Dissociative experiences are common transdiagnostically, and particularly prevalent in psychosis. Such experiences have long been under-recognised in routine clinical practice, despite evidence that dissociation is related to clinical complexity and increased risk of self-harm and suicidality. Adopting a symptom-specific, targeted approach to conceptualisation and intervention for dissociation may help improve outcomes.

The evidence base for psychological treatments targeting dissociation is building, but training and guidance for clinicians remains sparse. This review outlines a preliminary approach to the treatment of a subtype of dissociative experience (felt sense of anomaly dissociation), based on emerging research evidence and clinical practice. The guidance is tailored to the context of psychosis, and may also have broader clinical relevance.

We present symptom-specific guidance for clinicians, including factors to consider in the assessment, formulation, and intervention for felt sense of anomaly dissociation in the context of psychosis, and reflections on process issues. We present a cognitive behavioural model, where affect-related changes are interpreted as an internal threat, driving a maintenance cycle of catastrophic appraisals and safety behaviours. Using this formulation, evidence-based therapy techniques familiar to most readers can then be applied.

It is important for clinicians to consider dissociation. As well as generating new avenues for translational intervention research, we anticipate that the novel insights and specific advice outlined here will be of use to professionals working with dissociation in psychosis (and beyond). Encouragingly, we demonstrate that widely used, evidence-based skills and techniques can be employed to address distress arising from dissociation.

Dissociation may be important across many mental health disorders, but has been variously conceptualised and measured. We introduced a conceptualisation of a common type of dissociative experience, ‘felt sense of anomaly’ (FSA), and developed a corresponding measure, the Černis Felt Sense of Anomaly (ČEFSA) scale.

We aimed to develop a short-form version of the ČEFSA that is valid for adolescent and adult respondents.

Data were collected from 1031 adult NHS patients with psychosis and 932 adult and 1233 adolescent non-clinical online survey respondents. Local structural equation modelling (LSEM) was used to establish measurement invariance of items across the age range. Ant colony optimisation (ACO) was used to produce a 14-item short-form measure. Finally, the expected test score function derived from item response theory modelling guided the establishment of interpretive scoring ranges.

LSEM indicated 25 items of the original 35-item ČEFSA were age invariant. They were also invariant across gender and clinical status. ACO of these items produced a 14-item short-form (ČEFSA-14) with excellent psychometric properties (CFI=0.992; TLI=0.987; RMSEA=0.034; SRMR=0.017; Cronbach’s alpha=0.92). Score ranges were established based on the expected test scores at approximately 0.7, 1.25 and 2.0 theta (equivalent to standard deviations above the mean). Scores of 29 and above may indicate elevated levels of FSA-dissociation.

The ČEFSA-14 is a psychometrically valid measure of FSA-dissociation for adolescents and adults. It can be used with clinical and non-clinical respondents. It could be used by clinicians as an initial tool to explore dissociation with their clients.