Clin. Psychol. Psychother.9, 165–176 (2002)
Eye Movement Desensitization
and Reprocessing: A Treatment
Efficacy Model
Kenneth L. Welch
1* and Donald B. Beere
2 1Private Practice, Corydon, Indiana, USA2Central Michigan University, USA
Eye movement desensitization and reprocessing (EMDR), though controversial, is increasingly utilized for treatment of posttraumatic stress disorder (PTSD). This article reviews the debate concerning efficacy and concludes that the evidence, though not definitive, supports EMDR’s positive treatment effects. The authors argue that EMDR is a therapeutic intervention different from exposure. The authors set forth three interrelated hypotheses to explain EMDR’s therapeutic mechanism: bilateral hemispheric activation, normalized brain activation patterns, and activation/desensitization of emotion/arousal; avoidant/constricted attention is disrupted, allowing normalizing processes to occur. Lowered arousal then leads to a resumption of more adaptive cognitive processing. Some predictions to test this model are presented. Copyright2002 John Wiley & Sons, Ltd.
INTRODUCTION
The use of eye movement desensitization and reprocessing (EMDR) has evoked one of the most contentious and polarized debates in behavioural science. Apart from training and dissemination issues (Acierno, Hersen, Van Hasselt, Tremont, & Meuser, 1994; DeBell & Jones, 1997; Fish, 1992), the scientific issues revolve around treatment effi-cacy, similarity/differences relative to other PTSD treatments and the absence of a theoretical expla-nation for EMDR’s outcomes. The following article intends to briefly address these issues, discuss pro-posed models of EMDR’s therapeutic mechanism, and to present a new treatment efficacy model.
TREATMENT EFFICACY
While controversial in terms of effectiveness, the preponderance of the evidence to date suggests
* Correspondence to: Kenneth L. Welch, 520 Fox Chase Court, Corydon, IN 47112, USA. E-mail: [email protected]
that EMDR has utility in treating posttraumatic stress disorder (PTSD). Despite the criticism of methodological flaws in some studies (Herbert & Mueser, 1992; Lohr, Kleinknecht, Conley, Schmidt, & Sontag, 1992) an increasing number of con-trolled studies have demonstrated mixed treatment effects, from moderate to large reductions in PTSD symptoms in civilian samples (Marcus, Marquis, & Sakai, 1997; Rothbaum, 1997; Scheck, Schaef-fer, & Gillette, 1998; Wilson, Becker, & Tinker, 1995). Some of these studies have been criticized for lacking methodological rigour, dependence on self-report measures, and for the lack of neutrality on the part of the researchers (Lohr, Tolin, & Lilien-field, 1998). In military PTSD samples, study results have been more varied (Boudewyns & Hyer, 1996; Boudewyns, Stwertka, Hyer, Albrecht, & Sperr, 1993; Carlson, Chemtob, Rusnak, & Hedlund, 1996; Carlson, Chemtob, Rusnak, Hedlund, & Muraoka, 1998; Devilly, Spence, & Rapee, 1998; Jenson, 1994; Lipke & Botkin, 1992; Pittmanet al., 1996a; Silver, Brooks, & Obenchain, 1995), but generally a slight to large treatment response has been noted. Of interest, Pittman and his colleagues (Pittmanet al.,
1996a,b) compared exposure therapy to EMDR indirectly in two separate studies. While these studies were non-randomized, both studies uti-lized compensated military veterans with similar methodology. The results suggested that EMDR had several advantages over exposure including greater improvement in PTSD symptoms, was provocative of less anxiety for patients as well as therapists, and had fewer adverse complications.
Whether EMDR has utility beyond current PTSD treatments is a practical question to investigate, and future studies will continue to address this issue. It may be that EMDR, if it is in fact a new treatment method, could be used as an alternative to standard exposure methods that are unsuitable for certain individuals.
There have been case reports or studies which have suggested that EMDR is not an effective treat-ment for PTSD (Jensen, 1994; Oswalt, Anderson, Hagstrom, & Berkowitz, 1993). These studies have been criticized (as an example, Jensen, 1994) for the use of psychology interns as experimenters, the use of disability-dependent military veterans, inad-equate training in the procedure, and low fidelity to EMDR treatment protocols (Greenwald, 1996; Shapiro, 1996).
In a review of controlled studies, Lohr, Klein-knecht, Tolin, and Barrett (1995) conclude that EMDR has not been established as an effective intervention for PTSD. While reviewing the EMDR-related literature, Shapiro (1996) concludes that EMDR is the most researched treatment for PTSD, and that research supports the adoption of EMDR as an empirically validated treatment for PTSD. This difference in professional opinion appears to be based on interpretation of EMDR research studies. Shapiro appears to focus on a larger number of studies, while Lohr seems to focus on a smaller number of controlled studies in terms of rigourousness of research design and concludes that the controlled studies of EMDR have yet to demonstrate any effect greater than exposure PTSD treatments. While this issue is beyond the scope of this paper, a recent report focused on empirically validated therapies included EMDR for civilian PTSD as a ‘probably efficacious treatment’ along with other psychological therapies such as exposure treatment for social phobia, exposure treatment for PTSD or systematic desensitization for animal phobias (Chamblesset al., 1998). In addition, The International Society for Traumatic Stress Studies has included EMDR as an efficacious treatment of PTSD in its current practice guidelines (Chemtob, Tolin, van der Kolk, & Pitman, 2000).
Lohret al. (1998) in a recent analysis have further concluded that improvements in cases treated with EMDR are limited to self-report measures, and that eye movements are an unnecessary component of the procedure. However, there are studies of PTSD treatment (Montgomery & Ayllon, 1994b; Vaughan
et al., 1994) and other anxiety disorders (Lohr, Tolin, & Kleinknecht, 1996) that have suggested that eye movements were necessary components for treatment effects. In a meta-analysis of PTSD studies, Van Etten and Taylor (1998) concluded that eye movement trials were more effective than fixed eye control trials. In similar fashion, some studies have not detected significant physiological changes after EMDR treatment (Carlsonet al., 1996) but other studies reported significant changes after EMDR treatment such as decreased heart rate, increased skin temperature, and reductions in galvanic skin response (Forbes, Creamer, & Rycroft, 1994; Renfrey & Spates, 1994; Wilson, Silver, Covi, & Foster, 1996). Yet other studies reported a trend of lower, but not statistically significant, physiological arousal after EMDR treatment. The lack of statistical significance may be due to the low numbers of subjects or to the utilization of multi-traumatized military veterans (Montgomery & Ayllon, 1994a; Rogerset al., 1999).
Complicating the picture, an argument could be made that physiological measures of PTSD may not be as important as self-report measures in determining treatment efficacy because, from a cognitive framework, how an individual interprets a high level of arousal is a critical issue. That is to say, an individual may be highly emotionally aroused, but if this arousal is not interpreted as a difficulty, and the individual believes that he or she is coping with the arousal, self-report measures would reflect improvement while physiological measures might not indicate improvement. In terms of brain structures, the higher centres in the cortex, such as the orbital frontal cortex, modulate the more primitive emotional structures such as the amygdala (Brewin, 2001; LeDoux, 1996); how the cortex interprets arousal from lower brain structures may be critical in PTSD treatment.
In a meta-analysis of posttraumatic stress treat-ments (Van Etten & Taylor, 1998) in which pharmacotherapies and psychological treatments were reviewed in 68 outcome trials, EMDR and behaviour therapy were suggested as the most effi-cacious therapies with EMDR rated as most effec-tive. The authors of this analysis concluded that exposure alone was not the therapeutic mechanism
because of EMDR’s comparably shorter exposure time. The authors also suggest that clarification of the active ingredients of EMDR is needed as well as an explanation of the mechanisms by which symptom change occurs.
Even though current research in this area is far from definitive, and is controversial, it seems reasonable to suggest that EMDR is probably an efficacious treatment for civilian PTSD (Chambless et al., 1998; Spector & Read, 1999; Van Etten & Taylor, 1998) and that more research is needed. The results for EMDR’s treatment of military PTSD is more in question at this point.
RELATIONSHIP TO OTHER PTSD
TREATMENTS
A clinically related issue involved in the EMDR controversy is the similarity of EMDR to exposure methods. This criticism is separate from questions concerning treatment efficacy in asserting that, since EMDR is similar in some regards to other treatment methods, EMDR is nothing other than those similar treatment methods.
Some have suggested that EMDR treatment effi-cacy results from the imaginal exposure component of EMDR (Acierno et al., 1994; Lohr et al., 1998; Sanderson & Carpenter, 1992). Although EMDR involves imaginal exposure, EMDR has procedural differences when compared to traditional expo-sure treatments for PTSD. In fact, EMDR violates two of the three ‘rules of effective exposure’ (Per-sons, 1989). For exposure therapy to be effective, the exposure is prolonged (Persons, 1989). In con-trast, instead of attending to a traumatic image for a prolonged period of time, such as in imaginal flooding, EMDR encourages the subject to focus on whatever images or other experiences (thoughts, sensations, emotions) that come to mind after the initial traumatic image. It would be reasonable to expect that this component of EMDR would lead to avoidance of anxiety—that is, from an expo-sure perspective, to shift away from the anxiety should reinforce avoidance and should not allow the anxiety to habituate. Evidence from EMDR treatment, however, has demonstrated that this outcome is usually not the case. Subjects may imagine other scenes during the traumatic inci-dent and/or other traumatic inciinci-dents that they have witnessed (e.g. Kleinknecht & Morgan, 1992; McCann, 1992). In fact, subjects often report an intensification of anxiety (not avoidance) during
early stages of EMDR (Greenwald, 1994). Another ‘rule of exposure’ is that effective exposure is fre-quent (Persons, 1989). Often in the EMDR treatment of PTSD the exposure is occasional (depending on the client’s inner experience). Despite a lack of fre-quent exposure, PTSD symptoms appear to decline and maintain at a minimal level post treatment. (The third rule of exposure concerns exposure to affects).
A more relevant question may be whether the dif-ferences between traditional exposure treatments and EMDR are significant in a clinical sense. Stated in another way, does EMDR work differently than traditional PTSD exposure treatments and which procedure is clinically preferable?
From the authors’ point of view, equating EMDR with traditional exposure clouds the issue. Clearly, exposure to the traumatic incident is initially involved in EMDR. After the procedure is initiated, however, EMDR diverges from usual exposure methods: in exposure the anxiety and traumatic incident are maintained in awareness, while in EMDR there is no attempt to maintain either the anxiety/distress or the image of the trauma. From the foregoing, two fundamental differences are evident: one pertains to the subject’s experience of control or non-control of the inner subjective state; and another pertains to keeping the distress in awareness. It would appear, therefore, that EMDR is a different therapeutic method than exposure.
Besides procedural differences, there are an emer-gent number of research studies which may shed light on the question of EMDR’s similarity to other treatments. Several studies have directly compared EMDR to exposure methods. Ironson, Freund, Stru-ass, and Williams (2002) compared exposure to EMDR. After three sessions of active treatment, 70% of the EMDR group had achieved a significant reduction in PTSD symptoms versus 17% of the pro-longed exposure group. In general, the results of the study supported the relative effectiveness of both methods to treat PTSD, but found EMDR to more completely reduce symptoms, was faster in terms of reducing symptoms, and was better tolerated by study participants. The study authors added they had no particular ‘allegiance’ to either treat-ment method before the study and to standardize treatment, utilized treatment manuals.
In contrast, Devilly and Spence (1999) compared EMDR with a type of cognitive-behavioural treat-ment they developed; the method, Trauma Treat-ment Protocol (TTP) included prolonged exposure, cognitive restructuring, and stress inoculation.
Results of this study suggested that EMDR was not as effective in reducing PTSD symptoms as TTP and that at follow-up, gains in the EMDR treatment group were not maintained. The EMDR group also had a much higher drop-out rate.
Lee, Gavriel, Drummond, Richards, and Green-wald (2002) compared EMDR to a combined treat-ment package of prolonged exposure and stress inoculation. The results suggested both treatments were roughly equivalent, but the EMDR group appeared to have less intrusive symptoms post treatment. Later at 3-month follow-up the EMDR group had greater improvement on all measures. The Van Etten and Taylor (1998) meta-analysis also supported a greater reduction of intrusive symp-toms post treatment compared to exposure. Intru-sive symptoms are especially important because some researchers (Levin, Lazrove, & van der Kolk, 1999) have suggested that intrusive symptoms are ‘upstream events’ which lead to the other major symptoms of PTSD (avoidance and phys-iological hyperarousal). Some PTSD case studies (Welch, 1996) have also suggested that EMDR significantly deceases the vividness of intrusive imagery.
Viewed from a different perspective, the Lee
et al. (2002) study looked at 3-month follow-up using a clinical significance cut-off point of 2 standard deviations (Jacobson & Truax, 1991) below pre-treatment means; 91.7% of the EMDR group and 50% of the exposure/stress inoculation group was judged as significantly improved. Another difference between treatments was the estimated average of 42 h of homework in the exposure/stress inoculation condition versus 3 h for EMDR.
In an earlier study, (Vaughanet al., 1994) expo-sure (image habitation training) was compared to EMDR with traumatized individuals. The EMDR group had greater reductions on all standardized measures and was especially effective in regard to intrusive symptoms. A major problem with this study, however, was that some of the subjects did not have a PTSD diagnosis.
On the basis of the heterogeneity of these studies and by the apparent procedural differences between EMDR and exposure, the evidence to this point suggests that EMDR and exposure are not the same methods. In the future, further research may decide that EMDR offers little beyond exposure treatments for PTSD. However, this possible fact does not necessarily make EMDR equivalent to exposure nor does it mean that EMDR’s mechanism of action is the same as that for exposure.
EMDR TREATMENT EFFICACY
MODELS
A number of explanations of EMDR’s treatment effects have been proposed. In the remainder of this article, the authors intend to explain EMDR’s treatment effects by what is known about current treatments and to set forth hypotheses about other possible explanations for treatment outcomes. While speculative, this attempt provides a new interpretation of EMDR’s treatment efficacy by integrating physiological PTSD-linked findings with experiential elements.
To provide a context for the later sections of this article, the authors want to establish the phe-nomena that require explanation. First, and most obviously, EMDR’s probable efficacy at resolv-ing post-traumatic difficulties must be explained. Secondly, the links between EMDR and other treat-ments for trauma-related conditions should be established and clarified. Third, a variety of EMDR-related phenomena need to be included in any adequate explanation of EMDR’s efficacy. EMDR, for example, involves sustained, focused attention on an external, changing stimulus while at the same time attending to psychological and bodily events. Vividness of imagery, intensity of affect and sub-jective distress all increase and decrease together during successful EMDR treatments. There is often both an activation and neutralization of intense arousal, usually experienced as various emotions. Individuals can report a variety of experiences from bodily sensations, smells, and tastes, to fragmen-tary memories and recall of previously forgotten aspects not only of the traumatic experience, but similar traumatic experiences. Patients often report, throughout the whole process of EMDR, new cogni-tions associated with various aspects of the trauma, not simply a single, final new cognition. From the authors’ point of view, these phenomena provide an entry to an explanation of EMDR’s efficacy.
Shapiro (1989b) has suggested that EMDR may reverse pathological neural changes. The idea that neural changes maintain a traumatic incident in its original state was first introduced by Pavlov (1927) as an explanation for traumatic sequelae.
Shapiro (1989b) has also proposed that the eye movements in EMDR may be linked to REM sleep and information processing in REM states. Green-wald (1995) suggested that the mechanism of action in EMDR is related to conscious dreams. Analo-gously, Shapiro (1989b) hypothesized that EMDR activates REM-related neurological activity, which is hypothetically linked to resolving trauma in
dreams by Greenwald (1995). While plausible, these explanations fall short in describing how EMDR functions using bilateral kinesthetic sensations such as hand tapping or alternating auditory tones.
Macculloch and Feldman (1996) have offered a theoretical explanation of EMDR based on a combination of Pavlovian and Darwinian theory. The authors suggest that EMDR prompts an investigatory reflex that causes the individual to reassess traumatic memories. This reassessment allows for the individual to perceive no current danger and also allows for a subsequent lowering of arousal as well as a decrease in avoidance behaviour. This theory, while having face validity, does not account for processes noted during EMDR such as increases in arousal, increases in number of emotional mood states, and the frequent appearance of visual images of prior trauma.
Dyck (1993) has proposed that EMDR is a dis-traction/extinction procedure that breaks the links between conditioned stimulus and unconditioned stimulus by first interrupting the link between the traumatic event and anxiety. This formulation explains EMDR as no different from other exposure methods that might employ distraction procedures. While this explanation is simple and direct, it is yet to be established empirically.
Shapiro (1995) also explains how EMDR works with an accelerated information-processing model. In this general model, EMDR activates and facil-itates an accelerated processing of information, for example, linking isolated, possibly fragmentary memories with other, more adaptive information. During EMDR treatment, it is assumed that electri-cal pulses and organic systems, such as the limbic and cortical systems, are biochemically balanced. There are several levels or domains of explanation in this model: information, information processing, electrical pulses, biochemical states, and biochem-ical balance. The links between components and how they relate to PTSD and its resolution are complex and unspecified.
A critique of Shapiro’s (1995) information-processing model pertains to what subjects actually experience during EMDR. The ‘information’ pro-cessed is more properly termed ‘memory’. As a result, one way of describing the therapeutic action of EMDR pertains to the processing of memo-ries. This is consistent with resolving unresolved trauma, ‘located’ in an individual’s memory. One might, therefore, describe EMDR as facilitating the retrieval (activation and elicitation) and reprocess-ing (understandreprocess-ing and understandreprocess-ing differently) painful memories which include bodily sensations,
emotions, auditory information, visual scenes, and thoughts.
A simpler and explicit model of EMDR’s efficacy is proposed by Armstrong and Vaughan (1996). In this model, an orienting response, generated by EMDR’s hand tracking component, breaks the link between conditioned and unconditioned stimulus and leads to treatment effects. A problem with this model is that the orienting response ends once the new stimulus is perceived. It is difficult to discern how a slight stimulation, such as eye movement, would maintain an orienting response after their initiation. In addition, given the sustained tracking of the fingers with the eyes, the response of the patient is more properly described as sustained, outer-directed attention, and not orienting.
Taking a different point of view, Hyer and Brandsma (1997) have suggested that EMDR may be a successful intervention because of EMDR’s use of a number of factors common to other successful therapies, not because of any unique factors of EMDR. Among these factors identified by Hyer and Brandsma are the non-directedness of the therapist in the EMDR procedure within a structured format, the ‘free association’ nature of the procedure, the use of non-leading language, a less threatening exposure to the conditioned stimulus, attentiveness to the client’s negative beliefs, a reduced need for defensive operations on the part of the client, and an allowance for the ‘nodes’ of PTSD information to link up. Hyer and Brandsma suggest that an ‘alpha trance state’ is produced during the eye movements which leads to change. At the same time and inconsistent with the previous ‘suggestion’, the authors assume that eye movements are not critical for successful therapy. In contrast, other studies, have found eye movement essential for treatment efficacy (such as Montgomery & Ayllon 1994b; Van Etten & Taylor, 1998). Nonetheless, these authors raise some cogent points relating EMDR to other treatments, and provide a framework for understanding elements of EMDR.
While these models of EMDR’s therapeutic mech-anism may be helpful heuristics, most of them lack important characteristics of a scientific model or theory. Few of these models appear readily falsi-fiable, nor have predictions been made from most of these models; in short, many of these models cannot be readily supported or refuted.
Common to psychodynamic (Horowitz, 1986) or learning (Keane, Fairbank, Caddell, Zimering, & Bender, 1985) models, most known effective PTSD treatments involve exposure to the traumatic inci-dent. Since the EMDR protocol involves exposure
to traumatic imagery, affects, and cognitions, expo-sure must account for at least part of the treatment effects’ variance. However, there are apparently unique EMDR effects including reduced expo-sure time (Forbeset al., 1994; Ironsonet al., (2002); Kleinknecht & Morgan, 1992; Montgomery & Ayl-lon, 1994a; Pitman et al., 1996a; Shapiro, 1989a; Spates & Burnette, 1995; Van Etten & Taylor, 1998), as well as frequent intensification and reduction of the vividness of traumatic imagery (Armstrong & Vaughan, 1996; Kleinknecht & Morgan, 1992). Exposure time during EMDR, for example, can be quite brief (perhaps a minute per traumatic emo-tional scene) in contrast to tradiemo-tional exposure methods (hours over several weeks). In the follow-ing section, we set forth hypotheses which could account for these apparent differences.
THE HYPOTHESES
The authors set forth three, interrelated hypotheses to explain EMDR treatment effects. The first asserts that EMDR paradoxically both intensifies and reduces arousal, in particular, emotions. The process by which this occurs is explained by the two other hypotheses. The second hypothesis presupposes that the eye movements, sounds or touches to one side of the body activate the contralateral hemisphere. As a result, EMDR eye movements lead to bilateral stimulation of the cerebral hemispheres. This is significant for the treatment of PTSD since research has demonstrated a number of lateralization effects. EMDR, then, initiates a reconnection of the two hemispheres. The third hypothesis pertains to altering a patient’s constricted and avoidant attention through the EMDR procedure. As a result, the spontaneous flow of experience returns, and resolution of the PTSD follows naturally.
Hypothesis 1: Arousal Intensification and Reduction
Several researchers (Goodwin & Sher, 1993; Persons & Miranda, 1995) have emphasized the importance of activating mood states in assessing and treating disorders such as depression and anxiety. A feature of EMDR appears to be the activation and desensi-tization of different emotional mood states during PTSD treatment similar to exposure treatments. Subjects commonly first report a rapid intensifica-tion of anxiety (Greenwald, 1994). Then subjects
may report other associated emotions. Often these emotions are reported as being felt intensely, fre-quently with related cognitions. However, these emotions frequently appear and disappear rapidly during the EMDR treatment procedure (this is also common in exposure treatments). Subjective dis-tress increases as emotions peak and decreases as intensity drops; but in general there is a pattern of increased, followed by decreased arousal (Green-wald, 1994). Accompanying these emotions are bodily sensations frequently reported as intensely felt. Often there seems to be a sequence of affects, images, and/or cognitions before segments of the traumatic memory desensitize.
These observations suggest that EMDR is a mood state activator. Some research has suggested that sensations of arousal often precede the perception of emotion (Schachter & Singer, 1962; Worchel & Brown, 1984), and that arousal may act as a retrieval cue for activation of traumatic memory networks (Litz & Keane, 1989). Consequently, as these affects intensify they become potential cues for retrieval of associated traumatic memories.
We posit, as well, that the irrational beliefs held by those diagnosed with PTSD are linked to strong emotions. Once the pattern of emo-tional arousal, which is connected to a threatening belief, is activated and then desensitized dur-ing EMDR treatment, then, we hypothesize, it is easier to change the belief itself. This hypothe-sized process is somewhat similar to treatments of other anxiety disorders, such as phobic disor-ders (Hope & Heimberg, 1994), where the pat-tern of emotional arousal is reduced by typical exposure treatments. Subsequently, the strength of the accompanying irrational belief is also reduced.
In summary, we hypothesize that EMDR appears to activate and desensitize the arousal connected with specific dysfunctional beliefs. This hypoth-esis could be tested directly by desensitizing arousal using EMDR, but not addressing the related pathological cognitions. If the related cog-nitions change without direct intervention, then the results might support the critical role of affect in maintaining the pathological cognitions and, thus, PTSD. Furthermore, with significant reduc-tion in arousal, different and more adaptive cog-nitions should become available (Chemtob, Roit-blat, Hamada, Carlson, & Twentyman, 1988). In the next section, the authors provide two fur-ther, complementary hypotheses for this action of EMDR which help explain how arousal is desensitized.
Hypothesis 2: Bilateral Activation Hypothesis Since EMDR appears to involve bilateral stimu-lation in its various modes (visual, auditory, tac-tile), could this account for any specific effects of treatment?
Brende (1982) concluded, using bilateral electro-dermal sensors, that symptoms of PTSD appear to be lateralized. Intrusive images and flashbacks appeared to be lateralized in the right hemisphere, while hypervigilance and aggression appeared to be lateralized in the left hemisphere. Brende proposed that PTSD is maintained by abnormal suppression/activation and unintegrated function-ing of the right and the left hemispheres. More recent research (Morgan, Grillon, Lubin, & South-wick, 1997) has suggested that PTSD symptoms are asymmetrical and suggest a laterality effect. The left hemisphere has been suggested to be involved in inhibiting emotional responses (Gainotti, Cal-tagirone, & Zoccolotti, 1993). In addition, other researchers (Alvarez & Shipko, 1991; Fukunishi, Chishima, & Anze, 1994; Hyer, Woods, Summers, Boudewyns, & Harrison, 1990; Kosten, Krystal, Giller, Frank, & Dan, 1992) have suggested that the right hemisphere inactivation involved in alex-ithymia considerably overlaps the emotional numb-ing and avoidance symptoms of PTSD. Henry,
et al. (1992) have found shared neuroendocrine pat-terns between PTSD and alexithymia and suggest that these patterns are the result of dissociation of cerebral hemispheres. A further link between PTSD and alexithymia was provided by a study that associated repeated traumatization of PTSD patients with higher rates of alexithymia (Zeitlin, McNally, & Cassiday, 1993). Zeitlin, Lane, O’Leary, and Schrift (1989) also found a hemispheric trans-fer deficit in PTSD subjects which they suggested was a functional disconnection’ of the two cere-bral hemispheres and that this ‘disconnection’ was associated with alexithymia. Another related piece of evidence, based on PET scans of PTSD patients, suggested that when stimuli are presented rem-iniscent of trauma, there is an increase in right hemisphere activation and a subsequent decrease in left hemisphere activation (Rauchet al., 1996).
The inherently phasic, oscillating nature of PTSD in regard to emotional numbing/avoidance and intrusive thoughts/images may reflect the lack of integration between hemispheres of the brain and a disruption of brain activation patterns. This impression of dysfunctional phasic oscillation is similar to Horowitz’s (1986) conception of PTSD. If this dysfunctional oscillation in functioning of
brain hemispheres plays a role in maintaining PTSD, then EMDR, by stimulating both hemi-spheres, could possibly promote an integration of hemispheric functioning as well as a normalization of brain activation patterns. Preliminary research using quantitative electroencephalography (QEEG) has suggested that the cerebral hemispheres are more synchronized and exhibit slower brain waves after EMDR treatment (Nicosia, 1994). Neurologists (Ramichandran & Blakeslee, 1998) also have noted that stroke victims appear to be able to commu-nicate across brain hemispheres by induced eye movements to recognize deficiencies that were not previously acknowledged.
The extremely high level of arousal coupled with abnormal brain activation patterns in PTSD appears to impede ongoing cognitive processing; therefore, processing the traumatic incident is ‘inca-pacitated’ by that arousal. Cognitive models of PTSD have suggested that high levels of affective arousal interfere with cognitive processing in two ways (Chemtob et al., 1988). First, cognitive pro-cessing decreases with high emotional arousal, and secondly, more adaptive cognitive schemata are inhibited by the activation of threat expectancies. Consequently, after EMDR desensitizes the level of arousal linked to a belief, the lower arousal level allows further information about the traumatic inci-dent to be processed. Given our hypothesis, when arousal significantly drops, the irrational cognitions can more readily change. The high right hemi-sphere activation in PTSD with the subsequent low left hemisphere activation pattern may explain, in a physiological manner, why PTSD patients cannot integrate an intrusive traumatic experience (Allen, 1995) into existing cognitive schemas; simply put, a part of the brain needed to logically process the experience is not activated.
Further, researchers (Davidson & Fox, 1988; van der Kolk & Fisler, 1995) have concluded that the left hemisphere is associated with coping resources and organizing traumatic experiences into language. In the process of treatment with EMDR, the hypothesized reactivation of the left hemisphere may result in increased accessibility to coping resources as well as the organization of traumatic experiences into verbal concepts. The utilization of coping responses and logical conceptualization, then can lead to lower arousal because the individual can now begin to verbally process the experience, can organize memories in a integrated manner, and can begin to manage distress. Interestingly, in a single subject PTSD SPECT scan study, Levinet al. (1999) found after
three EMDR sessions, there was a hyperactive increase in left hemisphere activity. While this left hemisphere activation pattern may be common to all successful treatments of PTSD, it may help explain why EMDR is associated with rapid treatment response.
In a related theoretical conception, Brewin (2001) argues that PTSD involves two distinct memory systems: the verbally accessible memory (VAM) and the situational accessible memory (SAM). SAM contains memory that is processed non-verbally and accounts for the intrusive phenomena of PTSD. In the successful treatment of PTSD, Brewin suggests that information should be transferred between the two memory systems. By our hypoth-esis, the VAM would be in the left hemisphere. The location of SAM has yet to be determined by brain imaging procedures. However, since PTSD’s intrusion symptoms such as flashbacks have been localized by brain imaging on the right side of the brain, (Rauchet al., 1996) it is probable that SAM is at least, partially based in the right hemisphere. Hypothesis 3: Disruption of Avoidant or Constricted Attention
The third hypothesis considers the subjective state of the patient and provides an experiential link to the physiological explanation just articulated. Beere (1995a,b; Beere & Pica, 1995; Pica & Beere, 1995) has developed a theory of dissociation that relies on the narrowing of perception as a mechanism. Since avoidance is a major behavioural and experiential symptom of PTSD, a similar attentional/perceptual process would appear to operate in PTSD. Conse-quently, trauma-linked environmental cues, affects, memories, and thoughts are avoided. Successful EMDR treatment interferes with this subjective restriction of experience and decreases avoidance (Wilsonet al., 1995).
The experience of being an EMDR patient involves the following. Three facets of the traumatic incident are elicited: a visual image, a self-related cognition, and bodily states (primarily emotions, but also sensations). The patient is told to ‘let hap-pen whatever haphap-pens’, activates the three facets just described and attends to an external stimulus, such as the finger movement.
The experience of the patient ‘splits’ in order to track the external stimulus while attending to inner experience. Though focusing internally, the patient must also attend to the external stimulus whose speed is such that attention to it must be main-tained to track accurately. Awareness, therefore,
is focused externally, on the therapist’s fingers (in the visual mode) as well as on what is happen-ing internally. The authors hypothesize that this unique deployment of attention disengages previ-ously automatic avoidance responses triggered by intruding images, affects, and insights. As a result, memory of the natural sequela to trauma—the specifics of the event, the emotion, and the cog-nition—can naturally occur. In the context of the previous section, the shift away from constricted awareness and internal avoidance is parallel to the reconnection of the right and left hemispheres.
Of particular note is the implicit hypothesis that this avoidant or constricted state of awareness inhibits natural processes associated with memory, emotion, and cognition. In this regard, after the initial trauma-linked cues have been subjectively activated just previous to EMDR, all of the various and linked memories, emotions, and cognitions will have the opportunity to come to awareness. Emotion, previously avoided, can be allowed its freedom and, without inhibition, will increase and naturally decrease. Likewise, previously dis-remembered details can be allowed retrieval. As a result, alternative cognitions can develop naturally. An implication of this analysis is that when avoidant/constricted attention has been disrupted, then the patient will begin attending to the internal processing of the trauma. Should the patient not attend, then it cannot be successfully resolved. As a result, it would appear that the mental state requisite for resolution is one which neither avoids nor rigidifies but simply follows the internal experience as it proceeds.
Shapiro (1995), based on her clinical experience, states that EMDR facilitates the natural healing processes of the individual. Based on the authors’ clinical experience, for emotion to resolve it must be allowed to follow its natural progression of increas-ing and then decreasincreas-ing intensity. In almost all unresolved traumatic situations, emotions have not followed this natural course—rather they are inhib-ited. Inhibited affect, as in PTSD, cannot resolve. We hypothesize during EMDR that, when conscious, inhibitory processes have been disrupted; the nat-ural and healthy flow of subjective experience can lead to a resolution. This process connects to our neurological hypothesis.
As per hypothesis, if PTSD involves the later-alization of affective and cognitive memory, then bilateral stimulation of both hemispheres begins to provide a neurological context in which previously disjoined and disconnected facets of the traumatic experience can begin to join and connect again.
In other words, after establishing internal hooks (the picture, body sensation/emotion, cognition and negative self-concept) which evoke relevant neural networks, the EMDR process stimulates both hemispheres, allowing previously separated facets of the memory to join. In addition, the pro-cess disrupts conscious avoidance and attentional constriction of internal experience by engaging conscious attention on external experience at the same time. As arousal increases so also does the vividness of imagery, the intensity of associated emotion, and the amount of subjective discom-fort. These inner events serve as successive and sequential ‘memory hooks’, eliciting further rele-vant facets of the neural network—in other words, even stronger arousal, even more vivid imagery, even more discomfort, and additional facets of the trauma stored in memory (sensations, tastes, smells, thoughts and so on). Given the reality that the trauma is over, the individual’s experience of these powerful inner phenomena in the therapeu-tic context can lead to the rapid reorganization of the experiences. In addition, given the simultane-ous activation of both hemispheres, as well as an increase in left hemisphere activation, the previ-ously disconnected aspects of the trauma naturally link, and new cognitions spontaneously form.
PREDICTIONS STEMMING FROM THIS
MODEL
One of the most important functions of a model or theory is the ability to generate hypotheses. If EMDR is explained by a combination of arousal activation/desensitization, the connection of func-tionally disconnected hemispheres, left hemisphere activation, and disrupting avoidant/constricted attention, a number of predictions should follow. (1) Consistent with prior research during the
acti-vation of intrusive PTSD symptoms, there should be an increase in activity in the right hemisphere, measured by brain imagery tech-niques. At the end of successful EMDR treat-ment, there should be a subsequent increase in left hemisphere activation which should cor-relate with patient reports of decreased PTSD symptoms.
(2) In contrast to the Armstrong and Vaughan (1996) or Dyck (1993) models, stimulation that activates the orienting response or distracts to break conditioning bonds, could use unilateral stimulation which should be as effective as
bilateral stimulation. The authors’ conception suggests that only bilateral stimulation will be as effective as EMDR treatment for PTSD. (3) Patients who, during EMDR, continue to avoid
their experience or to focus attention narrowly so as not to allow other experiences (such as emotions, sensations, thoughts) will not demonstrate significant change. This effect should correlate with brain imaging techniques. (4) During EMDR treatment, the patient should report an increasing number of related stimuli that reflect increased awareness of aspects of the traumatic event and this should be reflected in brain imaging techniques.
CONCLUSION
In summary, though the evidence is mixed, EMDR is probably an efficacious treatment for civilian PTSD and possibly an efficacious treatment for military PTSD. The authors propose that EMDR’s treatment effect results from bilateral activation of the right and left cerebral hemispheres during exposure to the traumatic imagery, affects, and cognitions. In addition, the ‘reconnection’ of the hemispheres, the increase in left hemisphere acti-vation, and the resultant reduction in emotional arousal is facilitated by engaging conscious atten-tion via the EMDR procedures, as well as disrupting avoidant and constricted attention.
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