Abstract and Introduction
Evidence suggests that dissociation is associated with psychotic experiences, particularly hallucinations, but also other symptoms. However, until now, symptom-specific relationships with dissociation have not been comprehensively synthesized. This is the first prospectively registered (CRD42017058214) meta-analysis to quantify the magnitude of association between dissociative experiences and all symptoms of psychosis. MEDLINE, PsycINFO, PubMed, and Scopus databases were searched using exhaustive terms denoting dissociation and psychotic symptoms. We included both nonclinical (58 studies; 16 557 participants) and clinical (46 studies; 3879 patient participants) samples and evaluated study quality. Ninety-three eligible articles considering 20 436 participants were retained for analysis. There was a robust association between dissociation and clinical and nonclinical positive psychotic symptoms (r = .437; 95%CI: .386 −.486), with the observed effect larger in nonclinical studies. Symptom-specific associations were also evident across clinical and nonclinical studies, and included significant summary effects for hallucinations (r = .461; 95%CI: .386 −.531), delusions (r = .418; 95%CI: .370 −.464), paranoia (r = .447; 95%CI: .393 −.499), and disorganization (r = .346; 95%CI: .249 −.436). Associations with negative symptoms were small and, in some cases, not significant. Overall, these findings confirm that dissociative phenomena are not only robustly related to hallucinations but also to multiple positive symptoms, and less robustly related to negative symptoms. Our findings are consistent with proposals that suggest certain psychotic symptoms might be better conceptualized as dissociative in nature and support the development of interventions targeting dissociation in formulating and treating psychotic experiences.
The concept of dissociation has become a focus of considerable interest for the psychosis field over the past few years, with research examining its importance for the historical concept of schizophrenia, the prevalence of undiagnosed dissociative disorders in psychotic populations, the possibility of hybrid dissociative/psychotic disorders, and the role of dissociation in psychotic symptoms. The latter domain is the focus of this meta-analysis.
Dissociation has been defined by DSM-5 as "a disruption of and/or discontinuity in the normal integration of consciousness, memory, identity, emotion, perception, body representation, motor control, and behaviour." (p291) Dissociation, and the dissociative disorders, are generally seen as resulting from traumatizing experiences; in recognition of this, dissociative symptoms are now formally recognized in other disorders typically seen as trauma-related, including borderline personality disorder and posttraumatic stress disorder. As trauma is increasingly seen as a causal risk factor in the development of psychosis, the relevance of dissociative experiences to psychosis is being explored with more vigor. Indeed, some have gone so far to suggest that certain psychotic symptoms, particularly auditory hallucinations and delusions of control or passive influence experiences, are better classified as dissociative than psychotic.[3,7] The frequency with which the so-called first rank or Schneiderian symptoms are found in dissociative disorders lends weight to this argument. In turn, the concept of psychiatric disorders as discrete "disease entities" linked to distinct biological or genetic etiologies only present in those who meet criteria for specific conditions is increasingly contested. Considerable evidence further suggests that psychosis, like dissociative experiences, exists on a continuum with normal functioning and that its presentation cuts across diagnostic boundaries without being necessarily pathognomonic for any specific disorder.
The concept of dissociation refers to a range of phenomena, including experiences encompassing various forms of "psychological detachment" (eg, depersonalization, derealization) as well as compartmentalization of mental experiences (eg, identity disturbances and dissociative amnesia). Significantly, meta-analytic studies have confirmed that dissociation is elevated in people with diagnoses in the schizophrenia-spectrum,[12,13] suggesting that dissociation may be related to symptoms commonly observed in people who receive diagnoses of psychotic disorders. The association between auditory hallucinations and dissociation has attracted particular research attention, with a meta-analysis of 19 investigations reporting large associations between the two across both clinical and nonclinical populations. However, whilst the association with auditory hallucinations appears well-replicated, this does not imply that dissociation is uniquely associated with a greater predisposition to only report this symptom. In fact, research studies have found significant positive associations between dissociative experiences and both delusions and paranoia as well as respective subsyndromal psychotic-like symptoms in nonclinical samples. A significant relationship has also been reported, albeit less consistently, between dissociation and negative symptoms.
Whilst recent meta-analytic evidence suggests the presence of considerable symptom overlap between diagnoses of schizophrenia spectrum disorders and dissociative disorders, no evidence synthesis to date has systematically examined the magnitude and consistency of the associations between discrete symptoms of psychosis and measures of dissociation. The value of investigating symptom-specific associations is especially pertinent due to the fact that different psychotic experiences may have distinct etiologies. Furthermore, clarifying these associations would be relevant to recent trends toward more symptom-specific and personalized targeted therapies for distressing psychotic symptoms.
The primary aim of this meta-analysis was, therefore, to examine and synthesize associations between dissociation and the full range of psychosis symptomatology. A secondary aim was to assess the relationship between dissociation and psychosis symptomatology in both clinical and nonclinical populations and to report on the similarities and differences between them.
Schizophr Bull. 2020;46(5):1104-1113. © 2020 Oxford University Press