The relationship between dissociation and voices: A systematic literature review and meta-analysis.

There are an increasing number of studies exploring the association between voice-hearing (auditory verbal hallucinations) and dissociative experiences. The current study provides a systematic literature review and meta-analytic synthesis of quantitative studies investigating the relationship between voice-hearing and dissociation. A systematic search identified and included 19 clinical studies, comprising 1620 participants, and 12 non-clinical studies, comprising 2137 participants, published between 1986 and 2014. Nineteen of these studies provided sufficient data to be included within the meta-analysis. The narrative review findings suggested that dissociative experiences may be implicated in voice-hearing, and may potentially be a mediating factor within the well-established trauma and voice-hearing relationship. Similarly, the meta-analytic findings suggested that the majority of the identified studies showed a significant positive relationship between dissociative experiences and voice-hearing. The magnitude of the summary effect was large and significant (r=.52), indicating a robust relationship between these two phenomena. However, considerable heterogeneity within the meta-analytic results and methodological limitations of the identified studies were evident, highlighting areas for future investigation. As the majority of the studies were cross-sectional by design, we recommended future research to include longitudinal designs with a view to exploring directional effects. Additionally, future studies should control for potential confounding factors. Clinical implications of the findings were also considered.