Confinement of winter birth excess in schizophrenia to the urban-born and its gender specificity

Seasonality of births in affective disorder in an Irish population

Seasonal variation in the births of patients with schizophrenia is a consistently replicated epidemiological finding. Few studies have investigated this phenomenon among patients with a diagnosis of affective disorder. The majority of season of birth studies have employed the chi square test for statistical analysis, a method that has been subject to some criticism. Using a Kolgomorov-Smirnov type statistic, the quarterly birth distribution of 6,646 patients with an ICD 9/10 diagnosis of affective disorder were compared to the general population. Only the births of those individuals with unipolar forms of affective disorder (n = 4,393) differed significantly from the general population, with significant excesses and deficits in the second quarter and fourth quarter respectively. These results were not altered by application of the displacement test. © 1998 Elsevier, Paris

Failure to identify a male winter-born schizophrenia subgroup clinically

The distribution of 282 Research Diagnostic Criteria (RDC) and of 224 DSM-III-R schizophrenic patients, respectively, by month of their birth was studied. The winter-spring birth rate excess was confirmed with a maximum from January to March. Winterborn and summer-born schizophrenics were compared. No convincing differences were found with regard to a larger set of demographic, psychosocial and clinical variables in univariate comparisons, nor did we succeed in separating and identifying a special winter-born schizophrenia subgroup using the method of cluster analysis. Negative results were obtained in spite of the fact that many of the included variables reflected the course of the illness and the degree of chronicity. Either the set of the variables we used has not been ‘correct’ enough or the separation of a winter-born subgroup is not clinically feasible.

Social class and type of schizophrenia

Objective

Current and past research strongly indicates a high prevalence of schizophrenia in the lower class in the USA and other stratified societies. To date, no study has tested for a connection between type of schizophrenia and socioeconomic status (SES). We tested for an interrelationship between schizophrenic subtype, SES and race.

Methods

Positive and negative symptom scales were used to evaluate 436 schizophrenic patients at a state hospital in the USA. All patients were also diagnosed by DSM standards. Social class of origin was assessed by the Occupational Classification Distributions of the U.S. Bureau of the Census. Multivariate analysis was conducted with the likelihood ratio chi-square.

Results

We uncovered a distinct propensity for deficit schizophrenia to be elevated among the poor. The finding presents as a pure SES effect since the likelihood of deficit schizophrenia does not vary by race when social class is held constant.

Conclusion

The finding is potentially an important new insight into the epidemiology of schizophrenia. It offers a better understanding for poor outcome among lower class patients in stratified societies such as the United States. It is also consistent with longitudinal research by European investigators.

Season of birth and schizophrenia: Evidence from China

Controversies exist whether season of birth is associated with schizophrenia development later in life, and evidence has mainly come from studies done in developed countries. This study examines the association between season of birth and risk for schizophrenia in China, with special attention to geographical region, urbanity, and gender. Using data from China's Second National Sampling Survey on Disability, a large-scale, nationally representative sample (N=2,052,694), this study employs discrete-time hazard models to compare the risk for schizophrenia development for people born in different seasons, and conducts subsample analyses by geographical region, urbanity, and gender. People born in the spring have the highest risk when compared to people born in the winter, summer or autumn. Furthermore, the relatively higher risk for people born in the spring is greater in the southern half of the country, in rural areas, and for women. The findings are consistent with results from a robustness check done among people who were conceived and born from 1955 to 1965, periods before, during, and after the 1959-1961 Chinese Famine. This study supports the presence of an association between season of birth and risk for schizophrenia development and of heterogeneity by geographical region, urbanity, and gender.

Revitalizing sociology: urban life and mental illness between history and the present

This paper proposes a re-thinking of the relationship between sociology and the biological sciences. Tracing lines of connection between the history of sociology and the contemporary landscape of biology, the paper argues for a reconfiguration of this relationship beyond popular rhetorics of 'biologization' or 'medicalization'. At the heart of the paper is a claim that, today, there are some potent new frames for re-imagining the traffic between sociological and biological research - even for 'revitalizing' the sociological enterprise as such. The paper threads this argument through one empirical case: the relationship between urban life and mental illness. In its first section, it shows how this relationship enlivened both early psychiatric epidemiology, and some forms of the new discipline of sociology; it then traces the historical division of these sciences, as the sociological investment in psychiatric questions waned, and 'the social' become marginalized within an increasingly 'biological' psychiatry. In its third section, however, the paper shows how this relationship has lately been revivified, but now by a nuanced epigenetic and neurobiological attention to the links between mental health and urban life. What role can sociology play here? In its final section, the paper shows how this older sociology, with its lively interest in the psychiatric and neurobiological vicissitudes of urban social life, can be our guide in helping to identify intersections between sociological and biological attention. With a new century now underway, the paper concludes by suggesting that the relationship between urban life and mental illness may prove a core testing-ground for a 'revitalized' sociology.

Winter birth excess in schizophrenia and in non-schizophrenic psychosis: sex and birth-cohort differences

OBJECTIVE

Despite the fact that association between winter birth excess and schizophrenia in the northern Hemisphere is well established, possible sex or birth-cohort differences in this winter birth excess remain unclear. We aimed to evaluate sex and birth-cohort differences in the seasonal birth distribution of patients with schizophrenia or non-schizophrenic psychosis.

METHOD

The sample included 321 ICD-10 schizophrenia and 294 non-schizophrenic psychosis patients consecutively admitted into a psychiatric hospitalization unit in Granada, southern Spain, during a nine-year period (1998-2006). The distribution of births among the general population born over the same period as the patients was calculated.

RESULTS

Among schizophrenia males (n=258), it was possible to demonstrate that the observed proportion of winter birth (December, January or February) was significantly higher than expected. Among schizophrenia females (n=63), although proportions were as in males and the effect size of the difference between observed and expected winter births was not lower than for men, only a statistical trend could be demonstrated. Among patients with non-schizophrenic psychosis, the observed proportion of winter birth was significantly higher than expected in women, but not in men. The sex-adjusted proportion of winter birth among schizophrenia patients born in the 1940's (a time period characterized by poor economy and widespread food restrictions because of the Spanish post-civil-war period) was significantly higher than among those born later; a difference that does not occur among patients with a non-schizophrenic psychosis.

CONCLUSIONS

Among schizophrenia patients born in winter there appear to be slight sex-differences and strong birth-cohort differences, possibly due to epidemiological factors such as poverty or maternal nutritional deprivation. Epidemiological findings related to winter birth excess among patients with schizophrenia must be identified in longitudinal studies.

Schizophrenia and the city: A review of literature and prospective study of psychosis and urbanicity in Ireland

Urbanicity has been repeatedly associated with increased incidence of schizophrenia. This article (a) presents results of a prospective study of urbanicity and schizophrenia in Ireland and (b) reviews the literature relating to urbanicity and schizophrenia. We prospectively compared incidence of schizophrenia and other psychoses in urban and rural catchment areas (over 4years and 7years, respectively) using face-to-face, DSM-III-R diagnostic interviews. Incidence of schizophrenia in males was higher in urban compared to rural areas, with an age-adjusted incidence rate ratio (IRR) of 1.92 (1.52-2.44) for males and 1.34 (1.00-1.80) for females. Incidence of affective psychosis was lower in urban compared to rural areas for males (IRR 0.48; 0.34-0.67) and females (IRR 0.60; 0.43-0.83). These findings are consistent with the literature, which provides persuasive evidence that risk for schizophrenia increases with urban birth and/or upbringing, especially among males. Register-based studies support this conclusion more consistently than studies using face-to-face diagnostic interviews, the difference being related to power. The mechanism of association is unclear but may relate to biological or social/environmental factors or both, acting considerably before psychotic symptoms manifest. There is a diversity of potential candidates, including air pollution, cannabis and social exclusion. Urbanicity may have a synergistic effect with genetic vulnerability. Future research is likely to focus on the relationship between urbanicity and neural maldevelopment, the possibility of rural protective factors (e.g. social capital, low social fragmentation), urbanicity in developing countries, cultural variables and geographical location, and associations between urbanicity and other disorders (e.g. affective psychosis).

Correlation between schizophrenia and seasonality of birth in a tropical region

OBJECTIVE: To investigate the statistical relationship between season of birth and schizophrenia in 461 patients hospitalized in three psychiatric facilities in the towns of Araras, Itapira, and Espírito Santo do Pinhal, interior of São Paulo State, southeastern Brazil. METHODS: Date and place of birth of the patients were collected and used to determine the season of birth. Results were analyzed by the chi-square test. Data regarding temperature and rainfall between 1952 and 1986, corresponding to the years of birth of the patients studied, were also obtained. RESULTS: The results showed a higher prevalence of births in the winter months (p = 0.0044), a period characterized in this region by a decline in temperature and rainfall. CONCLUSION: These findings indicate a possible influence of seasonality on the pathogenesis of schizophrenia and suggest that the winter in this region, together with other factors, may contribute to the late development of the disease.

Explaining variation in the premorbid adjustment of schizophrenia patients: the role of season of birth and family history

Several studies have shown that patients with schizophrenia are more likely to be born in the winter and early spring than at any other time of the year. Furthermore, some studies have reported that winter-born patients differ from non-winter-born patients in terms of risk factors, symptoms, sensory abnormalities and brain morphology. Associations between season of birth and premorbid adjustment (PMA), however, are still unclear.

OBJECTIVE

The main purpose of this study was to determine whether winter-born and non-winter-born schizophrenia patients differ in terms of PMA and to examine how family history of schizophrenia-spectrum disorders may influence the association.

METHOD

Data on four PMA dimensions (attention, internalizing, externalizing and social problems) and family history were gathered from 37 schizophrenia patients (26 males and 11 females) and their mothers.

RESULTS

Non-winter-birth and a positive family history of schizophrenia-spectrum disorders were associated with worse PMA. Results suggest that, although no significant interaction was found, season of birth and family history appear to work together in explaining distinct dimensions of PMA.

What causes seasonality of birth in schizophrenia?

An excess of winter-spring births (and/or a decrease of summer births) has consistently been observed in schizophrenia (SCZ). This observation may provide a significant clue about the causes of the disease if specific factors which cause the phenomenon can be determined. This paper reviews several studies which investigated factors correlated with this observation in SCZ, in an attempt to determine which factors more likely cause the seasonality. Among the candidates of the factors are meteorological variables (such as ambient temperature), several infections, maternal hormones, sperm quality, nutrition and external toxins. A variation of procreation might also have an effect. Among the factors, the most extensively studied are temperature and viral infections. Some of them have appeared promising, but further studies are definitely required. Several challenges, including complicated correlations of the factors and determination of the susceptible period during pregnancy, need to be overcome. Comparisons of the data from areas and cohorts with different patterns of the candidate factors may be helpful. Animal studies may also help investigate the molecular and physiological mechanisms of the phenomenon.

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.

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.

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.

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.

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.

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.

Early and late environmental risk factors for schizophrenia

Although a high proportion of liability to schizophrenia is under genetic control, a number of environmental risk factors have been identified. The earliest of these are complications of pregnancy and birth, though whether these cause or reflect disturbed brain development is not absolutely clear. Neurodevelopmental deviance is also indicated by neurological dysfunction, social, behavioural and cognitive deficits during childhood. Immigrant status is a significant risk factor, especially prominent among the African Caribbean population in England, though the mechanism is unknown. Later environmental risk factors include adverse life events and substance abuse. An additive model of multiple genetic and environmental risk factors of small effect may be too simplistic and an interactive model where genetic predisposition is compounded by environmental effects is more in keeping with current evidence. The nature of such interactions can be explored more fully when susceptibility genes for schizophrenia are identified.

The neurodevelopmental basis of schizophrenia: clinical clues from cerebro-craniofacial dysmorphogenesis, and the roots of a lifetime trajectory of disease

A "read-back" analysis of schizophrenia, from chronic illness, through the first psychotic episode, to psychosocial and neurointegrative abnormalities of childhood and infancy, leads to the intrauterine period as a primary focus for etiological events. Evidence for a characteristic topography of cerebro-craniofacial dysmorphology in schizophrenia is reviewed, and interpreted to estimate: (i) the timing of dysmorphic event(s); (ii) the nature of early cellular and molecular mechanisms which might determine that topography of dysmorphogenesis; and (iii) the population homogeneity of these processes. It is argued that early cerebro-craniofacial dysmorphogenesis in schizophrenia should be conceptualized as a first stage not in a static but rather in a dynamic, lifetime trajectory of disease.

Seasonality of births in schizophrenia and bipolar disorder: a review of the literature

More than 250 studies, covering 29 Northern and five Southern Hemisphere countries, have been published on the birth seasonality of individuals who develop schizophrenia and/or bipolar disorder. Despite methodological problems, the studies are remarkably consistent in showing a 5-8% winter-spring excess of births for both schizophrenia and mania/bipolar disorder. This seasonal birth excess is also found in schizoaffective disorder (December-March), major depression (March-May), and autism (March) but not in other psychiatric conditions with the possible exceptions of eating disorders and antisocial personality disorder. The seasonal birth pattern also may shift over time. Attempts to correlate the seasonal birth excess with specific features of schizophrenia suggest that winter-spring births are probably related to urban births and to a negative family history. Possible correlations include lesser severity of illness and neurophysiological measures. There appears to be no correlation with gender, social class, race, measurable pregnancy and birth complications, clinical subtypes, or neurological, neuropsychological, or neuroimaging measures. Virtually no correlation studies have been done for bipolar disorder. Regarding the cause of the birth seasonality, statistical artifact and parental procreational habits are unlikely explanations. Seasonal effects of genes, subtle pregnancy and birth complications, light and internal chemistry, toxins, nutrition, temperature/weather, and infectious agents or a combination of these are all viable possibilities.

Season of birth of schizophrenics in a recent Japanese sample

An excess of schizophrenic births in winter or early spring is a well replicated finding in studies on Western populations. However, there are few studies on Asian populations, and their results are not consistent. We examined the seasonality of schizophrenic births in Japanese subjects (n = 1024) born between 1955 and 1960. Our results showed a significant inverse relationship between temperature and number of schizophrenic births, which is in line with the findings in Western populations. In our data, observed reduction of schizophrenic births in summer was more marked than excess births in winter. We suggest the possibility that birth in summer may have some advantage in brain growth early in life, which results in reducing the risk of developing schizophrenia.

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.

If Schizophrenia is enantiomorphism, is light the morphogen?

Schizophrenia remains an enigmatic condition. It would appear that both genetic and environmental influences are relevant to the aetiopathogenesis of the disorder. Although a great amount of research has been carried out concerning the condition, the results have often lead to further questions and attempts to more closely delineate the object of study have lead to the originally observed findings becoming tenuous. One way to objectively view some aspects of this large body of work is to consider the condition as a cerebral situs inversus, as data from various lines of reasoning have suggested an inversion of the situation seen in normal controls. The hypothesis presented here draws on existing biological evidence to argue the likely role of light as a relevant, stimulatory variable which may interact with asymmetrical cerebral maturation in the establishment of functional laterality.

Testing the effect of season of birth on familial risk for schizophrenia and related disorders

BACKGROUND

An excess of late winter and early spring births in schizophrenia has been repeatedly demonstrated. Previous evidence has suggested that the risk for schizophrenia may differ in relatives of schizophrenic probands born in this high risk period v. at other times of the year.

METHOD

In an epidemiologically based family study conducted in the west of Ireland, we examined the relationship between season of birth in schizophrenia and schizophrenia spectrum probands and the risk for schizophrenia and related disorders in first-degree relatives. Risk was assessed using the Cox proportional hazard method. We examined four birth seasons previously shown to significantly predict risk for schizophrenia.

RESULTS

Neither the risk for schizophrenia nor that for schizophrenia spectrum disorders in relatives was significantly associated with season of birth in probands.

CONCLUSIONS

Season of birth does not, in this sample, identify schizophrenic probands with particularly high or low familial vulnerability to illness.