David Chant

A Systematic Review of the Prevalence of Schizophrenia

Background Understanding the prevalence of schizophrenia has important implications for both health service planning and risk factor epidemiology. The aims of this review are to systematically identify and collate studies describing the prevalence of schizophrenia, to summarize the findings of these studies, and to explore selected factors that may influence prevalence estimates. Methods and Findings Studies with original data related to the prevalence of schizophrenia (published 1965–2002) were identified via searching electronic databases, reviewing citations, and writing to authors. These studies were divided into “core” studies, “migrant” studies, and studies based on “other special groups.” Between- and within-study filters were applied in order to identify discrete prevalence estimates. Cumulative plots of prevalence estimates were made and the distributions described when the underlying estimates were sorted according to prevalence type (point, period, lifetime, and lifetime morbid risk). Based on combined prevalence estimates, the influence of selected key variables was examined (sex, urbanicity, migrant status, country economic index, and study quality). A total of 1,721 prevalence estimates from 188 studies were identified. These estimates were drawn from 46 countries, and were based on an estimated 154,140 potentially overlapping prevalent cases. We identified 132 core studies, 15 migrant studies, and 41 studies based on other special groups. The median values per 1,000 persons (10%–90% quantiles) for the distributions for point, period, lifetime, and lifetime morbid risk were 4.6 (1.9–10.0), 3.3 (1.3–8.2), 4.0 (1.6–12.1), and 7.2 (3.1–27.1), respectively. Based on combined prevalence estimates, we found no significant difference (a) between males and females, or (b) between urban, rural, and mixed sites. The prevalence of schizophrenia in migrants was higher compared to native-born individuals: the migrant-to-native-born ratio median (10%–90% quantile) was 1.8 (0.9–6.4). When sites were grouped by economic status, prevalence estimates from “least developed” countries were significantly lower than those from both “emerging” and “developed” sites (p = 0.04). Studies that scored higher on a quality score had significantly higher prevalence estimates (p = 0.02). Conclusions There is a wealth of data about the prevalence of schizophrenia. These gradients, and the variability found in prevalence estimate distributions, can provide direction for future hypothesis-driven research.

Schizophrenia: A Concise Overview of Incidence, Prevalence, and Mortality

Recent systematic reviews have encouraged the psychiatric research community to reevaluate the contours of schizophrenia epidemiology. This paper provides a concise overview of three related systematic reviews on the incidence, prevalence, and mortality associated with schizophrenia. The reviews shared key methodological features regarding search strategies, analysis of the distribution of the frequency estimates, and exploration of the influence of key variables (sex, migrant status, urbanicity, secular trend, economic status, and latitude). Contrary to previous interpretations, the incidence of schizophrenia shows prominent variation between sites. The median incidence of schizophrenia was 15.2/100,000 persons, and the central 80% of estimates varied over a fivefold range (7.7-43.0/100,000). The rate ratio for males:females was 1.4:1. Prevalence estimates also show prominent variation. The median lifetime morbid risk for schizophrenia was 7.2/1,000 persons. On the basis of the standardized mortality ratio, people with schizophrenia have a two- to threefold increased risk of dying (median standardized mortality ratio = 2.6 for all-cause mortality), and this differential gap in mortality has increased over recent decades. Compared with native-born individuals, migrants have an increased incidence and prevalence of schizophrenia. Exposures related to urbanicity, economic status, and latitude are also associated with various frequency measures. In conclusion, the epidemiology of schizophrenia is characterized by prominent variability and gradients that can help guide future research.

A systematic review of the incidence of schizophrenia: the distribution of rates and the influence of sex, urbanicity, migrant status and methodology

BackgroundUnderstanding variations in the incidence of schizophrenia is a crucial step in unravelling the aetiology of this group of disorders. The aims of this review are to systematically identify studies related to the incidence of schizophrenia, to describe the key features of these studies, and to explore the distribution of rates derived from these studies.MethodsStudies with original data related to the incidence of schizophrenia (published 1965–2001) were identified via searching electronic databases, reviewing citations and writing to authors. These studies were divided into core studies, migrant studies, cohort studies and studies based on Other Special Groups. Between- and within-study filters were applied in order to identify discrete rates. Cumulative plots of these rates were made and these distributions were compared when the underlying rates were sorted according to sex, urbanicity, migrant status and various methodological features.ResultsWe identified 100 core studies, 24 migrant studies, 23 cohort studies and 14 studies based on Other Special Groups. These studies, which were drawn from 33 countries, generated a total of 1,458 rates. Based on discrete core data for persons (55 studies and 170 rates), the distribution of rates was asymmetric and had a median value (10%–90% quantile) of 15.2 (7.7–43.0) per 100,000. The distribution of rates was significantly higher in males compared to females; the male/female rate ratio median (10%–90% quantile) was 1.40 (0.9–2.4). Those studies conducted in urban versus mixed urban-rural catchment areas generated significantly higher rate distributions. The distribution of rates in migrants was significantly higher compared to native-born; the migrant/native-born rate ratio median (10%–90% quantile) was 4.6 (1.0–12.8). Apart from the finding that older studies reported higher rates, other study features were not associated with significantly different rate distributions (e.g. overall quality, methods related to case finding, diagnostic confirmation and criteria, the use of age-standardization and age range).ConclusionsThere is a wealth of data available on the incidence of schizophrenia. The width and skew of the rate distribution, and the significant impact of sex, urbanicity and migrant status on these distributions, indicate substantial variations in the incidence of schizophrenia.

Vitamin D supplementation during the first year of life and risk of schizophrenia: A Finnish birth-cohort study

OBJECTIVE Based on clues from epidemiology and animal experiments, low vitamin D during early life has been proposed as a risk factor for schizophrenia. The aim of this study was to explore the association between the use of vitamin D supplements during the first year of life and risk of developing schizophrenia. METHOD Subjects were drawn from the Northern Finland 1966 Birth Cohort (n=9,114). During the first year of life, data were collected about the frequency and dose of vitamin D supplementation. Our primary outcome measures were schizophrenia, psychotic disorders other than schizophrenia, and nonpsychotic disorders as diagnosed by age 31 years. Males and females were examined separately. RESULTS In males, the use of either irregular or regular vitamin D supplements was associated with a reduced risk of schizophrenia (Risk ratio (RR)=0.08, 95% CI 0.01-0.95; RR=0.12, 95% CI 0.02-0.90, respectively) compared with no supplementation. In males, the use of at least 2000 IU of vitamin D was associated with a reduced risk of schizophrenia (RR=0.23, 95% CI 0.06-0.95) compared to those on lower doses. There were no significant associations between either the frequency or dose of vitamin D supplements and (a) schizophrenia in females, nor with (b) nonpsychotic disorder or psychotic disorders other than schizophrenia in either males or females. CONCLUSION Vitamin D supplementation during the first year of life is associated with a reduced risk of schizophrenia in males. Preventing hypovitaminosis D during early life may reduce the incidence of schizophrenia.

Demographic and clinical correlates of comorbid substance use disorders in psychosis: multivariate analyses from an epidemiological sample ☆

BACKGROUND While there has been substantial research examining the correlates of comorbid substance abuse in psychotic disorders, it has been difficult to tease apart the relative importance of individual variables. Multivariate analyses are required, in which the relative contributions of risk factors to specific forms of substance misuse are examined, while taking into account the effects of other important correlates. METHODS This study used multivariate correlates of several forms of comorbid substance misuse in a large epidemiological sample of 852 Australians with DSM-III-R-diagnosed psychoses. RESULTS Multiple substance use was common and equally prevalent in nonaffective and affective psychoses. The most consistent correlate across the substance use disorders was male sex. Younger age groups were more likely to report the use of illegal drugs, while alcohol misuse was not associated with age. Side effects secondary to medication were associated with the misuse of cannabis and multiple substances, but not alcohol. Lower educational attainment was associated with cannabis misuse but not other forms of substance abuse. CONCLUSION The profile of substance misuse in psychosis shows clinical and demographic gradients that can inform treatment and preventive research.

Psychotic-like experiences in the general community: The correlates of CIDI psychosis screen items in an Australian sample

BACKGROUND Apart from individuals with clinical psychosis, community surveys have shown that many otherwise well individuals endorse items designed to identify psychosis. The aim of this study was to characterize the demographic correlates of individuals who endorse psychosis screening items in a large general community sample. METHOD The National Survey of Mental Health and Wellbeing interviewed 10641 individuals living in private dwellings in Australia. As part of a diagnostic interview (the CIDI), respondents were asked between three and six items originally designed to screen for potential psychosis. We examined the impact of selected demographic variables on endorsement of these items including sex, age, marital status, migrant status, urban/rural status, employment, education, and socio-economic status. RESULTS An estimated 11.7% of the Australian population endorsed at least one psychosis-screening item. Significantly higher endorsement was associated with younger age, migrants from non-English-speaking backgrounds, those who had never married or who were divorced/separated or unemployed, those living in urban regions and those from the lowest socio-economic levels. CONCLUSIONS Many of the correlates of endorsement of psychosis-screen items are also associated with psychosis. Unravelling the factors that contribute to this broader non-clinical phenotype will aid our understanding of psychosis.

Pterygium recurrence time

PURPOSE To define the amount of time necessary to follow patients after pterygium removal to identify a recurrence. METHODS The authors reviewed patients who supposedly had a recurrence of their pterygium and analyzed the records to determine the duration of these recurrences. RESULTS One hundred sixty-one known pterygium recurrences were identified from records. Those patients with frequent follow-up in whom recurrence could be determined to within 1 month were in group A, and those in whom the time of recurrence was indefinite were in group B. For patients in group A, there was an average time to the first recurrence of 123 +/- 113 days, with second and third recurrences at 97 +/- 58 and 67 +/- 47 days, respectively. Survival curve analysis showed that there was a 50% chance that there would be a recurrence within the first 120 days, and there was a 97% chance there would be a recurrence within 12 months of its removal. CONCLUSION This suggests that a 1-year follow-up time is likely to identify a recurrence.

Cell cycle alterations in biopsied olfactory neuroepithelium in schizophrenia and bipolar I disorder using cell culture and gene expression analyses

We previously demonstrated that olfactory cultures from individuals with schizophrenia had increased cell proliferation compared to cultures from healthy controls. The aims of this study were to (a) replicate this observation in a new group of individuals with schizophrenia, (b) examine the specificity of these findings by including individuals with bipolar I disorder and (c) explore gene expression differences that may underlie cell cycle differences in these diseases. Compared to controls (n = 10), there was significantly more mitosis in schizophrenia patient cultures (n = 8) and significantly more cell death in the bipolar I disorder patient cultures (n = 8). Microarray data showed alterations to the cell cycle and phosphatidylinositol signalling pathways in schizophrenia and bipolar I disorder, respectively. Whilst caution is required in the interpretation of the array results, the study provides evidence indicating that cell proliferation and cell death in olfactory neuroepithelial cultures is differentially altered in schizophrenia and bipolar disorder.

No association between serum 25-hydroxyvitamin D3 level and performance on psychometric tests in NHANES III

Background: Animal studies and in vitro experiments indicate that vitamin D is involved in a diverse range of neurobiological functions. We had the opportunity to examine the relationship between serum 25-hydroxyvitamin D3 [25(OH)D] levels and performance on various cognitive tasks, based on a large, representative community sample. Methods: Three age groups were available from the population-based NHANES III survey: adolescent group (n = 1,676, age range 12–17 years), adult group (n = 4,747, 20–60 years), elderly group (n = 4,809, 60–90 years). The associations between eight psychometric measures and serum 25(OH)D were assessed. Results: In the adolescent and adult groups, none of the psychometric measures were associated with 25(OH)D levels. In the elderly group there was a significant difference between 25(OH)D quintiles performance on a learning and memory task; however, those with the highest quintile of 25(OH)D were most impaired on the task, contrary to the hypotheses. Conclusion: Lower 25(OH)D levels were not associated with impaired performance on various psychometric measures. While it remains to be seen if chronic exposure to low 25(OH)D levels alters brain function in the long term, this cross-sectional study suggests that 25(OH)D levels do not influence neurocognitive performance.

The measurement of attitudes towards and beliefs about pain

&NA; This study compared the psychometric properties of two scales designed to measure attitudes towards and beliefs about pain. The Survey of Pain Attitudes (Revised) SOPA(R) (Jensen and Karoly 1987) and the Pain Beliefs and Perceptions Inventory (PBPI) (Williams and Thorn 1989) were examined in terms of internal consistency, discriminant validity, factor structure, construct validity and sensitivity to age and gender effects. Results provided strong support for the SOPA(R) as a useful measurement tool for use with patients with chronic low back pain. Further work is suggested for the PBPI, as the reported factor structure was not replicated. Discussion centred around the possible reasons for this finding, with issues such as the possible orientation of different treatment facilities, the possible differences in attitudes between patients with different types of pain, and the possible influence of length of years in pain or the receipt of workers compensation payments being considered.