In summary, these results suggest that patients with PTSD can have significantly different responses to traumatic script-driven imagery. Our studies may shed light on key biological dimensions of the disorder. As noted, about 70% of patients in our studies relived their traumatic experience and showed an increase in heart rate while recalling the traumatic memory,11 while the other 30% showed a dissociative response with no concomitant increase in heart rate. Interestingly, attempts to correctly classify PTSD cases through the use of discriminant functions based on psychophysiological responses to reminders, including expected increased heart rate, have historically resulted in false-negative classifications in the range of 30% or more.34

The fMRI findings that we have reported here add to the emerging evidence of experiential and neurobiological differences between dissociative versus nondissociative responses to traumatic reminders. These results also provide further support for a dissociative subtype of PTSD that may stem from more severe childhood experiences of abuse and neglect.1,35

However, all patients who are seen in clinical practice may not fit neatly into “reexperiencing/hyperaroused” versus “dissociative” subtypes of PTSD. Some exhibit both types of responses at different times and in different contexts (eg, those involving actual and perceived inability to physically escape). Indeed, our own (unpublished) data collected during a treatment study of more than 50 patients with PTSD showed that within a single experimental session that involved 2 script-driven trauma imagery exposures, one-third reported dissociative responses to one script and reexperiencing/hyperaroused responses to the other. Nevertheless, patients with a history of chronic early life trauma tend to exhibit significantly more dissociative symptoms than patients who have experienced adult traumatic events.1,2

Clinical implications

Exposure-based treatments for PTSD (eg, prolonged exposure and eye movement desensitization and reprocess) consist of repeated exposure to trauma-related stimuli and have the strongest empirical support.36 Critically, the in-session exposures are designed to overcome avoidance of such stimuli by providing a safe context in which patients can fully engage with trauma-related and “corrective” (safety) information. In this way, exposure treatment is designed to overcome and reduce avoidance symptoms, which, in turn, should reduce reexperiencing and hyperarousal symptoms and, ultimately, eliminate the disorder itself.37

However, as Foa and colleagues38 suggested, caution must be taken with patients who exhibit significant dissociative and numbing symptoms because these can prevent emotional engagement with trauma-related information and thereby reduce treatment effectiveness.39,40 It is therefore crucial to assess dissociative pathology and to provide interventions that reduce dissociative symptomatic responses to trauma-related stimuli before commencing exposure-based treatments.36 Failure to do so can exacerbate PTSD and related symptoms, including dissociation, and can increase the patient’s overall distress and functional impairment.

Cloitre and colleagues41 recently developed an integrative and empirically supported “phase-based” intervention for long-term, child abuse–related PTSD often associated with significant dissociative symptomatology. Their approach delivers a stage-oriented model that uses skills training in emotion regulation before engaging in exposure-based therapy. Their treatment manual42 has session-by-session guidelines; suggestions for tailoring interventions to individuals; and handouts, worksheets, and other tools for managing symptoms, building emotion regulation skills, and processing traumatic memories and associated feelings. Moreover, Ogden and colleagues43 have published a comprehensive book on key principles and practical clinical skills for addressing somatic, emotional, and cognitive components of self-regulation and stabilization in patients with PTSD and related disorders that result from early life trauma.

In addition, the International Society for the Study of Trauma and Dissociation (www.isst-d.org) offers in-person and distance-learning training for clinicians who work with clients with severe dissociative symptoms. Vermilyea44 has also published an excellent self-help book for patients with PTSD and dissociative symptoms that retails for around $20.

Future treatment outcome research should focus on complex childhood abuse–related PTSD with considerable dissociative symptomatology to shed light on which interventions are most effective and how they can be optimally timed in a phase-oriented treatment model. However, as all clinicians know, when it comes to helping the unique individuals who come to one’s office or clinic, there are limits to the applicability of findings from controlled clinical trials because of their selection biases and other limits to external validity.45 Mindful of this reality, we close this section with cogent observations from Judith Herman’s recently published editorial, “Craft and Science in the Treatment of Traumatized People.”46 A pioneer in the study and treatment of survivors of severe child abuse, Herman is also author of the classic Trauma and Recovery,47 which remains an authoritative text on “phase-oriented” treatment of psychological trauma, particularly for patients with significant dissociative pathology.

"When we prescribe, we have to figure out which antidepressant is right for each particular patient. Even in the simplest cases, we don’t currently know how to predict a successful fit. Most practitioners become familiar with a few medications and learn the nuances of prescribing within that repertoire. It turns out that some lucky patients will respond well to just about any of the medications, whereas about 10% or more won’t respond to anything currently available. For the rest, we resort to trial and error. It would be nice if we had some systematic basis for determining which medication will be best for which patient, but we don’t. So we use our clinical instincts, for lack of a better guide. . . .

The same may be true of the many psychotherapies for psychological trauma. We see some patients, particularly adults in good health with good social supports who suffer a single-incident trauma, who will probably do reasonably well with any of a wide range of treatment or self-help options. We see some patients at the extreme end of the complex trauma/dissociative disorder spectrum who may be beyond the reach of any treatment currently known. In between are all the rest—patients who may respond well to one form of treatment but not another—and as yet we don’t know very well how to predict the best match. We recognize that treatment of trauma is a complex biological, psychological, and social project that unfolds in stages over time and may involve many different treatment modalities to reach a stage of optimal recovery."46

Conclusion

There is compelling evidence not only from clinical practice but also from biological research that patients with PTSD can show both reexperiencing/hyperaroused and dissociative responses to recalling traumatic experiences and for corresponding subtypes of PTSD. These different responses and subtypes can be viewed as extremes of dysregulation that involve overengagement and underengagement with trauma-related emotional and somatosensory information. Each response type appears to have distinct CNS correlates, and the severities of each response type have been correlated in predicted ways with neural activity in brain regions that are responsible for emotional awareness and emotion regulation. Finally, these findings have important implications for treatment, including the need to assess patients with PTSD for dissociative symptomatology and to treat dissociative symptoms before using exposure-based approaches.
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