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

Recent advances in the genetics of schizophrenia

The genetic etiology of schizophrenia, a common and debilitating psychiatric disorder, is supported by a wealth of data. Review of the current findings suggests that considerable progress has been made in recent years, with a number of chromosomal regions consistently implicated by linkage analysis. Three groups have shown linkage to 1q21-22 using similar models, with HLOD scores of 6.5, 3.2, and 2.4. Other replicated loci include 13q32 that has been implicated by two independent groups with significant HLOD scores (4.42) or NPL values (4.18), and 5pl4.1-13.1, 5q21-33, 8p2l-22, and 10p11-15, each of which have been reported as suggestive by at least three separate groups. Different studies have also replicated evidence for a modest number of candidate genes that were not ascertained through linkage. Of these, the greatest support exists for the DRD3 (3q13.3), HTR2A (13q14.2), and CHRNA7 (15q13-q14) genes. The refinement of phenotypes, the use of endophenotypes, reduction of heterogeneity, and extensive genetic mapping have all contributed to this progress. The rapid expansion of information from the human genome project will likely further accelerate this progress and assist in the discovery of susceptibility genes for schizophrenia. A greater understanding of disease mechanisms and the application of pharmacogenetics should also lead to improvements in therapeutic interventions.

Infectious and immune factors in the pathogenesis of neurodevelopmental disorders: epidemiology, hypotheses, and animal models

Both genetic and environmental factors contribute to the pathogenesis of a wide variety of neurodevelopmental disorders, including autism, mental retardation, and schizophrenia. Some heritable disorders approach 100% penetrance; nonetheless, even in these disorders, subtle aspects of clinical disease expression may be influenced by the environment. In other disorders with genetic influences, exogenous factors, and the timepoint(s) during nervous system development at which they are introduced, modulate expression of disease. Elucidation of the mechanisms guiding this intricate interplay between host response genes, environmental agents, and the neurodevelopmental context within which these interactions occur, is necessary to understand the continuum of clinical outcomes. This chapter will review the evidence that infectious and immune factors may contribute to the pathogenesis of neurodevelopmental disorders, describe an animal model of neurodevelopmental disorders based upon viral infection, identify processes by which neural circuitry may be compromised, and outline areas for future research.

Review of immunological and immunopathological findings in schizophrenia

The involvement of immunological and immunopathological mechanisms in the etiopathogenesis of schizophrenia has been a matter of research, with recently increasing effort. This article reviews the findings focusing on postmortem neuropathology, the blood-brain barrier, antibodies, acute phase proteins, immunocompetent cells, and activation markers of immunocompetent cells. Evidence for the two primarily postulated hypotheses (the infectious hypothesis and the autoimmune hypothesis) is critically discussed. On the basis of the findings, perspectives for future research are outlined aiming at a precise and consequent strategy to elucidate a potential involvement of immune mechanisms in the etiopathogenesis of schizophrenia.

Maternal cytokine levels during pregnancy and adult psychosis

We investigated levels of maternal cytokines in late pregnancy in relation to the subsequent development of adult schizophrenia and other psychoses in their offspring. The sample included the mothers of 27 adults with schizophrenia and other psychotic illnesses and 50 matched unaffected controls from the Providence cohort of the Collaborative Perinatal Project. Serum samples were analyzed for interleukin 1 beta (IL-1-beta), interleukin 2 (IL-2), interleukin 6 (IL-6), interleukin 8 (IL-8), and tumor necrosis factor alpha (TNF-alpha) by enzyme immunoassay. Maternal levels of TNF-alpha were significantly elevated among the case series (t = 2.22, p =.04), with evidence of increasing odds of psychosis in relation to higher cytokine levels. We did not find significant differences between case and control mothers in the serum levels of IL-1, IL-2, IL-6, or IL-8. These data support previous clinical investigations reporting maternal infections during pregnancy as a potential risk factor for psychotic illness among offspring.

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.

Cytokine effects on cortical neuron MAP-2 immunoreactivity: implications for schizophrenia

BACKGROUND

Cytokines demonstrate diverse actions in the brain and modulate systemic and central nervous system (CNS) responses to injury, infection, and inflammation. Cytokines in the CNS are elevated during infection and ischemia, two neurodevelopmental insults associated with increased schizophrenia risk. We hypothesize that cytokine-mediated neuronal injury during development may contribute to schizophrenia pathophysiology, causing subtle alterations in neuronal number and density.

METHODS

We examined cytokine regulation of neuronal number in embryonic day 18 rat cortical cultures using MAP-2 immunohistochemistry. Mixed cultures derived from frontal cortex were fixed and stained after 48-hour exposure to the proinflammatory interleukin-1beta (IL-1beta), interleukin-6 (IL-6), or tumor necrosis factor-alpha (TNF-alpha; 0, 10, 100, or 1000 units/mL).

RESULTS

IL-1beta (maximum effect 35%) and IL-6 (maximum effect 29%) produced dose-dependent decreases in the number of cells (neurons) immunoreactive for MAP-2 antibody, suggesting decreased neuronal survival. TNF-alpha also tended to decrease MAP-2 immunostaining at the highest dose tested.

CONCLUSIONS

Our data suggest a role for cytokines in the modulation of neuronal survival during neurodevelopment, a finding potentially relevant to schizophrenia pathophysiology. If cytokine-mediated neuronal injury proves to be a common response to gestational insults associated with increased schizophrenia risk, the pharmacologic modulation of these molecules may have clinical utility.

Risk factors for schizophrenia

Over the last decade, much progress has been made towards identifying risk factors for schizophrenia. It is now thought that many genes of small effect contribute towards risk of developing schizophrenia and some of these probably confer susceptibility to environmental factors. Large population-based studies, using record linkage, have investigated environmental risk factors and found that urbanization is an important factor. Other population-based studies have followed up birth cohorts and found evidence for abnormal neurodevelopment in those who subsequently developed schizophrenia. Meta-analyses have clarified the role of obstetric and perinatal complications especially hypoxia. Low IQ has emerged as a risk factor and suggests that cognitive factors are important in the etiology of psychosis. Social risk factors are now being investigated with some evidence that discrimination and isolation are significant. The role of recreational drug use is still unclear. Finally, evidence suggests that there is a continuum of psychosis both within the disorders that present clinically, but also in the general population.

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.

Summer birth and deficit schizophrenia in Nithsdale, Scotland

Patients with deficit schizophrenia differ from other people with schizophrenia relative to course of illness, treatment response, and neurobiological correlates. An association between deficit schizophrenia and summer birth, in contrast to the winter birth risk factor associated with schizophrenia as a whole, has also been reported. We attempted to replicate the association between summer birth and deficit schizophrenia by using data from a prevalence survey in Nithsdale in southwest Scotland, in which all patients with schizophrenia in Nithsdale were identified and 87% were interviewed directly. Deficit schizophrenia was associated with summer birth, defined as birth in June/July/August (p < .02), June/July (p < .02), or July/August (p < .03). The association with summer birth is consistent with other evidence that patients with deficit schizophrenia have a pathophysiology that differs in some ways from that of other patients with schizophrenia.

Summer birth and deficit schizophrenia in the epidemiological catchment area study

Winter birth is a widely replicated risk factor for schizophrenia. However, previous studies have suggested that patients with the deficit syndrome of schizophrenia have an excess of summer births. We tested the summer birth effect in a population-based study. Data came from the Epidemiological Catchment Area study, which had a representative sample of the U.S. population. Psychotic patients with features of the deficit syndrome had a significant association with summer birth, compared with the general population. There was also a significant association between summer birth and the deficit syndrome within the psychotic population, after accounting for the variance due to disorganization, hallucinations and delusions, and demographic characteristics. These findings add to the evidence suggesting the etiopathophysiology of the deficit group differs from that found in other patients with schizophrenia.

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.

The common genetic liability between schizophrenia and bipolar disorder: a review

Current psychiatric nosology, strongly influenced by Kraepelin's dichotomy, classifies schizophrenia and bipolar disorder as separate diagnostic categories. However, growing evidence indicates that the two disorders may be more closely related than was thought in the past. Bipolar disorder and schizophrenia display considerable overlap in epidemiologic features; no risk factor is known to be specific to either. Furthermore, family studies reveal familial co-aggregation of the two disorders, and twin studies suggest a significant overlap in the genes contributing to schizophrenia, schizoaffective disorder, and mania. Finally, despite the difficulties in the identification of convincing genetic loci for psychiatric disorders, there are at least four genomic regions in which linkage has been shown for both schizophrenia and bipolar disorder. Thus, recent evidence increasingly supports a dimensional approach in the understanding of the functional psychoses, and this is expected to have implications for etiologic research and future clinical treatment.

Schizotypy and the shift from dextrality: a study of handedness in a large non-clinical sample

Numerous previous studies have reported associations between schizophrenia/schizotypy and atypical handedness. While there is broad agreement that schizophrenia/schizotypy is associated with a shift away from typical (strong right) handedness, it is not entirely clear what aspect of atypical handedness is implicated: 'ambiguous' handedness (the absence of hand preference for given actions) or 'mixed handedness' (different hand preferences for different actions). The present study used several indices of handedness (derived from the Annett scale) to address these questions in 3000 + (mostly) University student subjects recruited by electronic mail. It was found that positive schizotypy (indexed by a scale of 'unusual experiences') was associated with both aspects of atypical handedness. These findings are discussed in the light of various possible explanations of the association between handedness and schizophrenia/schizotypy.

Serial analysis of gene expression in the frontal cortex of patients with bipolar disorder

BACKGROUND

Bipolar disorder is a serious brain disease affecting more than a million individuals living in the USA. Epidemiological studies indicate a role for both genetic and environmental factors in the pathogenesis of this disorder.

AIM

To identify RNA transcripts that are up- or down-regulated in the frontal cortex regions of individuals with bipolar disorder.

METHOD

Serial analysis of gene expression (SAGE) and reverse transcriptase-polymerase chain reaction were used to identify RNA transcripts which are differentially expressed in the frontal cortex of brains obtained postmortem from individuals with bipolar disorder compared with other psychiatric and control conditions.

RESULTS

Levels of RNA transcripts encoding the serotonin transporter protein and components of the NF-kappa B transcription factor complex are significantly increased in individuals with bipolar disorder compared with unaffected controls. Increased levels of expression of these RNA transcripts were also detected in the brains of some individuals with schizophrenia and unipolar depression.

CONCLUSION

The SAGE technique offers promise for the characterisation of complex human brain diseases.

Outpatients with schizophrenia and bipolar I disorder: Do they differ in their cognitive and social functioning?

The authors used a battery of cognitive and social functioning measures to evaluate stable outpatients with schizophrenia (n=74) and bipolar I disorder (n=26) who were receiving care at community and rehabilitation programs. The groups did not differ significantly on 36 of 41 measures. For most variables, comparisons between groups yielded effect sizes of <0.5. These results suggest that individuals with bipolar I disorder receiving community and rehabilitation services have many social and cognitive deficits that are as severe as those in schizophrenia.

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.

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.

Schizophrenia and season of birth in a tropical region: relationship to rainfall

Winter birth has been shown to increase the risk of schizophrenia in adult life. It has been hypothesized that this effect is due to seasonal variation in infectious diseases, including influenza, as exposure to influenza during mid gestation also increases the risk of schizophrenia. However, in many areas there is little variation in temperature during the year, although rainfall may vary greatly. We tested the hypothesis that, in a tropical region with wet and dry seasons, schizophrenia births would be related to rainfall. The data came from the city of Mossoro in north-eastern Brazil. In this area there is no meaningful variation in temperature, but there is a rainy season with little precipitation during the rest of the year. In this region, the prevalence of influenza parallels that of rainfall. There was a significant relationship between rainfall and the number of schizophrenia births three months later. In contrast, there was no significant relationship between rainfall and general population births three months later. The relationship of birth to rainfall, rather than winter birth, may be associated with risk of schizophrenia in tropical regions; exposure to influenza during gestation may be the basis for such a relationship.

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.

Lifespan depends on month of birth

Month of birth influences adult life expectancy at ages 50+. Why? In two countries of the Northern Hemisphere-Austria and Denmark-people born in autumn (October-December) live longer than those born in spring (April-June). Data for Australia show that, in the Southern Hemisphere, the pattern is shifted by half a year. The lifespan pattern of British immigrants to Australia is similar to that of Austrians and Danes and significantly different from that of Australians. These findings are based on population data with more than a million observations and little or no selectivity. The differences in lifespan are independent of the seasonal distribution of deaths and the social differences in the seasonal distribution of births. In the Northern Hemisphere, the excess mortality in the first year of life of infants born in spring does not support the explanation of selective infant survival. Instead, remaining life expectancy at age 50 appears to depend on factors that arise in utero or early in infancy and that increase susceptibility to diseases later in life. This result is consistent with the finding that, at the turn of the last century, infants born in autumn had higher birth weights than those born in other seasons. Furthermore, differences in adult lifespan by month of birth decrease over time and are significantly smaller in more recent cohorts, which benefited from substantial improvements in maternal and infant health.

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.

Paternal factors and schizophrenia risk: de novo mutations and imprinting

There is a strong genetic component for schizophrenia risk, but it is unclear how the illness is maintained in the population given the significantly reduced fertility of those with the disorder. One possibility is that new mutations occur in schizophrenia vulnerability genes. If so, then those with schizophrenia may have older fathers, because advancing paternal age is the major source of new mutations in humans. This review describes several neurodevelopmental disorders that have been associated with de novo mutations in the paternal germ line and reviews data linking increased schizophrenia risk with older fathers. Several genetic mechanisms that could explain this association are proposed, including paternal germ line mutations, trinucleotide repeat expansions, and alterations in genetic imprinting in one or several genes involved in neurodevelopment. Animal models may be useful in exploring these and other explanations for the paternal age effect and they may provide a novel approach for gene identification. Finally, it is proposed that environmental exposures of the father, as well as those of the mother and developing fetus, may be relevant to the etiology of schizophrenia.

Obstetric complications in patients with depression--a population-based case-control study

BACKGROUND

To examine whether sufferers of affective disorders are more likely to be subject to obstetric complications than normal healthy people.

METHOD

Data based on prospectively recorded birth case-notes for patients with a diagnosis of depression (or related disorders) with early onset were compared to those of normal healthy controls, individually matched by gender, time and parity of birth, maternal age and marital status.

RESULTS

Forty-one case-controls pairs born between 1964 and 1978 were compared. No differences between cases and controls in gestational age or birthweight were significant, though depressive patients on average weighed 200 g less than controls at birth. Patients were more likely than controls to be small for their gestational age (22 vs. 1: chi(2)=4.34, P=0.03). They were significantly more likely than controls to have suffered at least one obstetric complication: 35 (85%) vs. 25 (60%), chi(2)=5.03, P=0.02; or more than one (two on average, as opposed to one on average among controls). No obstetric complication was seen significantly more among cases than controls, apart from bleeding during gestation, which was observed for four cases and no controls. The prevalence of complications with a clear brain damaging potential did not differ significantly between cases and controls: 11 (26%) vs. 8 (19%).

CONCLUSIONS

A developmental deficit, as indicated by lower birthweight and gestational age, may contribute to the risk of depressive breakdowns and affective disorders in later life. Severe, brain damaging obstetric complications are unlikely to be a significant risk factor for affective disorders, though some early onset cases may be accounted for by prenatal brain lesions.

LIMITATIONS

Sample size limits statistical power for isolation of a rare, single risk factor.

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.

Winter birth and biological family history in adopted schizophrenics

To investigate relationships between birth season and biological family history in schizophrenia, this study used a sample of schizophrenics that had the advantages of (a) particularly thorough diagnostic assessments of schizophrenics' relatives, including information from direct interviews as well as chart reviews, and (b) schizophrenic probands who were adopted at early age, mitigating the usual confounding of genetic and postnatal environmental influences of the family. Adopted schizophrenics with no biological family history of schizophrenia-spectrum disorders were significantly more likely to be born in winter months than were either (a) their own biological relatives, including their sibs and half-sibs, (b) schizophrenics with a positive family history for schizophrenia-spectrum disorders, or (c) people in the general population. Family-history-positive schizophrenics and their schizophrenic relatives were, in turn, significantly less likely than their own non-schizophrenic biological relatives to be born in the winter; schizophrenics in these families tended to be born in the milder-weather seasons, particularly the spring and fall. Results suggest that environmental factors associated with winter birth may be etiologically important in schizophrenia, particularly for cases in which familial liability factors are weak. By contrast, a familial, probably genetic, liability factor may be especially important in schizophrenics born in mild weather.

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.

Season of birth variations in dimensions of functioning evaluated by the diagnostic interview for borderline patients

In view of recent reports showing that cerebrospinal fluid (CSF) levels of monoamine metabolites exhibit season of birth variations, and that they are also associated with section II (impulse action patterns) of the diagnostic interview for borderline patients (DIB), we analyzed two samples of data to investigate the relationship between the season of birth and the DIB. The first sample comprised 202 patients participating in psychobiological research in Stockholm, and the second sample comprised 130 patients who had committed suicide in Västerbotten in northern Sweden. Those with intermediate score for section II (impulse action patterns) were significantly more likely to have been born during the season October to January in the pooled data, and this tendency persisted in separate analyses for the two samples and for the two diagnostic groups mood disorders and schizophrenia, respectively. Those with high score for section IV (psychosis) were significantly more likely to have been born during February to April in the pooled sample and in the nonschizophrenic group. In the group with schizophrenia, those born during February to April had significantly high scores for section III (affects). These results throw further light on the role of season of birth in suicidology and in psychiatric morbidity.

Seasonal birth patterns of neurological disorders

Existing seasonal birth studies were reviewed for multiple sclerosis (MS), Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis (ALS), epilepsy, cerebral palsy, congenital malformations of the central nervous system and mental retardation. Epilepsy appears to have the most consistent pattern, with an excess of births in winter and a deficit in September. MS, ALS and possibly Parkinson's disease appear to have an excess of spring births. Studies of cerebral palsy are not conclusive, although there are suggestions that there may be an excess of summer births. The findings for Alzheimer's disease, congenital malformations of the central nervous system, and mental retardation are contradictory and insufficient to draw any conclusions.

Seasonality of birth in patients with mood disorders in Japan

BACKGROUND

Findings about seasonality of birth in individuals with mood disorders have been inconsistent.

METHODS

Data were collected from the governmental statistics, the Patient Survey in Japan in 1996. The number of patients with mood disorders was 13,969. We obtained information about each patient's date of birth, sex, and diagnosis according to ICD-10. Distributions of monthly birth numbers of patients with mood disorders were compared to those of the general population.

RESULTS

Birth excess was observed from winter to early-spring in both sexes, compared to births of the general population. The magnitude of the excess was larger in females than in males. Although the same tendencies were observed in patients with bipolar disorder and depressive disorder, the differences were more marked in females.

LIMITATIONS

Insufficient birth data in the general population before 1940 and hospital diagnosis.

CONCLUSION

Among Japanese patients with mood disorders, there are excess births from winter to early-spring, compared to the general population. This difference is more marked in females than in males.

Type of feeding during infancy and later development of schizophrenia

Nutrition may be critical for neurodevelopment and can affect the later development of schizophrenia. Recently, a marked reduction in breast-feeding was reported in infants that developed schizophrenia in later life (McCreadie, R.G., 1997. The Nithsdale Schizophrenia Surveys. 16. Breast-feeding and schizophrenia: preliminary results and hypothesis. Br. J. Psychiatr. 170, 334-337). In the present study, we investigated feeding patterns during the infancy of 100 schizophrenia patients, 37 of their siblings and 200 age-matched healthy controls using a structured written questionnaire. Having been breast-fed was not negatively associated with schizophrenia.

Familial and genetic mechanisms in schizophrenia

A distinction should be made between genetic aspects of schizophrenia and familial aspects. Genetic aspects of the disease have been reviewed and found to be deficient in many respects. Until recent years, familial factors were assumed to be psychological in origin, but this assumption is now discredited. Research efforts should focus on familial factors that are biological, especially infectious agents that may be transmitted within the family. Most infectious agents are influenced by predisposing genes. The etiology of schizophrenia, then, may turn out to involve biological familial infectious agents that are influenced by susceptibility genes governing the infectious process and the clinical expression of the disease.

Mood disorders and influenza epidemics in Japan

The finding that influenza epidemics are associated with an increased risk of adult mood disorder has been controversial. In this study, data were collected from governmental statistics, the Patient Survey in Japan, in 1996. Index years were defined as 1957/58, 1962, and 1965, and comparison years were defined as 2 years before and 2 years after the index year. The subjects were 361 patients with mood disorders who were born in the index years of influenza epidemics. In order to isolate patients exposed to an influenza epidemic during their second prenatal trimester, the months of birth 5 months after the influenza epidemics were defined as risk exposure months. The proportions of patients born during the exposure period in the index years were compared with those of patients born in the corresponding months in the comparison years. The same procedures were conducted for the periods 2 and 8 months after the epidemics. For female inpatients only, the proportion of patients born in the A2 influenza-exposure months in 1965 with second-trimester exposure was smaller than that of patients born in the corresponding months in the comparison years; the same phenomenon was observed for third-trimester exposure in 1957-58. However, no differences were observed in other comparisons. These findings suggest that prenatal exposure to influenza might decrease the risk for adult mood disorders in females. However, whether there is a causal relationship is still unproven.

Schizophrenia: genes and environment

The historical and genetic foundations of our current understanding of schizophrenia are reviewed, as are the present and future directions for research. Genetic epidemiological investigations, including family, twin, and adoption studies have confirmed the contributions of genetic and environmental determinants of schizophrenia. For example, identical twins show average concordance rates of only 50%; rates of 100% would be expected on the basis of genetic equivalence alone. Genetic factors may cause errors in brain development and synaptic connections. A broad range of environmental components may further damage the brain. Biological components may include pregnancy and delivery complications, such as intrauterine fetal hypoxia, infections, and malnutrition. Primarily nonbiological components may include psychosocial stressors, such as residence in an urban area and dysfunctional family communication. It is likely that the environmental factors interact with the genetic liability in a negative manner to produce disorders in the schizophrenic spectrum. Genetic and environmental components of the disorder are examined, as well as their interactions in producing either neurodevelopmental syndromes or schizophrenia itself. The implication of these findings for prevention and treatment are considered.

Season of birth in schizophrenia: no latitude at the equator

BACKGROUND

If the established winter excess in births of people who subsequently develop schizophrenia is an effect of 'seasonality', this would be testable by examining the pattern of births in an equatorial region with no formal seasons.

AIMS

To investigate whether there is any variation in month of birth among patients from equatorial Singapore with a diagnosis of schizophrenia.

METHOD

All 9655 patients discharged from Singapore's national psychiatric hospital with a diagnosis of schizophrenia were included (year of birth range 1930-1984). We analysed aggregated data, as well as the data of subsamples grouped according to birth-year periods, in order to examine secular trends. One patient subsample (those born 1960-84) allowed exact matching against the general population data set and close testing of any seasonal influence.

RESULTS

Monthly variation in births was evident for both patients and controls; the patterns were very similar, apart from the patient sample showing a trough in March-April.

CONCLUSIONS

In an equatorial region, where 'seasons' are absent, no seasonal excess in births of those later developing schizophrenia was evident.

Hypothesis: is low prenatal vitamin D a risk-modifying factor for schizophrenia?

The central nervous system is increasingly being recognised as a target organ for vitamin D via its wide-ranging steroid hormonal effects and via the induction of various proteins such as nerve growth factor. This paper proposes that low maternal vitamin D may impact adversely on the developing foetal brain, leaving the affected offspring at increased risk of adult-onset schizophrenia. The hypothesis can parsimoniously explain diverse epidemiological features of schizophrenia, such as the excess of winter births, increased rates of schizophrenia in dark-skinned migrants to cold climates, the increased rate of schizophrenia births in urban versus rural setting, and the association between prenatal famine and schizophrenia. Studies that will allow rejection of the hypothesis are proposed.

Annual variation in birth rate of people who subsequently develop schizophrenia

BACKGROUND

Previous attempts to decide whether there is significant year-to-year variation in the birth rate of people who subsequently develop schizophrenia have given conflicting results, probably because of differences in the statistical methods employed.

AIMS

To determine whether there is significant year-to-year variation in the birth rate.

METHOD

Variation in the birth rate for the period 1921-1960 was studied in three separate national data sets--English, Danish and Scottish--using cubic splines to smooth the distribution curve before calculating residuals from a Poisson distribution.

RESULTS

Over-dispersion was found in all three data sets, particularly in the Danish and Scottish data. However, the correlation between the sets of standardised residuals derived from the three data sets was only statistically significant for Denmark v. England.

CONCLUSIONS

There was statistically significant year-to-year variation in the birth rate of people who subsequently developed schizophrenia in three countries in north-west Europe in the years 1921-1960. This is potentially a clue to the nature of the environmental determinants of schizophrenia, but better data will be needed before useful explanatory hypotheses can be generated and tested.

Early cerebro-craniofacial dysmorphogenesis in schizophrenia: a lifetime trajectory model from neurodevelopmental basis to 'neuroprogressive' process

Understanding the temporal origin(s) of schizophrenia, through specifying the earliest identifiable pathology, might indicate when to look for etiological factor(s), what their nature might be, and how course of illness might evolve from these origins. From this premise, earlier formulations are elaborated to offer a rigorously data-driven model that roots schizophrenia in cerebro-craniofacial dysmorphogenesis, particularly along the mid-line but involving other structures, over weeks 9/10 through 14/15 of gestation. However, a brain that has been compromised very early in fetal life is still subject to the normal endogenous programme of developmental, maturational and involutional processes on which a variety of exogenous biological insults and psychosocial stressors can impact adversely over later pregnancy, through infancy and childhood, to maturation and into old age, to sculpt brain structure and function; it should be emphasised that the effects of such endogenous programmes and exogenous insults on such an already developmentally-compromised brain may be different from their effects on a brain whose early fetal origins were unremarkable. From these early origins, a lifetime trajectory model for schizophrenia from developmental basis to 'neuroprogressive' process is constructed. Thereafter, consideration is given to what the model can explain, including cerebral asymmetry and homogeneity, what it cannot explain, what empirical findings would challenge or disprove the model, what cellular and molecular mechanisms might underpin the model, and what are its implications.

Interstitial cells of the white matter in the inferior parietal cortex in schizophrenia: An unbiased cell-counting study

Previous studies have found an increased density of the interstitial cells of the white matter (ICWMs) in the frontal and temporal cortex in schizophrenia. Some data suggested this abnormality was restricted to a subgroup of patients, whose clinical features were consistent with the presence of the deficit syndrome. Clinical studies suggest deficit features are due to an abnormality in a cortical-subcortical circuit that includes dorsolateral prefrontal and inferior parietal cortex. We compared the density of ICWMs labeled for MAP2 immunoreactivity in Brodmann area 39 (inferior parietal cortex) from nine schizophrenia subjects (three deficit and six nondeficit) and nine matched controls using an unbiased cell-counting technique. The density of ICWMs was significantly greater in the deficit syndrome subjects compared to the nondeficit schizophrenia group (respective means +/- SEM, 0.22 +/- 0.04, and 0. 13 +/- 0.02; P < 0.05). The density of ICWMs in the deficit group was also significantly greater (P < 0.05) than that of the control group (0.09 +/- 0.02), but the nondeficit and control groups were not significantly different. These findings 1) confirm that an abnormal placement of neurons in the white matter is found in schizophrenia, 2) provide evidence for a microscopic anatomical abnormality in the inferior parietal cortex, and 3) suggest the ICWM abnormality may be confined to deficit patients.

Month of birth in deficit and non-deficit schizophrenic patients

In order to test the hypothesis that an excess of summer births is a risk factor for deficit syndrome, the month of birth was studied in 53 deficit schizophrenic patients compared to 158 non-deficit patients. No significant difference in terms of month of birth or season of birth was observed between deficit and non-deficit patients, suggesting that summer births might not be a risk factor for deficit schizophrenia.

Epidemiological comparison of schizophrenia and bipolar disorder

Schizophrenia and bipolar disorder share many epidemiological features in common, but there are also differences. Both disorders share some risk factors, suggesting etiological antecedents that date to the perinatal period; these include excess of winter-spring births, abnormal dermatoglyphics, and probably an excess of perinatal complications. By contrast, an excess of urban births and an excess of minor physical anomalies are present in schizophrenia, but apparently not in bipolar disorder. Bipolar disorder also may be found in geographic, presumably genetic, isolates and in higher prevalence in higher socio-economic groups, which also differentiates it from schizophrenia. It is hypothesized that a subset of individuals with bipolar disorder constitutes a distinct disease entity, but that the majority share some common etiological antecedents with schizophrenia and may represent a disease continuum.

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.

Season of birth and schizophrenia: a systematic review and meta-analysis of data from the Southern Hemisphere

AIMS

Data from the Northern Hemisphere support an excess of winter-spring births of individuals who later develop schizophrenia when compared with the general population. The data from the Southern Hemisphere have been less consistent. This paper will present a systematic review and meta-analysis of relevant data from the Southern Hemisphere.

METHODS

To identify relevant studies we searched electronic databases, reviewed citations from target publications and wrote letters to published authors in the field. The counts for observed and expected births were assessed in four planned comparisons. In the absence of significant heterogeneity, the data were combined using Mantel-Haenzel odds ratio in a fixed effect model.

RESULTS

Twelve studies were identified. Published and unpublished data from eight of these were able to be included in the analyses. For the two seasonal comparisons (n = 20,017), small but non-significant excesses were found in the first comparison (winter versus other seasons; OR = 1.04, 0.99-1.08) and for the second comparison (winter and spring versus other seasons; OR = 1.03, 0.99-1.07). For the two quarterly comparisons (n = 14,799), there was a small but non-significant excess found in the third comparison (third quarter versus other quarters; OR = 1.03, 0.98-1.09), and a small but non-significant deficit in the fourth comparison (third and fourth quarter versus other quarters OR = 0.99, 0.95-1.04).

CONCLUSIONS

Assuming that season of birth acts as a proxy marker for fluctuating non-genetic risk-modifying factors for schizophrenia, this review suggests that in the Southern Hemisphere these factors may be weaker, less prevalent, less regular, and/or may be modified by other confounding or modifying variables.

Handedness and season of birth: a gender-invariant relation

In an earlier study, Dellatolas, Curt and Lellouch (1991) concluded that handedness is not related to season of birth. However, post-hoc exploration of their and other sets of data has shown that there is an apparent tendency for left-handedness to be more prevalent in the period March-July than in the period August-February. The present work tested this seasonal hypothesis prospectively among university students. It was found that the proportion of all left-handed participants who were born in the period March-July was indeed significantly greater than the proportion of all right-handed participants who were born in the same period. Furthermore, the pattern of seasonal influence upon handedness did not vary significantly between females and males. The relation between handedness and season of birth may be linked to seasonal variation in other factors such as the incidence of infectious agents.

Detection and sequence analysis of borna disease virus p24 RNA from peripheral blood mononuclear cells of patients with mood disorders or schizophrenia and of blood donors

Borna disease virus (BDV) p24 RNA was detected in the peripheral blood mononuclear cells (PBMCs) of psychiatric patients and blood donors by nested reverse transcriptase PCR (RT-PCR). The prevalences of BDV p24 RNA in patients with mood disorders (4%) and schizophrenia (4%) were not significantly different from that in blood donors (2%). This finding was inconsistent with previous reports that showed either a high prevalence or absence of BDV p24 RNA in patients with psychiatric disorders. The differences in BDV p24 RNA prevalence in these studies may be due to differences in the criteria for positivity, the number of PBMCs used for RNA extraction, or the amount of RNA tested for nested RT-PCR or to laboratory contamination. Sequence analysis of BDV p24 RNA from the PBMCs of patients and blood donors showed a high nucleotide sequence conservation but definite nucleotide mutations compared with horse BDV p24 RNA sequences. In comparison with human BDV p24 RNA sequences previously reported from Japan and Germany, there were several positions with silent nucleotide mutations among these clones.

A classification of sociomedical health indicators: perspectives for health administrators and health planners

The conceptualization and operationalization of measures of health status are considered. Health indicators are conceived as a subset of social indicators, and therefore, as any social indicator, they are viewed as derivative from social issues. The interrelationships of different frames of reference for defining and measuring health that have accompained three distinct health problem patterns in the United States are viewed from a developmental perspective. Mortality and morbidity rates, the traditional health indicators, by themselves no longer serve to assess health status in developed nations. Their deficiencies as indicators serve as background for a classification schema for sociomedical health status indicators that relates health definition frames of reference, measures of health status, and health problems. The role of a group of health indicators-sociomedical heath indicators-in the current formulation of health status measures is assessed.