way that CBT is delivered may increase the strength of the new memories that are formed in therapy, thereby reducing return of fear. For example, variation in the target to-belearned (e.g., varying focus to different elements of single traumatic event), the context of the learning (e.g., practice in multiple settings, and with multiple mood states), as well as the spacing of learning trials (e.g., with increasing intertrial intervals) can be altered to maximize therapeutic benefits. For example, studies have demonstrated that expanding-spaced trials are superior to massed (or single session) trials in reducing return of fear (Rowe & Craske, 1998a, 1998b; Tsao & Craske, 2000). This suggests that scheduling sessions at expanding intervals apart (e.g., 2 days apart, then 5 days apart, then 7 days apart, and so on) will reduce relapse after the final session. Other studies have demonstrated that

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Shipherd & Salters-Pedneault variation in the target stimulus reduces return of fear (Rowe & Craske, 1998a). This finding suggests that using variations of a trauma narrative (e.g., narratives that focus on different aspects of a single event), or varying the nature of in vivo exposure targets (e.g., having a motor vehicle accident survivor drive on many kinds of highways, rather than one that is most convenient), may improve outcomes. In addition, overlearning may prevent relapse following CBT (i.e., including multiple exposure trial sessions after extinction has already been achieved). In the future, this new line of research may refine our understanding of session scheduling, timing of at-home practice, multiple office settings (context), and what stimulus elements to include in exposure work to maximize outcomes. However, more work is needed to fully understand the implications of this research, particularly given recent findings from the infrahuman literature suggesting that straightforward context variations (e.g., holding sessions in different offices each time) during extinction training may not necessarily reduce the return of fear (Bouton et al., 2006). Trauma Narrative and Effects on the Trauma Memory Recent research can also inform traditional elements of treatment such as how the content of the trauma memory is accessed. A recent study of the degree of activation in the hippocampus and amygdala (using fMRI) when viewing negative pictures provides additional support that it is “necessary to revisit an emotional memory before it can be controlled” (Dupue, Curran, & Banich, 2007, p. 218). In many standard CBT for PTSD protocols, the role of therapist is to both help the survivor to “flesh-out” their memory of the trauma by including more details, and to help them to recognize any biases that may exist in memory (e.g., Brewin, Dalgleish, & Joseph, 1996; Dalgleish, 2004; Ehlers & Clark, 2000). Survivors may be encouraged to elaborate on the memory of their trauma, including aspects of the experience or the context that were positive or nontraumatic as well as expanding beyond sensory information (e.g., MeiserStedman et al., 2007). The goal of this work is to enhance the coherence and organization of the trauma memory, which may help that memory take on the properties of a qnormalq memory (e.g., less intrusive, more fully elaborated). This also broadens the survivor's access to other memories and increases the specificity of these memories, which is important given a tendency toward overly general memories in PTSD patients (e.g., Schonfeld & Ehlers, 2006). This may help the survivor to place the trauma in the context of their full lives. In addition to the peritraumatic response and dissociation literature reviewed above, there is other evidence to suggest that creating a cohesive narrative account of

traumatic experiences can be beneficial for well-being. The emotional disclosure writing paradigm developed by Pennebaker and colleagues (see Pennebaker, 1997) is a transtheoretical approach to guiding patients in creating a cohesive narrative of their experiences. Generally speaking, expressive writing has demonstrated improvements in both physical health and mental health outcomes (see Frattaroli, 2006; Harris, 2006; Pennebaker, Kiecolt-Glaser, & Glaser, 1988; Smyth, 1998, for metaanalyses). Writing about a traumatic event may help shape the narrative and meaning surrounding the trauma, and serve as a tool to promote habituation to the traumatic material. Most cognitive-behavioral treatments for PTSD include imaginal exposure (PE; Foa et al., 2007) or a written account of the event (CPT; Resick & Schnicke, 1992). Indeed, a study with five sessions of writing about trauma for 45 minutes each session resulted in significant symptom reduction that was sustained over a 2-month follow-up (Schoutrop, Lange, Hanewald, Cuurland, & Bermond, 1997; Schoutrop, Lange, Hanewald, Davidovich, & Salomon, 2002). However, it should be noted that not all studies of written disclosure show benefits (Batten, Follette, Hall, & Palm, 2002; Gidron, Peri, Connolly, & Shalev, 1996), and there are mixed findings even within some studies. One study found that writing about a traumatic event was associated with short-term increases in physiological arousal but longer-term health benefits (Pennebaker & Beall, 1986). Another study found that inmates who wrote about traumatic experiences for 20 minutes for 3 consecutive days reported more physical symptoms after the writing, but fewer visits to the infirmary as compared with inmates writing about minor issues or not at all (Richards, Beal, Seagal, & Pennebaker, 2000). Interestingly, the benefits to emotionally expressive writing about traumatic events may only happen when the person writes repeatedly about the same event (as happens in exposure therapy) rather than writing about multiple events (Sloan, Marx, & Epstein, 2005). The mixed findings could be due in part to methodological differences in the studies. There are many potentially relevant variables, including the number of events written about, time-frame of assessment and writing interval (as suggested by the learning literature reviewed above), gender of the participants, or levels of physiological arousal during the task. Overall, it is clear that further study is needed to elucidate the mechanism of action for obtaining benefit (if any) from writing about trauma (Sloan & Marx, 2004). Interestingly, studies that include elements similar to treatment strategies (e.g., repeated writing about the same event) show the most benefit (e.g., Richards et al., 2000; Schoutrop et al., 1997; Schoutrop et al., 2002). Although, there are some contradictory findings (e.g.,

Empirical Studies of PTSD when writing was focused on chronic childhood sexual abuse, no support was found for written disclosure; Batten et al., 2002), the results documenting initial distress followed by long-term benefit mirror what is anticipated in treatment. Further, meta-analytic review of the disclosure literature emphasizes that the best outcomes occur when writing sessions occur over 1-week intervals (Smyth, 1998; see also learning literature reviewed above about memory reconsolidation), which reflects what occurs in many treatment settings. Finally, the context of self-disclosure may also be relevant. When selfdisclosure occurs within the context of helpful social supports (e.g., to a significant other), survivors can access one of the strongest protective factors in trauma recovery (e.g., Brewin, Andrews, & Valentine, 2000; Bolton, Glenn, Orsillo, Roemer, & Litz, 2003; Schumm, Briggs-Phillips, & Hobfoll, 2006; Solomon & Mikulincer, 1990; Taft, Stern, King, & King, 1999). Importantly, expectations associated with disclosure also appear to be a significant predictor of outcome. A recent study documented that when participants had positive expectations about expressive writing, there was a reduction in emotional impact of the upsetting event they were writing about, along with health benefits (Langens & Schuler, 2007). In contrast, negative expectancies about the writing task led to poor outcomes (Langens & Schuler, 2007). Thus, these studies support the continued use of writing paradigm, and suggest some specific ways to approach expressive writing in therapy, including maximizing patient expectancies. Behavioral Neuroscience and the Trauma Memory Another exciting area of research in memory and PTSD concerns the application of findings from the behavioral neuroscience literature to the alteration of trauma memories. While still in the early stages, some findings suggest that novel pharmacological treatments may prevent PTSD and/or facilitate CBT for PTSD. For example, one model of PTSD has argued that the overstimulation of stress hormones at the time of the trauma leads to an overgeneralized fear response (e.g., Pitman et al., 1990). Findings from prospective studies support this hypothesis; a study of initial hyperarousal levels in the immediate aftermath of trauma were related to PTSD symptom levels at 3 and 12 months later (Schell, Marshall, & Jaycox, 2004). These findings have clear implications for the use of medications to lower arousal in the immediate aftermath of a trauma. One prospect being explored is the use of β-adrenergic antagonists (or “betablockers,” such as propranolol) to disrupt memory consolidation in the immediate aftermath of the trauma (Pitman, Sanders, Zusman, Healy, Cheema et al., 2002) and facilitate proper memory encoding. For emergency room workers and other front-line mental health clin-

icians, this line of research holds great promise with regard to the introduction of medications for the purpose of secondary prevention of PTSD. The results from this line of research are also being applied to chronic PTSD patients, where β-adrenergic antagonists like propranolol may prove to be efficacious as a an adjunct to exposure therapy. The behavioral neuroscience literature suggests that after previously acquired learning is reactivated, it undergoes a brief reconsolidation process that is vulnerable to interference (e.g., McGaugh, 2004). In fact, there is some evidence that during the reconsolidation process after a memory has been reactivated, the memory is more susceptible to the effects of propranolol than it is when the drug is given during the initial consolidation of new memories (Przybyslawski, Roullet, & Sara, 1999). Thus, use of a betablocking drug during exposure therapy may facilitate the reconsolidation of the fear memory with new, nonfearful associations. While one study has shown that adding propranolol to traditional exposure therapy in chronic PTSD patients appeared efficacious (Brunet et al., 2008), another failed to demonstrate an effect of propranolol on the acquisition or extinction of conditioned fear (Orr et al., 2006). Clearly, more research is needed in this area before these types of medications can be recommended for routine clinical use. Another medication that is being proposed as an adjunctive treatment to address aspects of the trauma memory is Prazosin. Prazosin is a centrally active alpha-1 adrenergic receptor agonist that is being examined for its utility in treating nightmares in PTSD (e.g., Raskind et al., 2007; Raskind et al., 2003; Raskind et al., 2002). In a review of medical charts of veterans with PTSD treated with Prazosin, Raskind and colleagues (2002) found initial clinical evidence to suggest that the medication was effective in reducing distressing dreams. These initial findings were followed up with two small (n’s = 10, 40) placebo-controlled trials in veterans, with additional evidence for improved sleep quality and reduced nightmares (Raskind et al., 2007; Raskind et al., 2003). Importantly, there was evidence that dream content had shifted to be more typical of normal dreams (e.g., involving home/work setting in present time) rather than trauma-related nightmares (Raskind et al., 2007). However, this research is in its earliest stages and has yet to be replicated by additional investigation teams in other samples. In addition to the use of beta-blockers as an adjunct to CBT and Prazosin to treat nightmares, a number of pharmacological agents that have been found to facilitate extinction learning (Cain, Blouin, & Barad, 2004; Ponnusamy, Nissim, & Barad, 2005; Walker, Ressler, Lu, & Davis, 2002), and may be used in the future in conjunction with CBT to treat chronic PTSD. This is an

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important development given the disappointments that have resulted from traditional pharmacological agents used to alleviate symptoms of PTSD in the past (Friedman & Davidson, 2007; Shalev, 2007). As an example, in the past, agents such as benzodiazepines were prescribed with the intention of directly alleviating PTSD symptoms, but are now contraindicated (Friedman & Davidson, 2007). These newer agents are not meant to directly alleviate symptoms per se, but instead facilitate extinction, a mechanism of change in CBT with already strong grounding in the basic scientific literature. Perhaps the most promising of these newer agents being examined is an N-methyl-D-aspartate (NMDA) partial agonist, D-Cycloserine (DCS; see Hofmann, 2007). The use of DCS to facilitate extinction arises from the infrahuman research literature demonstrating the role of NMDA in extinction learning (e.g., Falls, Miserendino, & Davis, 1992; Walker et al., 2002). DCS is particularly promising for the treatment of fear disorders in humans because it has a record of safety (it has been FDA-approved for over 20 years for the treatment of tuberculosis), and has already been shown to improve the results of exposure-based therapy protocols in anxiety disordered populations (Hofmann et al., 2006; Kushner et al., 2007; Ressler et al., 2004). However, one translational study failed to demonstrate effects of DCS on extinction of conditioned fear (Guastella, Dadds, Lovibond, Mitchell, & Richardson, 2007), and not all clinical trials in humans have shown an enhancement effect of DCS on exposure-based therapy (e.g., Guastella, Lovibond, Dadds, Mitchell, & Richardson, 2007; Storch et al., 2007). Further, there may be specific constraints around the use of DCS that are not yet fully understood. For example, a recent laboratory study in rats suggests that DCS may not facilitate extinction if the individual in treatment has taken antidepressant medication (Werner-Seidler & Richardson, 2007). More work is needed to establish the utility of DCS as an addition to CBT, and to establish the parameters for DCS adjunctive therapy. However, this exciting line of inquiry should be closely monitored by providers who utilize exposure-based therapy.

Intrusive Thoughts It is generally common for all people to experience unwanted intrusive thoughts (Rachman & de Silva, 1978; Salkovskis & Harrison, 1984). Intrusive thoughts are even more likely following traumatic events and are a hallmark and troublesome feature of PTSD. These thoughts are typically short sensory flashes (most commonly visual) of discrete aspects of the trauma (e.g., Ehlers & Steil, 1995; Hackmann, Ehlers, Speckens, & Clark, 2004). Additionally, intrusive thoughts tend to be experienced with a sense of “now-ness” (although the individual usually does not lose awareness of other aspects of the present moment, as in a flashback), and

are regarded as separate from intrusive ruminatory or evaluative thoughts about the trauma (Hackmann et al., 2004). In fact, the “now-ness” of intrusive thoughts is more intense in trauma survivors with PTSD as compared to those without (Schonfeld & Ehlers, 2006). As discussed previously, this is hypothesized to be related to the poorly elaborated memory and disjointed way that trauma memories are stored (see Ehlers, Hackmann, & Michael, 2004). Although intrusive thoughts are an expected and normative part of trauma recovery, trauma survivors often report that the thoughts are disturbing, and are an indication that they are “going crazy” (Shipherd, Beck, Hamblen, & Freeman, 2000). When an intrusive thought occurs, it can be associated with emotional distress, physiological arousal, and interference with concentration or task completion, lasting anywhere from minutes to hours. It is understandable that survivors would want to avoid this experience (e.g., Lazarus, 1983). Unfortunately, avoidance is central to the psychopathology of PTSD and turning off intrusive thoughts can undermine recovery. Indeed, the use of suppression as a coping strategy following trauma has been found to predict psychological distress in survey studies involving both adults and children (Aaron, Zaglul, & Emery, 1999; Amir et al., 1997; Ehlers et al., 1998; Morgan, Matthews, & Winton, 1995). These findings support the theoretical notion that survivors who attempt to avoid aversive memories by suppressing intrusive thoughts may, ironically, be facilitating the maintenance of these symptoms, a supposition that has been discussed by several authors (Amir et al., 1997; Amir, Cashman, & Foa, 1997; Ehlers et al., 2004; Gold & Wegner, 1995; Purdon, 1999; Purdon & Clark, 2000; Steil & Ehlers, 2000; Trinder & Salkovskis, 1994). Attempts to “push away” or suppress thoughts and emotions about the trauma are avoidance symptoms of PTSD, and are endorsed by individuals in survey research (e.g., Bryant & Harvey, 1995; Parkinson & Rachman, 1981; Roemer, Litz, Orsillo, & Wagner, 2001). Unfortunately, suppression or avoidance may lead to the return of (or increase in) intrusive thoughts about the trauma. Indeed, in a prospective study, avoidance-based coping styles (as measured prior to the trauma) were predictive of PTSD symptoms one month post-trauma (Gil, 2005). Conversely, approach-based coping has been shown to be helpful (e.g., Tiet et al., 2006) and is an important aspect of empirically supported treatments for PTSD (e.g., Butler et al., 2006). Thought Suppression and Intrusions An experimental paradigm called the thought suppression task was developed by Wegner and colleagues (Wegner, Schneider, Carter, & White, 1987) and has

Empirical Studies of PTSD been widely used in the study of thoughts (see also Wegner, 1994; Wegner & Erber, 1992). The thought suppression task is informative for studying the both the intentional and ironic effects of attempts to suppress thoughts about traumatic events. A series of studies have compared the performance of trauma survivors with and without PTSD (Amstadter & Vernon, 2006; Shipherd & Beck, 1999; 2005) to examine the relevance of thought suppression in PTSD psychopathology. While the findings vary somewhat, PTSD patients have most often demonstrated difficulty suppressing thoughts, with an increase in trauma-related thoughts after suppression instructions were lifted (a rebound effect). This effect has been discussed as an analogue for what occurs naturally when trauma survivors try to avoid intrusive trauma-related thoughts. Following suppression, the trauma-related thoughts become more likely to return with greater frequency, and can be subjectively more distressing and interfering. Indeed, distress related to the thoughts appears to be a central component the maintenance of PTSD (e.g., Denson, Marshall, Schell, & Jaycox, 2007), as regardless of PTSD status, all treatment seekers experienced a rebound following successful suppression (Beck, Gudmundsdottir, Palyo, Miller, & Grant, 2006). Indeed, a larger literature on “repressors” (a term for individuals who tend to suppress thoughts), indicates that repressors have more intrusive thoughts than people without this tendency (e.g., Geraerts, Merckelbach, Jelicic, & Smeets, 2006). Thus, the empirical literature supports the theoretical notion that attempts to avoid trauma-related thoughts will lead to an increase in intrusion. In sum, short-term relief from the thought is followed by longterm distress. Deconstructing Thought Suppression Given that intrusive thoughts are common following trauma, and that both avoidance and approach-based reactions to the thoughts are possible, it is important to consider specific thought suppression strategies more closely (e.g., Cioffi & Holloway, 1993; Lin & Wicker, 2007; Salkovskis & Campbell, 1994; Salkovskis & Reynolds, 1994). Recently, authors have begun to contemplate that thought suppression can occur via many different strategies and that there may be both adaptive and maladaptive strategies. The authors of the Thought Control Questionnaire (Wells & Davies, 1994) consider five different types of thought control, tapping both approach (social control, reappraisal) and avoidancebased strategies (distraction, worry, self-punishment). Sample items from this measure include: I ask my friends if they have similar thoughts (social control); I try a different way of thinking about it (reappraisal); I keep myself busy (distraction); I worry about more minor things instead (worry);

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I tell myself not to be so stupid (self-punishment). Interestingly, distraction (an avoidance-based strategy) is associated with increases in thoughts both when trying to suppress trauma-related thoughts (immediate enhancement) and following suppression (rebound effect), even after controlling for PTSD symptoms (Shipherd, Tanner, & Beck, 2007). In contrast, social control was associated with successful suppression and an absence of rebound effect (Shipherd et al., 2007). Further, reappraisal of intrusive thoughts was not associated with performance when trying to suppress, but was associated with the rebound effect, even after controlling for level of PTSD symptoms (Shipherd et al., 2007). Indeed, negative selfappraisals in the week following a traumatic event are related to PTSD symptom development over time (O'Donnell, Elliott, Wolfgang, & Creamer, 2007), and rumination over “what if” and “why” a trauma occurred is associated with poor outcomes (Michael, Halligan, Clark, & Ehlers, 2007). Together, these findings suggest that it is not the presence of symptoms that is abnormal, but responses and reactions to the presence of symptoms that is central to recovery.

Acceptance Consistent with the literature above, recent research in the broader information processing literature suggests that attempts to avoid mental events such as thoughts and emotions may be futile and/or harmful. In recognition of this emerging literature, information processing researchers have begun to explore acceptance (or “. . . to willingly take in what is offered, to hold without protest or reaction”; Walser & Westrup, 2007, p. 19) as a treatment strategy. Acceptance-based intervention strategies are grounded in cognitive behavioral theory but differ somewhat from traditional CBT strategies in practice. Rather than instructing patients on new ways to attempt to control internal experiences (e.g., cognitive reappraisal to control thought processes), acceptance-based strategies encourage people to decrease avoidance and problematic control of internal experiences (e.g., negative thoughts and emotions). Acceptance-based strategies for dealing with internal experiences have emerged in response to a large and growing literature suggesting that a variety of psychopathological conditions, including PTSD, develop as a result of attempts to avoid internal experiences such as thoughts, memories, and emotions (for reviews see Hayes et al., 1996; Salters-Pedneault, Tull, & Roemer, 2004), a phenomenon termed “experiential avoidance” (Hayes et al., 1996). For example, as discussed above, many patients with PTSD use thought suppression as a strategy to reduce trauma-related intrusive thoughts. While this strategy may produce short-term relief, this attempt to avoid their internal experience may create a rebound effect, which is

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implicated in the development of long-term symptoms. With both clinical and nonclinical samples, experiential avoidance is associated with increased psychological distress across a range of studies (Boeschen, Koss, Figueredo, & Coan, 2001; Forsyth, Parker, & Finlay, 2003; Kashdan, Barrios, Forsyth, & Steger, 2006; Polusny, Rosenthal, Aban, & Follette, 2004; Roemer et al., 2001; Roemer, Salters, Raffa, & Orsillo, 2005; Rosenthal, Rasmussen Hall, Palm, Batten, & Follette, 2005; Tull, Gratz, Salters, & Roemer, 2004; Ulmer et al., 2006). Further, a recent examination documented that peritraumatic dissociation (discussed above) and experiential avoidance were unique constructs (Marx & Sloan, 2005). Further, the researchers found that experiential avoidance was even more strongly associated with PTSD symptoms at 2 months posttrauma than was dissociation (Marx & Sloan, 2005). Together, these findings suggest that experiential avoidance may be central to the maintenance of PTSD symptoms. Thus, clinicians have become interested in learning ways to manipulate experiential avoidance through the converse: acceptance-based interventions. Acceptance Manipulations in the Laboratory In experimental settings, acceptance has been successfully manipulated even in studies that use brief (2- to 20minute) instructions. Experimental studies have demonstrated success in manipulating acceptance of physical pain (Gutierrez, Luciano, Rodriguez, & Fink, 2004; Hayes, Bissett, et al., 1999; Keogh, Bond, Hanmer, & Tilston, 2005; Masedo & Rosa Esteve, 2007) and reactions to CO2 inhalations, which produce panic-like symptoms (Eifert & Heffner, 2003; Levitt, Brown, Orsillo, & Barlow, 2004). In addition to acceptance levels being successfully increased, improvements in other outcomes have also been noted. Following a brief training in acceptance, pain tolerance is increased (Gutierrez et al., 2004; Hayes et al., 1999; Masedo & Rosa Esteve, 2007) and reports of level of physical pain is lessened (Keogh et al., 2005; Masedo & Rosa Esteve, 2007). Similarly, being trained in acceptance was associated with reductions in anxiety and reports of less intense panic symptoms following CO2 challenges, even when no differences in physiological arousal were present (Eifert & Heffner, 2003). Related studies of accepting emotions and thoughts also provide strong support for brief trainings. In a study of people with mood and anxiety disorders, patients given a 5-minute training in acceptance reported greater decreases in negative affect and lower heart rate after an upsetting film compared to those without the training (Campbell-Sills, Barlow, Brown, & Hofmann, 2006). Similarly, in a study of intrusive thoughts, a 5-minute acceptance metaphor was given to one group but not another group prior to a thought-suppression task. The

frequency of the thoughts were similar in both groups, but the acceptance group was significantly less distressed by the thoughts (Marcks & Woods, 2005). Thus, it is clear from this literature that brief training in acceptance can drastically alter interpretations of thoughts and emotion and can reduce symptoms. Acceptance-Based Treatments There is a growing literature about the efficacy of acceptance-based treatments for a variety of clinical problems. One treatment developed by Hayes and colleagues (Hayes, Strosahl, & Wilson, 1999), Acceptance and Commitment Therapy (ACT), has been applied in a variety of clinical populations (for review see Hayes, Masuda, Bissett, Luoma, & Guerrero, 2004), including PTSD (Walser & Hayes, 2006; Walser & Westrup, 2007). One of the compelling aspects of the ACT intervention is that it targets experiential avoidance and the problems associated with this psychological strategy rather than being disorder-based, making it appealing in cases where comorbidity is the norm, such as with PTSD. From this perspective, a context can be built wherein thoughts and emotions can be experienced without any need to suppress or avoid, but rather it is possible to observe the internal events as they come and go. Thus, it is not relevant if a thought is PTSD-related, depression-related, alcohol-related or any other comorbidity; the treatment addresses these all simultaneously using one approach. Acceptance-based treatment takes the individual out of the “battle” with internal experiences, thus decreasing the painful sequelae. The promising research work on acceptance in the laboratory and acceptance-based interventions may have broad implications for the treatment of PTSD. Given the prominence of a variety of distressing cognitive experiences associated with PTSD, including attentional difficulties, memory problems, and intrusive thoughts, this approach is particularly promising. While more translational and applied work is needed to support the efficacy of acceptance-based strategies in PTSD, there is a growing literature that supports the use of acceptance in traumatized populations. Clinicians may want to stay abreast of these intervention strategies to augment or replace more traditional CBT strategies.

Summary and Limitations Recent advances in information processing research have further elucidated the nature of information processing in PTSD and cognitive change in PTSD treatment at the multiple levels (e.g., attention, memory, expression of symptoms, responses to symptoms). This emerging literature has implications for the daily practice of CBT clinicians. At the level of attention, interference appears to play a vital role in PTSD-related

Empirical Studies of PTSD dysfunction. This finding may be of use to clinicians who find that patients with PTSD are resistant to change because they erroneously believe that their hypervigilance facilitates detection of threat. It is also important to encourage clinicians to repeat new information frequently during sessions and provide take-home materials to patients. In memory, a number of advances have been made in the understanding of peritraumatic reactions, memory consolidation, extinction learning, and new learning retrieval. These advances will likely significantly shape the parameters of CBT delivery in future years, including the timing, content, and context of sessions, in addition to the use of adjunctive medications to facilitate mechanisms of change. PTSD appears to be associated with a vacillation between attempts to suppress thoughts about the trauma (avoidance) and an increase in their frequency. Reactions to the symptoms of PTSD can influence the trajectory of recovery, with negative selfevaluations being associated with worse outcomes and acceptance being related to better outcomes. The research literature on acceptance shows promise for the development of new CBT treatment techniques for individuals with PTSD.

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