Increase in schizophrenia incidence rates: findings in a Canadian cohort born 1975-1985

Risk of Diagnosed Adolescent-Onset Non-Affective Psychotic Disorder by Migration Background in British Columbia: A Retrospective Cohort Study

OBJECTIVE

We recently found that the risk of diagnosed non-affective psychotic disorder between the ages of 13 and 19 was lower for immigrant adolescents compared to those without a personal or parental migration history in British Columbia (BC), Canada. In the current study, we further examined the risk for migrants compared to non-migrants by region of origin and immigrant generation (first vs. second), adjusting for several demographic factors and migration class.

METHODS

Administrative data were used to construct a cohort of individuals born 1990-98 and residing in South-Western BC (N = 193,400). Cases were identified by either one hospitalization or two outpatient physician visits with a primary diagnosis of a non-affective psychotic disorder. Poisson regression was used to estimate incidence rate ratios (IRR) of a diagnosed non-affective psychotic disorder by region of origin among first- and second-generation migrants compared to non-migrants, adjusting for sex, birth year, neighbourhood income and low family income.

RESULTS

Risk of diagnosed non-affective psychotic disorder was lower among first-generation migrants from East Asia (IRR = 0.34[95% CI: 0.25-0.46]), South-Asia (IRR = 0.47[95% CI: 0.25-0.89]) and South-East Asia (IRR = 0.55[95% CI: 0.32-0.93]) and second-generation migrants from East Asia (IRR = 0.49[95% CI: 0.35-0.69]) and South Asia (IRR = 0.52[95% CI: 0.37-0.73]), compared to non-migrants. Adjusting for migration class attenuated but did not fully explain variation in risk by region among first-generation migrants. No groups exhibited a significantly elevated risk of the diagnosed non-affective psychotic disorder compared to non-migrants.

CONCLUSION

Findings from this study underline the complexity of the association between migration and psychotic disorders. Future research should investigate why certain groups of migrants are less likely to be diagnosed and whether there are specific sub-groups that face an elevated risk.

Diagnosed Incidence of Non-Affective Psychotic Disorders Amongst Adolescents in British Columbia and Sociodemographic Risk Factors: A Retrospective Cohort Study

OBJECTIVES

To estimate the diagnosed incidence of non-affective psychotic disorder between the ages of 13 and 19 years in South-Western British Columbia (BC) and to examine variation in risk by sex, family and neighbourhood income, family migration background, parent mental health contact and birth year.

METHODS

Linked individual-level administrative data were used to construct a cohort of individuals born in 1990-1998 and residing in South-Western BC (n = 193,400). Cases were identified by either one hospitalization or two outpatient physician visits within 2 years with a primary diagnosis of a non-affective psychotic disorder (ICD-10: F20-29, ICD-9: 295, 297, 298). We estimated cumulative incidence, annual cumulative incidence and incidence rate between the ages of 13 and 19 years, and conducted Cox proportional hazards regression to estimate associations between sociodemographic factors and risk over the study period.

RESULTS

We found that 0.64% of females and 0.88% of males were diagnosed with a non-affective psychotic disorder between the ages of 13 and 19 years, with increasing risk observed over the age range, especially amongst males. Incidence rate over the entire study period was 106 per 100,000 person-years for females and 145 per 100,000 person-years for males. Risk of diagnosis was elevated amongst those in low-income families and neighbourhoods, those with a parent who had a health service contact for a mental disorder, and more recent birth cohorts. Risk was reduced amongst children of immigrants compared to children of non-migrants.

CONCLUSIONS

Findings from this study provide important information for health service planning in South-Western BC. Future work should examine whether variations in diagnosed incidence is driven by differences in health service engagement or reflect genuine differences in risk.

Incidence Rates and Cumulative Incidences of the Full Spectrum of Diagnosed Mental Disorders in Childhood and Adolescence

IMPORTANCE

Knowledge about the epidemiology of mental disorders in children and adolescents is essential for research and planning of health services. Surveys can provide prevalence rates, whereas population-based registers are instrumental to obtain precise estimates of incidence rates and risks.

OBJECTIVE

To estimate age- and sex-specific incidence rates and risks of being diagnosed with any mental disorder during childhood and adolescence.

DESIGN

This cohort study included all individuals born in Denmark from January 1, 1995, through December 31, 2016 (1.3 million), and followed up from birth until December 31, 2016, or the date of death, emigration, disappearance, or diagnosis of 1 of the mental disorders examined (14.4 million person-years of follow-up). Data were analyzed from September 14, 2018, through June 11, 2019.

EXPOSURES

Age and sex.

MAIN OUTCOMES AND MEASURES

Incidence rates and cumulative incidences of all mental disorders according to the ICD-10 Classification of Mental and Behavioral Disorders: Diagnostic Criteria for Research, diagnosed before 18 years of age during the study period.

RESULTS

A total of 99 926 individuals (15.01%; 95% CI, 14.98%-15.17%), including 41 350 girls (14.63%; 95% CI, 14.48%-14.77%) and 58 576 boys (15.51%; 95% CI, 15.18%-15.84%), were diagnosed with a mental disorder before 18 years of age. Anxiety disorder was the most common diagnosis in girls (7.85%; 95% CI, 7.74%-7.97%); attention-deficit/hyperactivity disorder (ADHD) was the most common in boys (5.90%; 95% CI, 5.76%-6.03%). Girls had a higher risk than boys of schizophrenia (0.76% [95% CI, 0.72%-0.80%] vs 0.48% [95% CI, 0.39%-0.59%]), obsessive-compulsive disorder (0.96% [95% CI, 0.92%-1.00%] vs 0.63% [95% CI, 0.56%-0.72%]), and mood disorders (2.54% [95% CI, 2.47%-2.61%] vs 1.10% [95% CI, 0.84%-1.21%]). Incidence peaked earlier in boys than girls in ADHD (8 vs 17 years of age), intellectual disability (5 vs 14 years of age), and other developmental disorders (5 vs 16 years of age). The overall risk of being diagnosed with a mental disorder before 6 years of age was 2.13% (95% CI, 2.11%-2.16%) and was higher in boys (2.78% [95% CI, 2.44%-3.15%]) than in girls (1.45% [95% CI, 1.42%-1.49%]).

CONCLUSIONS AND RELEVANCE

This nationwide population-based cohort study provides a first comprehensive assessment of the incidence and risks of mental disorders in childhood and adolescence. By 18 years of age, 15.01% of children and adolescents in this study were diagnosed with a mental disorder. The incidence of several neurodevelopmental disorders peaked in late adolescence in girls, suggesting possible delayed detection. The distinct signatures of the different mental disorders with respect to sex and age may have important implications for service planning and etiological research.

Annual Prevalence and Incidence of Schizophrenia and Similar Psychotic Disorders in the Republic of Korea: A National Health Insurance Data-Based Study

OBJECTIVE

We conducted this study to address the incidence and prevalence of schizophrenia and similar psychosis in South Korea with Health Insurance Review and Assessment (HIRA) database.

METHODS

We used HIRA database, which includes diagnostic information of nearly all Korean nationals to collect number of cases with diagnosis of schizophrenia and schizophrenia-similar disorders (SSP), including schizophreniform, acute/transient psychotic disorders, schizoaffective disorders, and other/unspecific nonorganic psychosis (ICD-10 codes F20/23/25/28/29) between 2010 and 2015. The annual prevalence and incidence were calculated using the population data from the Korean Statistical Office.

RESULTS

The 12-month prevalence of SSP of Korea between 2010 and 2015 were 0.48-0.66%. The 12-month prevalence of schizophrenia were 0.40-0.52%; The annual incidence rates (IR) of SSP between 2010 and 2015 were 118.8-148.7 per 100,000 person-year (PY). For schizophrenia, IR per 100,000 PY were 77.6-88.5 between 2010 and 2015.

CONCLUSION

The 12-month prevalence found in the present study was higher than that reported in community-based epidemiologic studies in South Korea but similar to those from other countries. The annual incidence of SSP and schizophrenia was found to steadily increase and was higher than that of other countries. The high incidence rate observed in the current study needs to be studied further.

Decline in the severity or the incidence of schizophrenia in Japan: A survey of university students

Clinical manifestations of schizophrenia are believed to be becoming less severe in Japan, but little evidence supports this theory. We investigated the percentages of undergraduate students attending national universities in Japan who required temporary leave and who dropped out because of schizophrenia in the academic years 1986-1987, 1994-1995, and 2013-2014. The percentages of students who required temporary leave and those who dropped out because of schizophrenia significantly decreased over time. The severity of clinical manifestations of schizophrenia may have decreased, enabling more students with schizophrenia to continue their study, or the incidence of schizophrenia might have declined.

Comparing cohort incidence of schizophrenia with that of bipolar disorder and affective psychosis in individuals born in Stockholm County 1955-1967

BACKGROUND

Perinatal factors are associated with increased risk for both schizophrenia and bipolar disorder. Improvements in obstetric and maternal healthcare and positive socioeconomic development in Sweden from the 1950s onwards could be expected to affect incidence estimates. However, commonly incidence rates are calculated during a specific year, i.e. time of diagnosis, which mirrors proximal precipitating risk factors. To examine whether incidence estimates are compatible with the hypothesis of an impact of perinatal exposures on the risk of the different disorders we here instead calculate incidence rates for consecutive birth cohorts born between 1955 and 1967. We hypothesized that schizophrenia incidence would be more affected compared to bipolar disorder and other affective psychoses since most perinatal risk factors are more pronounced in schizophrenia aetiology.

METHOD

Birth cohorts of individuals born in Sweden and resident in Stockholm (N = 2,16,322), were followed in The National Patient Register regarding incident inpatient episodes Incident cases/10,000 person-years and birth cohort were calculated. Linear regression was used to estimate change in incidence rate.

RESULTS

We found stable birth cohort-based incidence estimates for bipolar disorder and other affective psychoses, but a continuous reduction in incidence estimates for schizophrenia as well as other non-affective psychoses in subsequent birth cohorts from 1955 to 1967.

CONCLUSIONS

The consecutive birth cohort-based incidence estimates unveiled patterns that are compatible with the hypothesis of an impact of early life exposures decreasing over time, in the aetiology of schizophrenia, whereas this pattern is less apparent in affective psychoses..

Direct comparison of first-contact versus longitudinal register-based case finding in the same population: early evidence that the incidence of schizophrenia may be three times higher than commonly reported

BACKGROUND

The incidence of schizophrenia is commonly estimated by screening for psychosis among subjects presenting to psychiatric services. This approach (using a first-contact sampling frame) cannot account for cases that did not meet criteria for schizophrenia at first contact. We compared the usual approach directly with a register-based approach (using a longitudinal sampling frame) that also includes subjects initially diagnosed with other non-schizophrenic disorders.

METHOD

We compared data from the Longitudinal Psychiatric Register (LPR) of The Hague over 1980-2009 with data previously collected in a first-contact study, and applied both methods to calculate the incidence of schizophrenia for subjects aged 20-54 years in the same catchment area and over the same period (October 2000 to September 2005). We reconstructed treatment pathways and diagnostic histories up to the end of 2009 and performed sensitivity analyses.

RESULTS

The LPR identified 843 first onsets of schizophrenia, corresponding to a treated incidence rate (IR) of 69 per 100,000 person-years [95% confidence interval (CI) 64-74]. The first-contact study identified 254 first onsets, corresponding to a treated IR of 21 per 100,000 person-years (95% CI 18-23). Two-thirds of the difference was accounted for by subjects treated for other disorders before the onset of psychosis, and by patients in older age groups.

CONCLUSIONS

The incidence of schizophrenia was three times higher in a longitudinal register study than in a high-quality first-contact study conducted in the same population. Risk estimates based only on first-contact studies may have been affected by selection bias.

A population-based cohort study to elucidate temporal relationship between schizophrenia and metabolic syndrome (KCIS no. PSY3)

BACKGROUND

The bidirectional relationships between metabolic syndrome (MetS) and schizophrenia (SCZ) play a crucial role in clinical treatment of both diseases but such bidirectional causal effects have not been comprehensively elucidated.

AIMS

To investigate the influence of MetS on incident SCZ and the opposite direction as well as their predictors for each direction with a population-based cohort sample.

METHOD

We enrolled 76,545 subjects who had participated in a community-based health screening program during 1999-2004. After excluding those with the existing MetS or SCZ at baseline, the two normal prospective cohorts corresponding to each independent variable of MetS or SCZ, respectively, were followed over time to ascertain incident outcome of SCZ and MetS. The crude and adjusted hazard ratios for the effect of the predictor on each incident outcome were estimated after controlling for the possible confounding factors.

RESULTS

The overall incidence rate (per 10(5)person-years) of SCZ was 61.15. The incidence rate in patients with MetS was lower than those without (44.24 versus 64.20), indicating the presence of MetS failed to find an increased risk of developing incident SCZ. However, participants with abnormal waist circumference (WC) were two times (95% CI: 1.37 to 2.93) more likely to yield incident SCZ compared to those with normal WC. In the opposite direction, the incidence of MetS was statistically higher in patients with SCZ than those without SCZ (11.25% vs 7.94%, respectively), suggesting SCZ conferred a higher risk for yielding incident MetS (adjusted hazard ratio=1.89, 95% CI: 1.36, 2.63).

CONCLUSIONS

After examining the bidirectional causal relationships between SCZ and MetS with the theoretically sound and large population-based prospective cohort study, central obesity, one of the individual components of MetS, was corroborated as an independent predictor for incident SCZ. Patients diagnosed with SCZ were at greater risk of having incident cases of MetS. Such significant temporal bidirectional relationships between SCZ and central obesity suggest a reciprocal interaction exits between SCZ and central obesity.

Are the rates of schizophrenia unusually high in Canada? A comparison of Canadian and international data

Two major risk factors for schizophrenia are present in Canada, high latitude and a large and growing immigrant population. Consequently, one would expect unusually high rates of schizophrenia and an increase in these rates over time. This systematic review tests these two hypotheses. Searches of electronic databases were performed through 2011. Out of 45 studies 12 fulfilled all the inclusion criteria. The means of Canadian and international rates were compared by one-tailed unequal variance t-test. Trends with time in Canadian rates were tested by the Spearman rank correlation coefficient. Prevalence and incidence rates in Canada were significantly higher than those in international studies. Rates increased over time, with a significant increase for prevalence and a trend for incidence. This rise was supported by historical data, recent hospital admission data, and the only Canadian cohort study. The findings of elevated rates in Canada and their increase over time give concern due to the serious personal, social, and financial burden of schizophrenia. These results, based on a small number of studies, warrant confirmation by specially designed studies. They could explain the discrepant results of the risk associated with immigration in Canadian studies.

The incidence of first-episode schizophrenia-spectrum psychosis in adolescents and young adults in montreal: an estimate from an administrative claims database

OBJECTIVE

There has been increasing interest in the psychiatric literature on research and service delivery focused on first-episode psychosis (FEP), and accurate information on the incidence of FEP is crucial for the development of services targeting patients in the early stages of illness. We sought to obtain a population-based estimate of the incidence of first-episode schizophrenia-spectrum psychosis (SSP) among adolescents and young adults in Montreal.

METHODS

Population-based administrative data from physician billings, hospitalizations, pharmacies, and public health clinics were used to estimate the incidence of first-episode SSP in Montreal. A 3-year period (2004-2006) was used to identify patients with SSP aged 14 to 25 years. We used a 4- to 6-year clearance period to remove patients with a history of any psychotic disorder or prescription for an antipsychotic.

RESULTS

We identified 456 patients with SSP, yielding a standardized annual incidence of 82.9 per 100 000 for males (95% CI 73.7 to 92.1), and 32.2 per 100 000 for females (95% CI 26.7 to 37.8). Using ecologic indicators of material and social deprivation, we found a higher-incidence proportion of SSP among people living in the most deprived areas, relative to people living in the least deprived areas.

CONCLUSIONS

Clinical samples obtained from psychiatric services are unlikely to capture all treatment-seeking patients, and epidemiologic surveys have resource-intensive constraints, making this approach challenging for rare forms of psychopathology; therefore, population-based administrative data may be a useful tool for studying the frequency of psychotic disorders.

Treatment prevalence and incidence of schizophrenia in Quebec using a population health services perspective: different algorithms, different estimates

PURPOSE

Using a population health services perspective, this article defines and assesses an efficient criteria-based algorithm to identify treatment prevalent and incident cases of schizophrenia. We refer here "treatment" prevalence and incidence since its evaluation depends on a patient receiving a health care service with a diagnosis of schizophrenia.

METHODS

A population-based cohort study was conducted among all adults having a hospital discharge or a physician claim for schizophrenia in the public health plan databases between January 1996 and December 2006. Four algorithms to characterize patients with schizophrenia were defined. To identify treatment incident cases in 2006, we removed from the treatment prevalent pool patients with a previous record of schizophrenia between 1996 and 2006 (10-year clearance period). Using this 10-year period as reference, Kappa coefficients (KC) and positive predictive values (PPV) were calculated to determine the "optimal" length of clearance period to identify incident cases.

RESULTS

The lifetime treatment prevalence and incidence of schizophrenia varied from 0.59 to 1.46% and from 42 to 94 per 100,000, respectively. When compared to the 10-year clearance period, the KC is excellent in a clearance period of 6-7 years. To achieve a PPV of 90%, a clearance period of 7-8 years would be necessary.

CONCLUSIONS

With an appropriate algorithm, treatment prevalence and incidence of schizophrenia can be conveniently estimated using administrative data. These estimates are a vital step toward appropriate planning of services for schizophrenia.

Incidence of hospitalised schizophrenia in Finland since 1980: decreasing and increasing again

BACKGROUND

It is suggested that the incidence of schizophrenia is decreasing. However, changes in the number of psychiatric beds available and diagnostic practice have not always been taken into account. We studied the annual first-admission rate (per 100,000) for schizophrenia (FARsch) during a rapid deinstitutionalisation period in Finland.

METHOD

From the National Finnish Hospital discharge register, we identified all 30,041, 15- to 64-year-old patients admitted for the first time with schizophrenia to hospitals in Finland between 1980 and 2003.

RESULTS

FARsch decreased from 56.39 in 1980 to 29.51 in 1991 and slightly increased thereafter. Changes in FARsch corresponded with changes in all admissions. FARsch was higher when using ICD-8, but lower when DSM-IIIR and ICD-10 were used.

CONCLUSION

Changes in the number of psychiatric beds available, admission policy and diagnostic practice may explain the majority of variations in FARsch. Possibly, increased use of illegal drugs and improved treatment of depression are reflected in the increase in FARsch.

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

OBJECTIVE

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.

METHOD

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.

RESULTS

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%.

CONCLUSION

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.

Ethnic origin and increased risk for schizophrenia in immigrants to countries of recent and longstanding immigration

OBJECTIVES

Compare the risk for schizophrenia in immigrants to countries of recent and longstanding immigration. Compare prevalence and incidence rates in black subjects under different conditions.

METHOD

An electronic literature search was complemented by review articles and cross-references. Studies reporting standard diagnosis and incidence or prevalence rates were included.

RESULTS

Immigrants had an increased risk for schizophrenia in countries of longstanding immigration, but with lower risk ratios than in those of recent immigration. The risk was higher in black immigrants and the black population living in the United States. But incidence and prevalence rates in Africa and the Caribbean were similar to those of international studies.

CONCLUSION

Comparing the most recent generation of immigrants with descendants of previous ones may account for the lower risk ratios observed in countries of longstanding vs. recent immigration. Two neurobiological hypotheses are proposed to explain the epidemiological findings in black populations and in immigrants.

Epidemiological factors associated with treated incidence of first-episode non-affective psychosis in Cantabria: insights from the Clinical Programme on Early Phases of Psychosis

AIM

The aim of the study was to analyse the treated incidence of schizophrenia in Cantabria (Northern Spain) and the sociodemographic risk factors associated with the illness onset.

METHODS

Data were obtained from patients included in the Cantabria's Clinical Programme on First-Episode Psychosis (schizophrenia spectrum DSM-IV diagnosis) from 2001 to 2005, from the Cantabria first-episode schizophrenia study (carried out between 1988 and 1989) and from the 2001 Spanish census.

RESULTS

Annual incidence was 1.38 per 10,000 inhabitants in the risk-ageperiod. Identified risk factors were male gender (relative risk (RR): 1.61), age 15-25 years (RR: 3.48), unemployment (RR: 2.82), single status (RR: 5.88), low educational level (RR: 4.38), urban environment (RR: 1.62) and cannabis consumption (odds ratio: 12.83). The incidence in females was significantly lower than the one obtained 15 years ago.

CONCLUSIONS

The reported factors suggest that underlying biological and social factors modulate the risk of psychosis. This balance operates differently in males and females.