Hannah Jongsma1, Craig Morgan2, Peter Jones1, James Kirkbride3; 1Department of Psychiatry University of Cambridge, 2Society and Mental Health Research Group, Health Service and Population Research Department, Institute of Psychiatry, Psychology & Neuroscience, King’s College London, London, UK, 3PsyLife Group, Division of Psychiatry, University College London
The incidence of psychotic disorders varies across social and environmental gradients at both an individual and a population level. However, the factors underpinning this are unclear. We conducted a population-based study of the incidence of non-organic adult ICD-10 psychotic disorders across the 17 catchment areas in the six countries (England, France, Italy, Netherlands, Spain, Brazil). Crude incidence rates were standardised to the 2011 England and Wales Census population to account for population differences in age, sex and ethnicity. Multilevel Poisson regression was carried out to investigate variance in incidence between catchment areas by latitude, population density, and percentage of unemployment, owner-occupied houses and single-person households. We identified a total of 2,774 cases over 12.94 million person-years at risk, leading to a crude incidence of 21.4 per 100,000 person-years (95%CI=19.4-23.4). By age 35, 68% of male cases had presented to services, compared with 51% of female cases. Poisson regression revealed higher rates of all psychotic disorders in minority groups (IRR=1.6, 95%CI=1.5-1.7), and an association between greater catchment area-level owner-occupancy and lower incidence (IRR for a 10% increase: 0.8, 95%CI=0.7-0.8). A higher population density was associated with an increased incidence of psychosis in England (IRR=1.2, 95%CI=1.1-1.2) and Netherlands (IRR=1.9, 95%CI=1.4-2.6), and was associated with a lower incidence in Italy (IRR=0.7, 95%CI=0.6-0.8). Services focused on early intervention should not have an upper age limit as half of all female (and 32% of male) cases present after age 35; future examinations of variance should be locally informed and take socioenvironmental risk factors into account.
