A Systematic Review on Psychological and Biological Mediators Between Adversity and Psychosis: Potential Targets for Treatment

Various psychological and biological pathways have been proposed as mediators between childhood adverse events (CA) and psychosis. A systematic review of the evidence in this domain is needed. The aim of this work is to systematically review the evidence on psychological and biological mediators between CA and psychosis across the psychosis spectrum. This systematic review followed Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines (registration number: CRD42018100846). Articles published between 1979 and July 2019 were identified through a literature search in OVID (PsychINFO; Medline and Embase). The evidence by each analysis and each study results are presented by group of mediator categories found in the review. The percentage of total effect mediated was calculated. 47 studies were included, with a total of 79,668 from general population (GP) and 3,189 from clinical samples. The quality of studies was judged as 9fair9. Our results showed (i) solid evidence of mediation between CA and psychosis by negative cognitive schemas about the self, the world, and others (NS); by dissociation and other PTSD symptoms; (ii) evidence of al mediation through an affective pathway (affective dysregulation, anxiety, and depression) in GP; (iii) lack of studies exploring biological mediators. To conclude, we found evidence suggesting that various overlapping and not competing pathways contribute partially to the link between adversity and psychosis. Experiences of adversity, along with relevant mediators such as PTSD and mood related symptoms and NS, should be routinely assessed in patients with psychosis. Targeting such mediators through cognitive behavioural aproaches using trauma-focused therapy and/or pharmacological means could be a useful addition to the traditional treatment of positive symptoms.