Emerging Trends in The Social and Behavioral Sciences · Dissociation and Dissociative Identity Disorder (DID)

Dissociation and Dissociative Identity Disorder (DID)

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Title: Dissociation and Dissociative Identity Disorder (DID)
extracted text: Dissociation and Dissociative Identity
Disorder (DID)
RAFAËLE J. C. HUNTJENS and MARTIN J. DORAHY

Abstract
Dissociative experiences are thought to occur acutely (e.g., during or immediately
following trauma) or chronically and are considered to reduce the subjective
distress accompanying stressful events. Growing evidence is consistent with a
model that distinguishes between two qualitatively different types of phenomena—
“compartmentalization” and “detachment.” Compartmentalization involves a deficit
in the ability to deliberately control processes or actions that would normally be
amendable to such control (e.g., amnesia and dissociative identities). Detachment
refers to an experienced state of disconnection from the self or the environment
(e.g., depersonalization, derealization, and numbing).
In the present contribution, we discuss both detachment and compartmentalization
phenomena. In addition, we discuss both dissociation as an acute response to trauma
and persistent dissociation in the form of the most severe and chronic of the dissociative disorders, dissociative identity disorder (DID). We attend to the burgeoning
empirical literature on memory processing and dissociation given the central role of
these cognitive operations in the development and maintenance of the dissociative
disorders, and more broadly, posttraumatic symptomatology.
We end with a more general appeal for more transdiagnostic studies of dissociative
phenomena, both in the areas of detachment and compartmentalization, emphasizing that dissociative disorders are not a category of mysterious diagnoses that need
to be understood outside of well-known cognitive operations.

INTRODUCTION
Often controversial, rarely well understood, and at times in the history of
mainstream psychological science blatantly ignored, dissociation and the dissociative disorders are now taking their place within the established psychological and psychiatric literatures. As society and science understands more
fully the psychological cost of war, child abuse and interpersonal violence,
dissociation and the dissociative disorders are being more clearly identified.
Ever increasing sophistication in assessment and diagnostic tools are helping clinicians more accurately detect dissociative symptoms, which are the
Emerging Trends in the Social and Behavioral Sciences. Edited by Robert Scott and Stephen Kosslyn.
© 2015 John Wiley & Sons, Inc. ISBN 978-1-118-90077-2.

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hallmark of dissociative disorders such as dissociative identity disorder
(DID). Research is showing that dissociative disorders should no longer be
considered rare (¸Sar, 2011) and that dissociative symptoms are present in a
wide range of clinical conditions including borderline personality disorder,
panic disorder, eating disorders, and psychotic disorders. In addition, the
most recent version of the Diagnostic and Statistical Manual of Mental
Disorders (DSM-5; American Psychiatric Association, 2013) has formulated
a dissociative subtype of posttraumatic stress disorder (PTSD). Consequently, the study of dissociation and dissociative disorders is becoming an
increasingly important scientific endeavor.
The DSM-5 (American Psychiatric Association, 2013) broadly refers to
pathological dissociation as “a disruption of and/or discontinuity in the
normal integration of consciousness, memory, identity, emotion, perception,
body representation, motor control, and behavior” (p. 291). While there is
some contention, the available evidence can be interpreted to distinguish
both conceptually and empirically between two qualitatively different types
of dissociative phenomena—“compartmentalization” and “detachment”
(for an overview see Holmes et al., 2005). Compartmentalization involves
a deficit in the ability to deliberately control processes or actions that
would normally be amendable to such control. It encompasses amnesia
(i.e., the inability to remember seemingly unforgettable events), fugues (i.e.,
unexpected travel accompanied with forgetting one’s identity or assuming
a new self), bodily or somatoform symptoms (e.g., sensory loss and loss
of motor control), and dissociative identities (i.e., aspects of self that seem
to have their own memories and sense of identity). Detachment refers to an
experienced state of disconnection from the self or the environment. People
experiencing detachment often report feeling “spaced out,” “unreal,” or that
they are “in a dream.”
In more acute dissociative presentations, the dissociation is related to
traumatic or other overwhelming experiences, where dissociative symptoms are considered to reduce the subjective distress accompanying these
events (Cardeña & Carlson, 2011). The dissociation response may also
persist outside the immediate trauma context, reducing full awareness of
the traumatic event. In addition, it may generalize to milder aversive events,
developing into the more chronic and recurrent conditions of dissociative
disorders (Spiegel et al., 2011).
The concept of dissociation and particularly DID has often courted
controversy that has gone beyond existing data. We stay focused in the
current paper on empirical data, believing it offers the most judicious
way forward. Specifically, we will attend to the burgeoning empirical
literature on memory processing and dissociation. Investigations into these
processes have generated sophisticated and exciting studies, with findings

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showing the central role of cognitive operations in the development and
maintenance of the dissociative disorders, and more broadly, posttraumatic
symptomatology (Brewin & Holmes, 2003; Dorahy, 2001; Ehlers & Clark,
2000; Huntjens, Dorahy, & Van Wees-Cieraad, 2013). For example, the lack of
temporal continuity caused by the gaps in memory reported by dissociative
patients lies at the heart of the disturbed sense of personal identity in DID.
We start off discussing encoding processes associated with acute, temporary
dissociative reactions to trauma in the first section and then go on to discuss
amnesia between identities in the DID section.
ACUTE TRAUMA-RELATED DISSOCIATION
Dissociation, in the form of detachment, is commonly experienced during
or immediately after a traumatic or other highly stressful event, such as a
motor vehicle accident, assault, or rape (Marmar et al., 1994). These experiences of disconnection from the self or the environment relate to the person’s
sense of self (depersonalization), the external world (derealization), and emotional experience (e.g., emotional numbing). The antecedent and timing of
these experiences have them referred to as peritraumatic dissociation (i.e., dissociation occurring at or around the time of trauma) and they are a strong
predictor of PTSD development (Ozer, Best, Lipsey, & Weiss, 2003).
Several trauma theories posit that experiences of dissociation during or
in the immediate aftermath of trauma result in inadequate encoding of the
trauma memory. More specifically, trauma memories are considered to be
encoded more perceptually (i.e., processing the sensory impressions and
perceptual details) while they lack conceptual processing (i.e., processing
the meaning of the situation in an organized way and placing it into context
with other memories) (e.g., Brewin, 2014; Brewin, Gregory, Lipton, &
Burgess, 2010; Ehlers & Clark, 2000). As an example, consider a victim of a
shooting who remembers vividly and involuntarily the smell of blood and
the sight of the murder weapon, but does not have a complete picture of the
event nor can make meaningful sense of what happened. The perceptual
encoding of the traumatic event is considered to be a causal factor in the later
development of intrusive memories (Lyttle, Dorahy, Hanna, & Huntjens,
2010; Michael, Ehlers, & Halligan, 2005), which are vivid memories of the
event involuntarily triggered by cues that are similar to those present during
the trauma.
Recent empirical data on perceptual encoding of trauma memories comes
from priming studies. Priming refers to the advantage in ease of processing
and processing speed obtained by familiar stimuli. Priming was studied
both in patients with PTSD and analog samples (i.e., samples exposed to
laboratory-controlled stimuli designed to mimic trauma at a lower level).

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Results indicate enhanced perceptual priming and decreased conceptual
priming specifically for trauma-related words in the PTSD patients compared to control groups with comparable aversive experiences. Similar
findings are evident in analog studies. In addition, enhanced perceptual
priming has been found to predict the later development of intrusive memories. Moreover, state dissociation (i.e., dissociation experienced during the
stimulus encoding in the laboratory) has been found to predict perceptual
priming (e.g., Kleim, Ehring, & Ehlers, 2012; Lyttle, Dorahy, Hanna &
Huntjens, 2010; Sündermann, Hauschildt, & Ehlers, 2013). This suggests that
those who experience dissociation while they are experiencing a distressing
event are more likely to limit processing of that experience to perceptual
representations (e.g., visual, auditory, bodily sensations, and olfactory),
rather than more complex conceptual representations, which leaves them
vulnerable to develop later intrusive memories.
In addition to perceptual encoding, peritraumatic dissociation has also
been related to a form of inadequate encoding of trauma-related information, which leads to memory fragmentation. This term refers to an inability to
voluntarily retrieve and describe in an organized, coherent manner a trauma
memory. While several studies have provided evidence for an association
between experiences of acute dissociation and trauma memory fragmentation, this relation seems restricted to contexts in which participants who
experience dissociation rate the fragmentation of their own narrative of a
distressing event (rather than using objective measures of fragmentation).
Those with higher levels of dissociation tend to rate their narrative as more
fragmented and less coherent than those who have lower dissociation. However, interestedly, when the narratives are examined, no objective evidence is
found for heightened fragmentation in the high dissociators (Kindt, Van den
Hout & Buck, 2005). Thus, dissociation appears to impact on the perception
(or subjective experience) of having a fragmented memory of an event,
rather than the memory of that event actually being fragmented [for reviews
see Huntjens, Dorahy, and Van Wees-Cieraad (2013) and Bedard-Gilligan
and Zoellner (2012)].
DISSOCIATIVE IDENTITY DISORDER (DID)
DID, previously known as multiple personality disorder, is the most severe
dissociative disorder. International prevalence data using structured clinical
interviews shows the prevalence of DID between 0.4% and 7.5% (studies
averaged to approximately 5%) of inpatients and outpatients, depending on
the country assessed, the methodology adopted and the structured clinical
interview used (¸Sar, 2011). DID is associated with among other variables,
chronic, attachment-related abuse commencing before middle childhood

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(e.g., Lewis, Yeager, Swica, Pincus, & Lewis, 1997; Ross & Ness, 2010; see
Dorahy et al., 2014).
The disorder is characterized by different dissociative identities, which
report differences in autobiographical experiences and memories, and which
also report having their own sense of self and agency (i.e., they perceive
themselves as different and unique from other dissociative identities and
have a subjective awareness of willing and initiating their own behavior). When patients move (switch) between identities, they report related
alterations in affect, behavior, memory, perception, bodily experience and
cognition. Moreover, DID patients report recurrent gaps in their memory as a
result of knowledge and events experienced in the past being “compartmentalized” in the different identities. The compartmentalization of information
learned in one identity state may render it unavailable for retrieval in other
identity states. This may pertain to the inability to retrieve autobiographical
information, but also learned behavior (i.e., skills such as playing the piano).
In the previous version of the DSM (DSM-IV) amnesia in DID was limited
to the inability to recall important personal information. However, in the
DSM-5, the amnesia criterion for DID also includes not being able to recall
everyday events, that may account for amnesia experienced when different
identities are moved between (APA, 2013).
In experimental research, interidentity amnesia (i.e., amnesia one identity
reports for material contained in another identity) is assessed by one identity
learning a set of stimuli and another identity, self-reporting amnesia for the
learning trial, being tested on retrieval ability for the learned information.
Earlier studies supported the existence of interidentity amnesia in DID,
especially for more complex information, such as stories that contained a
lot of contextual (rich, detailed) information. These studies, however, relied
on the single case method or assessed only a small number of DID patients
(e.g., Eich, Macauley, Loewenstein, & Dihle, 1997; Nissen, Ross, Willingham,
MacKenzie & Schacter, 1988). Some also exclusively used self-report measures of amnesia (e.g., Bryant, 1995; Schacter, Kihlstrom, Kihlstrom, & Berren,
1989; for a review see Dorahy, 2001; Dorahy & Huntjens, 2007). More recent
studies, employing more sophisticated methodological designs, adequate
control groups, and larger patient samples, have revealed different results.
For example, Huntjens, Postma, Peters, Woertman, and Van der Hart (2003)
had DID patients learn a set of neutral words in identity A and were tested
on word recall. The patients then switched to another identity (identity B).
Identity B subjectively reported amnesia for what was learned in identity A.
Subsequently, identity B learned and recalled a list of related words. When
healthy control subjects perform this task, the learning of the first word
list interferes with the retention of the second word list. However, in the
case of dissociative amnesia between identities, no detrimental effect of list

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A learning on the retrieval of list B is expected, resulting in an improved
performance in DID for list B words in comparison to healthy controls.
In other words, no interference in learning and retrieval is expected if the
amnesic barrier between identities is as strong as subjectively experienced
by the patients. The results, however, did not follow expectations. DID
patients experienced as much interference in list B as the healthy controls,
resulting in a comparable decreased performance on the recall of list B
compared to list A. Moreover, they even reported list A words during list B
recall. These results thus indicated transfer of information between identities
that are experienced as compartmentalized and amnesic (i.e., not able to be
remembered). Importantly, this test constitutes an assessment of whether
patients were able to consciously retrieve information learned in another
identity, and this contrasts with their self-reported dissociative amnesia (see
also Kong, Allen, & Glisky, 2008).
It may be that dissociative barriers are more operative for negatively
valenced or autobiographical material. Several studies have investigated
some of these issues (Huntjens, Peters, Woertman, Van der Hart, & Postma,
2007; Huntjens, Verschuere, & McNally, 2012; for a review see Dorahy
& Huntjens, 2007). An example of this is a study in which an evaluative
conditioning procedure was administered to DID participants in a particular
identity state (Huntjens et al., 2005). This procedure results in previously
neutral words acquiring an emotional connotation by repeatedly pairing
them with positive and negative words. In a subsequent affective priming
procedure in a second amnesic identity, participants displayed transfer
of this newly acquired emotional valence in amnesic identities, which
was not to be expected in cases of total interidentity amnesia. Although
acknowledging important, and possibly meaningful, differences between
laboratory-based tasks and real-life autobiographical events, the most
striking finding in recent experimental studies of compartmentalization is
an absence of objective evidence for interidentity amnesia. This absence
of objective amnesia has been present when DID participants subjectively
reported complete amnesia in the “test” identity for material and instructions given to the “learn” identity. Importantly, these empirical studies
suggest a revision in definition of compartmentalization emphasizing the
meta-cognitive beliefs that patients hold. While the patient subjectively
may experience an inability to deliberately control the retrieval process, this
inability resides in the subjective arena. Just as the experience of being “fat”
in someone with anorexia nervosa resides in the subjective arena. The results
offer potential avenues for therapeutic focus, as the subjectively experienced
deficits in recall may be overcome as these beliefs become more centrally
examined in therapy.

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KEY ISSUES FOR FUTURE RESEARCH
Experimental studies aimed at establishing the causal role of dissociative
experiences on information processing are hampered by the lack of valid
and reliable methods to induce dissociation in the lab. Previous attempts to
induce state dissociation (e.g., sleep deprivation, use of drugs, and mirror
staring) have been nonspecific in their effects (e.g., inducing confounds) and
the effect sizes of these previous manipulations have generally been small
(e.g., Holmes, Brewin, & Hennessy, 2004; Krystal et al., 1994). Moreover, previous attempts were nonspecific in the type of dissociation (i.e., detachment,
compartmentalization) induced (e.g., Brewin, Ma, & Colson, 2013; Leonard,
Telch, & Harrington, 1999; Miller, Brown, DiNardo, & Barlow, 1994; Zoellner,
Sacks, & Foa, 2007). New methods to specifically induce different types of
dissociation are thus essential for progress in the field.
In the section on acute, trauma-related dissociation, we described perceptual memory encoding as a possible mechanism underlying the relationship
between acute dissociation and later posttraumatic complaints. Future studies may reveal other mechanisms. One of these possible mechanisms could
be a lack of self-referential encoding, or not fully relating the event to the self
(Halligan, Michael, Clark, & Ehlers, 2003). Clinically, a lack of self-referential
encoding is evident in statements such as “I know this happened to me, but
it does not seem real” (Huntjens, Dorahy, & Van Wees-Cieraad, 2013).
Controlled experimental studies as well as longitudinal studies should
incorporate measures of peritraumatic and persistent dissociation, along
with related emotional and cognitive factors to shed more light on the causal
and maintaining factors of posttraumatic symptomatology (Panasetis &
Bryant, 2003). Longitudinal studies could extend the timeline of dissociative
response measurement to explore how dissociation at different points
following trauma impacts on information processing. Such studies could
examine correlates and predictors of acute dissociation including prior
low control of emotions, dissociative trait tendencies, and lower education
(Engelhard, Van den Hout, Kindt, Arntz, & Schouten, 2003).
Regarding interidentity amnesia, we have suggested a change in definition
emphasizing the meta-cognitive beliefs that patients may hold. Future
research will have to further elucidate the content and scope of these
meta-cognitive beliefs. However, meta-cognitive beliefs that are inconsistent
with objective reality are not specific to dissociative disorders, but are also
seen in many other psychiatric conditions, including PTSD (e.g., “I’m having
intrusive memories so I must be going crazy”). We thus argue that memory
anomalies evident in DID are consistent with memory mechanisms and
processing issues evident in other psychiatric problems.

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Relatedly, we would like to conclude with a more general appeal for
more transdiagnostic (i.e., across different disorders) studies of dissociative phenomena. Meta-cognitive beliefs associated with the central
symptomatology are seen in many psychiatric conditions (e.g., the
meta-belief that one is going crazy when their mind starts racing during
panic), including for compartmentalization in DID. Moreover, experiences
of temporary or persistent detachment are evident in the context of other
conditions. A review indicated that symptoms of depersonalization and
derealization have been described in many clinical conditions including
agoraphobia, panic disorder, obsessive-compulsive disorder, eating disorders, depression, psychosis, and personality disorders (Hunter, Sierra,
& David, 2004). Transdiagnostic studies assessing the subjective nature of
amnesia, along with the prevalence of detachment, it is (differing) content in
separate disorders, it is association with trauma, and it is role in information
processing are thus needed to emphasize that dissociative disorders are not
a category of mysterious disorders that need to be understood outside of
well-known cognitive operations.
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FURTHER READING
Dorahy, M. J., Brand, B. L., S¸ ar, V., Krüger, C., Stavropoulos, P., Martínez-Taboas, A.,
… Middleton, W. (2014). Dissociative identity disorder: An Empirical overview.
Australian & New Zealand Journal of Psychiatry, 48, 402–417.
Dorahy, M. J., & Huntjens, R. J. C. (2007). Memory and attentional processes in dissociative identity disorder: A review of the empirical literature. In E. Vermetten, M.
Dorahy & D. Spiegel (Eds.), Traumatic dissociation: Neurobiology and treatment (pp.
55–75). Arlington, VA: American Psychiatric Publishing, Inc.
Dalenberg, C. J., Brand, B. L., Gleaves, D. H., Dorahy, M. J., Loewenstein, R. J.,
Cardeña, E., … Spiegel, D. (2012). Evaluation of the evidence for the trauma and
fantasy models of dissociation. Psychological Bulletin, 138, 550–588.
Giesbrecht, T., Lynn, S. J., Lilienfeld, S. O., & Merckelbach, H. (2008). Cognitive processes in dissociation: An analysis of core theoretical assumptions. Psychological
Bulletin, 134, 617–647. doi:10.1037/0033-2909.134.5.617
Huntjens, R. J. C., Dorahy, M. J., & Van Wees-Cieraad, R. (2013). Dissociation and
memory fragmentation. In F. Kennedy, H. Kennerley & D. Pearson (Eds.), Dissociation and cognitive therapy (pp. 92–103). London, England: Routledge.

RAFAËLE J. C. HUNTJENS SHORT BIOGRAPHY
Rafaële J. C. Huntjens is Assistant Professor in the Department of
Clinical Psychology, University of Groningen, the Netherlands. She has
published on memory processes in trauma-related disorders. More information and a list of publications can be found on her university webpage
http://www.rug.nl/staff/r.j.c.huntjens/.
MARTIN J. DORAHY SHORT BIOGRAPHY
Martin J. Dorahy is Associate Professor in the Department of Psychology,
University of Canterbury, Christchurch, New Zealand. He also maintains a
private practice focused primarily on complex trauma disorders. More information and a list of publications can be found on his university webpage
http://www.psyc.canterbury.ac.nz/people/dorahy.shtml.
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Dissociation and Dissociative Identity Disorder (DID)

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13; Dissociation and Dissociative Identity
Disorder (DID)
RAFAËLE J. C. HUNTJENS and MARTIN J. DORAHY

Abstract
Dissociative experiences are thought to occur acutely (e.g., during or immediately
following trauma) or chronically and are considered to reduce the subjective
distress accompanying stressful events. Growing evidence is consistent with a
model that distinguishes between two qualitatively different types of phenomena—
“compartmentalization” and “detachment.” Compartmentalization involves a deficit
in the ability to deliberately control processes or actions that would normally be
amendable to such control (e.g., amnesia and dissociative identities). Detachment
refers to an experienced state of disconnection from the self or the environment
(e.g., depersonalization, derealization, and numbing).
In the present contribution, we discuss both detachment and compartmentalization
phenomena. In addition, we discuss both dissociation as an acute response to trauma
and persistent dissociation in the form of the most severe and chronic of the dissociative disorders, dissociative identity disorder (DID). We attend to the burgeoning
empirical literature on memory processing and dissociation given the central role of
these cognitive operations in the development and maintenance of the dissociative
disorders, and more broadly, posttraumatic symptomatology.
We end with a more general appeal for more transdiagnostic studies of dissociative
phenomena, both in the areas of detachment and compartmentalization, emphasizing that dissociative disorders are not a category of mysterious diagnoses that need
to be understood outside of well-known cognitive operations.

INTRODUCTION
Often controversial, rarely well understood, and at times in the history of
mainstream psychological science blatantly ignored, dissociation and the dissociative disorders are now taking their place within the established psychological and psychiatric literatures. As society and science understands more
fully the psychological cost of war, child abuse and interpersonal violence,
dissociation and the dissociative disorders are being more clearly identified.
Ever increasing sophistication in assessment and diagnostic tools are helping clinicians more accurately detect dissociative symptoms, which are the
Emerging Trends in the Social and Behavioral Sciences. Edited by Robert Scott and Stephen Kosslyn.
© 2015 John Wiley & Sons, Inc. ISBN 978-1-118-90077-2.

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EMERGING TRENDS IN THE SOCIAL AND BEHAVIORAL SCIENCES

hallmark of dissociative disorders such as dissociative identity disorder
(DID). Research is showing that dissociative disorders should no longer be
considered rare (Şar, 2011) and that dissociative symptoms are present in a
wide range of clinical conditions including borderline personality disorder,
panic disorder, eating disorders, and psychotic disorders. In addition, the
most recent version of the Diagnostic and Statistical Manual of Mental
Disorders (DSM-5; American Psychiatric Association, 2013) has formulated
a dissociative subtype of posttraumatic stress disorder (PTSD). Consequently, the study of dissociation and dissociative disorders is becoming an
increasingly important scientific endeavor.
The DSM-5 (American Psychiatric Association, 2013) broadly refers to
pathological dissociation as “a disruption of and/or discontinuity in the
normal integration of consciousness, memory, identity, emotion, perception,
body representation, motor control, and behavior” (p. 291). While there is
some contention, the available evidence can be interpreted to distinguish
both conceptually and empirically between two qualitatively different types
of dissociative phenomena—“compartmentalization” and “detachment”
(for an overview see Holmes et al., 2005). Compartmentalization involves
a deficit in the ability to deliberately control processes or actions that
would normally be amendable to such control. It encompasses amnesia
(i.e., the inability to remember seemingly unforgettable events), fugues (i.e.,
unexpected travel accompanied with forgetting one’s identity or assuming
a new self), bodily or somatoform symptoms (e.g., sensory loss and loss
of motor control), and dissociative identities (i.e., aspects of self that seem
to have their own memories and sense of identity). Detachment refers to an
experienced state of disconnection from the self or the environment. People
experiencing detachment often report feeling “spaced out,” “unreal,” or that
they are “in a dream.”
In more acute dissociative presentations, the dissociation is related to
traumatic or other overwhelming experiences, where dissociative symptoms are considered to reduce the subjective distress accompanying these
events (Cardeña & Carlson, 2011). The dissociation response may also
persist outside the immediate trauma context, reducing full awareness of
the traumatic event. In addition, it may generalize to milder aversive events,
developing into the more chronic and recurrent conditions of dissociative
disorders (Spiegel et al., 2011).
The concept of dissociation and particularly DID has often courted
controversy that has gone beyond existing data. We stay focused in the
current paper on empirical data, believing it offers the most judicious
way forward. Specifically, we will attend to the burgeoning empirical
literature on memory processing and dissociation. Investigations into these
processes have generated sophisticated and exciting studies, with findings

Dissociation and Dissociative Identity Disorder (DID)

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showing the central role of cognitive operations in the development and
maintenance of the dissociative disorders, and more broadly, posttraumatic
symptomatology (Brewin & Holmes, 2003; Dorahy, 2001; Ehlers & Clark,
2000; Huntjens, Dorahy, & Van Wees-Cieraad, 2013). For example, the lack of
temporal continuity caused by the gaps in memory reported by dissociative
patients lies at the heart of the disturbed sense of personal identity in DID.
We start off discussing encoding processes associated with acute, temporary
dissociative reactions to trauma in the first section and then go on to discuss
amnesia between identities in the DID section.
ACUTE TRAUMA-RELATED DISSOCIATION
Dissociation, in the form of detachment, is commonly experienced during
or immediately after a traumatic or other highly stressful event, such as a
motor vehicle accident, assault, or rape (Marmar et al., 1994). These experiences of disconnection from the self or the environment relate to the person’s
sense of self (depersonalization), the external world (derealization), and emotional experience (e.g., emotional numbing). The antecedent and timing of
these experiences have them referred to as peritraumatic dissociation (i.e., dissociation occurring at or around the time of trauma) and they are a strong
predictor of PTSD development (Ozer, Best, Lipsey, & Weiss, 2003).
Several trauma theories posit that experiences of dissociation during or
in the immediate aftermath of trauma result in inadequate encoding of the
trauma memory. More specifically, trauma memories are considered to be
encoded more perceptually (i.e., processing the sensory impressions and
perceptual details) while they lack conceptual processing (i.e., processing
the meaning of the situation in an organized way and placing it into context
with other memories) (e.g., Brewin, 2014; Brewin, Gregory, Lipton, &
Burgess, 2010; Ehlers & Clark, 2000). As an example, consider a victim of a
shooting who remembers vividly and involuntarily the smell of blood and
the sight of the murder weapon, but does not have a complete picture of the
event nor can make meaningful sense of what happened. The perceptual
encoding of the traumatic event is considered to be a causal factor in the later
development of intrusive memories (Lyttle, Dorahy, Hanna, & Huntjens,
2010; Michael, Ehlers, & Halligan, 2005), which are vivid memories of the
event involuntarily triggered by cues that are similar to those present during
the trauma.
Recent empirical data on perceptual encoding of trauma memories comes
from priming studies. Priming refers to the advantage in ease of processing
and processing speed obtained by familiar stimuli. Priming was studied
both in patients with PTSD and analog samples (i.e., samples exposed to
laboratory-controlled stimuli designed to mimic trauma at a lower level).

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EMERGING TRENDS IN THE SOCIAL AND BEHAVIORAL SCIENCES

Results indicate enhanced perceptual priming and decreased conceptual
priming specifically for trauma-related words in the PTSD patients compared to control groups with comparable aversive experiences. Similar
findings are evident in analog studies. In addition, enhanced perceptual
priming has been found to predict the later development of intrusive memories. Moreover, state dissociation (i.e., dissociation experienced during the
stimulus encoding in the laboratory) has been found to predict perceptual
priming (e.g., Kleim, Ehring, & Ehlers, 2012; Lyttle, Dorahy, Hanna &
Huntjens, 2010; Sündermann, Hauschildt, & Ehlers, 2013). This suggests that
those who experience dissociation while they are experiencing a distressing
event are more likely to limit processing of that experience to perceptual
representations (e.g., visual, auditory, bodily sensations, and olfactory),
rather than more complex conceptual representations, which leaves them
vulnerable to develop later intrusive memories.
In addition to perceptual encoding, peritraumatic dissociation has also
been related to a form of inadequate encoding of trauma-related information, which leads to memory fragmentation. This term refers to an inability to
voluntarily retrieve and describe in an organized, coherent manner a trauma
memory. While several studies have provided evidence for an association
between experiences of acute dissociation and trauma memory fragmentation, this relation seems restricted to contexts in which participants who
experience dissociation rate the fragmentation of their own narrative of a
distressing event (rather than using objective measures of fragmentation).
Those with higher levels of dissociation tend to rate their narrative as more
fragmented and less coherent than those who have lower dissociation. However, interestedly, when the narratives are examined, no objective evidence is
found for heightened fragmentation in the high dissociators (Kindt, Van den
Hout & Buck, 2005). Thus, dissociation appears to impact on the perception
(or subjective experience) of having a fragmented memory of an event,
rather than the memory of that event actually being fragmented [for reviews
see Huntjens, Dorahy, and Van Wees-Cieraad (2013) and Bedard-Gilligan
and Zoellner (2012)].
DISSOCIATIVE IDENTITY DISORDER (DID)
DID, previously known as multiple personality disorder, is the most severe
dissociative disorder. International prevalence data using structured clinical
interviews shows the prevalence of DID between 0.4% and 7.5% (studies
averaged to approximately 5%) of inpatients and outpatients, depending on
the country assessed, the methodology adopted and the structured clinical
interview used (Şar, 2011). DID is associated with among other variables,
chronic, attachment-related abuse commencing before middle childhood

Dissociation and Dissociative Identity Disorder (DID)

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(e.g., Lewis, Yeager, Swica, Pincus, & Lewis, 1997; Ross & Ness, 2010; see
Dorahy et al., 2014).
The disorder is characterized by different dissociative identities, which
report differences in autobiographical experiences and memories, and which
also report having their own sense of self and agency (i.e., they perceive
themselves as different and unique from other dissociative identities and
have a subjective awareness of willing and initiating their own behavior). When patients move (switch) between identities, they report related
alterations in affect, behavior, memory, perception, bodily experience and
cognition. Moreover, DID patients report recurrent gaps in their memory as a
result of knowledge and events experienced in the past being “compartmentalized” in the different identities. The compartmentalization of information
learned in one identity state may render it unavailable for retrieval in other
identity states. This may pertain to the inability to retrieve autobiographical
information, but also learned behavior (i.e., skills such as playing the piano).
In the previous version of the DSM (DSM-IV) amnesia in DID was limited
to the inability to recall important personal information. However, in the
DSM-5, the amnesia criterion for DID also includes not being able to recall
everyday events, that may account for amnesia experienced when different
identities are moved between (APA, 2013).
In experimental research, interidentity amnesia (i.e., amnesia one identity
reports for material contained in another identity) is assessed by one identity
learning a set of stimuli and another identity, self-reporting amnesia for the
learning trial, being tested on retrieval ability for the learned information.
Earlier studies supported the existence of interidentity amnesia in DID,
especially for more complex information, such as stories that contained a
lot of contextual (rich, detailed) information. These studies, however, relied
on the single case method or assessed only a small number of DID patients
(e.g., Eich, Macauley, Loewenstein, & Dihle, 1997; Nissen, Ross, Willingham,
MacKenzie & Schacter, 1988). Some also exclusively used self-report measures of amnesia (e.g., Bryant, 1995; Schacter, Kihlstrom, Kihlstrom, & Berren,
1989; for a review see Dorahy, 2001; Dorahy & Huntjens, 2007). More recent
studies, employing more sophisticated methodological designs, adequate
control groups, and larger patient samples, have revealed different results.
For example, Huntjens, Postma, Peters, Woertman, and Van der Hart (2003)
had DID patients learn a set of neutral words in identity A and were tested
on word recall. The patients then switched to another identity (identity B).
Identity B subjectively reported amnesia for what was learned in identity A.
Subsequently, identity B learned and recalled a list of related words. When
healthy control subjects perform this task, the learning of the first word
list interferes with the retention of the second word list. However, in the
case of dissociative amnesia between identities, no detrimental effect of list

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EMERGING TRENDS IN THE SOCIAL AND BEHAVIORAL SCIENCES

A learning on the retrieval of list B is expected, resulting in an improved
performance in DID for list B words in comparison to healthy controls.
In other words, no interference in learning and retrieval is expected if the
amnesic barrier between identities is as strong as subjectively experienced
by the patients. The results, however, did not follow expectations. DID
patients experienced as much interference in list B as the healthy controls,
resulting in a comparable decreased performance on the recall of list B
compared to list A. Moreover, they even reported list A words during list B
recall. These results thus indicated transfer of information between identities
that are experienced as compartmentalized and amnesic (i.e., not able to be
remembered). Importantly, this test constitutes an assessment of whether
patients were able to consciously retrieve information learned in another
identity, and this contrasts with their self-reported dissociative amnesia (see
also Kong, Allen, & Glisky, 2008).
It may be that dissociative barriers are more operative for negatively
valenced or autobiographical material. Several studies have investigated
some of these issues (Huntjens, Peters, Woertman, Van der Hart, & Postma,
2007; Huntjens, Verschuere, & McNally, 2012; for a review see Dorahy
& Huntjens, 2007). An example of this is a study in which an evaluative
conditioning procedure was administered to DID participants in a particular
identity state (Huntjens et al., 2005). This procedure results in previously
neutral words acquiring an emotional connotation by repeatedly pairing
them with positive and negative words. In a subsequent affective priming
procedure in a second amnesic identity, participants displayed transfer
of this newly acquired emotional valence in amnesic identities, which
was not to be expected in cases of total interidentity amnesia. Although
acknowledging important, and possibly meaningful, differences between
laboratory-based tasks and real-life autobiographical events, the most
striking finding in recent experimental studies of compartmentalization is
an absence of objective evidence for interidentity amnesia. This absence
of objective amnesia has been present when DID participants subjectively
reported complete amnesia in the “test” identity for material and instructions given to the “learn” identity. Importantly, these empirical studies
suggest a revision in definition of compartmentalization emphasizing the
meta-cognitive beliefs that patients hold. While the patient subjectively
may experience an inability to deliberately control the retrieval process, this
inability resides in the subjective arena. Just as the experience of being “fat”
in someone with anorexia nervosa resides in the subjective arena. The results
offer potential avenues for therapeutic focus, as the subjectively experienced
deficits in recall may be overcome as these beliefs become more centrally
examined in therapy.

Dissociation and Dissociative Identity Disorder (DID)

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KEY ISSUES FOR FUTURE RESEARCH
Experimental studies aimed at establishing the causal role of dissociative
experiences on information processing are hampered by the lack of valid
and reliable methods to induce dissociation in the lab. Previous attempts to
induce state dissociation (e.g., sleep deprivation, use of drugs, and mirror
staring) have been nonspecific in their effects (e.g., inducing confounds) and
the effect sizes of these previous manipulations have generally been small
(e.g., Holmes, Brewin, & Hennessy, 2004; Krystal et al., 1994). Moreover, previous attempts were nonspecific in the type of dissociation (i.e., detachment,
compartmentalization) induced (e.g., Brewin, Ma, & Colson, 2013; Leonard,
Telch, & Harrington, 1999; Miller, Brown, DiNardo, & Barlow, 1994; Zoellner,
Sacks, & Foa, 2007). New methods to specifically induce different types of
dissociation are thus essential for progress in the field.
In the section on acute, trauma-related dissociation, we described perceptual memory encoding as a possible mechanism underlying the relationship
between acute dissociation and later posttraumatic complaints. Future studies may reveal other mechanisms. One of these possible mechanisms could
be a lack of self-referential encoding, or not fully relating the event to the self
(Halligan, Michael, Clark, & Ehlers, 2003). Clinically, a lack of self-referential
encoding is evident in statements such as “I know this happened to me, but
it does not seem real” (Huntjens, Dorahy, & Van Wees-Cieraad, 2013).
Controlled experimental studies as well as longitudinal studies should
incorporate measures of peritraumatic and persistent dissociation, along
with related emotional and cognitive factors to shed more light on the causal
and maintaining factors of posttraumatic symptomatology (Panasetis &
Bryant, 2003). Longitudinal studies could extend the timeline of dissociative
response measurement to explore how dissociation at different points
following trauma impacts on information processing. Such studies could
examine correlates and predictors of acute dissociation including prior
low control of emotions, dissociative trait tendencies, and lower education
(Engelhard, Van den Hout, Kindt, Arntz, & Schouten, 2003).
Regarding interidentity amnesia, we have suggested a change in definition
emphasizing the meta-cognitive beliefs that patients may hold. Future
research will have to further elucidate the content and scope of these
meta-cognitive beliefs. However, meta-cognitive beliefs that are inconsistent
with objective reality are not specific to dissociative disorders, but are also
seen in many other psychiatric conditions, including PTSD (e.g., “I’m having
intrusive memories so I must be going crazy”). We thus argue that memory
anomalies evident in DID are consistent with memory mechanisms and
processing issues evident in other psychiatric problems.

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EMERGING TRENDS IN THE SOCIAL AND BEHAVIORAL SCIENCES

Relatedly, we would like to conclude with a more general appeal for
more transdiagnostic (i.e., across different disorders) studies of dissociative phenomena. Meta-cognitive beliefs associated with the central
symptomatology are seen in many psychiatric conditions (e.g., the
meta-belief that one is going crazy when their mind starts racing during
panic), including for compartmentalization in DID. Moreover, experiences
of temporary or persistent detachment are evident in the context of other
conditions. A review indicated that symptoms of depersonalization and
derealization have been described in many clinical conditions including
agoraphobia, panic disorder, obsessive-compulsive disorder, eating disorders, depression, psychosis, and personality disorders (Hunter, Sierra,
& David, 2004). Transdiagnostic studies assessing the subjective nature of
amnesia, along with the prevalence of detachment, it is (differing) content in
separate disorders, it is association with trauma, and it is role in information
processing are thus needed to emphasize that dissociative disorders are not
a category of mysterious disorders that need to be understood outside of
well-known cognitive operations.
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Schacter, D. L., Kihlstrom, J. F., Kihlstrom, L. C., & Berren, M. B. (1989). Autobiographical memory in a case of multiple personality disorder. Journal of Abnormal
Psychology, 98, 508–514.
Spiegel, D., Loewenstein, R. J., Lewis-Fernández, R., Sar, V., Simeon, D., Vermetten,
E., … Dell, P. F. (2011). Dissociative disorders in DSM-5. Depression and Anxiety,
28, 824–852.
Sündermann, O., Hauschildt, M., & Ehlers, A. (2013). Perceptual processing during
trauma, priming and the development of intrusive memories. Journal of Behavior
Therapy and Experimental Psychiatry, 44, 213–220.
Zoellner, L. A., Sacks, M. B., & Foa, E. B. (2007). Dissociation and serenity induction.
Journal of Behavior Therapy and Experimental Psychiatry, 38, 252–262.

Dissociation and Dissociative Identity Disorder (DID)

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FURTHER READING
Dorahy, M. J., Brand, B. L., Şar, V., Krüger, C., Stavropoulos, P., Martínez-Taboas, A.,
… Middleton, W. (2014). Dissociative identity disorder: An Empirical overview.
Australian & New Zealand Journal of Psychiatry, 48, 402–417.
Dorahy, M. J., & Huntjens, R. J. C. (2007). Memory and attentional processes in dissociative identity disorder: A review of the empirical literature. In E. Vermetten, M.
Dorahy & D. Spiegel (Eds.), Traumatic dissociation: Neurobiology and treatment (pp.
55–75). Arlington, VA: American Psychiatric Publishing, Inc.
Dalenberg, C. J., Brand, B. L., Gleaves, D. H., Dorahy, M. J., Loewenstein, R. J.,
Cardeña, E., … Spiegel, D. (2012). Evaluation of the evidence for the trauma and
fantasy models of dissociation. Psychological Bulletin, 138, 550–588.
Giesbrecht, T., Lynn, S. J., Lilienfeld, S. O., & Merckelbach, H. (2008). Cognitive processes in dissociation: An analysis of core theoretical assumptions. Psychological
Bulletin, 134, 617–647. doi:10.1037/0033-2909.134.5.617
Huntjens, R. J. C., Dorahy, M. J., & Van Wees-Cieraad, R. (2013). Dissociation and
memory fragmentation. In F. Kennedy, H. Kennerley & D. Pearson (Eds.), Dissociation and cognitive therapy (pp. 92–103). London, England: Routledge.

RAFAËLE J. C. HUNTJENS SHORT BIOGRAPHY
Rafaële J. C. Huntjens is Assistant Professor in the Department of
Clinical Psychology, University of Groningen, the Netherlands. She has
published on memory processes in trauma-related disorders. More information and a list of publications can be found on her university webpage
http://www.rug.nl/staff/r.j.c.huntjens/.
MARTIN J. DORAHY SHORT BIOGRAPHY
Martin J. Dorahy is Associate Professor in the Department of Psychology,
University of Canterbury, Christchurch, New Zealand. He also maintains a
private practice focused primarily on complex trauma disorders. More information and a list of publications can be found on his university webpage
http://www.psyc.canterbury.ac.nz/people/dorahy.shtml.
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