Neighbourhood effects on psychotic and depressive symptoms in the context of religious sectarianism in Northern Ireland: A data linkage study

Background: The incidence of psychotic disorders is higher in ethnic minorities groups. The ‘ethnic density effect’, in which living in a neighbourhood with a low own-group proportion increases the risk of psychosis, is one explanatory factor. The density effect in the ethno-religious and sectarian context of Northern Ireland has been found to be reversed, particularly for Catholics, in which there is harmful effect of high own-group density areas. This is partly explained by high urbanicity, deprivation and unemployment, but is otherwise not well understood. Aims: This study aimed to examine the density effect at the level of symptomology (positive and negative psychosis symptoms and depressive symptoms) in a representative sample of people with a first episode of psychosis in Northern Ireland. Method: Data linkage methodology was used drawing on data from the Northern Ireland First Episode Psychosis Study (NIFEPS) and the 2001 Census of Northern Ireland. Results: In total, 223 people between the ages of 18 to 64 were included in the study. A significant density effect was found for Catholics for total psychosis scores, but not for positive, negative and depressive symptoms, nor for general psychopathology, after adjusting for individual and area characteristics. The model accounted for just over 12% of the variance. No effect was found for Protestants. Conclusion: The findings suggest that the density effect for Catholics is unrelated to the core features of psychosis (hallucinations, delusions and anhedonia) but rather to broader cognitive and emotional disturbances and area deprivation. Explanations of exposure to social adversity and inequality are proposed, with implications for public mental health and social policy.