Geographical variation in treated psychotic and other mental disorders in Finland by region and urbanicity

Abstract

Purpose In Finland, prevalence of schizophrenia is higher in the eastern and northern regions and co-occurs with the distribution of schizophrenia polygenic risk scores. Both genetic and environmental factors have been hypothesized to contribute to this variation. We aimed to examine the prevalence of psychotic and other mental disorders by region and degree of urbanicity, and the impacts of socio-economic adjustments on these associations. Methods Nationwide population registers from 2011 to 2017 and healthcare registers from 1975 to 2017. We used 19 administrative and three aggregate regions based on the distribution of schizophrenia polygenic risk scores, and a seven-level urban–rural classification. Prevalence ratios (PRs) were calculated by Poisson regression models and adjusted for gender, age, and calendar year (basic adjustments), and Finnish origin, residential history, urbanicity, household income, economic activity, and physical comorbidity (additional adjustments) on an individual level. Average marginal effects were used to visualize interaction effects between region and urbanicity. Results A total of 5,898,180 individuals were observed. All mental disorders were slightly more prevalent (PR 1.03 [95% CI, 1.02–1.03]), and psychotic disorders (1.11 [1.10–1.12]) and schizophrenia (1.19 [1.17–1.21]) considerably more prevalent in eastern and northern than in western coastal regions. After the additional adjustments, however, the PRs were 0.95 (0.95–0.96), 1.00 (0.99–1.01), and 1.03 (1.02–1.04), respectively. Urban residence was associated with increased prevalence of psychotic disorders across all regions (adjusted PR 1.21 [1.20–1.22]). Conclusion After adjusting for socioeconomic and sociodemographic factors, the within-country distribution of mental disorders no longer followed the traditional east–west gradient. Urban–rural differences, on the other hand, persisted after the adjustments.

Enhancing the accuracy of register-based metrics: Comparing methods for handling overlapping psychiatric register entries in Finnish healthcare registries

“…Its inclusion has significantly enhanced the comprehensiveness of the registers, potentially influencing results in register-based psychiatric epidemiological research, especially due to the common utilization of primary care for mental health treatment in Finland. 11,12…”

“…Its inclusion has significantly enhanced the comprehensiveness of the registers, potentially influencing results in register-based psychiatric epidemiological research, especially due to the common utilization of primary care for mental health treatment in Finland. 11,12 The International Statistical Classification of Diseases and Related Health Problems, Tenth Revision (ICD-10) has been used in Finland since 1996. Prior to that, the Finnish version of the ICD-9 was used from 1987 to 1995, and ICD-8 from 1969 to 1986.…”

Enhancing the accuracy of register‐based metrics: Comparing methods for handling overlapping psychiatric register entries in Finnish healthcare registers

“…The Register of Primary Health Care visits (RPHC) encompasses publicly organized outpatient primary health care since 2011. Its inclusion has significantly enhanced the comprehensiveness of the registers, potentially influencing results in register-based psychiatric epidemiological research, especially due to the common utilization of primary care for mental health treatment in Finland (Suokas et al, 2022(Suokas et al, , 2023.…”