Does social deprivation during gestation and early life predispose to later schizophrenia?

The association between social deprivation and the rate of identification of individuals at Ultra-High Risk for psychosis and transition to psychosis

BACKGROUND

There is a higher incidence of psychotic disorders in neighbourhoods of greater social deprivation. However, it is not known whether this represents a causal relationship, as the stage at which social deprivation exerts its influence on the development of psychotic disorders is yet to be elucidated. We aimed to investigate the association between neighbourhood-level social deprivation and the rate of identification of individuals at Ultra-High Risk for psychosis (UHR), as well as the risk of transition to psychosis in UHR individuals.

METHODS

The cohort included all young people aged 15 to 24 identified as UHR attending an Early Intervention clinic in northwestern Melbourne over a 5-year period (2012-2016). Australian census data were used to obtain the at-risk population and social deprivation information according to the postcode of residence. Levels of social deprivation were arranged into quartiles. Poisson regression was used to calculate rate ratios and Cox regression analysis determined hazard ratios.

RESULTS

Of the 461 young people identified as UHR, 11.1% (n = 49) lived in the most affluent neighbourhoods (Quartile 1) compared to 36.7% (n = 162) in the most deprived neighbourhoods (Quartile 4). There was a 35% higher rate of identification of young people who were UHR from the most deprived neighbourhoods (aIRR = 1.35, 95% CI [0.98, 1.86]). Over a median follow-up of approximately 10 months (308 days (IQR: 188-557), 17.5% (n = 77) were known to have transitioned to a full-threshold psychotic disorder. Residing in a neighbourhood of above average deprivation had a hazard ratio of 2.05 (95% CI [0.88, 4.80]) for risk of transition, when controlling for age, sex and substance use.

CONCLUSIONS

These findings provide more support that EI services should be funded as per the expected incidence of psychotic disorders.

Schizophrenia and education in Chinese metropolises: a population-based study

OBJECTIVE

Schizophrenia is a public concern in metropolises. Increases in city size may strengthen the correlation between prevalence of schizophrenia and indices of socioeconomic status, such as education. This study used population-based data of adults to investigate the association between education and schizophrenia in Chinese metropolises and its differences between inner city areas and outer suburbs.

METHODS

Data was obtained from the Second China National Sample Survey on Disability in 2006, and analysis was restricted to 189,143 participants aged 18 years or older in all counties (districts) of Beijing, Shanghai, and Tianjin. Schizophrenia diagnoses were ascertained according to the International Statistical Classification of Diseases, 10th Revision. Logistic regression models were fitted to examine the association between education and schizophrenia.

RESULTS

An inverse U-shaped pattern between education and schizophrenia was found in inner city areas of Chinese metropolises. Compared with the primary school or below group, the odds ratios of junior high school group and senior high school or above group was 2.79 (95% CI 1.96, 3.96) and 1.45(95% CI 0.99, 2.13), respectively. In outer suburbs, junior high school (OR = 0.87, 95% CI 0.63, 1.19) and senior high school or above groups (0.58, 95% CI 0.38, 0.87) were less likely to develop schizophrenia than the primary school or below group.

CONCLUSIONS

This study showed an association between education and schizophrenia in Chinese metropolises. In inner city areas, the association was an inverse U-shaped pattern between education and schizophrenia, whereas in suburban areas, the association was a negative linear pattern. Our findings can help identify high-risk populations of schizophrenia in Chinese metropolises. Programs for prevention and early intervention of schizophrenia will need to consider the socioeconomic disparities between inner city and outer suburban areas. Public policies can help improve mental health by developing social security for migrants in inner city areas and promoting regional equality.

Gender difference in the association between education and schizophrenia in Chinese adults

BACKGROUND

Improving education level was evidenced to decrease the risk of schizophrenia, but whether this strength of education role depends on gender is not. This study aimed to investigate whether there was gender difference in the association between education and schizophrenia in Chinese adults.

METHODS

Data were obtained from the Second China National Sample Survey on Disability in 2006, including 1,909,205 participants aged 18 years or older. Schizophrenia was ascertained according to the International Statistical Classification of Diseases, Tenth Revision. Logistics regression models were fitted to examine the combined effect of gender and education on schizophrenia.

RESULTS

The lifetime prevalence of schizophrenia in female groups was higher than in male groups, with 0.44% (95%CI: 0.42-0.45%) and 0.36% (95%CI: 0.35-0.37%), respectively. Compared with schizophrenia male patients, more females with schizophrenia experienced severe or extreme difficulty in understanding and communicating. However, more males with schizophrenia suffered from severe or extreme difficulty in the function of daily activities. The combined effect of education and schizophrenia was statistically significant, indicating that, as the level of education increased, schizophrenia risk of females decreased faster than the risk of males.

CONCLUSIONS

This study showed that additional years of education associated with lower risk of schizophrenia, and this association was stronger in females than in males. As education elevated, the risk of schizophrenia decreased more for women than for men. The findings indicate that improving education level may have an effect on reducing the gender disparities in mental health of China. Actions to prevent schizophrenia and address its gender disparities will require attention to the improving educational opportunities.

Association Between Parental Income During Childhood and Risk of Schizophrenia Later in Life

IMPORTANCE

Evidence linking parental socioeconomic position and offspring's schizophrenia risk has been inconsistent, and how risk is associated with parental socioeconomic mobility has not been investigated.

OBJECTIVE

To elucidate the association between parental income level and income mobility during childhood and subsequent schizophrenia risk.

DESIGN, SETTING, AND PARTICIPANTS

National cohort study of all persons born in Denmark from January 1, 1980, to December 31, 2000, who were followed up from their 15th birthday until schizophrenia diagnosis, emigration, death, or December 31, 2016, whichever came first. Data analyses were from March 2018 to June 2019.

EXPOSURE

Parental income, measured at birth year and at child ages 5, 10, and 15 years.

MAIN OUTCOMES AND MEASURES

Hazard ratios (HRs) for schizophrenia were estimated using Cox proportional hazard regression. Cumulative incidence values (absolute risks) were also calculated.

RESULTS

The cohort included 1 051 033 participants, of whom 51.3% were male. Of the cohort members, 7544 (4124 [54.7%] male) were diagnosed with schizophrenia during 11.6 million person-years of follow-up. There was an inverse association between parental income level and subsequent schizophrenia risk, with children from lower income families having especially elevated risk. Estimates were attenuated, but risk gradients remained after adjustment for urbanization, parental mental disorders, parental educational levels, and number of changes in child-parent separation status. A dose-response association was observed with increasing amount of time spent in low-income conditions being linked with higher schizophrenia risk. Regardless of parental income level at birth, upward income mobility was associated with lower schizophrenia risk compared with downward mobility. For example, children who were born and remained in the lowest income quintile at age 15 years had a 4.12 (95% CI, 3.71-4.58) elevated risk compared with the reference group, those who were born in and remained in the most affluent quintile, but even a rise from the lowest income quintile at birth to second lowest at age 15 years appeared to lessen the risk elevation (HR, 2.80; 95% CI, 2.46-3.17). On the contrary, for those born in the most affluent quintile, downward income mobility between birth and age 15 years was associated with increased risks of developing schizophrenia.

CONCLUSIONS AND RELEVANCE

This study's findings suggest that parental income level and income mobility during childhood may be linked with schizophrenia risk. Although both causation and selection mechanisms could be involved, enabling upward income mobility could influence schizophrenia incidence at the population level.

Individual-level and area-level socioeconomic status (SES) and schizophrenia: cross-sectional analyses using the evidence from 1.9 million Chinese adults

OBJECTIVES

Health disparities in schizophrenia are well established. However, it is less understood whether area-level socioeconomic status (SES) is differentially associated with schizophrenia depending on individual-level SES. Therefore, using a nationally large representative data, this study investigated the association between individual-level SES, area-level SES and their interaction with schizophrenia in Chinese adults from a multilevel perspective.

SETTING

Household interviews in 734 counties (districts), 2980 towns (streets) and 5964 communities (villages) from 31 provinces, People's Republic of China, as part of the cross-sectional survey of Second China National Sample Survey on Disability.

PARTICIPANTS

1 909 205 men and women aged 18 years old and above.

PRIMARY AND SECONDARY OUTCOME MEASURES

A screen followed by clinical diagnosis was used to identify schizophrenia, and schizophrenia was ascertained according to the International Statistical Classification of Diseases, 10th Revision (code F20).

RESULTS

1-SD increase in individual SES was associated with decreased risk of schizophrenia (OR=0.45, 95% CI 0.43 to 0.46). 1-SD increase in area-level SES was associated with increased risk of schizophrenia (OR=1.30, 95% CI 1.24 to 1.37). The interaction of individual SES and area-level SES was statistically significant (OR=1.05, 95% CI 1.02 to 1.08); as the level of area SES increased, schizophrenia risk of lower SES people grew faster than the risk of higher SES people.

CONCLUSIONS

Area-level SES is particularly important to mental health of low SES individuals, with low SES people in high SES counties having the highest risk of schizophrenia than other groups. Action to reduce SES disparities in schizophrenia will require attention to the area-level context of low SES adults.

Non-Genetic Factors in Schizophrenia

PURPOSE OF REVIEW

We review recent developments on risk factors in schizophrenia.

RECENT FINDINGS

The way we think about schizophrenia today is profoundly different from the way this illness was seen in the twentieth century. We now know that the etiology of schizophrenia is multifactorial and reflects an interaction between genetic vulnerability and environmental contributors. Environmental risk factors such as pregnancy and birth complications, childhood trauma, migration, social isolation, urbanicity, and substance abuse, alone and in combination, acting at a number of levels over time, influence the individual's likelihood to develop the disorder. Environmental risk factors together with the identification of a polygenic risk score for schizophrenia, research on gene-environment interaction and environment-environment interaction have hugely increased our knowledge of the disorder.

Neighbourhood level social deprivation and the risk of psychotic disorders: a systematic review

PURPOSE

The incidence of psychotic disorders varies according to the geographical area, and it has been investigated whether neighbourhood level factors may be associated with this variation. The aim of this systematic review is to collate and appraise the literature on the association between social deprivation and the incidence or risk for psychotic disorders.

METHOD

A systematic review was conducted, and studies were included if they were in English, provided a measure of social deprivation for more than one geographically defined area and examined either the correlation, rate ratio or risk of psychotic disorder. A defined search strategy was undertaken with Medline, CINAHL Plus and PsychInfo databases.

RESULTS

A total of 409 studies were identified in the search, of which 28 fulfilled the inclusion criteria. Of these, four examined the association between social deprivation at the time of birth, three examined the putative prodrome of psychosis or those at ultra-high risk (UHR) for psychosis, and 23 examined the time at presentation with a first episode of psychosis (FEP) (one study examined two time points and one study included both UHR and FEP). Three of the studies that examined the level of social deprivation at birth found an association with a higher risk for psychotic disorders and increased social deprivation. Seventeen of the 23 studies found that there was a higher risk or rate of psychotic disorders in more deprived neighbourhoods at the time of presentation; however, adjusting for individual factors tended to weaken this association. Limited research has been conducted in the putative prodromal stage and has resulted in conflicting findings.

CONCLUSIONS

Research conducted to date has not definitively identified whether the association is a result of social causation or social drift; however, the findings do have significant implications for service provision, such as the location and access of services.

Socioeconomic status at birth and risk for first episode psychosis in rural Ireland: Eliminating the features of urbanicity in the Cavan-Monaghan First Episode Psychosis Study (CAMFEPS)

BACKGROUND

There is a paucity of research on the relationship between social environment at birth and risk for psychosis in rural settings. This study examined the relationship between individual- and neighbourhood-level socioeconomic indicators proximal to the time of birth and risk for a first psychotic episode in a rural context using a prospective dataset of unusual epidemiological completeness.

METHODS

A matched case-control design was used. 186 cases were identified from the Cavan-Monaghan First Episode Psychosis Study (CAMFEPS) and 679 age- and sex-matched controls from the same rural setting were identified and analysed for relationships with individual and neighbourhood-level socioeconomic indicators at the level of Electoral Divisions.

RESULTS

While neither the distribution nor the ordinal scale of parental social class differed between cases and controls, logistic regression revealed both parental social class III and increasing level of rurality to be associated (p≤0.05) with reduced risk for affective psychosis. There was a prominent relationship (p<0.001) between lower parental social class and older age at first presentation [mean age at first presentation for all psychoses: social class I, 22.8; social class VI, 44.3].

CONCLUSIONS

These findings indicate modest effects of individual- and neighbourhood-level socioeconomic indicators and risk for psychosis by place at birth within a rural environment. Thus, these factors are not confined to large urban settings and apply across the urban-rural continuum. The substantive finding in relation to age at first presentation may indicate that a gradient of socioeconomic position is influential on delay in presentation to mental health services.

Social class at birth and risk of psychosis

BACKGROUND

Individuals with psychotic disorders are represented more in the lower social classes, yet there is conflicting evidence to whether these individuals drift into the lower social classes or whether lower social class is a risk factor for developing psychosis. The aim of this study was to examine whether the social class at birth is a risk factor for developing psychosis.

METHODS

We included individuals with a first episode of psychosis (FEP) whose social class at birth was determined from birth records. We employed a case-control study design and also compared the distribution of the social classes at birth of the cases to that of the general population.

RESULTS

A total of 380 individuals with an FEP and 760 controls were included in the case-control study. The odds ratio for developing an FEP associated with social class (low vs high) was .62 (95% confidence interval (CI): .46-.85, p < .001), indicating that individuals from a lower social class at birth have a reduced risk of psychosis. Individuals born between 1961 and 1980 with an FEP were more likely to be from a higher social class at birth compared to the general population (60.8% vs 36.7%, χ(2) = 60.85, df = 1, p < .001). However, this association was not observed for those born between 1981 and 1990.

CONCLUSION

A higher social class at birth is associated with a greater risk for developing a psychotic disorder; however, this effect may show temporal variation.

Common or distinct pathways to psychosis? A systematic review of evidence from prospective studies for developmental risk factors and antecedents of the schizophrenia spectrum disorders and affective psychoses

BACKGROUND

Identifying the unique and shared premorbid indicators of risk for the schizophrenia spectrum disorders (SSD) and affective psychoses (AP) may refine aetiological hypotheses and inform the delivery of universal versus targeted preventive interventions. This systematic review synthesises the available evidence concerning developmental risk factors and antecedents of SSD and AP to identify those with the most robust support, and to highlight remaining evidence gaps.

METHODS

A systematic search of prospective birth, population, high-risk, and case-control cohorts was conducted in Medline and supplemented by hand searching, incorporating published studies in English with full text available. Inclusion/exclusion decisions and data extraction were completed in duplicate. Exposures included three categories of risk factors and four categories of antecedents, with case and comparison groups defined by adult psychiatric diagnosis. Effect sizes and prevalence rates were extracted, where available, and the strength of evidence synthesised and evaluated qualitatively across the study designs.

RESULTS

Of 1775 studies identified by the search, 127 provided data to the review. Individuals who develop SSD experience a diversity of subtle premorbid developmental deficits and risk exposures, spanning the prenatal period through early adolescence. Those of greatest magnitude (or observed most consistently) included obstetric complications, maternal illness during pregnancy (especially infections), other maternal physical factors, negative family emotional environment, psychopathology and psychotic symptoms, and cognitive and motor dysfunctions. Relatively less evidence has accumulated to implicate this diversity of exposures in AP, and many yet remain unexamined, with the most consistent or strongest evidence to date being for obstetric complications, psychopathology, cognitive indicators and motor dysfunction. Among the few investigations affording direct comparison between SSD and AP, larger effect sizes and a greater number of significant associations are commonly reported for SSD relative to AP.

CONCLUSIONS

Shared risk factors for SSD and AP may include obstetric complications, childhood psychopathology, cognitive markers and motor dysfunction, but the capacity to distinguish common versus distinct risk factors/antecedents for SSD and AP is limited by the scant availability of prospective data for AP, and inconsistency in replication. Further studies considering both diagnoses concurrently are needed. Nonetheless, the prevalence of the risk factors/antecedents observed in cases and controls helps demarcate potential targets for preventative interventions for these disorders.

Childhood residential mobility, schizophrenia, and bipolar disorder: a population-based study in Denmark

INTRODUCTION

Childhood adversity is gaining increasing attention as a plausible etiological factor in the development of psychotic disorders. Childhood residential mobility is a potential risk factor that has received little attention in this context.

METHODS

We used registry data to estimate associations of residential mobility with narrow and broad schizophrenia and bipolar disorder across the course of childhood among 1.1 million individuals born in Denmark 1971-1991 and followed from age 15 through 2010. We assessed effect modification by sex, family history of mental disorder, the presence of siblings close in age, and distance moved.

RESULTS

In individual-year models adjusted for family history, urbanicity at birth, and parental age, mobility at all ages except the year of birth was associated with heightened risk of narrow and broad schizophrenia, and risk increased with age at moving and with the number of moves. Further adjustment for mobility at all ages 0-15 revealed associations mainly during the latter half of childhood, which were strongest during adolescence. Associations between mobility and bipolar disorder were fewer and weaker compared to schizophrenia. There was modest evidence of interaction with family history of psychiatric diagnosis, but little evidence for interaction by sex, the presence of closely-aged siblings, or distance moved. Schizophrenia associations did not appear attributable to increased mobility among adolescents with earlier onset.

CONCLUSIONS

Mobility may increase risk for psychotic disorders, particularly schizophrenia. Children may be especially vulnerable during adolescence. Future research should investigate the importance of school changes and the potential for interaction with genetic risk.

Is there evidence that social class at birth increases risk of psychosis? A systematic review

BACKGROUND

In the 1950s, researchers showed an association between low socio-economic status (SES) and psychosis. Two competing theories social causation and social drift were proposed to explain the findings. In the intervening years, contrasting evidence emerged as some studies showed no association between SES and schizophrenia. At present, the nature of the relationship is still unclear; currently, there are no reviews in the literature examining the association between social class at birth and psychosis.

AIM

To search the literature to clarify the relationship between social class at birth, measured by paternal occupation at birth, and the risk of adult-onset psychosis.

METHODS

A systematic search of the literature using a combination of keywords in Group 1 together with the keywords in Group 2 was performed in October 2012 in the following online databases: (a) MEDLINE (1946-2012), (b) PubMed, (c) Embase (1980-2012), (d) PsycINFO (1806-2012) and (e) Web of Science (1899-2012). Reference lists were also hand searched. The search provided 3,240 studies; following screening of the titles and abstracts by inclusion and exclusion criteria and quality assessment of the full text, 14 studies were identified to be appropriate for the review. The keywords used for the search were as follows: Group 1 - social class, social status, socioeconomic, socio-economic, SES; Group 2 - psychosis, psychoses, schizophrenia.

RESULTS

Seven studies showed an association between low SES and psychosis. Four studies showed no association, and three studies showed an association with high SES.

CONCLUSION

There is not enough evidence to support the association between social class and psychosis. While some findings showed an association between low social class and psychosis, there were a number of conflicting studies showing no association or a link with higher social class. Interestingly, the results followed a temporal pattern, as all the studies conducted after 2001 supported an association between low SES at birth and psychosis. Four of the six studies employed a prospective design with large sample populations, indicating the need for further investigation.

Identifying aspects of neighbourhood deprivation associated with increased incidence of schizophrenia

BACKGROUND

Several studies have found an association between area deprivation and incidence of schizophrenia. However, not all studies have concurred and definitions of deprivation have varied between studies. Relative deprivation and inequality seem to be particularly important, but which aspects of deprivation or how this effect might operate is not known.

METHODS

The Lambeth Early Onset case register is a database of all cases of first episode psychosis aged 16 to 35years from the London Borough of Lambeth, a highly urban area. We identified 405 people with first onset schizophrenia who presented between 2000 and 2007. We calculated the overall incidence of first onset schizophrenia and tested for an association with area-level deprivation, using a multi-domain index of deprivation (IMD 2004). Specific analyses into associations with individual sub-domains of deprivation were then undertaken.

RESULTS

Incidence rates, directly standardized for age and gender, were calculated for Lambeth at two geographical levels (small and large neighbourhood level). The Poisson regression model predicting incidence rate ratios for schizophrenia using overall deprivation score was statistically significant at both levels after adjusting for ethnicity, ethnic density, population density and population turnover. The incidence rate ratio for electoral ward deprivation was 1.03 (95% CI=1.004-1.04) and for the super output area deprivation was 1.04 (95% CI=1.02-1.06). The individual domains of crime, employment deprivation and educational deprivation were statistically significant predictors of incidence but, after adjusting for the other domains as well as age, gender, ethnicity and population density, only crime and educational deprivation, remained statistically significant. Low income, poor housing and deprived living environment did not predict incidence.

CONCLUSIONS

In a highly urban area, an association was found between area-level deprivation and incidence of schizophrenia, after controlling for age, gender, ethnicity and population density; high crime and low levels of education accounted for this. As both of these are potentially modifiable, this suggests a possible means to reduce the incidence of schizophrenia.

Epigenetic epidemiology in psychiatry: A translational neuroscience perspective

Accumulating evidence from the field of neuroscience indicates a crucial role for epigenetic regulation of gene expression in development and aging of nervous system and suggests that aberrations in the epigenetic machinery are involved in the etiology of psychiatric disorders. Epidemiologic evidence on epigenetics in psychiatry, however, is currently very sparsely available, but is consistent with a mediating role for epigenetic mechanisms in bringing together inherited and acquired risk factors into a neurodevelopmental etiological model of psychiatric disorders. Here, we review evidence from the epidemiological and neuroscience literature, and aim to converge the evidence into an etiological model of psychiatric disorders that encompasses environmental, genetic and epigenetic contributions. Given the dynamic nature of the epigenetic machinery and the potential reversibility of epigenetic modifications, future well-designed interdisciplinary and translational studies will be of key importance in order to identify new targets for prevention and therapeutic strategies.

Schizophrenia, social class and immigrant status: the epidemiological evidence

Background — By the mid-1960s, the importance of socio-economic status for schizophrenia had been demonstrated in terms of differences between social-class groups in prevalence and incidence rates, illness course and outcome, and treatment experience. In the causation – selection debate, however, opinion had swung in favour of the selection hypothesis. Aims — To reassess evidence on the social-class distribution of schizophrenia in Britain, and to compare this body of research with population-based studies of schizophrenia risk in socially disadvantaged ethnic minorities. Method — Systematic review of medical and psychological data-bases. Results — Epidemiological research, while confirming the importance of premorbid social decline, has also provided support for the environmental ‘breeder’ hypothesis. High psychosis rates have been confirmed in ethnic minori-ties; in particular among Afro-Caribbean and other Black immigrants whose low social status cannot be accounted for by selective downward social drift or segregation. Conclusions — There are striking parallels, both in the epidemiology of schizophrenia and in social characteristics, between the lower-class indigenous groups highlighted by earlier psychiatric surveys and African-Caribbean populations in Britain's inner cities today. These similarities underline the need for a broader perspective in the search for environmental risk factors.

Declaration of Interest: none.

The relationship between risk of hospitalization for schizophrenia, SES, and cognitive functioning

Although most studies find low socioeconomic status (SES) to be associated with prevalence of schizophrenia, incidence studies do not generally support this, and some even report an inverse association. The objective of the current historical prospective study was to examine the relationship between SES, cognitive functioning, and risk of hospitalization for schizophrenia in a population-based sample of Israeli adolescents. Subjects were 811 487 adolescents, assessed by the Israeli military draft board for socio-demographic factors and cognitive functioning. Data on later hospitalization for schizophrenia were obtained from a population-based hospitalization registry. Findings indicated that when simply examining SES and schizophrenia, lower SES was associated with greater risk of hospitalization for schizophrenia (Hazard Ratio [HR] = 1.193, 95% CI = 1.091-1.303). When dividing the cohort into low, average, and high cognitive functioning, SES did not influence the risk for schizophrenia among individuals with high and average cognitive functioning, whereas among individuals with low cognitive functioning, high SES was found to slightly increase the risk for schizophrenia (HR = 1.21, 95% CI = 1.03-1.42). One possible explanation for this finding might be that among individuals from low socioeconomic backgrounds, low IQ may reflect decreased opportunities related to SES, whereas among individuals from high SES backgrounds, low IQ might reflect risk for later psychopathology.

Epigenetic mechanisms in schizophrenia

Epidemiological research suggests that both an individual's genes and the environment underlie the pathophysiology of schizophrenia. Molecular mechanisms mediating the interplay between genes and the environment are likely to have a significant role in the onset of the disorder. Recent work indicates that epigenetic mechanisms, or the chemical markings of the DNA and the surrounding histone proteins, remain labile through the lifespan and can be altered by environmental factors. Thus, epigenetic mechanisms are an attractive molecular hypothesis for environmental contributions to schizophrenia. In this review, we first present an overview of schizophrenia and discuss the role of nature versus nurture in its pathology, where 'nature' is considered to be inherited or genetic vulnerability to schizophrenia, and 'nurture' is proposed to exert its effects through epigenetic mechanisms. Second, we define DNA methylation and discuss the evidence for its role in schizophrenia. Third, we define posttranslational histone modifications and discuss their place in schizophrenia. This research is likely to lead to the development of epigenetic therapy, which holds the promise of alleviating cognitive deficits associated with schizophrenia.

Effect of socioeconomic status and parents' education at birth on risk of schizophrenia in offspring

Although it is known that schizophrenia is associated with social class, controversy exists as to the nature of this association. The authors studied the incidence of schizophrenia in relation to social class at birth in a population-based cohort of 88,829 offspring born in Jerusalem in 1964-1976. They constructed a six-point scale to index social class, based on paternal occupation at the time of birth, with each of 108 occupations being ranked by mean education. Cox proportional hazards methods were used in adjusting for sex, parents' ages, duration of marriage and birth order. Linkage with Israel's Psychiatric Registry identified 637 people admitted to psychiatric care facilities with schizophrenia-related diagnoses, before 1998. There was no gradient of risk for schizophrenia associated with social class at birth; however, offspring of fathers in the lowest social class showed a modest increase in risk (adjusted Relative Risk = 1.4; 95% Confidence interval = 1.1-1.8, P = 0.002). These data suggest that in contrast to many other health outcomes, there is not a continuous gradient for increasing schizophrenia with decreasing social class of origin. Instead, a modest increase in risk for schizophrenia was observed only for those born at the bottom of the social ladder.

Associations between ethnicity and self-reported hallucinations in a population sample of young adults in The Netherlands

BACKGROUND

Psychotic disorders are more common in people from ethnic minorities. If psychosis exists as a continuous phenotype, ethnic disparities in psychotic disorder will be accompanied by similar ethnic disparities in the rate of psychotic symptoms. This study examined ethnic disparities in self-reported hallucinations in a population sample of young adults. MethodA cross-sectional population survey (n=2258) was carried out in the south-west Netherlands. Seven ethnic groups were delineated: Dutch natives, Turks, Moroccans, Surinamese/Antilleans, Indonesians, other non-Western immigrants (mostly from Africa or Asia) and Western immigrants (mostly from Western Europe). Self-reported auditory and visual hallucinations were assessed with the Adult Self-Report (ASR). Indicators of social adversity included social difficulties and a significant drop in financial resources.

RESULTS

Compared to Dutch natives, Turkish females [odds ratio (OR) 13.48, 95% confidence interval (CI) 5.97-30.42], Moroccan males (OR 8.36, 95% CI 3.29-21.22), Surinamese/Antilleans (OR 2.19, 95% CI 1.05-4.58), Indonesians (OR 4.15, 95% CI 1.69-10.19) and other non-Western immigrants (OR 3.57, 95% CI 1.62-7.85) were more likely to report hallucinations, whereas Western immigrants, Turkish males and Moroccan females did not differ from their Dutch counterparts. When adjusting for social adversity, the ORs for self-reported hallucinations among the non-Western immigrant groups showed considerable reductions of 28% to 52%.

CONCLUSIONS

In a general population sample, several non-Western immigrant groups reported hallucinations more often than Dutch natives, which is consistent with the higher incidence of psychotic disorders in most of these groups. The associations between ethnicity and hallucinations diminished after adjustment for social adversity, which supports the view that adverse social experiences contribute to the higher rate of psychosis among migrants.

Socioeconomic status at birth is associated with risk of schizophrenia: population-based multilevel study

BACKGROUND

Inconsistent findings obscure understanding the relationship between socioeconomic status (SES) and schizophrenia. The aim of the current study was to test the association between individual and community SES at birth and risk of schizophrenia.

METHOD

Population-based longitudinal follow forward study of a 13-year birth cohort (n = 71 165). Effects of individual and community socioeconomic variables were examined using multilevel regression in MLwiN.

RESULTS

Years of education of fathers and mothers, respectively, (0-8 vs 13+ odds ratio [OR] = 1.17, P < .0001; OR = 1.14, P < .001) lower occupational status of fathers (OR = 1.29, P = .036), and poorer residential area SES (OR = 1.26, P = .012) were risk factors for schizophrenia.

CONCLUSIONS

Individual- and community-level SES at the time of birth are associated with an increased risk of schizophrenia.

Treated incidence of first-episode psychosis in the catchment area of EPPIC between 1997 and 2000

OBJECTIVE

To identify the treated incidence of psychosis in catchment of the Early Psychosis Prevention and Intervention Centre (EPPIC), Melbourne, Australia.

METHOD

Cases were aged 15-29 years with a first episode of a psychotic disorder accepted into EPPIC between 1997 and 2000. Age- and sex-specific incidence rates per 10,000 person-years were calculated in 5 year age bands. Rate ratios were used for age group comparisons.

RESULTS

The age-specific treated incidence of first-episode psychosis in 15-29-year old individuals was 16.7 per 10,000 person-years in males, and 8.1 per 10,000 person-years in females. The incidence was highest in 20-24-year-old males and in 15-19-year-old females. For both sexes, incidence rates were significantly lower in the 25-29-year age group.

CONCLUSIONS

The incidence of psychosis in the catchment of EPPIC was higher than previously reported, especially in female teenagers. Peak rates in 15-24 year olds suggest a youth model approach to early psychosis may be indicated.

First psychiatric hospitalizations in the US military: the National Collaborative Study of Early Psychosis and Suicide (NCSEPS)

BACKGROUND

Military samples provide an excellent context to systematically ascertain hospitalization for severe psychiatric disorders. The National Collaborative Study of Early Psychosis and Suicide (NCSEPS), a collaborative study of psychiatric disorders in the US Armed Forces, estimated rates of first hospitalization in the military for three psychiatric disorders: bipolar disorder (BD), major depressive disorder (MDD) and schizophrenia.

METHOD

First hospitalizations for BD, MDD and schizophrenia were ascertained from military records for active duty personnel between 1992 and 1996. Rates were estimated as dynamic incidence (using all military personnel on active duty at the midpoint of each year as the denominator) and cohort incidence (using all military personnel aged 18-25 entering active duty between 1992 and 1996 to estimate person-years at risk).

RESULTS

For all three disorders, 8723 hospitalizations were observed in 8,120,136 person-years for a rate of 10.7/10,000 [95% confidence interval (CI) 10.5-11.0]. The rate for BD was 2.0 (95% CI 1.9-2.1), for MDD, 7.2 (95% CI 7.0-7.3), and for schizophrenia, 1.6 (95% CI 1.5-1.7). Rates for BD and MDD were greater in females than in males [for BD, rate ratio (RR) 2.0, 95% CI 1.7-2.2; for MDD, RR 2.9, 95% CI 2.7-3.1], but no sex difference was found for schizophrenia. Blacks had lower rates than whites of BD (RR 0.8, 95% CI 0.7-0.9) and MDD (RR 0.8, 95% CI 0.8-0.9), but a higher rate of schizophrenia (RR 1.5, 95% CI 1.3-1.7).

CONCLUSIONS

This study underscores the human and financial burden that psychiatric disorders place on the US Armed Forces.

Association between schizophrenia and social inequality at birth: case-control study

BACKGROUND

The association between social inequality at birth and subsequent risk of schizophrenia is uncertain.

AIMS

To investigate the relationship between adult-onset schizophrenia and two indicators of social inequality at birth: social class and area of residence.

METHOD

A matched case-control design was used with data from birth certificates of first-episode cases and age- and gender-matched controls.

RESULTS

Risk increased with increasing levels of deprivation at birth. Subjects whose fathers were social class IV-V or who were born in deprived areas were at increased risk of schizophrenia (odds ratio=2.1; 95% Cl=0.8-5.5). Risk was greater in those with both of these indicators (odds ratio=8.1; 95% Cl=2.7-23.9). There was some evidence that associations were stronger in older subjects. Exclusion of African-Caribbeans or cases with positive family history somewhat attenuated the association.

CONCLUSIONS

Indicators of social inequality at birth are associated with increased risk of adult-onset schizophrenia, suggesting that environmental factors are important determinants of schizophrenic disorders.

Understanding the excess of psychosis among the African-Caribbean population in England. Review of current hypotheses

BACKGROUND

Increased rates of schizophrenia continue to be reported among the African-Caribbean population in England.

AIMS

To evaluate the competing biological, psychological and social explanations that have been proposed.

METHOD

Literature review.

RESULTS

The African-Caribbean population in England is at increased risk of both schizophrenia and mania; the higher rates remain when operational diagnostic criteria are used. The excess of the two psychotic disorders are probably linked: African-Caribbean patients with schizophrenia show more affective symptoms, and a more relapsing course with greater social disruption but fewer chronic negative symptoms, than White patients. No simple hypothesis explains these findings.

CONCLUSIONS

More complex hypotheses are needed. One such links cultural variation in symptom reporting, the use of phenomenological constructs by psychiatrists and social disadvantage.

Obstetric factors, urbanization and psychosis

BACKGROUND

Epidemiologic evidence as early as the 1930s has suggested urbanization is linked to schizophrenia, either by place of admission, place of upbringing, or, more recently, place of birth. In the past decade, obstetric complications have been implicated in the etiology of schizophrenia.

METHODS

With appropriate protections for anonymity, the files of the Danish Medical Birth Register were linked with the files of the Danish Psychiatric Case Register. The linkage produced 132 cases of schizophrenia and 69 cases of affective psychosis, who were born in 1973 or later, who entered a Danish psychiatric hospital before 1994. Controls were drawn from a 10% sample of the Medical Birth Register. Analysis was by logistic regression.

RESULTS

The risk of hospitalization for schizophrenia was 4.20 times higher (95% CI=2.4-7.4) for those born in Copenhagen versus those born in rural areas of Denmark, and a linear relationship was demonstrated between urbanization of birthplace and risk. There was no difference in risk of hospitalization for affective psychosis for those born in Copenhagen versus rural areas. Obstetric complications had a moderate sized relationship to schizophrenia, but the relationship of urban birth to schizophrenia was unaffected by adjustment for obstetric complications.

CONCLUSION

Urban birth is a strong risk factor for schizophrenia, not mediated by obstetric complications, which deserves further exploration.

Characteristics of early- and late-diagnosed schizophrenia: implications for first-episode studies

First-episode studies of schizophrenia are being carried out in many places. However, previous work has suggested that only half of the patients with schizophrenia receive the diagnosis in the initial stages of the illness. We examined whether cases of early- and late-diagnosed schizophrenia differed with respect to key sociodemographic characteristics and indicators of service use that might bias first-episode studies. Individuals who (i) presented for the first time between 1983 and 1993 to psychiatric services in a defined urban area with a cumulative mental health case register; and (ii) received a diagnosis of schizophrenia at least once during their mental health career were identified (n = 186). This sample was divided into those who received the diagnosis of schizophrenia for the first time within the first year of service contact (early-diagnosed schizophrenia; EDS), and those who received it for the first time after the first year of service contact (late-diagnosed schizophrenia; LDS). The 10-year incidence of EDS and LDS were 10.4 and 7.0 per 100,000 person-years, respectively. EDS and LDS did not differ in their pattern of association with sex, single marital status and higher levels of neighbourhood socioeconomic deprivation. However, EDS was more incident in the higher age groups, and the level of service use was higher for EDS cases in the first years of contact with mental health services, with LDS cases gradually catching up and exceeding EDS service use later in the illness course. Although differences between EDS and LDS were few, studies of patients with schizophrenia in the 'first' episode are likely to be most representative if patients who receive the diagnosis for the first time after previous episodes of care for non-schizophrenic episodes are also included.

Seasonality of birth in schizophrenia: the effect of regional population density

It has been suggested that winter birth in urban areas may be associated with an increased risk of schizophrenia. Data on 4139 patients with a hospital diagnosis of schizophrenia were obtained from a survey of public departments of psychiatry in metropolitan France. Place of birth was classified according to the administrative subdivision of French territory into 95 'départements'. Density of population in the decade and in the département of birth was identified using successive census data. A 20% excess (OR, 1.20; 95% CI, 1.03-1.40; p = 0.02) of winter births (January-March) was found among patients born in highly densely populated areas (> 136 inhabitants/km2) compared to those born in other areas. These results suggest that seasonal early environmental risk factor(s) linked to schizophrenia predominantly operate in urban areas.

Psychotic illness in ethnic minorities: clarification from the 1991 census

Age and sex-adjusted first admission rates for operationally-defined schizophrenia and other non-affective psychosis in different ethnic groups were calculated over the period 1988-1992 in a defined catchment area in South London. Standardized rates for schizophrenia, corrected for age- and gender-related under-reporting in the 1991 census and a 20% underestimate of the size of the ethnic minority populations in the area, were not only higher in the Afro-Caribbean group (SMR: 3.1; 95% C1:2.0-4.7), but also in the African group (SMR: 4.2; 95% C1: 2.8-6.2). It was further found that higher rates were not specific to schizophrenia. These findings suggest that some common factor associated with ethnic minority membership is important in producing an excess of psychotic illness.

Premorbid abnormalities in mania, schizomania, acute schizophrenia and chronic schizophrenia

The aim of this study was to examine the hypothesis that differences in outcome among affective and non-affective psychoses are associated with differences in the degree of developmental deviance. We conducted a retrospective survey of first contact cases treated over a 20-year period in a psychiatric hospital serving a catchment area in South London. All patients with non-depressive functional psychosis residing in the catchment area who received their first psychiatric treatment between 1965 and 1984 were included in the study. Cases were classified according to the relative chronicity of their illness into four non-overlapping groups: mania, schizomania, acute schizophrenia and chronic schizophrenia. There was a linear trend in the association between illness chronicity and proxy measures of development deviance, such as premorbid unemployment, single status and poor academic achievement. Compared to individuals with mania, schizophrenic patients had a 3-6 times increased risk of premorbid abnormality. For patients with schizomania and acute schizophrenia, the risk was 1.5-3 times greater than for manic subjects. We conclude that the prevalence of premorbid abnormalities is highest among chronic schizophrenia, but similar disturbances also occur, to a lesser degree, in less disabling affective and non-affective psychotic disorders.

The criminal careers of incident cases of schizophrenia

We present a population-based, longitudinal study of all incident cases (N = 538) of schizophrenia in the London Borough of Camberwell between 1964 and 1984. Cases were selected from the Camberwell Cumulative Psychiatric Case Register. Case-notes were obtained, and further classified using a computerized operational check list for rating psychotic illness. Cases are not restricted to hospital discharges, as in previous studies, and account is taken of time at liberty to offend. In order to test the hypothesis that schizophrenia makes an independent contribution to criminality over other mental disorders, controls were chosen to be representative of nonschizophrenic mental disorders matched for age, sex and period. The rate of conviction is increased in women with schizophrenia compared to other mental disorders for most offence categories (rate ratio = 3.3). In men overall rates do not differ (rate ratio = 1.03), although there is an interaction between gender, schizophrenia and ethnicity, with young black men with schizophrenia being most at risk. The rate ratio for violent offences in men with schizophrenia is 3.8, confirming recent studies from Sweden. Subjects with schizophrenia were more likely to acquire any criminal record than those with other mental disorders. The rate of lifetime conviction was greater in those with schizophrenia than either a sample of working-class boys from the same area followed by Farrington & West, or National data. The risk of first conviction is increased by schizophrenia, unemployment, ethnic group, substance abuse and low social class, and decreased by being employed, married, female and older age of onset. Adjustment using survival analysis showed that schizophrenia made a small independent contribution to the risk of acquiring a criminal record (hazard ratio = 1.4) but gender, substance abuse, ethnicity and age of onset were more substantial. Previous criminality was the strongest independent association of post-illness conviction, with schizophrenia only a trend. Although subjects with schizophrenia were more likely to acquire a criminal record, criminal careers began later and were shorter than those of the controls. The risk of criminality increased throughout the study period, but suggestions of a specific increase in those with schizophrenia as a result of changes in community care were not confirmed. These results confirm that women with schizophrenia are at increased risk of acquiring a criminal record, but the effect in men is for violent convictions only. The strongest associations of criminal conviction remain those recognized in non-schizophrenic subjects.