Urban Living and Serious Mental Disorder
: Deciphering the Link

Student thesis: Doctoral ThesisDoctor of Philosophy

Abstract

Epidemiological studies have repeatedly observed higher rates of psychotic disorders in urban areas compared with rural areas. These findings have been consistently replicated. However, little is known about what aspect of living in an urban environment increases risk of developing psychotic illness. The aim of this thesis was to investigate the relationship between urbanicity and psychosis, and to explore whether individual and area level measures of social isolation may explain this complex relationship.

Data was drawn from a Europe-wide incidence and case-control study of first episode psychosis conducted in 17 centres across 6 countries (France, Spain, Italy, the UK, Brazil, and the Netherlands). Data was available for 2,748 incidence cases of psychosis (1,094 assessed intensively) and 1,497 population-based controls (also intensively assessed).

Results showed marked geographical variation in rates of all psychotic disorders, with crude incidence ranging from 6.3- 61.4 per 100,000 person-years. Moreover, incidence rates varied by urbanicity. Higher rates of all psychotic disorders were observed in urban (IR 25.1 per 100,000 person years) compared with rural settings (IR 17.5 per 100,000 person-years). This pattern of results continued for non-affective psychosis (urban 19.3 per 100,000 person years vs. rural 11.6 per 100,0000 person years). Interestingly, reduced rates of affective psychosis were observed in urban sites (3.1 per 100,000 person years) compared with rural (5.7 per 100,000 person years).

When broken down into each country for all psychotic disorders and non-affective psychosis the urban effect was only observed in the UK, Netherlands and to a less degree France, with no association in France or Italy.

When exploring the role of area level social isolation, percentage of single person households was associated with higher rates of psychosis in urban settings (adj. IRR 1.96, 95% CI 1.48-2.59), with no association in rural settings (adj. IRR 1.20, 95% CI 0.91-1.57). However, percentage unemployed was associated with reduced rates in urban settings for all psychotic disorders (adj. IRR 0.54, 95% CI 0.34-0.86) and affective psychosis (adj. IRR 0.42, 95% CI 0.18-
0.99).

Individual level data was analysed using logistic regression. Single relationship status, unemployment and infrequent church attendance were associated with increased odds of psychosis at the time of onset, one year prior to onset and 5 years prior to onset. Whilst controls from urban sites were more likely to report isolation compared with controls from rural sites, urban residence did not modify the relationship between case status and isolation.

The results highlight the substantial variation in risk of psychosis by both person and place. The main finding from this thesis is that the role of urbanicity does not by default increase risk of psychosis as previously believed. In addition, whilst social isolation and urban residence were both strongly associated with the onset of psychoses, there was limited evidence to suggest that isolation underlies the increased rates of psychoses in urban areas.
Date of Award1 Aug 2022
Original languageEnglish
Awarding Institution
  • King's College London
SupervisorCraig Morgan (Supervisor) & Jayati Das-Munshi (Supervisor)

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