Effects of family history and place and season of birth on the risk of schizophrenia

Cumulative risk and population attributable fraction in prevention

Compares the use of relative risk versus population attributable fraction in determining the target population for multirisk prevention programs in psychology. Results show that relative risk generally increases as a function of cumulative risk. Guided by this measure, prevention programs should target populations with the largest cumulative risk. However, relative risk does not account for the prevalence of a particular level of cumulative risk in the population. Therefore, because the largest cumulative risk is experienced by only a small portion of the population, prevention programs guided by this measure will not always have the greatest public health benefit to reduce the incidence of problem outcomes in the population. On the other hand, the population attributable fraction, which does take into account the prevalence of a particular level of cumulative risk, does not increase appreciably after a cumulative risk of one, two, or three because the majority of people in the population will experience these levels of cumulative risk. Guided by this measure, prevention programs that target the higher proportion of people who have a more moderate level of risk would have the maximum impact on the population. National data sets from Great Britain (the British Births Cohort Study [BCS]) and the United States (National Longitudinal Study of Youth [NLSY]) are used to explore this pattern of effects.

Linkage analysis of candidate regions using a composite neurocognitive phenotype correlated with schizophrenia

As schizophrenia is genetically and clinically heterogeneous, systematic investigations are required to determine whether ICD-10 or DSM-IV categorical diagnoses identify a phenotype suitable and sufficient for genetic research, or whether correlated phenotypes incorporating neurocognitive performance and personality traits provide a phenotypic characterisation that accounts better for the underlying variation. We utilised a grade of membership (GoM) model (a mathematical typology developed for studies of complex biological systems) to integrate multiple cognitive and personality measurements into a limited number of composite graded traits (latent pure types) in a sample of 61 nuclear families comprising 80 subjects with ICD-10/DSM-IV schizophrenia or schizophrenia spectrum disorders and 138 nonpsychotic first-degree relatives. GoM probability scores, computed for all subjects, allowed individuals to be partly assigned to more than one pure type. Two distinct and contrasting neurocognitive phenotypes, one familial, associated with paranoid schizophrenia, and one sporadic, associated with nonparanoid schizophrenia, accounted for 74% of the affected subjects. Combining clinical diagnosis with GoM scores to stratify the entire sample into liability classes, and using variance component analysis (SOLAR), in addition to parametric and nonparametric multipoint linkage analysis, we explored candidate regions on chromosomes 6, 10 and 22. The results indicated suggestive linkage for the familial neurocognitive phenotype (multipoint MLS 2.6 under a low-penetrance model and MLS>3.0 under a high-penetrance model) to a 14 cM area on chromosome 6, including the entire HLA region. Results for chromosomes 10 and 22 were negative. The findings suggest that the familial neurocognitive phenotype may be a pleiotropic expression of genes underlying the susceptibility to paranoid schizophrenia. We conclude that use of composite neurocognitive and personality trait measurements as correlated phenotypes supplementing clinical diagnosis can help stratify the liability to schizophrenia across all members of families prior to linkage, allow the search for susceptibility genes to focus selectively on subsets of families at high genetic risk, and augment considerably the power of genetic analysis.

Is earlier better? At the beginning of schizophrenia: timing and opportunities for early intervention

The fundamental tenet is treating psychotic patients as quickly and as effectively as possible. Few would oppose this idea. Increasing community awareness of the services, enhancing accessibility, optimizing the treatment approaches, improving compliance, and addressing substance misuse should hopefully translate into improved outcomes for the patients and their families and are extremely encouraging and welcome developments. However, the field urgently needs properly designed randomized controlled trials to definitively determine their efficacy. If they are shown to be efficacious the emphasis should then shift to randomized controlled trials of prodromal intervention. If prodromal intervention is proven to be successful then earlier might indeed be better and primary prevention within reach.

Human influenza viral infection in utero alters glial fibrillary acidic protein immunoreactivity in the developing brains of neonatal mice

Epidemiological reports describe a strong association between prenatal human influenza viral infection and later development of schizophrenia. Postmodern human brain studies, however, indicate a lack of gliosis in schizophrenic brains presumably secondary to absence of glial cells during the second trimester viral infection in utero. We hypothesized that human influenza infection in day 9 pregnant mice would alter the expression of glial fibrillary acidic protein (GFAP, an important marker of gliosis, neuron migration, and reactive injury) in developing brains of postnatal days 0, 14 and 35 mice. Determination of cellular GFAP immunoreactivity (IR) expressed as cell density in cortex and hippocampus of control and experimental brains showed increases in GFAP-positive density in exposed cortical (P = 0.03 day 14 vs control) and hippocampal cells (P = 0.035 day 14, P = 0.034 day 35). Similarly, ependymal cell layer GFAP-IR cell counts showed increases with increasing brain age from day 0, to days 14 and 35 in infected groups (P = 0.037, day 14) vs controls. The GFAP-positive cells in prenatally exposed brains showed 'hypertrophy' and more stellate morphology. These results implicate a significant role of prenatal human influenza viral infection on subsequent gliosis, which persists throughout brain development in mice from birth to adolescence.

Migration as a risk factor for schizophrenia: a Danish population-based cohort study

BACKGROUND

A growing body of evidence suggests that migration is a risk factor for the development of schizophrenia, although the putative mechanism remains obscure.

AIMS

To examine immigrant background and history of foreign residence as risk factors for schizophrenia.

METHOD

Using data from the Danish Civil Registration System, we established a population-based cohort of 2.14 million persons resident in Denmark by their fifteenth birthday. Schizophrenia in cohort members and parental psychiatric disorder were identified by cross-linkage with the Danish Psychiatric Case Register.

RESULTS

The relative risk of developing schizophrenia was 2.45 (95% Cl 2.25-2.67) and 1.92 (95% Cl 1.74-2.12) among first- and second-generation immigrants respectively, and 1.60 (95% Cl 1.25-2.05) among Danes with a history of foreign residence.

CONCLUSIONS

Migration confers an increased risk for schizophrenia that is not solely attributable to selection factors and may also be independent of foreign birth.

Schizophrenia: solving the puzzle

BACKGROUND

Schizophrenia is a common mental illness with an incidence of 15 new cases per 100,000 population per year.

AIM

To review evidence for current neurodevelopmental models of the aetiology of schizophrenia.

METHODS

We performed a literature search using Medline and PsychINFO. We evaluated the relevance of each article and tracked other relevant articles through references.

RESULTS

There is considerable evidence to support neurodevelopmental models of the aetiology of schizophrenia. One or more aetiological events occur between conception and birth that disturb central nervous system (CNS) development, leading to persisting alterations in brain structure and function. These early events, acting in concert with genetic loading and later influences or insults, predispose to the development of schizophrenia in early adulthood.

CONCLUSIONS

There have been considerable advances in schizophrenia research over the past 20 years. Future study of Indices of neural development will help advance our understanding of this common, disabling mental illness.

Adjustment for misclassification in studies of familial aggregation of disease using routine register data

This paper discusses the misclassification that occurs when relying solely on routine register data in family studies of disease clustering. A register study of familial aggregation of schizophrenia is used as an example. The familial aggregation is studied using a regression model for the disease in the child including the disease status of the parents as a risk factor. If all the information is found in the routine registers then the disease status of the parents is only known from the time when the register started and if this information is used unquestioningly the parents who have had the disease before this time are misclassified as disease-free. Two methods are presented to adjust for this misclassification: regression calibration and an EM-type algorithm. These methods are used in the schizophrenia example where the large effect of having a schizophrenic mother hardly shows any signs of bias due to misclassification. The methods are also studied in simulations showing that the misclassification problem increases with the disease frequency.

Perinatal risk factors for schizophrenia: diagnostic specificity and relationships with maternal psychopathology

Although a growing body of evidence supports the hypothesis that exposure to obstetric complications (OCs) increases the vulnerability for schizophrenia, some questions remain unanswered regarding the diagnostic specificity and the etiological significance of this association. Associations with a history of OCs have been reported for other severe psychiatric disorders, such as autism, anorexia nervosa, or psychotic affective disorder. Thus, OCs may increase in a relatively non-specific way the vulnerability for a range of severe mental disorders, the expression of this vulnerability depending on the interaction between OCs and other risk factors, such as the genetic liability for specific psychiatric disorder, or exposure to later environmental risk factors. The causal pathway between OCs, maternal psychopathology, and psychotic outcome in the offspring is not fully elucidated. The directions of the associations are often bi-directional, and the mediating variables, if any, are not clearly identified. OCs may have a direct negative impact on fetal brain development, may be on the causal pathway between prepartum maternal depression/exposure to stress and increased risk of schizophrenia, or may indirectly increase the risk of child's later psychiatric disorder by acting as risk factors for maternal postpartum depression. The links and possible interactions between somatic perinatal risk factors and maternal psychopathology in the association with offspring's increased vulnerability for psychosis have to be further explored.

Genetic and physiological data implicating the new human gene G72 and the gene for D-amino acid oxidase in schizophrenia

A map of 191 single-nucleotide polymorphism (SNPs) was built across a 5-Mb segment from chromosome 13q34 that has been genetically linked to schizophrenia. DNA from 213 schizophrenic patients and 241 normal individuals from Canada were genotyped with this marker set. Two 1,400- and 65-kb regions contained markers associated with the disease. Two markers from the 65-kb region were also found to be associated to schizophrenia in a Russian sample. Two overlapping genes G72 and G30 transcribed in brain were experimentally annotated in this 65-kb region. Transfection experiments point to the existence of a 153-aa protein coded by the G72 gene. This protein is rapidly evolving in primates, is localized to endoplasmic reticulum/Golgi in transfected cells, is able to form multimers and specifically binds to carbohydrates. Yeast two-hybrid experiments with the G72 protein identified the enzyme d-amino acid oxidase (DAAO) as an interacting partner. DAAO is expressed in human brain where it oxidizes d-serine, a potent activator of N-methyl-D-aspartate type glutamate receptor. The interaction between G72 and DAAO was confirmed in vitro and resulted in activation of DAAO. Four SNP markers from DAAO were found to be associated with schizophrenia in the Canadian samples. Logistic regression revealed genetic interaction between associated SNPs in vicinity of two genes. The association of both DAAO and a new gene G72 from 13q34 with schizophrenia together with activation of DAAO activity by a G72 protein product points to the involvement of this N-methyl-d-aspartate receptor regulation pathway in schizophrenia.

Schizophrenia as a disorder of neurodevelopment

A combination of genetic susceptibility and environmental perturbations appear to be necessary for the expression of schizophrenia. In addition, the pathogenesis of the disease is hypothesized to be neurodevelopmental in nature based on reports of an excess of adverse events during the pre- and perinatal periods, the presence of cognitive and behavioral signs during childhood and adolescence, and the lack of evidence of a neurodegenerative process in most individuals with schizophrenia. Recent studies of neurodevelopmental mechanisms strongly suggest that no single gene or factor is responsible for driving a highly complex biological process. Together, these findings suggest that combinatorial genetic and environmental factors, which disturb a normal developmental course early in life, result in molecular and histogenic responses that cumulatively lead to different developmental trajectories and the clinical phenotype recognized as schizophrenia.

Associations between premorbid intellectual performance, early-life exposures and early-onset schizophrenia. Cohort study

BACKGROUND

Impaired intellectual performance is associated with an increased risk of schizophrenia.

AIMS

To investigate whether this association is due to the influence of prenatal and early childhood exposures on both intellectual development and the risk of schizophrenia.

METHOD

Cohort of 197 613 Swedish male conscripts with linked birth, census and hospital admission data together with five measures of verbal and non-verbal intellectual performance recorded at conscription.

RESULTS

109 643 subjects had complete data; over a mean 5-year follow-up, 60 developed schizophrenia and 92 developed other non-affective psychoses. Poor scores for each of the five tests were associated with 3- to 14-fold increased risk of psychosis, particularly schizophrenia. Controlling for birth-related exposures, including birth weight, and parental education did not attenuate these associations.

CONCLUSIONS

Poor intellectual performance at 18 years of age is associated with early-onset psychotic disorder. Associations do not appear to be confounded by prenatal adversity or childhood circumstances, as indexed by parental education.

Micrometer-sized particles in cerebrospinal fluid (CSF) in patients with schizophrenia

The etiology of schizophrenia is unknown, but the pathogenetic process involves organic changes in brain tissue, which may alter the composition of cerebrospinal fluid (CSF). For the present study, CSF was obtained by lumbar puncture from 22 schizophrenic patients and 38 control patients. We have used scanning electron microscopy combined with filtration techniques to search for pathogenic correlates and diagnostic biomarkers in the nano-micrometer range. Micrometer-sized spherical particles were isolated from CSF in 20 of the 22 patients with schizophrenia compared to only two of the 38 controls (P < 0.001). Reverse transcription-polymerase chain reaction analysis did not reveal bacterial DNA material in the particles. The particles have not replicated in culture. The micrometer-sized particles may serve as biological disease markers in schizophrenia. Hypothetically, they may be involved in development of the disease or may result from the disease process in brains of schizophrenic patients.

Molecular genetic studies of schizophrenia: challenges and insights

Schizophrenia (SCZ) is a mental disease that affects approximately 1% of the population with life-long devastating consequences. Based on evidence for a major contribution of genetic factors, a decade of extensive efforts has been dedicated to the search of DNA sequence variations that increase the risk to SCZ. Search for genes in rare multiplex SCZ families with a large number of affected individuals and quasi-Mendelian mode of inheritance using genetic linkage methodology has been one of the favorite strategies in psychiatric genetics. Although several genomic regions were suggested for linkage to SCZ, not a single gene causing or predisposing to SCZ has been identified thus far. Furthermore, it is not clear whether the genes of familial SCZ are also involved in sporadic cases that represent the overwhelming majority of SCZ patients. For sporadic cases, genetic association studies comparing the distribution of allelic frequencies of candidate genes in SCZ patients and controls have been performed but the outcome of such studies has also been quite modest. Several factors such as possible involvement of numerous interactive genes of minor effect, yet unknown environmental effects and diagnostic ambiguities of the disease have made genetic studies in SCZ quite unproductive. In terms of future studies, a genome-wide association search is a promising approach; however, this approach requires genotyping of thousands of genetic markers in large samples. In addition, a detailed analysis of the genes, expression of which changes under the influence of environmental factors, can indicate good candidates for genetic association studies. In this connection, investigations of the epigenetic regulation of genes and not only the DNA sequence variation, may be necessary for complete understanding of the etiopathogenic mechanisms of SCZ.

In utero infection and adult schizophrenia

We review emerging evidence indicating that in utero exposure to infection is a risk factor for schizophrenia. It is hypothesized that a prenatal infection increases the liability to schizophrenia in adulthood by adversely affecting the maturation of critical brain structural and functional components implicated in the pathogenesis and pathophysiology of the disorder. Early evidence for a role of in utero infection includes investigations linking schizophrenia with birth during the winter and in urban regions, and ecologic studies demonstrating associations between influenza epidemics and births of pre-schizophrenic patients. The findings of the latter studies are, however, equivocal. To more rigorously address this question, our group has used increasingly sophisticated research designs that incorporate more refined measures of exposure and outcome, and continuous follow-up of treated cases. This work has already yielded several intriguing findings, including associations between schizophrenia and two in utero infections--rubella and respiratory infection. We also describe our ongoing birth cohort investigations that are expected to advance this work further, including studies that utilize maternal serum samples drawn during pregnancy of offspring who were later diagnosed with schizophrenia.

The psychopathology, medical management and dental implications of schizophrenia

BACKGROUND

Schizophrenia is a psychiatric illness characterized by thought disturbances, bizarre behaviors and cognitive impairments that may diminish a person's abilities in the areas of social relations, school or work and self-care. The onset of the disorder typically occurs between the late teens and mid-30s. Advanced dental disease is seen frequently in patients with schizophrenia for several reasons: the disease impairs these patients' ability to plan and perform oral hygiene procedures; some of the antipsychotic medications they take have adverse orofacial effects such as xerostomia; and these patients sometimes have limited access to treatment because of a paucity of financial resources and adequate number of dentists comfortable in providing care. The recent introduction of more effective medications has permitted the majority of patients to receive their psychiatric care from community-based providers rather than in the hospital. Consequently, dentists in the private sector also are being called on more frequently to care for these people.

CONCLUSIONS

Dentists cognizant of the signs and symptoms of schizophrenia are likely to feel more secure in treating patients with schizophrenia and more confident when obtaining consultative advice from the patients' psychiatrists. Dentists usually can provide a full range of services to such patients, can enhance these patients' self-esteem and can contribute to the psychotherapeutic aspect of management.

CLINICAL IMPLICATIONS

To effectively provide treatment to patients with schizophrenia, dentists must be familiar with the disease process so that they can communicate effectively with the patient, the treating psychiatrist and family members who serve as caregivers. In addition, dental treatment may need to be modified because of the patient's impaired ability to think logically, the local and systemic effects of psychiatric medications, and adverse interactions between these drugs and medications used in dentistry.

Excess mortality associated with antimicrobial drug-resistant Salmonella typhimurium

In a matched cohort study, we determined the death rates associated with drug resistance in Salmonella Typhimurium. We linked data from the Danish Surveillance Registry for Enteric Pathogens with the Civil Registration System and the Danish National Discharge Registry. By survival analysis, the 2-year death rates were compared with a matched sample of the general Danish population, after the data were adjusted for differences in comorbidity. In 2,047 patients with S. Typhimurium, 59 deaths were identified. Patients with pansusceptible strains of S. Typhimurium were 2.3 times more likely to die 2 years after infection than persons in the general Danish population. Patients infected with strains resistant to ampicillin, chloramphenicol, streptomycin, sulfonamide, and tetracycline were 4.8 times (95% CI 2.2 to 10.2) more likely to die, whereas quinolone resistance was associated with a mortality rate 10.3 times higher than the general population.

Season of birth variations in suicide methods in relation to any history of psychiatric contacts support an independent suicidality trait

BACKGROUND

Due to reports on season of birth variations in suicidal behaviour as well as in cerebrospinal fluid levels of monoamine metabolites, we investigated season of birth variations in suicide methods for completed suicides in relation to any history of psychiatric contacts. Relationships with the psychiatric diagnoses for those with psychiatric contacts were also studied.

METHODS

Sociodemographic variables and suicide methods were examined for all the 693 suicide victims during 1961-1980 in Västerbotten, Sweden. Information on any history of psychiatric contacts was obtained from psychiatric in-patient and out-patient records.

RESULTS

Gender differences in the choice of suicide method were found in the group without any history of psychiatric contacts, but not in those with such a history. Only those without a history of psychiatric contacts showed season of birth variations for suicide methods -- those born during February to April were significantly more likely, and those born during October to January significantly less likely, to have preferred hanging rather than poisoning or petrol gases. These associations were stronger for the determined suicides, for males, and for urban residence. Suicide victims with a history of psychiatric contacts were significantly younger than those without.

LIMITATIONS

No psychological autopsies for those without psychiatric contacts. No information on eventual contacts with general practitioners. No measures of monoamine neurotransmitters were available.

CONCLUSIONS

Season of birth association for suicide methods is likely to be mediated by a suicidality trait independently of specific major psychiatric disorders. Monoamine neurotransmitters, particularly serotonin, are likely to underlie such a trait.

Season of birth in Japanese patients with schizophrenia

A number of North American and European studies have observed a higher proportion of winter births in schizophrenia patients. Fewer studies have investigated this issue in Asian populations, and the findings are not as consistent as in the studies of Western populations. A statistically significant excess of winter births has not been observed in Japanese or Korean studies, while some of the studies found a decreased number of summer births among their patients. We further investigated the issue in Japanese patients with schizophrenia (n=2985). No significant excess of winter births was observed. Spearman correlation between schizophrenia births and ambient temperature was not significant. However, a decrease in the summer births was found, consistent with most of the previous Japanese studies. When analyzed by gender, a decrease in summer births was found in males, but not in females. In addition, a trend towards an increase in winter births was observed and Spearman correlation between low ambient temperature and schizophrenia births was significant in male subjects. More significant seasonality of birth in male patients than in female patients might be related to more susceptibility to pre- or perinatal disturbances in neurodevelopment in males than in females.

The goals and method of the Andalusian Case Register for Schizophrenia

BACKGROUND

Psychiatric case registers have been acknowledged as a valuable source of data, a long time ago. However, a growing interest exists in data on service utilization by patients belonging to groups with a related diagnosis to enable adequate planning of health resources.

AIMS

The aims of the Andalusian Case Register for Schizophrenia are to determine the prevalence of schizophrenia of those cared for by the public network of mental health services and to describe their pattern of care.

METHODS

Cases included on the Register are those persons resident in South Granada area with a diagnosis of schizophrenia and related disorders. The agencies which sent the information to the Register are all the mental health facilities in the catchment area.

CONCLUSIONS

The Register is a flexible instrument to use for epidemiological research and mental health care planning.

The schizophrenia-rheumatoid arthritis connection: infectious, immune, or both?

Schizophrenia and rheumatoid arthritis share an impressive number of similarities. Both are chronic, relapsing diseases of unknown etiology. Both became prominent in the early 19th century and have prevalences of approximately 1% in North America and Europe. Both run in families, have pairwise concordance rates of approximately 30% among monozygotic twins, and are more common among individuals born in urban areas. For both diseases, studies have reported greater exposure to cats in childhood than in controls. Both diseases have been associated with similar class II HLA antigens. Both have also been suspected of having infectious etiology, with similar agents--retroviruses, herpesviruses including EBV, and Toxoplasma gondii--having been associated in some cases. Since there is also a well-documented inverse correlation between these two diseases, it is possible that they share a common infectious and/or immune etiology and that once a person gets one of the diseases then they are relatively immune to the other.

Signs of asphyxia at birth and risk of schizophrenia. Population-based case-control study

BACKGROUND

Previous research has found an association between obstetric complications and schizophrenia, but in many studies the sample size was limited, and no assessment of specific exposures was possible.

AIMS

To assess the role of different complications, and in particular to distinguish between disordered foetal development and hypoxia at birth.

METHOD

From the Stockholm County In-Patient Register and community registers, we identified 524 cases of schizophrenia and 1043 controls, matched for age, gender, hospital and parish of birth. Data on obstetric complications were obtained from birth records.

RESULTS

There was a strong association between signs of asphyxia at birth and schizophrenia (OR 4.4; 95% C11.9-10.3) after adjustment for other obstetric complications, maternal history of psychotic illness and social class.

CONCLUSIONS

Signs of asphyxia at birth are associated with an increased risk of schizophrenia in adults.

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.

Estimated yield of early detection of prodromal or first episode patients by screening first degree relatives of schizophrenic patients

Screening a population of relatives of current schizophrenic patients could be an efficient means to accrue a sample of early first episode or prodromal patients for a prediction study or an intervention study. The risk of new onset schizophrenia cases in any one year in a population of relatives depends on the number of schizophrenic probands and three additional factors: (1) the age of onset distribution for schizophrenia; (2) the lifetime risk of the at-risk group of relatives selected; and (3) the number of at-risk relatives per proband and their age distribution. Estimates are made for each of these parameters, and calculations are presented. The base model suggests that screening all siblings and children of patients with schizophrenia would yield approximately 19 new cases of schizophrenia per year per 10,000 relatives screened. The results of the calculation are relatively insensitive to reasonable variation of most model parameter estimates. The yield of new cases obtained by screening relatives of current patients appears to be low if the purpose is to recruit a sample for an early intervention study over a relatively short period of time.

Comparison of the incidence of schizophrenia in rural Dumfries and Galloway and urban Camberwell

BACKGROUND

Being born or living in urban areas is associated with high rates of schizophrenia. However, few studies have compared the incidence in urban/rural areas using the same methodology.

AIMS

To compare service-based incidence rates for schizophrenia in rural Dumfries and Galloway in south-west Scotland with urban Camberwell in south-east London.

METHOD

Using Research Diagnostic Criteria diagnoses from the OPCRIT computer algorithm, we compared the incidence of schizophrenia over 12 years (1979-1984 and 1992-1997) using indirect standardisation techniques and Poisson regression modelling.

RESULTS

The incidence was 61% higher in urban Camberwell than in rural Dumfries and Galloway (standardised incidence ratio (SIR)=1.61; 95% CI=1.42-1.81). There was no difference in incidence when we compared the White population in Camberwell with Dumfries and Galloway (SIR=1.12; 95% CI=0.86-1.43).

CONCLUSIONS

The incidence of schizophrenia in urban Camberwell was higher than that in rural Dumfries and Galloway; the high incidence of non-Whites in Camberwell largely explains the urban/rural difference.

Season of birth, gender and negative symptoms in schizophrenia

The aim of this study was to ascertain whether the symptom profile distinguishes between schizophrenic patients born in the winter and early spring and those born in other seasons. The sample consisted of 204 patients with a DSM-III-R diagnosis of schizophrenia who had been hospitalized for acute psychotic decompensation. Symptom ratings were based on the Positive and Negative Syndrome Scale (PANSS). The use of demographic and anamnestic data as dependent variables did not detect any season-of-birth effect. In contrast, clear gender-specific differences emerged from the comparison focusing on symptom dimensions and clinical subtype. Female patients born in the winter and early spring had higher scores on the PANSS negative scale and anergia factor whereas male patients born in other seasons had higher scores on the PANSS anergia factor. In addition, we found a gender-specific association between season of birth and clinical subtype. Most paranoid female patients were born in the non-winter months whereas, among men, a slightly higher percentage of paranoid patients were born in winter months. These results suggest that gender plays a role in modulating the effect of the season of birth on symptoms of schizophrenia.

Season of birth in females with anorexia nervosa in Northeast Scotland

OBJECTIVE

To determine whether patients with anorexia nervosa exhibit an abnormal pattern in their season of birth.

METHOD

Case records of female patients presenting to secondary services in Northeast Scotland from 1965 to 1997 who received a clinical diagnosis of anorexia nervosa were examined. The months of birth of the 446 anorexic patients with a confirmed diagnosis were compared with 5,766 female control subjects born locally in 1951, 1961, 1971, and 1981.

RESULTS

Patients with anorexia nervosa had an excess of births in the first 6 months of the year (p =.013). The greatest excess was from March to June.

DISCUSSION

This provides further evidence that birth dates of anorexics peak in the late spring and early summer. There are parallels with the epidemiology of schizophrenia. The evidence suggests that a seasonally fluctuating factor, most plausibly an intrauterine effect of common infectious agents during the winter months, is of etiological significance.

Season of birth variations in the temperament and character inventory of personality in a general population

BACKGROUND

Since several studies show season of birth variations in morbidity, suicidal behavior and CSF (cerebrospinal fluid) monoamine metabolites, we investigated season of birth variations in personality in the population.

METHODS

We analyzed by multiple logistic regressions the Temperament and Character Inventory (TCI) for 2,130 individuals taking part in the Betula prospective random cohort study of Umeå, Sweden.

RESULTS

The personality dimensions were correlated significantly with age and gender. We stratified the data according to age, gender and the season of TCI measurement. By the median split in each stratum, a high-value group and a low-value group were obtained for each of the personality dimensions. Those born during February to April were significantly more likely than those born during October to January to have high NS (novelty seeking) among women, particularly the subscale NS2 (impulsiveness vs. reflection), and to have high PS (persistence) among men. Temperament profiles also showed season of birth variations.

CONCLUSIONS

We discuss the associations in the literature between personality and the monoamines serotonin and dopamine, and suggest that our results are compatible with a hypothesis of season of birth variation in the monoamine turnover. The personality traits are likely to be influenced by several genetic and environmental factors, one of them being the season of birth.

Nature vs. nurture: two brothers with schizophrenia

TOPIC

The nature vs. nurture argument as it pertains to two brothers.

PURPOSE

To explore the synergistic effects of heritability and environment in the cases of two brothers with schizophrenia.

SOURCES

Review of the literature and the authors' clinical experience.

CONCLUSIONS

The nature vs. nurture dichotomy may not be as relevant as looking at the interaction between these two forces.

Family history, place and season of birth as risk factors for schizophrenia in Denmark: a replication and reanalysis

BACKGROUND

Although a family history of schizophrenia is the strongest individual risk factor for schizophrenia, environmental factors related to urbanicity may contribute to a substantial proportion of the population occurrence of the disease.

AIMS

This study replicates previous findings in four mutually exclusive Danish study populations, including out-patient information, ICD-10 diagnoses of schizophrenia, and a broader adjustment for mental illness in family members.

METHOD

We established a population-based cohort of 2.66 million Danish people using data from the Civil Registration System linked with the Psychiatric Case Register.

RESULTS

Overall, 10 264 persons developed schizophrenia during the 50.7 million person-years of follow-up. The risk of schizophrenia was increased by urbanicity of place of birth and by family history of schizophrenia or other mental disorders.

CONCLUSIONS

Urban-rural differences of schizophrenia risk were replicated and could not be associated with the potential sources of bias we assessed. Environmental factors underlying the effect of place of birth are major determinants of schizophrenia occurrence at the population level, although the effect of family history is the strongest at the individual level.

Schizophrenia

To provide the most effective care for this difficult patient population, it is helpful to remember that patients with schizophrenia have disease-intrinsic limitations that limit their ability to participate in their care. These limitations are symptoms of a disease and not volitional. For the physician to substitute for these deficits, a certain degree of flexibility as well as the willingness to use unorthodox interventions is necessary. Good medical care is as important for the patient with schizophrenia as for any other patient.

Risk factors and confounders in the geographical clustering of schizophrenia

In response to previous reports of geographical clustering of individuals with psychosis, a study was carried out in Denmark utilizing the national case register. Two-thousand one-hundred and ninety-nine (2199) individuals with schizophrenia were divided by place of birth into 217 geographical areas and analyzed by age, gender, month of birth, genetic relatedness, and degree of urbanization of birthplace. Heterogeneity was ascertained using log-linear Poisson regression. The greatest amount of heterogeneity was associated with degree of urbanization of place of birth. Heterogeneity was also associated with age-gender interaction and calendar period. When adjusted for these factors, there was no remaining heterogeneity, suggesting that all geographical clustering in our study was explained by the above factors.

Retroviral RNA identified in the cerebrospinal fluids and brains of individuals with schizophrenia

Schizophrenia is a serious brain disease of uncertain etiology. A role for retroviruses in the etiopathogenesis of some cases of schizophrenia has been postulated on the basis of clinical and epidemiological observations. We found sequences homologous to retroviral pol genes in the cell-free cerebrospinal fluids (CSFs) of 10 of 35 (29%) individuals with recent-onset schizophrenia or schizoaffective disorder. Retroviral sequences also were identified in the CSFs of 1 of 20 individuals with chronic schizophrenia. However, retroviral sequences were not identified in any of the CSFs obtained from 22 individuals with noninflammatory neurological diseases or from 30 individuals without evidence of neurological or psychiatric diseases (chi(2) = 19.25, P < 0.001). The nucleotide sequences identified in the CSFs of the individuals with schizophrenia or schizoaffective disorder were related to those of the human endogenous retroviral (HERV)-W family of endogenous retroviruses and to other retroviruses in the murine leukemia virus genus. Transcription of RNA homologous to members of the HERV-W family of retroviruses also was found to be up-regulated differentially in the frontal cortex regions of brains obtained postmortem from individuals with schizophrenia, as compared with corresponding tissue from individuals without psychiatric diseases. The transcriptional activation of certain retroviral elements within the central nervous system may be associated with the development of schizophrenia in at least some individuals. The further characterization of retroviral elements within the central nervous system of individuals with schizophrenia might lead to improved methods for the diagnosis and management of this disorder.

Household crowding in early adulthood and schizophrenia are unrelated in Denmark: a nested case-control study

A number of studies have found that being born in an urban area is a risk factor for developing schizophrenia. It has been hypothesized that increased exposure to infectious agents through household crowding might account for this association. Using Danish longitudinal registers, we have established a population-based sample of 191 cases of schizophrenia where the first admission occurred between 1981 and 1993. These cases were compared with 17413 individually matched controls of the same gender and age. Information regarding parents' and siblings' psychiatric history, urbanization, season and place of birth, and square meter per dweller were included in a conditional logistic regression model. We found square meter per dweller to be insignificant and without any trend when included as a risk factor for schizophrenia, whereas previous findings of schizophrenia associated with being born in an urban area and with schizophrenia in parents and siblings were replicated.

Number of older siblings of individuals diagnosed with schizophrenia

One of the most consistent epidemiological findings in schizophrenia research is the small excess of late winter/early spring births. There is also evidence that schizophrenia is associated with urban birth and with later birth order. One interpretation of these three findings is that respiratory viral infections brought into the household by children in crowded areas could disrupt foetal brain development and predispose to schizophrenia in later life. To further explore this hypothesis, case register data were used to assess if schizophrenics with a greater number of older siblings are more likely to be born in urban areas and during late winter/early spring months. Data from the Dublin and Three County Case Register were compiled relating to 2969 patients with schizophrenia and 5904 patients with neurosis. We used logistic regression analysis to determine if the number of older siblings differentiated schizophrenia from neurosis after controlling for the effects of gender, urban/rural birth, season of birth and sibship size, and to examine whether any interactions existed. The number of older siblings did not predict a diagnosis of schizophrenia over neurosis. There was no interaction between number of older siblings and urban birth, between number of older siblings and spring birth, or between number of older siblings, season of birth and urban birth. These data do not support the hypothesis that schizophrenia, by comparison with neurosis, is associated with an increased number of older siblings or that there is an interaction between number of older siblings, urban birth or season of birth.

Prenatal exposure to maternal infection alters cytokine expression in the placenta, amniotic fluid, and fetal brain

Prenatal exposure to infection appears to increase the risk of schizophrenia and other neurodevelopmental disorders. We have hypothesized that cytokines, generated in response to maternal infection, play a key mechanistic role in this association. E16 timed pregnancy rats were injected i.p. with Escherichia coli lipopolysaccharide (LPS) to model prenatal exposure to infection. Placenta, amniotic fluid and fetal brains were collected 2 and 8h after LPS exposure. There was a significant treatment effect of low-dose (0.5mg/kg) LPS on placenta cytokine levels, with significant increases of interleukin (IL)-1beta (P<0.0001), IL-6 (P<0.0001), and tumor necrosis factor-alpha (TNF-alpha) (P=0.0001) over the 2 and 8h time course. In amniotic fluid, there was a significant effect of treatment on IL-6 levels (P=0.0006). Two hours after maternal administration of high-dose (2.5mg/kg) LPS, there were significant elevations of placenta IL-6 (P<0.0001), TNF-alpha (P<0.0001), a significant increase of TNF-alpha in amniotic fluid (P=0.008), and a small but significant decrease in TNF-alpha (P=0.035) in fetal brain. Maternal exposure to infection alters pro-inflammatory cytokine levels in the fetal environment, which may have a significant impact on the developing brain.

Molecular genetics of schizophrenia

1. Schizophrenia is a chronic, disabling brain disease that affects approximately 1% of the world's population. It is characterized by delusions, hallucinations and formal thought disorder, together with a decline in socio-occupational functioning. While the causes for schizophrenia remain unknown, evidence from family, twin and adoption studies clearly demonstrates that it aggregates in families, with this clustering largely attributable to genetic rather than cultural or environmental factors. Identifying the genes involved, however, has proven to be a difficult task because schizophrenia is a complex trait characterized by an imprecise phenotype, the existence of phenocopies and the presence of low disease penetrance. 2. The current working hypothesis for schizophrenia causation is that multiple genes of small to moderate effect confer compounding risk through interactions with each other and with non-genetic risk factors. The same genes may be commonly involved in conferring risk across populations or they may vary in number and strength between different populations. To search for evidence of such genetic loci, both candidate gene and genome-wide linkage studies have been used in clinical cohorts collected from a variety of populations. Collectively, these works provide some evidence for the involvement of a number of specific genes (e.g. the 5-hydroxytryptamine (5-HT) type 2a receptor (5-HT2a) gene and the dopamine D3 receptor gene) and as yet unidentified factors localized to specific chromosomal regions, including 6p, 6q, 8p, 13q and 22q. These data provide suggestive, but no conclusive, evidence for causative genes. 3. To enable further progress there is a need to: (i) collect fine-grained clinical datasets while searching the schizophrenia phenotype for subgroups or dimensions that may provide a more direct route to causative genes; and (ii) integrate recent refinements in molecular genetic technology, including modern composite marker maps, DNA expression assays and relevant animal models, while using the latest analytical techniques to extract maximum information in order to help distinguish a true result from a false-positive finding.

The nature of schizophrenia: signposts to prevention

OBJECTIVE

To describe the characteristics of schizophrenia relevant to conducting indicated preventive interventions.

METHOD

A systematic review of the literature informed by experiences at the Personal Assistance and Crisis Evaluation (PACE) clinic.

RESULTS

Primary prevention requires a sophisticated knowledge of key causal risk factors relevant to the expression of a disorder. The causal risk factors most useful from an intervention standpoint may turn out to be somewhat removed from the neurobiology of the disorder and may even be relatively non-specific, so that tackling them could reduce the risks for a range of mental disorders. The frontier for more specific prevention in schizophrenia and related psychosis is currently represented by indicated preventive interventions for subthreshold symptoms. Again, these may be relatively broad spectrum early in the prepsychotic phase but more proximal to onset, greater treatment specificity can be explored. However, this can be viewed more as preventively orientated treatment rather than primary prevention per se. Early detection of first episode psychosis and optimal intensive treatment of first episodes and the critical early years after diagnosis also represent increasingly attractive preventive foci in psychotic disorders.

CONCLUSION

As evidence accumulates, implementation of evidence-based practice in real work settings is a major challenge as it is throughout the mental health service system. The momentum of preventively orientated treatment must be maintained through the 2nd National Mental Health Strategy and in the face of recent misleading polemic regarding the treatability of psychotic disorders, especially schizophrenia. The evidence demonstrates that schizophrenia and related disorders have never been more treatable.

Cytokine and growth factor involvement in schizophrenia--support for the developmental model

Medical treatment with various cytokines can provoke psychiatric symptoms. Conversely, psychiatric patients can display abnormalities in cytokine and neurotrophic factor expression. Such observations have pointed to the potential contribution of cytokines and growth factors to schizophrenic pathology and/or etiology. The cellular targets of the relevant factors and the nature of their actions remain to be explored in mental illness, however. Recent physiological studies demonstrate that cytokines and neurotrophic factors can markedly influence synaptic transmission and plasticity upon acute or chronic application. Moreover, many of the molecular alterations observed in the schizophrenic brain are consistent with abnormalities in cytokine and neurotrophic factor regulation of these molecules. In this review, we summarize these molecular pathology findings for schizophrenia and highlight the neurodevelopmental activities of cytokines and neurotrophic factors that may contribute to the etiology or pathology of this illness.

Universal interventions for the primary prevention of schizophrenia

OBJECTIVE

To speculate on the role of universal (population-based) interventions designed to prevent schizophrenia.

METHOD

A nonsystematic review of candidate risk factors for schizophrenia, with particular emphasis on the quality of the evidence, effect size of the risk factor, population attributable risk and potential for population-based intervention.

RESULTS

In order to design population-based interventions for the prevention of schizophrenia, we need to identify weak but prevalent risk factors. Based on current knowledge, the leading risk factors for schizophrenia include genes, season and place of birth, obstetric complications, prenatal exposure to viruses and prenatal nutrition. For the nongenetic exposures, we need to consider if potential interventions are effective, safe, cheap and acceptable.

CONCLUSIONS

Vaccinations and interventions related to improving prenatal nutrition and antenatal care appear to be the most plausible options for universal prevention.

Prevention in psychiatry: Australian contributions

OBJECTIVE

To provide a historic context for developing a framework for preventive mental health research in Australia.

METHOD

A literature review was undertaken and references were selected for their relevance to describing the contributions of Australian researchers and clinicians to an epidemiological approach to mental health disorders, particularly schizophrenia.

RESULTS

Australian researchers and clinicians have made major innovative contributions to preventive mental health research.

CONCLUSIONS

Australian mental health services, in collaboration with academic departments, are in a highly favourable position to expand preventive research activities into schizophrenia.

The epidemiology of the genetic liability for schizophrenia

OBJECTIVE

The low incidence of schizophrenia prohibits large scale prevention trials, and the question arises whether such studies become more feasible by taking into account genetic factors. The aim of the paper was to inform preventive endeavours with an account of the genetic background to schizophrenia.

METHOD

The family, twin and adoptive studies of schizophrenia are reviewed and recent molecular genetic data presented.

RESULTS

Children of a parent diagnosed with schizophrenia have a ten-fold increased risk of developing the disorder. Twin and adoption studies strongly suggest the risk increase is mainly due to genetic factors. On an individual level, a positive family history is the strongest known risk factor for schizophrenia. For a prevention study, very large numbers of families have to be screened in order to reach a sufficient sample size.

CONCLUSIONS

One obvious way to increase the accuracy of predicting who is at high risk of developing schizophrenia would be to find specific mutations in the human genome. Attempts to isolate specific genes by means of linkage and association studies have been unsuccessful so far and, given the number of genes involved, it is extremely unlikely that the predictive value of individual genes will be high enough to warrant intervention. Genetic studies also suggest the genetic liability extends beyond the traditional clinical phenotypes. Prevention trials might become possible by adopting a broader approach.

What risk factors tell us about the causes of schizophrenia and related psychoses

Genetic, epidemiologic, and molecular studies concur that liability to schizophrenia is transmitted through the inheritance of a number of genes of relatively small effect, some of which are shared with other psychoses. Each of these susceptibility genes causes minor deviations that are relatively innocent in themselves, for example, increased lateral ventricular volume, schizotypal personality, or subtle cognitive difficulties. However, when an individual is unlucky enough to inherit several of these traits, their cumulative effect, often compounded by environmental hazards, propels that person over a threshold for the expression of frank psychosis. Early environmental risk factors for schizophrenia include urban and winter birth, fetal malnutrition and hypoxia, and possibly prenatal viral infections; these early hazards have only a modest risk-increasing effect, and operate in the context of genetic risk. Preschizophrenic children are more likely to have minor psychomotor and cognitive problems; low IQ has a linear relationship with risk for schizophrenia. However, schizophrenia is not simply a neurodevelopmental disorder, because risk factors have been identified that have their effects proximal to the onset of psychosis: drug abuse, immigrant status, and social adversity and isolation. Both genetic and environmental risk factors appear to operate across diagnostic categories and therefore support a dimensional model of psychosis.

Seasonality of schizophrenia and stillbirths in The Netherlands

Studies from Denmark and the USA have reported a strong correlation between the seasonal pattern for stillbirths and the seasonal birth pattern for people who develop schizophrenia. It has been suggested that the correlation could be caused by a common seasonal factor (e. g. intra-uterine infections during the third trimester of pregnancy), which produces death in some fetuses and nonfatal brain changes in others, changes that are manifested in later life as schizophrenia. The aims of our study were (i) to assess the seasonal patterns for stillbirths and for pre-schizophrenic births in The Netherlands and (ii) to examine their relationship. The Dutch psychiatric registry provided data on all Dutch-born subjects who had been hospitalized at least once with a diagnosis of schizophrenia in the period 1970-1994. We selected data on patients born in the period 1926-1970 (n=29891). The government provided monthly numbers of live births and stillbirths in the latter period. Seasonality of birth was examined using Poisson regression analysis. The risk of an admission for schizophrenia was highest for people born in the months of May and June and lowest for those born in August and September. When the risk for subjects born in June was compared with the risk for subjects born in September, the Relative Risk was 1.14 [95% confidence interval (CI): 1.07 to 1.22]. The seasonal pattern of stillbirths was different, in that it showed a peak in the month of January. The low, however, as in schizophrenia, occurred in the months of August and September. The two seasonal patterns were found to be weakly correlated: Spearman's rank correlation coefficient rho=0.41 (95% CI: -0.22 to 0.80). This was the largest European study on birth seasonality in schizophrenia. The hypothesis that a common factor is responsible for a seasonal excess of stillbirths and for a seasonal birth excess of people who develop schizophrenia was not supported. The possibility remains, however, that a common factor explains seasonal (birth rate) deficits in these disorders.