تفکیک تحت بالینی، اسکیزوتایپی و پریشانی پس از سانحه

The current study looked at the overlap between dissociation and schizotypy and examined two potential sources from which this overlap might originate: fantasy proneness and traumatic distress. From a sample of 191 undergraduates, those scoring in the upper and lower quartile of the Dissociative Experiences Scale (DES) were selected. Next, the scores of these groups on well-established schizotypy scales were compared to each other. The high-DES group had significantly higher schizotypy scores than the low-DES group. Although both groups also differed with regard to fantasy proneness and, to a lesser extent, traumatic distress, analyses of covariance showed that these variables could not explain group differences in schizotypy. Alternative interpretations of the dissociation–schizotypy link are discussed.

A number of studies have noted that dissociative symptoms (e.g., feelings of derealization, depersonalization, memory complaints, absorption) overlap with the tendency to report psychotic-like experiences (i.e., schizotypy). For example, Pope and Kwapil (2000) had their undergraduate sample fill out the Dissociative Experiences Questionnaire (DES; Bernstein & Putnam, 1986), which is the standard measure of dissociation, as well as the Chapman scales of psychosis proneness. Several of these scales have proven to be effective predictors of psychosis (e.g., the Perceptual Aberration Scale; PerAb; and the Magical Ideation Scale; MagId). The authors found correlations in the order of 0.44 between dissociation on the one, and schizotypy (as indexed by PerAb and MagId), on the other hand. Using a different measure of schizotypy, Merckelbach, Rassin, and Muris (2000) noted a similar overlap between dissociation and schizotypy in their undergraduate samples (r = 0.64). In what seems to be the largest study so far, with two samples including more than 1000 undergraduates, Watson (2001) reported correlations varying from 0.49 to 0.57 between schizotypy and dissociation. Summarizing his own findings, but also clinical data on, for example, dissociative symptoms in schizophrenic patients, this author concluded that “clearly, the association between dissociation and schizotypy is quite robust and is not limited to self-ratings” ( Watson, 2001, p. 533). The question arises as to what may account for the shared variance between dissociation and schizotypy. Three ideas have been put forward in the literature. To begin with, some authors have considered the possibility that shared item content is responsible for the overlap between dissociation and schizotypy. For example, Watson (2001) found that scales measuring dissociation and schizotypy both contain items pertaining to detachment and depersonalization. Obviously, shared item content inflates correlations between constructs. However, Watson (2001) also noted that the overlap between dissociation and schizotypy remains substantial, even when one corrects for the detachment/depersonalization items. A second interpretation assumes that dissociation and schizotypy are both lower order traits that are nested under the same superordinate trait. Thus, McCrae and Costa (1997) have argued that dissociation, aberrant perception, and magical thinking all reflect the fantasy facet of the big five factor Openness to Experience. Although this interpretation is intuitively plausible, the empirical support for it so far is weak. Indirect evidence comes from studies on transliminality, a concept which refers to some individuals’ heightened sensitivity to and preoccupation with imagery, ideation, and affect. These studies reported that absorption—which is an important dimension of dissociation, belief in paranormal phenomena, verbal creativity, and schizotypy are all strongly related to each other (see for a review of this work, Thalbourne and Houran, 2000; see also Van den Ven & Merckelbach, 2003). However, in an initial study relying on an unselected sample of undergraduates, we (Merckelbach et al., 2000) found that fantasy proneness does not fully account for the dissociation–schizotypy link. A third interpretation of the overlap between dissociation and schizotypy emphasizes the traumatic aetiology that may contribute to both constructs (Berenbaum, 1999). The idea is that a history of trauma fosters peculiar perceptions and beliefs, which are tapped by instruments measuring dissociation and schizotypy. Germane to this issue is the renewed interest in how post-traumatic intrusions may lead to a breakdown in reality testing, thereby giving rise to psychotic phenomena like hearing voices. One speculation is that this development only occurs in people who suffer from dissociative symptoms, precisely because these symptoms reflect dysfunctional reality testing abilities (see for a review, Morrison, Frame, & Larkin, 2003). In line with such formulations, Allen and Coyne (1995) found in their sample of women undergoing inpatient treatment of trauma-related disorders that dissociative symptoms were related most strongly to the schizophrenia scale of the MMPI. In a study that sought to test the traumatic aetiology of the dissociation–schizotypy link in a more direct way, Startup (1999) reported that self-reported childhood trauma does not fully explain the variance that dissociation and schizotypy have in common. However, to measure self-reported trauma in his sample, this author employed two yes/no items and therefore, one could argue that his trauma measure was too crude to examine its precise contribution to dissociation and schizotypy. In his sample of Australian adults, Irwin (2001) also looked at the extent to which self-reported trauma might account for the dissociation–schizotypy link. His study relied on a well-established, 60-items scale to measure self-reported childhood trauma. Yet, Irwin (2001) too, noted that the dissociation–schizotypy link survives correction for self-reported childhood trauma, leading the author to conclude that “the relationship between dissociative tendencies and schizotypy is not an artefact of childhood abuse” (Irwin, 2001, p. 331). The aim of the current study was to further explore the link between dissociation and schizotypy and the extent to which fantasy proneness and self-reported trauma might account for this link. Our study deviated from previous work in this domain in four ways. First, we did not address our research question by studying a large, non-clinical sample, but rather selected individuals scoring high or low on dissociation from an undergraduate sample (Kihlstrom, 2005). This was done so as to ensure that we could examine the dissociation–schizotypy link in an extreme group that might be more similar to patient samples, at least as far as dissociation levels are concerned. Secondly, we used a dedicated instrument for measuring fantasy proneness. Thirdly, we employed an instrument tapping current, trauma-related distress as it is conceivable that the dissociation–schizotypy link depends on current traumatic intrusions rather than childhood trauma per se (see also Morrison et al., 2003). This point was inspired by the experimental work of Holmes and Steel (2004), who found that individuals scoring high on schizotypy experience heightened levels of trauma-related intrusions when they have been exposed to emotionally provocative material. Fourthly, in most previous work on dissociation and schizotypy, data were collected during a single test session. Yet, as Council (1993) demonstrated in a thoughtful review, this practice may inflate correlations between measures. To prevent such context effect, we had two separate test sessions.