Hypnotizability as a Potential Risk Factor for Posttraumatic Stress: A Review of Quantitative Studies

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Hypnotizability as a Potential Risk Factor for Posttraumatic Stress: A Review of Quantitative Studies Samantha S. Yard a; Katherine N. DuHamel b; Igor I. Galynker a a Beth Israel Medical Center, New York, New York, USA b Memorial Sloan-Kettering Cancer Center, New York, New York, USA Online Publication Date: 01 July 2008 To cite this Article: Yard, Samantha S., DuHamel, Katherine N. and Galynker, Igor I. (2008) 'Hypnotizability as a Potential Risk Factor for Posttraumatic Stress: A Review of Quantitative Studies', International Journal of Clinical and Experimental Hypnosis, 56:3, 334 — 356 To link to this article: DOI: 10.1080/00207140802042007 URL: http://dx.doi.org/10.1080/00207140802042007

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Intl. Journal of Clinical and Experimental Hypnosis, 56(3): 334–356, 2008 Copyright © International Journal of Clinical and Experimental Hypnosis ISSN: 0020-7144 print / 1744-5183 online DOI: 10.1080/00207140802042007

HYPNOTIZABILITY AS A POTENTIAL RISK FACTOR FOR POSTTRAUMATIC STRESS: A Review of Quantitative Studies 1744-5183 0020-7144 NHYP Intl. Journal of Clinical and Experimental Hypnosis Hypnosis, Vol. 56, No. 3, March 2008: pp. 1–41

Hypnotizability SAMANTHA S. and YARD posttraumatic ET AL. stress

SAMANTHA S. YARD1,2,3 Beth Israel Medical Center, New York, New York, USA

KATHERINE N. DUHAMEL Memorial Sloan-Kettering Cancer Center, New York, New York, USA

IGOR I. GALYNKER Beth Israel Medical Center, New York, New York, USA

Abstract: The authors review the literature relating hypnotizability and posttraumatic stress. Sixty-seven abstracts containing the key terms ASD, acute stress, trauma, traumatic, or PTSD in combination with either hypnotic susceptibility or hypnotizability were reviewed. Six articles were found containing data on hypnotizability and posttraumatic stress symptoms. Each of the studies showed some relation between hypnotizability and posttraumatic stress, but, in all of them, hypnotizability was measured after the potentially traumatizing event. High hypnotizability might be a risk factor for both acute and chronic posttraumatic symptoms. However, this cannot be determined until prospective studies measure hypnotizability in individuals before and after a potentially traumatizing event, perhaps by targeting populations that are at risk for experiencing trauma.

In an era of natural disasters, terrorism, and violence, posttraumatic psychopathology is an urgent issue for research. In recent years, much research has explored factors that contribute to the development of acute and chronic posttraumatic stress symptoms. One of the factors studied most, across a wide variety of trauma survivors, is peritraumatic Manuscript submitted October 4, 2006; final revision accepted August 9, 2007. 1 The authors acknowledge Antoine McNamara and Lisa Cohen, Ph.D., as well as the research staff and volunteers in the Department of Psychiatry at Beth Israel Medical Center for their contributions to the preparation of this manuscript. Some of the content of this manuscript was presented at the 56th Annual Meeting of the Society for Clinical and Experimental Hypnosis on October 29, 2005. 2 Ms. Yard is now at the University of Washington, Seattle, Wash. 3 Address correspondence to Samantha S. Yard, Department of Psychology, Box 351525, University of Washington, Seattle, WA 98105, USA. E-mail: [email protected] 334

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dissociation, the experience of dissociation at the time of the traumatic event (e.g., Birmes et al., 2003; Briere, Scott, & Weathers, 2005; Classen, Koopman, Hales, & Spiegel, 1998; Engelhard, Van den Hout, Kindt, Arntz, & Schouten, 2003; Koopman, Classen, & Spiegel, 1994; McFarlane, 1986). The majority of studies find a positive relationship (Candel & Merckelbach, 2004). In fact, one empirical study and one meta-analysis found that peritraumatic dissociation was the strongest predictor of future chronic mental illness (Marmar et al., 1999; Ozer, Best, Lipsey, & Weiss, 2003). Much less attention has been paid to the possible role of survivors’ hypnotizability, which might be a serious omission, given the likely relation between hypnotizability and trauma-related symptoms (Carlson & Putnam, 1989; D. Spiegel, 1993). In this paper, we review studies that have measured and evaluated a relation between hypnotizability and posttraumatic stress symptoms. Hypnotizability is an individual’s capacity to respond to suggestion during hypnosis. Hilgard (1991) emphasized that the term hypnotizability denotes the degree of responsitivity to suggestions and must be distinguished from hypnotic depth, which can differ in the same individual at any given time. A full understanding of hypnotic capacity depends upon a clear definition of hypnosis itself, which is continually evolving and heavily debated among experts in the field (Green, Barabasz, Barrett, & Montgomery, 2005). The most recent American Psychological Association Division 30 definition describes hypnosis as when “one person (the subject) is guided by another (the hypnotist) to respond to suggestions for changes in subjective experience, alterations in perception, sensation, emotion, thought, or behavior” and that these experiences are believed by many theorists to indicate that the subject is in a “hypnotic state” (Green et al.). H. Spiegel and Spiegel (1978) theorize that the hypnotic state consists of three intertwining components: absorption, dissociation, and suggestibility (see also D. Spiegel, 1990, 1994). They assert that as hypnosis heightens the intensity of an individual’s focus on one experience (e.g., the sound of the hypnotist’s voice), other perceptions, memories, and cognitions are dissociated from conscious awareness, resulting in a separation of processes that would otherwise be integrated; at the same time, they add, this level of absorption suspends ordinary thought processes like reflection, critical thinking, and doubt, leading the individual to follow instructions automatically—to be more suggestible. Of particular relevance for this review, D. Spiegel (1993) also draws analogies between the above three components of hypnosis and major symptoms of posttraumatic stress disorder. He conceptualizes the experience of stimulus sensitivity (or avoidance) as similar to suggestibility; intrusive reexperiencing as reminiscent of absorption; and emotional numbing (or loss of pleasure) as consistent with dissociative experiences in hypnosis. For more detailed descriptions of these and other theories of

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hypnosis see H. Spiegel and Spiegel, Brown and Fromm (1986), and A. Barabasz and Watkins (2005). The definition of dissociation is also frequently debated in the literature. Some researchers consider any type of disconnection with ordinary awareness, including feelings of numbness and detachment, as a kind of dissociation. Counts (1990), for example, sees dissociation as an underlying mechanism in a large array of mental processes, including psychodynamic defense mechanisms, that range from temporary to more permanent, from generalized to confined, and from little to vital significance for the individual. Other theorists prefer a stricter definition. Van der Hart, Nijenhuis, Steele, and Brown (2004) warn of both over- and underinclusiveness and highlight the importance of distinguishing between changes in an individual’s overall degree of conscious awareness or field of awareness and the structural dissociation (i.e., breakdown of fundamental systems that comprise an individual’s identity, ego, and personality) that Janet described in his seminal research on the subject (Janet, 1907). To avoid confusion, this review will use Van der Hart and colleagues’ terms structural dissociation, for the breakdown of the psychobiological systems of personality, and alterations in consciousness, for experiences like daydreaming, absorption, and time distortion that have to do with changes in the level/degree or field of consciousness. Inspired by the extensive literature linking peritraumatic dissociation and posttraumatic stress, this review examines the evidence for considering hypnotizability as a risk factor for posttraumatic stress.

METHOD To investigate the relation between hypnotizability and posttraumatic stress, we conducted a literature search on PsycINFO and MEDLINE of articles published between January 1985 and May 2006, using the terms ASD, acute stress, trauma, traumatic, and PTSD in combination with either hypnotic susceptibility or hypnotiz(s)ability (using both spellings). We reviewed 67 abstracts and only found six articles that provided quantitative data on the relationship between hypnotizability and posttraumatic symptoms (either acute or chronic). Articles were included if they measured both hypnotizability and posttraumatic stress symptoms in a sample greater than 10.

HYPNOTIZABILITY MEASURES Hypnosis practitioners and researchers alike use both informal tests and standardized scales to assess hypnotizability (A. Barabasz & Watkins, 2005). The six studies that we review in this paper used the following hypnotizability scales: the Stanford Hypnotic Susceptibility Scale: Form C (SHSS:C; Weitzenhoffer & Hilgard, 1962), the Stanford Hypnotic

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Clinical Scale (SHCS; Morgan & Hilgard, 1978–1979), the Hypnotic Induction Profile (HIP; H. Spiegel & Spiegel, 1978), and the Creative Imagination Scale (CIS; Wilson & Barber, 1978). Although the Dissociative Experiences Scale (DES) is widely used as a measure of dissociative experiences and relates strongly to various dissociative disorders, the scale has not correlated highly with hypnotizability scales in metaanalysis (Van Ijzendoorn & Schuengel, 1996). This might be because the scale measures the retrospective self-report of the intensity of everyday spontaneous dissociative experiences rather than clinician-rated in vivo response to suggestion in a clinical-hypnosis context (Carlson & Putnam, 1989). Since this review focuses on the relation of posttraumatic pathology to the latter, we did not include studies that used the DES. The SHSS:C is a 12-item measure of hypnotizability based on a series of increasingly difficult exercises administered by an experienced hypnotist after a hypnotic induction. The administration of the scale takes about 1 hour, while the hypnotist scores each item as passed or failed, and individuals are defined by standard ranges for low, medium, and high hypnotizability. The SHSS:C is generally regarded as the gold standard of hypnotizability measures (A. Barabasz & Barabasz, 1992; Register & Kihlstrom, 1986). The SHCS was originally intended to be used with hospital patients who might be experiencing pain (Hilgard & Hilgard, 1975). The scale involves a hypnotic induction followed by five suggestions taken from the SHSS (i.e., hand lowering, age regression, dream, posthypnotic suggestion, and posthypnotic amnesia) and requires about 20 to 25 minutes to administer. The HIP is an eight-item ordinal scale derived from a behavioral measure of hypnotizability that consists of scores from 0 to 16 and takes 5 to 10 minutes to administer. The scale’s three major components include an eye up-gaze and roll to demonstrate biological trance capacity, an idiomotor arm-levitation suggestion, and an item of subjective control differential between arms. The HIP is the only hypnotizability scale that was standardized and validated on a clinical population and formulated for the purpose of deciding whether to use clinical hypnosis in treatment (H. Spiegel & Spiegel, 1978). The CIS is a 10-item measure of hypnotizability based on a subject’s response to hypothetical scenarios involving the ability to imagine senses of weight, feeling, thirst, taste, smell, sound, heat, time, memory, and relaxation. Administering the scale takes about 25 minutes and does not involve a hypnotic induction (Wilson & Barber, 1978).

STUDIES WITH ACUTELY TRAUMATIZED SUBJECTS Three controlled studies have measured subjects’ hypnotizability and their posttraumatic stress symptoms in the month-long acute phase following a life-threatening event. In each of these studies, a

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significant positive correlation was found between high hypnotizability and the development of posttraumatic stress symptoms. These studies were conducted with victims of severe burns, nonsexual assaults, and motor vehicle accidents; hypnotizability was assessed using the SHCS in two studies and the HIP in the other; all studies used the Impact of Event Scale (IES; Horowitz, Wilner, & Alvarez, 1979) and additional scales to assess posttraumatic stress symptoms. DuHamel, Difede, Foley, and Greenleaf (2002) investigated the experience of 43 hospitalized burn patients within the first 2 weeks of hospitalization. Subjects were divided into three hypnotizability groups (7 participants were indicated as low, 23 as midrange, and 13 as high) using previously validated categorical scoring procedures for the HIP (H. Spiegel & Spiegel, 1978). Univariate analyses (ANOVA) found that the high hypnotizability group had significantly higher frequencies— compared with both other groups—of intrusive, F(2, 40)=4.15, p=.023, and avoidance symptoms, F(2, 40) = 6.49, p = .004, on the IES, and arousal symptoms, F(2, 40) = 3.38, p = .04, on the Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders-III-R, Posttraumatic Stress Disorder module (SCID-PTSD). Multivariate analysis (with degree of hypnotizability as the independent variable and multiple posttraumatic stress symptoms as the dependent variables) also indicated a relation, F = 2.80, p < .01, between hypnotizability category and the following five trauma variables: IES avoidance and intrusive symptoms and SCID-PTSD Clusters B, C, and D symptoms. Since acute stress disorder (ASD) was not a recognized diagnosis at the time, the study did not include direct assessment of ASD. The authors did find that younger age was associated with arousal symptoms on the SCID-PTSD, r = −.344, n = 41, p < .05, and that low income was associated with both arousal symptoms, t = 2.297, p < .05, and total SCID-PTSD symptoms, t = 2.257, p < .05. Indeed, when covarying for age and income in regression analyses, previously significant differences in SCID-PTSD arousal between the high hypnotizability group and the other two groups lost significance, suggesting the importance of sociodemographic factors and potentially confounded results and/or insufficient power due to small sample size. Using the IES, the Acute Stress Disorder Interview (ASDI), and the SHCS, Bryant, Guthrie, and Moulds (2001) rated posttraumatic stress symptoms and hypnotizability of 61 hospital patients who had been exposed to an automobile accident or nonsexual assault and then divided them into three groups: those with ASD (n = 23), those with subclinical ASD—who met all criteria for ASD except dissociative symptoms—(n = 18), and those with no ASD (n = 20). Hypnotizability was measured separately from the other scales 1 to 3 days after the first assessment. One-way analysis of variance found that the ASD group had significantly higher SHCS scores than either of the other two groups. However, when scores on the dissociative cluster of the ASDI

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were controlled for, these findings were no longer significant. There were no group differences in age or length of time between trauma and assessment, though the latter may have been due to limited range—all subjects were assessed within 1 month of a potentially traumatizing event. Pearson product-moment correlations indicated that scores on the SHCS were significantly correlated with the dissociative and reexperiencing clusters of the ASDI (r = .37, p < .01; and r = .26, p < .05, respectively). The authors also conducted paired chi-square comparisons on the proportion of subjects in each of the three groups that responded to each item on the SHCS. These comparisons showed that subjects with ASD were significantly more likely to: respond to the dream item than subjects with no ASD (χ2 = 6.69, N = 43, p < .01, with Yates correction); respond to the posthypnotic amnesia item than either the subclinical ASD group (χ2 = 3.86, N = 41, p < .05, with Yates correction) or the no ASD group (χ2 = 6.80, N = 43, p < .01, with Yates correction), and display reversible posthypnotic amnesia than either the subclinical ASD group (χ2 = 4.32, N = 41, p < .05, with Yates correction) or the no ASD group (χ2 = 4.72, N = 43, p < .05, with Yates correction). In 2003, the above authors were joined by Nixon and Felmingham and assessed hypnotizability in the context of a study to see whether administering six sessions of a CBT intervention to ASD patients would have an effect on future PTSD. They administered the SHCS—preintervention—to 45 victims of either nonsexual assault or automobile accident (within 1 month of the event), and then again 6 months after the intervention, at which point they also assessed the presence of PTSD. They found general stability of SHCS scores across assessments (r = .47, p < .001), though the majority of participants (65%) had different scores—38% decreased and 27% increased. The authors acknowledge that SHCS scores might have been affected by circumstances at each assessment (e.g., raters were blind at baseline but not at follow-up, and SHCS scores were measured on a different day than psychopathology scores at baseline but were measured at the same sitting at follow-up). Although hypnotizability did not correlate with posttraumatic stress symptoms at either time point or with a presence of PTSD at follow-up, the authors did find that an increase in avoidance symptoms, as measured by the IES, was correlated with an increase in SHCS scores (r = −.41, p < .01). In addition to the different circumstances at each assessment, hypnotizability scores could have been influenced by the therapeutic intervention, which for some subjects involved a hypnotic induction. This potential confound was not explored.

STUDIES OF CHRONIC POSTTRAUMATIC STRESS Three empirical studies examined hypnotizability in subjects diagnosed with PTSD (more than a month after a traumatic event). Two of the studies were conducted with war veterans and the other with

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college students. Each study showed that individuals with PTSD had significantly higher scores on measures of hypnotizability than the general population. The first study to look at hypnotizability and PTSD was Stutman and Bliss’ (1985) investigation of 26 Vietnam veterans in rural Utah. All but 1 of the participants had engaged in combat during the war, and very few had ever received treatment. The 14 participants who scored above 7 on a 15-item self-report measure of PTSD—based on DSM-III criteria—were considered to have PTSD (M = 11.8, SE = 0.64), while the 12 who scored between 0 and 2 were not (M = 0.67, SE = 0.19). In addition to the PTSD self-report measure, subjects were administered Sheehan’s Vividness of Imagery Scale, a 313-item general psychopathology selfreport scale, and the SHSS:C. The mean SHSS:C score for the PTSD group was found to be significantly higher than the non-PTSD group, t = 6.6, p < .001. Based on a stepwise multiple regression analysis, the authors concluded that there was a strong relation between high hypnotizability and PTSD (b = 1.94; β = .78), which explained 62% of the variance from the mean PTSD score. However, stepwise multiple regression analysis is traditionally only used with a sample size that is 40 times the number of independent variables and the authors do not provide a rationale for this deviation. Furthermore, a PTSD diagnosis is ideally determined by structured interview rather than self-report (Olde, Van der Hart, Kleber, & Van Son, 2006; Shalev, Freedman, Peri, Brandes, & Sahar, 1997). D. Spiegel, Hunt, and Dondershine (1988) compared the hypnotizability scores of 65 war veterans suffering from PTSD to those of 108 psychiatric patients (inpatient and outpatient) and 83 normal volunteer controls. The psychiatric patients were further divided according to their diagnoses: 23 subjects had schizophrenia, 18 had generalized anxiety disorder, 56 had some form of depression (bipolar, major depression, or dysthymia), and 18 had miscellaneous disorders. The authors conducted an analysis of covariance with age as the covariate and found that the PTSD group’s mean induction score on the HIP was significantly higher than that of both the normal control group, t = 2.48, p < .01, and each of the psychiatric groups (schizophrenia: t = 2.48, p < .01; generalized anxiety disorder: t = 2.48, p < .01; affective disorders: t = 2.48, p < .01; miscellaneous: t = 2.48, p < .01). While there was a significant main effect for age (F = 7.17, p < .008), this did not explain the hypnotizability differences between groups. Unfortunately, little information is provided about the context of hypnotizability ratings, except that subjects with PTSD were rated on admission to the hospital. This could be a serious omission considering the acknowledged impact of context on hypnotizability (Brown & Fromm, 1986, p. 27). Another potential confound is the sampling of PTSD subjects who have sought treatment rather than those from a community sample.

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Indeed, these subjects may have been more motivated and open to treatment; both factors that could influence hypnotizability (Barber & Calverley, 1963). Furthermore, by sampling PTSD subjects already in treatment, the authors also run the risk of excluding individuals who are in what Brown and Fromm termed the “denial” phase of PTSD, which manifests in restricted cognition and emotional numbing, symptoms that can be mistaken for depression (p. 263). Given the clinical sample, these results may not generalize to nonclinical, perhaps higher avoidant samples of PTSD. Sapp, Ioannidis, and Farrell (1995) examined the relation between PTSD and hypnotizability within a group of college students at a midwestern university. The study was conducted in two parts. In the first part, the authors used self-report measures with 194 college students to assess PTSD, imaginative involvement, anxiety, and depression for the purpose of determining reliability of the scales and which variables might significantly predict PTSD in the second part of the study. In part two, the investigators collected hypnotizability data for a new sample of 50 college students using the CIS, which was administered both by the subject and again by an experimenter. Approximately 30% of subjects (in both parts) met DSM-III-R criteria for PTSD using a cutoff of 65 on the Posttraumatic Stress Disorder/Keane Scale of the Minnesota Multiphasic Personality Inventory–II (PK; a 46-item self-report scale designed to measure PTSD) and confirmatory interview by a graduate assistant. Correlations at p < .05 were found for all variables, including both subject and experimenter-rated hypnotizability with scores on the Modified Posttraumatic Stress Disorder Scale (.61 and .57, respectively) and the PK (.59 for both subject and experimenter ratings), test anxiety (.61 and .59), depression (.73 and .71), and imaginative involvement (.57 and .55). Results are likely not representative of symptom severity for PTSD patients in general due to the homogeneity of the student sample and the relatively low incidence of PTSD in this sample. Also, the CIS, while validated as a measure of hypnotizability, does not include a trance induction.

DISCUSSION While there is some indication in the literature that a relation between hypnotizability and posttraumatic stress symptoms exists, there is still little empirical data to support it. That being said, of the six studies that have measured the hypnotizability of individuals with posttraumatic stress symptoms, each one of them indicated some relation between the two variables. With regard to determination of hypnotizability as a potential risk factor for posttraumatic stress, we are far from being able to draw any conclusions, primarily because no study has measured hypnotizability in individuals before a traumatic event.

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Without prospective data we can only speculate possible meanings behind statistical relationships. In addition, a number of other methodological and theoretical problems impact the findings in these studies. Sample Characteristics The studies sampled a wide variety of populations: male Vietnam veterans both from the community and from inpatient psychiatric programs; college students with low severity posttraumatic stress symptoms; hospital burn patients (a majority of whom were low-income male African Americans); and assault or automobile accident survivors admitted to hospital trauma centers. With this variety of populations, we can see that there is some consistency of findings across severity of symptoms, time since traumatic event, nature of trauma, and level of treatment-seeking. Little was reported about recruitment or drop-out rates (three studies conducted multiple assessments), which could have had an impact on findings if rates were affected by severity of symptoms or initial psychological distress (Engelhard et al., 2003; Shalev et al., 1997). Most of the sample sizes hovered around 55 (ranging from 43 to 65), with one exception being the Stutman and Bliss study, which only had 26 subjects. Future studies with larger prospective cohorts are needed to provide confirmation of a relation between hypnotizability and posttraumatic stress. In addition, likely due to the emphasis on physical and war traumas, there was an oversampling of male trauma survivors and a paucity of information about women’s hypnotizability as it relates to sexual traumas or traumatic labor. This is particularly problematic considering that PTSD is more prevalent in women (Resnick, Kilpatrick, Dansky, Saunders, & Best, 1993). For a review of research on posttraumatic stress and childbirth, see Olde and colleagues (2006). Also, DuHamel and colleagues (2002) found that differences in arousal between low and high hypnotizables were no longer significant after covarying for age and income, which suggests that these factors (and perhaps other sociodemographics) might influence a relation between hypnotizability and posttraumatic stress. Context Many different contextual factors have been shown to affect hypnotizability, including hypnotic response expectancy (Braffman & Kirsch, 1999; Council, Kirsch, & Hafner, 1986; Kirsch, 1985, 1991; Kirsch, Silva, Comey, & Reed, 1995), order of scale administration (P. Butler & Bryant, 1997; Oakman, Woody, & Bowers, 1996), relaxation (Kaplan & Barabasz, 1988), motivation (Barber, 1969; Barber & Calverley, 1963), attitude toward hypnosis (Spanos, 1991), and rapport with hypnotist (Flynn, DuBreuil, Gabora, & Jones, 1990). However, rarely were these factors taken into consideration in the studies of hypnotizability and posttraumatic stress. This is problematic considering that traumatized

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individuals are likely to be in a particularly delicate state, especially in the first few days and weeks following the traumatic event, and may be more influenced than others by the context of scale administration. Describing the context of hypnotizability ratings and covarying for these factors in analysis when appropriate would strengthen findings. With regard to using hypnotizability scores from within the context of a treatment comparison, researchers must investigate the potential confounds that could result from such a design because of the likely impact of hypnosis treatment and the motivations of both the patient and the treatment provider on hypnotizability ratings. In addition, discussion of the potential influence of a study’s assessment contexts would help future researchers to account for these variables in study design. Hypnotizability Scales In any review of hypnotizability, close attention must be paid to its assessment, because a division between state and nonstate conceptualizations of hypnosis is reflected in the use of hypnotizability scales that test different constructs (Hutchinson-Phillips, Gow, & Jamieson, 2007). For a discussion of the division between state and nonstate theories, see Kirsch and Lynn (1995). The state conceptualized scales (i.e., scales that seek to assess hypnotic ability from within a trance hypnotic state) all correlate strongly with one another. Specifically, both the SHCS and the HIP, despite having been designed for a clinical population with vastly shorter administration times, correlate strongly (r=.72; r=.63) with the SHSS:C (Frischholz, 1980; Weitzenhoffer & Hilgard, 1962). Nonstate theorists (i.e., sociocognitivists) have developed and used a number of different scales (e.g., the Barber Suggestibility Scale and the Carleton University Responsiveness to Suggestion Scale); however, only one nonstate hypnotizability scale has been administered with a scale of posttraumatic stress: the CIS. This scale only correlates moderately with the Harvard Group Scale of Hypnotic Susceptibility (r=.28, .55, .57), another state-conceptualized scale administered in a similar format as the CIS. Indeed, Laidlaw and Large (1997) found that, in factor analysis with items from the Harvard scale, the two scales loaded on completely separate factors. In general, the CIS has been seen as a weak predictor of state- conceptualized hypnotizability (Kurtz & Strube, 1996). In addition, performance on it has been shown to increase substantially when it is defined as a scale of imagination rather than hypnotic ability (Spanos, Gabora, Jarrett, & Gwynn, 1989), and the scale has been criticized for primarily testing visualization and omitting other important sensory components of hypnosis like somatesthesia (Sacerdote, 1982). Many theorists argue that hypnotizability is made up of multiple constructs, some (and perhaps not all) of which are related to various other experiences (Frankel, 1990; Nash, 2006;

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Woody, Barnier, & McConkey, 2005). It is not clear in the reviewed studies which aspects (if not all) of hypnotizability are actually correlated with posttraumatic stress symptoms, so we must be careful not to assume that the entire entity is related and not just some aspect (e.g., dissociation, absorption, or suggestibility). There is some evidence to show, in fact, that absorption, as rated by the Tellegen Absorption Scale, is correlated with traumatic experiences (Scroppo, Drob, Weinberger, & Eagle, 1998). The Tellegen Absorption Scale also correlates (.56) with hypnotizability as measured by the SHSS:C (Smyser & Baron, 1993). Study Design One might also consider Woody’s (1997) argument that typical hypnotizability research uses quasi-experimental designs (dividing individuals into high and low scorers and then investigating group differences), which are inherently weaker than true experiments. Woody suggests that theorists (typically nonstate) who point to context effects as the primary variable affecting hypnotizability directly manipulate the variables that they believe underlie differences in hypnotizability. He asserts that neo-dissociative (state) theorists should reconsider their reliance on hypnotizability scales as definitive measurements of hypnotic response and look more closely at the underlying constructs being assessed and the original statistical strategies used to establish their scales in the first place. Woody mentions, for example, that the Stanford scales were designed to show a normal distribution of scores in the population by adding easier items, which even Hilgard himself considered perhaps unwise in retrospect (Hilgard, 1965, p. 227). Indeed, Oakman and Woody’s (1996) analysis of hypnotizability data from thousands of subjects led them to propose that hypnotizability may be more of a typological construct than a dimensional one, meaning that individuals are either hypnotizable or not, without so many people falling in between. A debate about the nature of the hypnotizability construct and its measurement is quite beyond the scope of this paper; however, both sides of the debate must be considered when evaluating research that attempts to represent the construct using scores from a hypnotizability scale. Explanations Since we were only able to find six studies, and several of them have small samples, even the finding of a noncausal relation must be bolstered by further investigations with larger samples. Furthermore, we cannot decidedly favor one explanation for this tentative finding, due to the lack of prospective data on hypnotizability (that which is gathered both before and after experiencing a potentially traumatizing event).

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Nonetheless, we will discuss some potential explanations for a relation between hypnotizability and posttraumatic stress symptoms. One possibility is that the experience of helplessness, horror, and overwhelming fear that accompanies a potentially traumatizing event heightens an individual’s hypnotizability, perhaps through the experience of structural dissociation that can occur both peritraumatically or posttraumatically (i.e., during or following the event). While research has shown hypnotizability to be a stable and normally distributed trait (Piccione, Hilgard, & Zimbardo, 1989), there is some evidence that experiences can enhance it. For instance, both restricted environmental stimulation and brief isolation in the Antarctic have been shown to increase hypnotizability (A. Barabasz, 1982; A. Barabasz & Barabasz, 1989; M. Barabasz, Barabasz, & Mullin, 1983). Brown and Fromm (1986) theorized about the modification of hypnotic susceptibility through the intense experience of a state that they describe as “drastically discontinuous with the structure and experience of normal, waking consciousness” (p. 39). Perhaps hypnotizability is only stable in populations unexposed to such experiences. No findings have ruled out the possibility that after experiencing a trauma-related dissociative state, an individual is more likely to reenter the state within the safer, structured context of hypnosis. In fact, this explanation is compatible with J. R. Hilgard’s theory of two developmental pathways to hypnotizability, one being through traumatic experience in childhood (Carlson & Putnam, 1989). Based on this theory, we might also consider that perhaps children who experience trauma develop high hypnotizability and then are simply more likely to encounter other traumas, since research has shown that a past history of childhood abuse increases the risk of future traumas (Van der Kolk, 2003). This could mean that posttraumatic stress is related to a history of childhood trauma rather than to hypnotizability directly. Another possibility is that high hypnotizables are at risk for experiencing posttraumatic stress. This could be because they have a Dionysian personality style characterized by hypersensitivity to the external world and their own self-injury (H. Spiegel & Greenleaf, 1992). And perhaps this sensitivity manifests as exaggerated perception of threat, an aspect of traumatic experience that is particularly high in hypnotizable individuals, according to Wickramaskera’s High Risk Model of Threat Perception (Wickramasekera, 1995). Within this multidimensional model, high hypnotizability, negative affect, and catastrophizing are seen as predisposing factors that increase the likelihood of psychological or somatic symptoms resulting from trauma or stress. The model also proposes that high hypnotizables have “surplus empathy” and are, thus, hypersensitive to the perception of threat in others (Wickramasekera, Pope, & Kolm, 1996). Finally, low hypnotizables might be just as affected by traumatic experience but might simply manifest it in nondissociative

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defense mechanisms, like denial and repression, that have their own pathological consequences (D. Spiegel, 1986). According to the Fix-Flex Continuum, pathologies associated with low hypnotizability (and the Apollonian personality) include cognitive impairments, avoidant interpersonal styles, and proneness to despair and are affiliated with Axis I disorders such as obsessive compulsive disorder, anorexia, generalized anxiety, and schizophrenia, in addition to schizoid, paranoid, and avoidant personality disorders (H. Spiegel & Greenleaf, 1992). Further Theory Some theorists advocate a diathesis-stress hypothesis to explain a relation between hypnotizability and pathological reactions to trauma (L. Butler, Duran, Jasiukaitis, Koopman, & Spiegel, 1996). This model suggests that the interaction between an individual’s predisposition to enter hypnotic states and one’s exposure to a traumatic event is “a necessary and sometimes sufficient condition” for the development of dissociative pathologies (p. 60). The individual’s innate tendency to enter a hypnotic or dissociative state reacts with the traumatic event to create a particular psychological reaction—the greater the tendency to dissociate and the more intense the traumatic event, the more pathological the reaction. Popular, diathesis-stress theories still have potential conflicts to resolve. Kihlstrom, Glisky, and Anguilo (1994), for example, argue that hypnotizability, absorption, and fantasy proneness, all considered as possible diatheses for dissociative disorders, are not inherently pathological— and suggest that perhaps they only play a role in shaping the nature of pathology if it occurs. In addition, Monroe and Simons (1991), in an extensive review on diathesis-stress theories, raise important questions about how the diathesis may be impacting the stress, suggesting that perhaps a cognitive or social vulnerability may influence the reporting and generation of life stress in addition to putting an individual at risk for psychological reasons. An important assumption of the diathesis-stress theory of hypnotizability and posttraumatic stress, which is not shared by all researchers, is that the hypnotic state and the trauma-related dissociative state share the same underlying mechanism. A resolution to this question will not be attempted here; however, a brief discussion of the major issues is essential to an understanding of the studies we review. The parallel between hypnosis and spontaneous dissociation was originally drawn by Pierre Janet in 1907: In a word, it seems there is no reason for making a special place for the hypnotic state; it is a somnambulism analogous to [hysterical somnambulism], and differs from it only in that it is obtained artificially instead of developing spontaneously. (pp. 115–116)

It is important to note that Janet describes “hysterical somnambulism” as a structural dissociation such that there is a “system of ideas and

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functions” that is dissociated from the remainder of the personality; he did not see lighter forms of hypnosis as dissociative (Van der Hart & Friedman, 1989). Janet provided five “principal reasons” for equating dissociative states experienced in hypnosis and spontaneously occurring structural dissociation: (a) all manifestations of the hypnotic state can be found in “natural hysteric somnambulisms”; (b) subjects who are capable of entering this highly hypnotized state (those who can demonstrate posthypnotic amnesia) also have various forms of hysteria; (c) nonhysterical patients (e.g., epileptics) cannot be hypnotized; (d) the recovery (or exit) from both “artificial” and “natural” somnambulisms is the same; and (e) a clinician can move a patient from one state into the other through suggestion, an idea that follows from Janet’s observation that all hysterical patients are highly suggestible (pp. 114–115). Some of these rationales have been refuted in more recent research. We know, for instance, that many highly hypnotizable subjects are quite healthy (H. Spiegel & Spiegel, 1978; Greenleaf, 2006). A remaining question, however, one that is crucial to understanding a relation between hypnotizability and posttraumatic stress, is whether the structural dissociation that is more commonly present in individuals suffering from dissociative illnesses can be demonstrated by a healthy individual in a hypnotic context. Many present-day theorists have described the hypnotic state and the traumatically induced dissociative state as one and the same (L. Butler et al., 1996; Evans, 1991; D. Spiegel, 1986). Indeed, studies show that individuals who structurally dissociate are also highly hypnotizable, including bulimics (Covino, Jimerson, Wolfe, Franko, & Frankel, 1994), persons with dissociative identity disorder (Kluft, 1984), and panic patients experiencing depersonalization and derealization (Van Dyck & Spinhoven, 1997). Still, other researchers caution equating the two states (Carlson & Putnam 1989; Frankel, 1990). Frankel argued that neither the hypnotic nor the dissociative state had been defined well enough (with all of its components) to liken the two. Indeed, while some theorists are careful to differentiate between structural dissociation and alterations in consciousness, others do not adhere to the same definitions or labels, making it difficult to interpret findings. L. Butler and colleagues analyzed the major components of each state, highlighting the similarities and differences between hypnosis and a variety of dissociative phenomena broken down into specific experiences (e.g., diminished perceptual awareness, flashbacks, emotional numbing, trance, amnesia, fugue). Hopefully, future theorists will continue this practice of specification. Enacting dissociation in the face of trauma has also been discussed in the literature as a coping strategy, and several case studies have been described where individuals intentionally use dissociation (sometimes considered auto-hypnosis) as an escape from sexual abuse or other traumatizing events, and some subjects have even reported initiating

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new personalities to help them cope (D. Spiegel, 1986, 2003; Van der Kolk & Van der Hart, 1989). However, repeated use of this strategy also appears to be correlated with the development of serious pathology. Indeed, studies show that the experience of dissociation (whether considered either “automatic” or self-induced) at the time of a potentially traumatizing event puts an individual at higher risk for subsequent general distress, posttraumatic stress symptoms, and even borderline personality disorder and bulimia (Classen et al., 1998; Gershuny, Najavits, Wood, & Heppner, 2004; Koopman et al., 1994; McFarlane, 1986; Taal & Faber, 1997). For these reasons, one might recognize peritraumatic dissociation as the type of coping strategy—perhaps like drug or alcohol use—that serves a clear purpose in the short term (i.e., removing the individual psychologically from an intensely unpleasant situation that he or she cannot physically escape), but may also be maladaptive for the longer term. Indeed, dissociation serves a defensive role in posttraumatic stress disorders by keeping an apparently normal part of the personality dissociated from the unpleasant, emotional, and traumatized part (Van der Hart et al., 2004). However, many researchers theorize that an individual’s dissociative and/or avoidant coping style, which may be active both during and after a traumatizing event, obstructs adaptive cognitive, social, or grief processing, thereby preventing the individual from overcoming trauma (Foa & Hearst-Ikeda, 1996). Limitations The findings in this review have several limitations. As discussed, the small number of studies available and the relatively small samples make it difficult to trust findings definitively. A general lack of information about the context of scale administrations and limited discussions of possible context effects was pervasive. Also, more careful attention to sociodemographic variables is desirable, considering their potential role in a relation between hypnotizability and posttraumatic stress. In addition, current debates in the literature about the very nature of hypnotic susceptibility cast doubt on the precision of hypnotizability scales and raise questions about which aspects of hypnotizability are at play in correlations with posttraumatic stress. Finally, the age-old debate about an overlap between hypnotic and dissociative states is still muddy and more precise terminology about specific hypnotic and dissociative experiences (e.g., structural dissociation and alterations in consciousness) is needed to clean up the waters. Future Research Most urgently, to understand the relation between hypnotizability and posttraumatic stress symptoms, investigators must measure hypnotizability in at-risk individuals before and after potentially

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traumatizing experiences. Further research might also elucidate which aspects (beyond specific symptoms) of posttraumatic pathology are predicted by hypnotizability (e.g., severity, outcome, chronicity) to increase the understanding of implications from the risk. Clinical Implications If highly hypnotizable individuals are at increased risk for posttraumatic stress symptoms, this information could perhaps be used to help identify and prepare those individuals in society at greatest risk for experiencing trauma. Soldiers, rescue workers, police officers, and pregnant women could be measured for hypnotizability, and those who were found to be highly hypnotizable could be made aware of the risks and prepared for potential future traumatic events, which might help them to cope if one should occur. In the case of pregnant women, hypnotic relaxation practiced by a trained hypnotist during the birth has been shown to decrease the pain and traumatic experience of labor (A. Barabasz & Watkins, 2005). After such an event, these individuals should be encouraged to promptly seek appropriate treatment, if needed. Of course, the development of such interventions would need to be guided by clinical research. The most compelling clinical implication from this review is the likely benefit of hypnosis in the treatment of traumatized individuals. Although the activation of a dissociative state in therapy for dissociative pathology might appear counterintuitive, there is a great deal of evidence to support the use of hypnosis in this context (Brown & Fromm, 1986; Evans, 1991; Ffrench, 1995; Leung, 1994; D. Spiegel, 1988, 1993; D. Spiegel & Cardeña, 1990; Van der Hart, Brown, & Van der Kolk, 1989). Brom, Kleber, and Defares (1989) found that hypnotherapy decreased both intrusive and avoidance symptoms in individuals diagnosed with posttraumatic stress disorder. Some hypnotherapy researcher-practitioners suggest that activating patients’ uncontrolled thoughts and memories and then teaching them how to control these images (and restructure their related cognitions) can help patients overcome their victimization (Cardeña, 2000; Godoy & Araoz, 1999; D. Spiegel, 2003). Having sometimes immediate access to dissociated memories, feelings, and cognitions related to the traumatic event through hypnosis can speed up the recovery process and facilitate cognitive restructuring. It can be helpful to teach patients how to conduct self-hypnosis so that they are able to remedy panic or fear outside of the clinician’s office (D. Spiegel & Cardeña, 1990). Plus, the hypnotic context allows the patient to make decisions and to resolve feelings free from the constraints of normal consciousness (Ffrench, 1995). Lynn and Cardeña (2007) outline an evidence-based approach to supporting exposure and cognitive-behavioral therapy with hypnosis, which details procedures for each step of the treatment, beginning

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with assessment and affect management and ending with cognitive restructuring. Evans (1991) recommends treating patients with acute versus chronic posttraumatic symptoms according to the different stages of social and personal dysfunction they are experiencing. In the only study to date investigating the use of hypnotherapy for acute stress disorder, Bryant, Moulds, Guthrie, and Nixon (2005) compared three treatments for preventing posttraumatic stress disorder: cognitive-behavioral therapy (CBT), CBT+ hypnosis, and standard of care. The study found that individuals treated with CBT + hypnosis had fewer reexperiencing symptoms at posttreatment than those treated with standard CBT or with standard of care. Since hypnosis can be easily integrated into already popular and empirically supported treatments and has been shown to increase the efficacy of such treatments, many hypnosis researchers argue that it should be used more extensively. One barrier to widespread use of hypnosis in general is the lack of adequate training in many graduate clinical psychology and psychiatry residency programs (A. Barabasz & Watkins, 2005). Therefore, a first step in increasing the availability of hypnosis is to encourage schools to hire faculty who can teach it. Based on the likely relation between hypnotizability and posttraumatic stress and on extensive reviews of hypnosis for the treatment of posttraumatic stress (e.g., Cardeña, 2000), at the very least, clinicians who specialize in treating traumatized individuals would be well advised to seek out the necessary training in hypnotic techniques, so as to provide the best possible treatment for their clients. REFERENCES Barabasz, A. F. (1982). Restricted environmental stimulation and the enhancement of hypnotizability: Pain, EEG alpha, skin conductance and temperature processes. International Journal of Clinical and Experimental Hypnosis, 30, 147–166. Barabasz, A. F., & Barabasz, M. (1989). Effects of restricted environmental stimulation: Enhancement of hypnotizability for experimental and chronic pain control. International Journal of Clinical and Experimental Hypnosis, 37, 217–231. Barabasz, A. F., & Barabasz, M. (1992). Research designs and considerations. In E. Fromm & M. R. Nash (Eds.), Contemporary hypnosis research (pp. 173–200). New York: Guilford. Barabasz, A. F., & Watkins, J. G. (2005). Hypnotherapeutic techniques. New York: BrunnerRoutledge. Barabasz, M., Barabasz, A. F., & Mullin, C. S. (1983). Effects of brief Antarctic isolation on absorption and hypnotic susceptibility—Preliminary results and recommendations: A brief communication. International Journal of Clinical and Experimental Hypnosis, 31, 235–238. Barber, T. X. (1969). An empirically-based formulation of hypnotism. American Journal of Clinical Hypnosis, 12, 100–130. Barber, T. X., & Calverley, D. S. (1963). Toward a theory of hypnotic behavior: Effects on suggestibility of task motivating instructions and attitudes toward hypnosis. Journal of Abnormal and Social Psychology, 67, 557–565.

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Hypnotisierbarkeit as möglicher Risikofaktor für posttraumatische Belastungsstörung: Eine Literaturübersicht über quantitative Untersuchungen Samantha S. Yard, Katherine N. DuHamel und Igor I. Galynker Zusammenfassung: Die Autoren geben eine Übersicht über die Literatur zu Hypnotisierbarkeit und posttraumatischem Stress. 67 Zusammenfassungen, welche die Schlüsselbegriffe ASD, akuter Stress, traumatischer oder PTSD in Kombination mit entweder hypnotischer Susceptibilität oder Hypnotisierbarkeit wurden berücksichtigt. 6 Artikel enthielten Daten zu Hypnotisierbarkeit und Posttraumatischen Stressymptomen. Jede der Studien berichtete einen Zusammenhang zwischen Hypnotisierbarkeit und posttraumatischem Stress, allerdings wurde Hypnotisierbarkeit bei allen Untersuchungen erst nach dem traumatischen Ereignis erhoben. Gute Hypnotisierbarkeit könnte einen Risikofaktor für akute und chronische posttraumatische Symptomatik darstellen. Dies kann aber erst zweifelsfrei festgestellt werden, wenn prospektive Studien die Hypnotisierbarkeit bei Individuen vor und nach einem traumatischen Ereignis erfassen. Dies könnte z. B. durch gezielte Erhebungen in Populationen mit erhöhtem Traumatisierungsrisiko geschehen. RALF SCHMAELZLE University of Konstanz, Konstanz, Germany L’hypnotisabilité en tant que facteur de risque potentiel de stress post-traumatique : Une analyse documentaire des études quantitatives Samantha S. Yard, Katherine N. DuHamel et Igor I. Galynker Résumé: Les auteurs ont passé en revue les publications portant sur le lien pouvant exister entre l’hypnotisabilité et le stress post-traumatique. Soixantesept résumés contenant à la fois les termes TSA (trouble de stress aigu), stress aigu, traumatisme ou SSPT avec soit le terme susceptibilité hypnotique, soit le terme hypnotisabilité ont été examinés. Six articles contenaient des données sur l’hypnotisabilité et les symptômes de stress post-traumatique. Chacune de ces études montrait une relation quelconque entre l’hypnotisabilité et le stress post-traumatique mais, dans le cas de toutes ces études, l’hypnotisabilité avait été mesurée après l’événement potentiellement traumatisant. Un haut niveau d’hypnotisabilité pourrait se révéler un facteur de risque associé à la présence de symptômes post-traumatiques tant aigus que chroniques. Toutefois, cela ne peut être déterminé tant que des études

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prospectives n’auront pas mesuré l’hypnotisabilité d’individus avant et après un événement potentiellement traumatisant, peut-être en ciblant des populations susceptibles de faire l’expérience d’un traumatisme. JOHANNE REYNAULT C. Tr. (STIBC) La hipnotizabilidad como un factor de riesgo potencial para estrés postraumático: Una revisión de estudios cuantitativos Samantha S. Yard, Katherine N. DuHamel, y Igor I. Galynker Resumen: Los autores revisan la literatura que relaciona a la hipnotizabilidad con el estrés postraumático. Revisamos 77 resumenes con los términos clave ASD (TAE), estrés agudo, trauma, traumático, o PTSD (TEP) en combinación con susceptibilidad hipnótica o hipnotizabilidad. Encontramos 6 artículos con datos sobre hipnotizabilidad y síntomas de estrés postraumático. Todos los estudios mostraron alguna relación entre la hipnotizabilidad y el estrés postraumático, pero en todos ellos se midió la hipnotizabilidad después del suceso potencialmente traumático. La hipnotizabilidad alta puede ser un factor de riesgo para síntomas postraumáticos agudos y crónicos. Sin embargo, esto no puede concluirse definitivamente hasta que hayan estudios que midan la hipnotizabilidad en individuos antes y después de un suceso potencialmente traumático, tal vez en poblaciones con riesgo de experimentar trauma. ETZEL CARDEÑA Lund University, Lund, Sweden

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