Incidence Rates Of Schizophrenia Research Articles

Association between Arachidonic Acid and the Risk of Schizophrenia: A Cross-National Study and Mendelian Randomization Analysis.

Polyunsaturated fatty acids (PUFAs), especially long-chain PUFAs (LCPUFAs), are crucial for both the structural and functional integrity of cells. PUFAs have been reported to be insufficient in schizophrenia, and the resulting cell membrane impairments have been hypothesized as an etiological mechanism. However, the impact of PUFA deficiencies on the onset of schizophrenia remain uncertain. We investigated the associations between PUFAs consumption and schizophrenia incidence rates through correlational analyses and conducted Mendelian randomization analyses to reveal the causal effects. Using dietary PUFA consumption and national schizophrenia incidence rates in 24 countries, we found that incidence rates of schizophrenia were inversely correlated with arachidonic acid (AA) and ω-6 LCPUFA consumption (rAA = -0.577, p < 0.01; rω-6 LCPUFA = -0.626, p < 0.001). Moreover, Mendelian randomization analyses revealed that genetically predicted AA and gamma-linolenic acid (GLA) were protective factors against schizophrenia (ORAA = 0.986, ORGLA = 0.148). In addition, no significant relationships were observed between schizophrenia and docosahexaenoic acid (DHA) or other ω-3 PUFAs. These findings show that the deficiencies of ω-6 LCPUFAs, especially AA, are associated with schizophrenia risk, which sheds novel insight into the etiology of schizophrenia and a promising diet supplementation for the prevention and treatment of schizophrenia.

Incidence rate of schizophrenia after the Tangshan earthquake in China: a 44-year retrospective birth cohort study

Preliminary evidence indicates that natural disasters are associated with an increased risk for schizophrenia. With few longitudinal studies on earthquakes, this retrospective cohort study examined exposure to the 1976 Tangshan earthquake and the subsequent risk of schizophrenia. Population counts and visits to all nine psychiatric hospitals in Tangshan city were collected. We created three cohort groups by earthquake exposure: infant (August 1972 to July 1976 births), fetal (August 1976 to May 1977 births), and unexposed (June 1977 to May 1981 births). The cumulative incidence of schizophrenia in each cohort was calculated by dividing the number of schizophrenia patients by total births in the corresponding period. Altogether, 6424 schizophrenia patients were identified, with 2786 in the infant group, 663 in the fetal group, and 2975 in the unexposed group. The crude cumulative incidence of schizophrenia in the infant, fetal and unexposed groups were 7.64 (95% confidence interval [CI] = 7.36–7.92), 9.07 (95% CI = 8.38–9.76), and 7.40 (95% CI = 7.13–7.66) per thousand population respectively. Adjusted for mortality, the corresponding figures were 7.73 (95% CI = 7.44–8.01), 9.30 (95% CI = 8.60–10.01) and 7.44 (95% CI = 7.18–7.71) per thousand population respectively. The mortality-adjusted risk ratio (aRR) was 1.25 (95% CI = 1.15–1.36) between fetal and unexposed groups (χ2 = 27.31, P < 0.001). Males exposed as infants did not differ from the unexposed in cumulative schizophrenia incidence. People with fetal exposure to the 1976 earthquake had 25% higher risk of developing schizophrenia compared to unexposed counterparts.

The prevalence, incidence, and admission rate of diagnosed schizophrenia spectrum disorders in Korea, 2008-2017: A nationwide population-based study using claims big data analysis.

This study estimated the prevalence and incidence rate of schizophrenia, schizotypal, and delusional disorders (SSDD) in Korea from 2008 to 2017 and analyzed the hospital admission rate, re-admission rate, and hospitalization period. It used the Korean nationwide National Health Insurance Service claims database. SSDD patients who had at least one visit to Korea’s primary, secondary, or tertiary referral hospitals with a diagnosis of SSDD, according to the International Classification of Diseases, 10th Revision (ICD-10), were identified as SSDD cases if coded as F20-F29. Data were analyzed using frequency statistics. Results showed that the 12-month prevalence rate of SSDD increased steadily from 0.40% in 2008 to 0.45% in 2017. Analysis of the three-year cumulative prevalence rate of SSDD showed an increase from 0.51% in 2011 to 0.54% in 2017. In 2017, the five-year cumulative prevalence rate was 0.61%, and the 10-year cumulative prevalence rate was 0.75%. The hospital admission rate among SSDD patients decreased from 2008 (30.04%) to 2017 (28.53%). The incidence of SSDD was 0.05% and no yearly change was observed. The proportion of SSDD inpatients whose first hospital visit resulted in immediate hospitalization was 22.4% in 2017. Epidemiological indicators such as prevalence, incidence, and hospitalization rate play an important role in planning social and financial resource allocation. Therefore, efforts to produce more accurate epidemiological indicators are very important and this study’s findings could have a significant social impact.

Cigarette smoking as a risk factor for schizophrenia or all non-affective psychoses.

Smoking tobacco is regarded as an epiphenomenon in patients with schizophrenia when it may be causal. We aimed to examine whether smoking status is related to the onset of schizophrenia or the broader diagnosis of non-affective psychosis, including schizophrenia. We used data from The Health Improvement Network primary care database to identify people aged 15-24 between 1 January 2004 and 31 December 2009. We followed them until the earliest of: first diagnosis of schizophrenia (or psychosis), patient left the practice, practice left THIN, patient died or 31 December 2014. In men, incidence rates for schizophrenia per 100 000 person years at risk were higher in smoking initiators (non-smoker who became a smoker during the study) than in non-smokers (adjusted IRR 1.94; 95% CI 1.29-2.91) and higher still in smokers (adjusted IRR 3.32; 95% CI 2.67-4.14). Among women, the incidence rate of schizophrenia was higher in smokers than in non-smokers (adjusted IRR 1.50; 95% CI 1.06-2.12), but no higher in smoking initiators than non-smokers. For non-affective psychosis, the pattern was similar for men but more evident in women where psychosis incidence rates were higher in smoking initiators (adjusted IRR 1.90; 95% CI 1.40-2.56) and in smokers (adjusted IRR 2.13; 95% CI 1.76-2.57) than in non-smokers. We found an important and strong association between smoking and incidence of schizophrenia. Smoking may increase risk through as yet unknown pathways or smoking may share genetic risk with schizophrenia and non-affective psychoses.

Neighbourhood and mortality in severe mental illness

Neighbourhood and mortality in severe mental illness

Racializing Mental Illness

All multiracial societies have to grapple with the benefits versus the costs of the integration of minorities into majority communities. Indeed, in relation to the costs of integration, it could be argued that integration and assimilation increases non-White people’s exposure to racialized experiences and racism, which in turn predisposes them to mental illness. As such, it is worth considering the case of the UK, where Black integration and assimilation is particularly intense, and where the high rates of schizophrenia in the African-Caribbean population have been an area of concern for over three decades. This paper argues that the interplay between racial minority status stress, racism-induced stress, and racial bias in diagnosis may be significant factors influencing the high Black incidence rate of schizophrenia in the UK.

Autoimmune diseases are associated with an increased risk of schizophrenia: A nationwide population-based cohort study

ObjectivesStudies have suggested a possible autoimmune contribution in a subset of patients with schizophrenia. The purpose of this study was to determine if a history of autoimmune diseases (AD) is associated with an increased risk of later onset of schizophrenia. MethodsTaiwan's National Health Insurance Research Database was used to identify a total of 64,817 AD patients and an equal number of age-matched control patients. The incidence rates of schizophrenia with a maximum follow-up period of 10 years between patients with and without AD were compared using a Cox proportional hazard model to estimate the hazard ratio (HR) and 95% confidence interval (95% CI). ResultsThe main finding was the discovery of a higher incidence of subsequent schizophrenia in patients with AD (HR: 1.72, 95% CI: 1.23–2.4) after adjustment for other demographic characteristics. Specifically, the risk of schizophrenia was observed to be a significant increase in systemic lupus erythematosus (3.73, 2.07–6.72), rheumatoid arthritis (2.89, 1.97–4.23), dermatomyositis (5.85, 1.32–25.94) and autoimmune vasculitis (2.44, 1.17–5.06). Also, this study revealed some potential risk factors for developing schizophrenia, including younger age (less than or equal to 50 years) and some comorbidities (hypertension, chronic obstructive pulmonary disease, and alcohol use disorder). Conversely, this study found that steroid use was a potential protective factor for the development of schizophrenia. ConclusionsThis study found that AD were associated with an increased risk of developing schizophrenia, suggesting that the abnormal autoimmune process was associated with an increase in the expression of psychiatric disturbances.

Certifiable Disability in First Episode Schizophrenia: The Role of Adherence to Antipsychotic Treatment

The incidence rate of schizophrenia in India is about 3 per 10,000 per year—every year around 200,000 individuals get afflicted with it. Patients with disability greater than 40 % are eligible for disability benefits from the government of India. However, it is not known as to what proportion of patients with new-onset schizophrenia would be eligible for this. At the National Institute of Mental Health and Neurosciences, Bangalore, 80 patients with FES were studied prospectively. Diagnosis was confirmed using the Computerized Diagnostic Interview Schedule Version-4. Disability was assessed after about 2 years of follow-up using the Indian Disability Assessment and Evaluation scale. Those with 40 % or more disability on the IDEAS were categorized as ‘disabled’. ‘Non-adherence’ was defined as a continuous 3 months period of not taking antipsychotic medication. At the end of 2 years of follow-up, 19/80 (23.8 %) of the 80 patients had met the criterion for certifiable disability. Only 3 (9.7 %) of the 31 patients who were adherent to medication met this criteria, vis-a-vis 16 (32.7 %) of the 49 who were non-adherent (p = 0.02; odds ratio = 4.52; 95 % CI: 1.2–17.2). Older age and higher psychopathology score were also associated with disability. Psychopathology emerged as a significant predictor of disability after controlling for the effects age and treatment adherence. Only a small proportion of patients with FES remain disabled if they are adherent to medications. Efforts towards enhancing adherence could be cost-effective from a public health perspective.

Migration Status, Familial Risk for Mental Disorder, and Schizotypal Personality Traits

Markedly raised incidence rates of schizophrenia and other psychotic disorders have been observed in several migrant and ethnic minority groups. To contribute to a better understanding of the elevated risk for psychotic disorders that is conferred by migration status, the present study examined effects associated with migration risk status on schizotypal personality traits, which are thought to reflect an underlying vulnerability to psychotic disorder. Effects of migration status were also compared to effects associated with a family history of psychopathology, which represents a robust nonspecific risk factor. We assessed schizotypal traits, using the Schizotypal Personality Questionnaire (SPQ), in a community-based sample of 62 Moroccan migrants and 41 Dutch nonmigrants, who were classified by the presence or absence of a family history of psychopathology. Overall, Moroccan migrants obtained higher SPQ scores than Dutch nonmigrants. However, migrants who had been classified as having a familial load of psychopathology displayed higher SPQ scores than migrants without such a family history, who in turn did not differ from Dutch nonmigrants. Furthermore, migrants with a familial load, relative to migrants without such a family history, reported higher levels of substance use and feelings of anxiety or depression, and perceived more often ethnic discrimination, which closely paralleled their SPQ scores. These findings indicate that primarily those migrants who are both intrinsically vulnerable and chronically exposed to social adversity, particularly ethnic discrimination, are at elevated risk for psychotic and other disorders. The results add to the evidence that migration status and perceived discrimination are associated with mental health.

Income inequality and schizophrenia: increased schizophrenia incidence in countries with high levels of income inequality.

Income inequality is associated with numerous negative health outcomes. There is evidence that ecological-level socio-environmental factors may increase risk for schizophrenia. The aim was to investigate whether measures of income inequality are associated with incidence of schizophrenia at the country level. We conducted a systematic review of incidence rates for schizophrenia, reported between 1975 and 2011. For each country, national measures of income inequality (Gini coefficient) along with covariate risk factors for schizophrenia were obtained. Multi-level mixed-effects Poisson regression was performed to investigate the relationship between Gini coefficients and incidence rates of schizophrenia controlling for covariates. One hundred and seven incidence rates (from 26 countries) were included. Mean incidence of schizophrenia was 18.50 per 100,000 (SD = 11.9; range = 1.7-67). There was a significant positive relationship between incidence rate of schizophrenia and Gini coefficient (β = 1.02; Z = 2.28; p = .02; 95% CI = 1.00, 1.03). Countries characterized by a large rich-poor gap may be at increased risk of schizophrenia. We suggest that income inequality impacts negatively on social cohesion, eroding social capital, and that chronic stress associated with living in highly disparate societies places individuals at risk of schizophrenia.

Annual incidence rate of schizophrenia and schizophrenia spectrum disorders in a longitudinal population-based cohort study

Longitudinal incidence studies of schizophrenia spectrum disorders (SSD) performed in mental health service organizations are prone to confounding factors not found in research performed in the general population. To estimate the incidence rates (IRs) over a 10-year period of SSD (broadly defined) and schizophrenia (narrowly defined) in the general population and to analyze associated risk factors. A cohort study (1996-2006) in a large general practitioners research database was conducted with longitudinal medical records of 350,524 patients throughout the Netherlands. Cases of SSD were identified and classified by systematic review of medical records. Age- and gender-specific IRs were calculated per calendar year, date of birth, degree of urbanicity and deprivation. Overall IR of SSD in this population was 22/100,000 person years (PY) (95% CI 19-24). IR of schizophrenia was 12/100,000 PY (95% CI 10-14). Period prevalence was 3.5 per 1,000 PY. IRs were higher in men compared to women, had a peak at age 15-25 years, decreasing rapidly after 25 years by 40% per 10 years. IRs of SSD were significantly higher in urban areas, irrespective of deprivation. No association was found between IRs of SSD and living in deprived areas or month of birth. There was no significant time trend of the IR during the period under study. IRs of SSD are higher in urban areas, independent of social deprivation. Age- and gender-specific differences in IR were found. The magnitude of these differences was larger in narrowly defined schizophrenia than in SSD.

Systematic review and collaborative recalculation of 133 693 incident cases of schizophrenia

This systematic review and collaborative recalculation was set up to recalculate schizophrenia incidence rates from previously published studies by age and sex. PubMed, EMBASE and PsycINFO databases were searched (January 1950 to December 2009) for schizophrenia incidence studies. Numerator and population data were extracted by age, sex and, if possible, study period. Original data were requested from the authors to calculate age- and sex-specific incidence rates. Incidence rate ratios (IRRs) with their 95% confidence intervals (CIs) were computed by age and sex from negative binomial regression models. Forty-three independent samples met inclusion criteria, yielding 133 693 incident cases of schizophrenia for analysis. Men had a 1.15-fold (95% CI 1.00-1.31) greater risk of schizophrenia than women. In men, incidence peaked at age 20-29 years (median rate 4.15/10,000 person-years, IRR 2.61, 95% CI 1.74-3.92). In women, incidence peaked at age 20-29 (median rate 1.71/10,000 person-years, IRR 2.34, 95% CI 1.66-3.28) and 30-39 years (median rate 1.24/10,000 person-years, IRR 2.25, 95% CI 1.55-3.28). This peak was followed by an age-incidence decline up to age 60 years that was stronger in men than in women (χ² = 57.90, p < 0.001). The relative risk of schizophrenia was greater in men up to age 39 years and this reversed to a greater relative risk in women over the age groups 50-70 years. No evidence for a second incidence peak in middle-aged women was found. Robust sex differences exist in the distribution of schizophrenia risk across the age span, suggesting differential susceptibility to schizophrenia for men and women at different stages of life.

Les facteurs de risque environnementaux de la schizophrénie

Evidence of variations in schizophrenia incidence rates has been found in genetically homogenous populations, depending on changes within time or space of certain environmental characteristics. The consideration of the impact of environmental risk factors in etiopathogenic studies has put the environment in the forefront of research regarding psychotic illnesses. Various environmental factors such as urbanicity, migration, cannabis, childhood traumas, infectious agents, obstetrical complications and psychosocial factors have been associated with the risk of developing schizophrenia. These risk factors can be biological, physical, psychological as well as social and may operate at different times in an individual's life (fetal period, childhood, adolescence and early adulthood). Whilst some of these factors act on an individual level, others act on a populational level, modulating the individual risk. These factors can have a direct action on the development of schizophrenia, or on the other hand act as markers for directly implicated factors that have not yet been identified. This article summarizes the current knowledge on this subject. An extensive literature search was conducted via the search engine Pubmed. Eight risk factors were selected and developed in the following paper: urbanicity (or living in an urban area), cannabis, migration (and ethnic density), obstetrical complications, seasonality of birth, infectious agents (and inflammatory responses), socio-demographic factors and childhood traumas. For each of these factors, we provide information on the importance of the risk, the vulnerability period, hypotheses made on the possible mechanisms behind the factors and the level of proof the current research offers (good, medium, or insufficient) according to the amount, type, quality and concordance of the studies at hand. Some factors, such as cannabis, are "unique" in their influence on the development of schizophrenia since it labels only one risk factor. Others, such as obstetrical complications, are grouped (or "composed") in that they include various sub-factors that can influence the development of schizophrenia. The data reviewed clearly demonstrates that environmental factors have an influence on the risk of developing schizophrenia. For certain factors - cannabis, migration, urbanicity, obstetrical complications, seasonality - there is enough evidence to establish an association with the risk of schizophrenia. This association, however, remains weak (especially for seasonality). With the exception of cannabis, no direct link can yet be established. Concerning the three remaining factors - childhood traumas, infectious agents, socio-demographic factors - the available proof is insufficient. One main limitation concerning all environmental factors is the generalization of results due to the fact that the studies were conducted on geographically limited populations. The current state of knowledge does not allow us to determine the mechanisms by which these factors may act. Further research is needed to fill the gaps in our understanding of the subject. In response to this need, a collaborative European project (European Study of Gene-Environment Interactions [EU GEI]) was set-up. This study proposes the analysis of those environmental factors that influence the incidence of schizophrenia in various European countries, in both rural and urban settings, migrant and native populations, as well as their interaction with genetic factors.

Changes in the diagnosed incidence of early onset schizophrenia over four decades

To explore changes in the diagnosed incidence of early onset schizophrenia (EOS) from 1971 to 2010. Examination of incidence rates of schizophrenia in patients under 18 years of age, using a nationwide, population-based, mental health register. The age-standardized incidence rate (IR) of EOS in the period 1971-2010 was 3.17 (95% CI: 3.16, 3.18) per 100 000 person years in the age group 0-18 years, and 9.10 (95% CI: 9.00, 9.21) in the age group 12-18 years. In the period 1971-1993, the age-standardized IR of EOS was 1.80 (95% CI: 1.79, 1.82) per 100 000 person years in the age group 0-18 years, and 5.02 (95% CI: 4.92, 5.11) in the age group 12-18 years. In the period 1994-2010, the age-standardized IR of EOS was 5.15 (95% CI: 5.10, 5.20) per 100 000 person years in the age group 0-18 years, and 15.73 (95% CI: 15.22, 16.22) in the age group 12-18 years. The IR was higher for males than females in the periods 1971-1993 and 1971-2010, but in the period 1994-2010 the IR was higher for females than males. In recent years, the diagnosed incidence of EOS has increased and the usual male excess has disappeared. The changes in IR could be a result of changes in the diagnostic system, increased awareness of early psychosis or a reflection of actual underlying incidence of the disorder.

Immigration, Social Environment and Onset of Psychotic Disorders

The recent decade has been characterized by a resurging interest for socio-environmental determinants of psychotic disorders, largely as a result of findings from studies of migration and psychotic disorders. This contribution reviews recent meta-analytic findings which confirm higher incidence rates of schizophrenia and related disorders among first- and second-generation immigrants than in non-immigrant populations, as well as substantial risk variation according to both ethnic minority groups and host society contexts. The relevance of social contexts in the onset of psychosis is also suggested by incidence variation according to the neighbourhood level ethnic density. While limited, an emerging literature suggests potential variations in psychotic-like experiences and at-risk mental states according to ethnic minority status. We then discuss the meaning of findings from migrant studies, as well as integrative models that attempt to account for ethnic variations in the incidence of psychosis and psychotic-like phenomena. In conclusion, there remain numerous gaps in our understanding of the relation between migration, ethnicity, social contexts and the onset of psychosis and we propose future research avenues to address these. In particular, there is a need for multilevel approaches integrating disciplines and methodologies across the psychosis continuum.

No association observed between schizophrenia and non‐HLA coeliac disease genes: Integration with the initial MYO9B association with coeliac disease

Schizophrenia is a severe psychotic illness with a heterogeneous presentation and a devastating impact on social and occupational function. Worldwide variations in schizophrenia incidence rates suggest that local conditions may modify disease risk. The human leukocyte antigen (HLA) region has been confirmed to be associated with schizophrenia by genome-wide association studies in populations across the world. While the presence of autoimmune processes in a subgroup of schizophrenia cases is contentious, the immune system could allow environmental exposures to lead to schizophrenia by generating improper immune response. To investigate this topic, we reviewed the current evidence of the relationship between schizophrenia and coeliac disease. Based on this review, we performed genetic analysis of the MYO9B gene and the IL-2/IL-21 locus by genotyping SNPs that have been previously associated with coeliac disease or schizophrenia in 223 families, 108 unrelated individuals with schizophrenia and 120 controls. Finding no evidence for association with these two loci in our study samples, we applied meta-analytic techniques to combine our findings with previous reports. This synthesis, in light of our review of previous reports, suggests a differing developmental trajectory for schizophrenia and coeliac disease. It is possible that these two conditions do not share any functional overlap.

Do risk factors for schizophrenia predispose to emigration?

ObjectiveIncreased incidence rates of schizophrenia in immigrants still lack a satisfactory explanation. The aim of this study was to examine the hypothesis that risk factors for schizophrenia also increase the risk of emigration to a foreign country. If valid, Danes emigrating from Denmark carry a higher predisposition to develop schizophrenia compared to Danes living in Denmark. MethodsUtilizing data from the Danish Civil Registration System, we established a population-based cohort of 1.10 million native Danes. We assessed relative risks of emigration to a foreign country in relation to sex, age, urban birth, parental age, and a history of mental illness. ResultsUrban birth in Denmark was a significant predictor of emigration to a foreign country. A maternal history of psychiatric contact during childhood and a parental history of bipolar affective disorder increased the risks of emigration. A personal history of mental illness decreased the risk of emigration, mostly for people diagnosed with schizophrenia. ConclusionsOur study provided evidence that Danish emigrants residing in a foreign country have both a higher predisposition of schizophrenia due to differential exposure to birth in urban areas and a lower predisposition of schizophrenia due to differential exposure to a history of mental illness. Although competing selection mechanisms operate, the combined effect of these different selection mechanisms was limited, thus suggesting a potential role for yet to be identified adverse environmental effects operating either before or after emigration.

The Stockholm non‐affective psychoses study (snaps): the importance of including out‐patient data in incidence studies

To estimate the incidence rate of schizophrenia and non-affective psychoses from registers, to highlight the importance of including data from out-patient care, and to assess the proportion of persons treated in out-patient care only. Data from out-patient and in-patient psychiatric care in Stockholm and information from several national registers constitute 'The Stockholm Non-Affective Psychoses Study' (SNAPS). Incidence rates based on SNAPS data were calculated and compared to in-patient care incidence rates. The incidence rate was 72/100 000 for non-affective psychoses (age group 18-44) and 28/100 000 for schizophrenia (age group 18-34) in the SNAPS. This was higher compared to in-patient based incidence rates (42 and 13/100 000 respectively). The proportion of individuals with psychosis treated in out-patient care only was 25%. There are substantial differences in the incidence rates of non-affective psychoses and schizophrenia depending on the availability of data. Not including out-patient care will underestimate the incidence rates.

The need for culture sensitive diagnostic procedures

We examine the procedural validity of a standardized instrument for the diagnosis of psychotic disorders in Morocco. Twenty-nine patients from Casablanca, Morocco, with a psychotic or mood disorder were examined using the Comprehensive Assessment of Symptoms and History (CASH) an adapted version using cultural formulation to make the instrument more culturally sensitive (CASH-CS). Chance corrected agreement was calculated between diagnoses based on these two versions of CASH and independent clinical diagnoses according to local psychiatrists. Agreement for traditional CASH versus clinical diagnosis and for CASH versus CASH-CS was low (kappa = -0.19; SD 0.16 and kappa = 0.21; SD 0.16, respectively). De CASH-CS, showed good agreement with clinical diagnosis (kappa = 0.79; SD 0.11). Standardized instruments for the assessment of psychosis such as the CASH may be liable to cultural misinterpretations. This may be relevant to the interpretation of the high incidence rates of schizophrenia among immigrants. Agreement between a culturally naïve version of a standardized diagnostic instrument for the assessment of psychosis and clinical diagnosis by Moroccan psychiatrists is poor. Adding additional probes and decision rules based on cultural formulation improves agreement with clinical diagnosis significantly. The study was conducted in a small sample. Both versions of CASH were administered by the same interviewer in a single interview session.

Hospital‐treated psychosis and suicide in a rural community (1877–2005). Part 1: Incidence rates

To calculate the incidence rates of hospital-treated psychosis and suicide in historical cohorts of a small rural community in southeast Norway, and to compare the local findings with the national ones. We have carried out a longitudinal epidemiological study, reviewing the patient records at the mental hospitals of people born in the rural community after 1845. Based on these records, we have constructed a local register of psychosis and suicide in this population. The local incidence rates of psychosis and suicide have been compared with the national ones. The overall local incidence rates of psychosis and suicide were similar to the national ones. The local rates of schizophrenia dropped considerably after World War II. The overall local incidence rates of psychosis and suicide seem to be representative for the country at large despite frequent endogamy. The recent drop in the incidence rate of schizophrenia seems to be in agreement with several international studies.