A systematic review and meta-analysis of the ethnic density effect in psychotic disorders.

PURPOSE: A number of studies have found an ethnic density effect in psychotic disorders, where the incidence for ethnic minorities increases as the neighbourhood proportional ethnic composition decreases [Morgan and Hutchinson, Psychol Med 40:705-709, (2010); Singh, Psychol Med 39:1402-1403, (2009); Schofield et al., Psychol Med 41:1263-1269, (2010)]. However, there is a mixed picture with some studies reporting no effect [Schofield et al., Psychol Med 41:1263-1269, (2010)]. This review aimed to establish the existence of the effect by answering the review question: is there an ethnic density dose effect in the prevalence of psychotic disorders? METHODS: A systematic review and meta-analysis was conducted by two independent reviewers using PsychINFO, Web of Science and PubMed databases. Studies were measured against eligibility criteria and then pooled with any discrepancies discussed between reviewers. Studies were then assessed for quality using a standardised quality assessment. RESULTS: In total, eight studies were included. A meta-analysis was conducted which found that the incidence of psychotic disorders was higher in low ethnic density areas than high ethnic density areas. A narrative synthesis reflected the complexity when results were broken down by individual ethnic groups where some ethnic groups had inverse or no associations with ethnic density. The synthesis also analysed methodological differences between studies. CONCLUSIONS: The review reports evidence of an overall ethnic density dose effect for ethnic minorities, but with more mixed results for individual ethnic groups. The possible mechanisms behind this effect are explored, including exposure to racism, social capital and social cohesion hypotheses. The wide-ranging implications of the review are discussed along with recommendations for future research to continue to inform public health policy.

Childhood trauma and hippocampal and amygdalar volumes in first-episode psychosis.

OBJECTIVE: A history of childhood trauma is common in individuals who later develop psychosis. Similar neuroanatomical abnormalities are observed in people who have been exposed to childhood trauma and people with psychosis. However, the relationship between childhood trauma and such abnormalities in psychosis has not been investigated. This study aimed to explore the association between the experience of childhood trauma and hippocampal and amygdalar volumes in a first-episode psychosis (FEP) population. METHODS: The study employed an observational retrospective design. Twenty-one individuals, who had previously undergone magnetic resonance imaging procedures as part of the longitudinal Northern Ireland First-Episode Psychosis Study, completed measures assessing traumatic experiences and were included in the analysis. Data were subject to correlation analyses (r and r (pb)). Potential confounding variables (age at FEP and delay to scan from recruitment) were selected a priori for inclusion in multiple regression analyses. RESULTS: There was a high prevalence of lifetime (95%) and childhood (76%) trauma in the sample. The experience of childhood trauma was a significant predictor of left hippocampal volume, although age at FEP also significantly contributed to this model. There was no significant association between predictor variables and right hippocampal volume. The experience of childhood trauma was a significant predictor of right and total amygdalar volumes and the hippocampal/amygdalar complex volume as a whole. CONCLUSIONS: The findings indicate that childhood trauma is associated with neuroanatomical measures in FEP. Future research controlling for childhood traumatic experiences may contribute to explaining brain morphology in people with psychosis.