Dissociation is common in psychosis, and the variation between patients is the real finding

Pooling 51 datasets covering 3,878 people, a review found moderately elevated dissociation in non-affective psychosis. Heterogeneity above 85% means the average describes almost nobody in particular.

Dissociation - detachment from one's own experience, body or sense of self - is common in non-affective psychosis and is linked to markers of clinical risk including sleep disturbance and negative affect. Until now nobody had quantified how severe it typically is. Researchers led by Adam O'Neill searched six databases from inception, screened against ICD or DSM criteria or service-defined categories, and included first-episode psychosis, brief intermittent psychotic symptoms and at-risk mental states. They extracted data on 22 measures and ran random-effects meta-analyses on the four with at least three independent datasets. The Dissociative Experiences Scale, the largest with 51 datasets and 3,878 people, gave a pooled mean of 21.28, which is moderately elevated. The Cambridge Depersonalization Scale pooled to 36.38, also raised against community norms. Both scoring methods of the Examination of Anomalous Self Experience indicated clinically relevant levels of basic self-disturbance. The number that deserves attention is not any of these. Heterogeneity exceeded 85% across measures, meaning the studies disagree with each other far more than sampling error explains, and the pooled average is therefore a poor description of any individual patient. The authors say so directly: dissociation is not uniform in this population. Read the right way, this is an argument for assessing dissociation in people with psychosis rather than assuming a typical level - because the review's own strongest result is that there isn't one.