Regional variation in the incidence of schizophrenia in Finland: a study of birth cohorts born from 1950 to 1969

Haukka, Jari; Suvisaari, Jaana; Varilo, Teppo; Lönnqvist, Jouko

doi:10.1017/s0033291701004299

Cited by 58 publications

(59 citation statements)

References 31 publications

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“…76 More recent studies in Denmark also cast doubt on whether urban findings should be interpreted solely in terms of social factors. A cohort study in Denmark that included over 5 million people found no evidence of time trends in the urban-rural differences in schizophrenia risk during the period 1910 to 1986, 77 in contrast to previous findings from Finland 78 and The Netherlands 79 that showed an increase in the urban effect over time. The stability of the urban effect over time found in Denmark is puzzling because most factors related to the environment, whether social or physical, would undergo major changes during this period.…”

Section: Does the Urban Effect In Schizophrenia Lend Support To The Smentioning

confidence: 63%

The Contribution of Social Factors to the Development of Schizophrenia: A Review of Recent Findings

Cantor‐Graae

2007

Can J Psychiatry

169

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Objective: To investigate recent evidence suggesting that social factors are causally related to the development of schizophrenia.Method: I conducted a sytematic review of MEDLINE to identify possibly relevant studies. The search was limited to peer-reviewed studies and review articles appearing in English-language journals since 1996. Studies were included if they used standardized diagnostic criteria for schizophrenia or standardized assessment instruments for psychotic symptoms.Results: Studies of migrants to western Europe provide compelling support for the notion that social factors contribute to the development of schizophrenia. Findings such as excessively high risk for schizophrenia in second-generation immigrants are difficult to explain solely in terms of biological or genetic factors. A growing number of studies implicate childhood exposure to social adversity as a risk factor for schizophrenia, although few studies have used prospective designs. The increased incidence of schizophrenia risk associated with urban birth and (or) urban upbringing suggests possible social causation, but these findings are more ambiguous. Thus far, no studies have explored actual mechanisms by which exposure to social factors might generate psychotic symptoms, although animal experiments suggest that social defeat or social exclusion may cause dopamine dysregulation or sensitization. Conclusions:The accumulating evidence suggesting a role for social factors in the development of schizophrenia arises primarily from studies of migrants conducted in Europe. The mechanisms by which social factors exert their influence remain unknown. Future investigations of social causation should clarify the temporal relation between exposure to social defeat and (or) social adversity and the development of psychotic symptoms.(Can J Psychiatry 2007;52:277-286) Information on funding and support and author affiliations appears at the end of the article. Clinical Implications· Social factors may play an etiologic role in the development of schizophrenia. · A common denominator may be chronic experiences of social defeat and (or) exclusion, resulting in dopamine dysregulation or sensitization. · The implementation of interventions and preventive strategies may reduce the risk associated with social factors. Limitations· Thus far, few prospective studies specifically target social factors. · Animal models of social defeat may not be satisfactory analogues for the migrant experience. · The role of substance abuse in individuals exposed to social adversity cannot be excluded.

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Section: Does the Urban Effect In Schizophrenia Lend Support To The Smentioning

confidence: 63%

The Contribution of Social Factors to the Development of Schizophrenia: A Review of Recent Findings

Cantor‐Graae

2007

Can J Psychiatry

169

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“…In total, we identified 4 studies that met our strict inclusion criteria (diagnosis of schizophrenia, more than 2 levels of urbanicity exposure, and premorbid measurement) 9-13 and 4 additional studies [14][15][16][17] that met our broader criteria (see online supplementary material table 1). These were conducted between 1974 and 2007 in 6 Western industrialized countries with predominantly European populations and comprised a total of 46 820 cases with psychosis.…”

Section: Resultsmentioning

confidence: 99%

“…Because only 4 studies met our primary inclusion criteria (table 1), [9][10][11][12][13] we repeated the analysis with more liberal characteristics, which included studies with broader psychosis outcome, 2 comparison groups, and urbanicity exposure at the time of disease onset (see online supplementary material table 1). [14][15][16][17] The Danish studies 11,12 were supplemented with new, unpublished data provided by co-author Pedersen.…”

Section: Methodsmentioning

confidence: 99%

Meta-Analysis of the Association of Urbanicity With Schizophrenia

Vassos

Pedersen

Murray

et al. 2012

Schizophrenia Bulletin

406

261

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The association between urbanicity and risk of schizophrenia is well established. The incidence of schizophrenia has been observed to increase in line with rising levels of urbanicity, as measured in terms of population size or density. This association is expressed as Incidence Rate Ratio (IRR), and the results are usually presented by comparing the most urban with the most rural environment. In this study, we undertook to express the effect of urbanicity on the risk of schizophrenia in a linear form and to perform a meta-analysis of all available evidence. We first employed a simple regression analysis of log (IRR) as given in each study on the urbanicity category, assuming a uniform distribution and a linear association. In order to obtain more accurate estimates, we developed a more sophisticated method that generates individual data points with simulation from the summary data presented in the original studies, and then fits a logistic regression model. The estimates from each study were combined with meta-analysis. Despite the challenges that arise from differences between studies as regards to the number and relative size of urbanicity levels, a linear association was observed between the logarithm of the odds of risk for schizophrenia and urbanicity. The risk for schizophrenia at the most urban environment was estimated to be 2.37 times higher than in the most rural environment. The same effect was found when studies measuring the risk for nonaffective psychosis were included.

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“…more underweight newborns in rural Eastern and Northern regions) and genetic predisposition (Perälä et al 2008). Suvisaari et al (1999) identified a decline in the incidence of schizophrenia in Finland in the period 1954-1965and Haukka et al (2001 found that urban birth increased incidence in cohorts born since 1955.…”

Section: Introductionmentioning

confidence: 99%

A comparison of the cumulative incidence and early risk factors for psychotic disorder in young adults in the Northern Finland Birth Cohorts 1966 and 1986

Filatova

Marttila

Koivumaa‐Honkanen

et al. 2016

Epidemiol Psychiatr Sci

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Aims. Few studies have compared time trends for the incidence of psychosis. To date, the results have been inconsistent, showing a decline, an increase or no significant change. As far as we know, no studies explored changes in prevalence of early risk factors. The aim of this study was to investigate differences in early risk factors and cumulative incidences of psychosis by type of psychosis in two comparable birth cohorts.Methods. The Northern Finland Birth cohorts (NFBCs) 1966 (N = 12 058) and 1986 (N = 9432) are prospective general population-based cohorts with the children followed since mother's mid-pregnancy. The data for psychoses, i.e. schizophrenia (narrow, spectrum), bipolar disorder with psychotic features, major depressive episode with psychotic features, brief psychosis and other psychoses (ICD 8-10) were collected from nationwide registers including both inpatients and outpatients. The data on early risk factors including sex and place of birth of the offspring, parental age and psychosis, maternal education at birth were prospectively collected from the population registers. The follow-up reached until the age of 27 years.Results. An increase in the cumulative incidence of all psychoses was seen (1.01% in NFBC 1966 v. 1.90% in NFBC 1986; p < 0.001), which was due to an increase in diagnosed affective and other psychoses. Earlier onset of cases and relatively more psychoses in women were observed in the NFBC 1986. Changes in prevalence of potential early risk factors were identified, but only parental psychosis was a significant predictor in both cohorts (hazard ratios ≥3.0; 95% CI 1.86-4.88). The difference in psychosis incidence was not dependent on changes in prevalence of studied early risk factors. Conclusions. Surprisingly, increase in the cumulative incidence of psychosis and also changes in the types of psychoses were found between two birth cohorts 20 years apart. The observed differences could be due to real changes in incidence or they can be attributable to changes in diagnostic practices, or to early psychosis detection and treatment.

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Regional variation in the incidence of schizophrenia in Finland: a study of birth cohorts born from 1950 to 1969

Abstract: Urban birth is a risk factor for schizophrenia in Finland in cohorts born since 1955. However, genuine spatial clustering of schizophrenia in eastern Finland was also observed, possibly caused by genetic isolation.

Cited by 58 publications

References 31 publications

The Contribution of Social Factors to the Development of Schizophrenia: A Review of Recent Findings

The Contribution of Social Factors to the Development of Schizophrenia: A Review of Recent Findings

Meta-Analysis of the Association of Urbanicity With Schizophrenia

A comparison of the cumulative incidence and early risk factors for psychotic disorder in young adults in the Northern Finland Birth Cohorts 1966 and 1986

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