Does affect mediate the relationship between interpersonal trauma and psychosis? A systematic review and meta-analysis

Introduction: The relationship between interpersonal trauma and psychosis is well established, and research is now focused on identifying mechanisms that may explain this relationship. Models of trauma and psychosis increasingly emphasize a broad range of affective processes, yet the overall effect of these affective processes is not well understood. Aim: This review systematically examined the effect of any form of long-term affective dysfunction on the relationship between interpersonal trauma and psychosis. Where possible, it used meta-analytic techniques to quantify the overall magnitude of this effect. Method: Searches were conducted using PsychINFO, MEDLINE and CINAHL databases, and eligible studies were appraised for methodological quality. Narrative synthesis and meta-analytic methods were used to evaluate evidence. Results: Twenty-nine studies met criteria for inclusion. Five affective mediators were found; depression, anxiety, affective dysregulation, loneliness and attachment. Findings from both the narrative synthesis (n = 29) and metaanalysis (n = 8) indicated that, overall, affect is a small but significant mediator of the relationship between interpersonal trauma and psychosis (pooled Cohen's d = 0.178; pooled 95 % CI: 0.022-0.334). Conclusions: Overall, findings support affective pathways to psychosis, though highlight the need for further research on broader affective mediators (loneliness, shame). The small effect size found in the meta-analysis also points to the potential importance of non-affective mediators. Clinically, these findings highlight the value of treatment modalities that attend to multiple mechanisms in the relationship between interpersonal trauma and psychosis. Future research should focus on the interplay and causal sequence between these mechanisms to further understand pathways between interpersonal trauma and psychosis.