What causes seasonality of birth in schizophrenia?

Season of birth has no effect on symptoms of depression and anxiety in older adults

There remains a lack of conclusive evidence as to the merit of season of birth as a predictor of mental illness across contexts. We studied 72,370 individuals (55% women; mean age 66) from the Survey on Health, Ageing and Retirement in Europe. Depressive symptoms were assessed with EURO-D scale and symptoms of anxiety with modified Beck Anxiety Inventory. Multilevel modeling was used to assess the association of season of birth as well as month of birth with symptoms of depression and anxiety, by sex and region. Adjusting for sex and age, month of birth explained only 0.01% to 0.07% of anxiety and depressive symptoms with non-significant improvement in the overall models; using season of birth instead of month of birth added 0.00% to 0.04% of explained variance. When stratified by sex and European region, age explained 0.23% to 5.19% of anxiety and depressive symptoms; the addition of month of birth or season of birth improved the models by negligible amount. Season of birth and month of birth are not reliable predictors of anxiety and depression across the life course.

The dual hit hypothesis of schizophrenia: Evidence from animal models

Schizophrenia is a heterogeneous psychiatric disorder, which can severely impact social and professional functioning. Epidemiological and clinical studies show that schizophrenia has a multifactorial aetiology comprising genetic and environmental risk factors. Although several risk factors have been identified, it is still not clear how they result in schizophrenia. This knowledge gap, however, can be investigated in animal studies. In this review, we summarise animal studies regarding molecular and cellular mechanisms through which genetic and environmental factors may affect brain development, ultimately causing schizophrenia. Preclinical studies suggest that early environmental risk factors can affect the immune, GABAergic, glutamatergic, or dopaminergic system and thus increase the susceptibility to another risk factor later in life. A second insult, like social isolation, stress, or drug abuse, can further disrupt these systems and the interactions between them, leading to behavioural abnormalities. Surprisingly, first insults like maternal infection and early maternal separation can also have protective effects. Single gene mutations associated with schizophrenia did not have a major impact on the susceptibility to subsequent environmental hits.

Association Between Season of Birth and Cognitive Aging in Older Adults: Pan-European Population-Based Study on 70,000 Individuals

BACKGROUND

Several early-life factors have been associated with higher risk of developing dementia. It is unclear whether season of birth (SOB) can affect cognitive aging in older adults or not.

OBJECTIVE

We aimed to study the association of SOB with the level of cognitive performance as well as with the rate of cognitive decline.

METHODS

We studied 70,203 individuals who participated in the Survey of Health, Aging and Retirement in Europe. Cognition was measured with tests on verbal fluency and immediate and delayed recall. We assessed the association of SOB with the level of cognitive performance using multiple linear regression and with the rate of cognitive decline using linear mixed-effects models.

RESULTS

When compared to individuals born in winter and adjusted for sociodemographic and health-related characteristics, being born in summer was associated with a higher level of delayed recall (B 0.05; 95%CI 0.01 to 0.09) and verbal fluency (B 0.15; 95%CI 0.00 to 0.29) and being born in fall with a higher level of immediate recall (B 0.04; 95%CI 0.01 to 0.08) and verbal fluency (B 0.15; 95%CI 0.01 to 0.29). Individuals born in summer had a higher yearly decline in delayed recall (B -0.005; 95%CI -0.009 to 0.000), while the scores in delayed recall in participants born in spring showed an inverse trend (B 0.005; 95%CI 0.000 to 0.010).

CONCLUSION

Individuals born in winter seem to carry a life-long disadvantage in a lower level of cognitive performance; however, being born in winter does not seem to affect the rate of cognitive decline.

Month of birth and mental disorders: A population-based study and validation using global meta-analysis

OBJECTIVE

Month of birth (MOB) is associated with specified mental disorders (MDs). However, whether these relationships extend to all MDs remains unclear. We investigate the association using a population-based cohort study and a meta-analysis.

METHODS

First, we examined patients with 34 DSM-5-classified MDs in the Taiwan national database. We estimated the relative risk ratios (RR) of each illness in each MOB relative to that in the general population and assessed the periodicity, with six further sensitivity analyses. Second, we searched PubMed, Embase, and Cochrane for related articles through 31 December 2020. We used a random-effects model, pooled RRs with 95% confidence intervals of each MOB from the identified studies, and transformed them from MOB to relative age in a year or season.

RESULTS

The cohort included 1,951,777 patients. Except for posttraumatic stress disorder, dissociative disorders, feeding/eating disorders, gender dysphoria, and paraphilic disorders, the other MDs had significant MOB periodicity. The meta-analysis included 51 studies investigating 10 MDs. The youngest age at the start of school owing to MOB was associated with the highest RRs of intellectual disability (1.13), autism (1.05), attention-deficit/hyperactivity disorder (1.13). Winter births had significant risks of schizophrenia (1.04), bipolar I disorder (1.02), and major depressive disorder (1.01), and autumn births had a significant risk of alcohol use disorder (1.02). No significant associations between season of birth and Alzheimer's disease, or eating disorders were found.

CONCLUSIONS

MOB is related to the risks of certain MDs. This finding provides a reference for future research on the etiology of MDs.

Season of birth and the risk of dementia in the population-based Rotterdam Study

Early-life environmental factors have been suggested in the pathophysiology of dementia. Season of birth has previously been used as a proxy for these external exposures. We investigated the link between season of birth and the risk of dementia and further explored underlying pathways by studying structural brain changes on MRI. From the Dutch, population-based Rotterdam Study, 12,964 participants born between 1887 and 1960 were followed between 1990 and 2018 for dementia. Cox regression was conducted to assess the association between season of birth and dementia. In addition, we distinguished between mild and cold winters. The association of season of birth with structural brain markers on MRI was examined in 5237 participants. The risk of dementia in participants born in winter and fall was higher than of those born in summer (hazard ratio (HR) 1.15 [95% confidence interval (CI) 1.01–1.31] for winter and HR 1.17 [95% CI 1.01–1.33] for fall), especially for Alzheimer’s disease (HR 1.23 [1.06–1.43] for winter and HR 1.15 [95% CI 0.99–1.35] for fall). The risk was particularly increased for participants born in a cold winter. Except for slightly lower hippocampus in fall born participants (β − 0.03; 95% CI − 0.06 to 0.00), we did not find associations with brain imaging markers. In conclusion, winter and fall births were associated with a higher incidence of dementia, especially of AD. We did not find evidence for structural brain changes as an underlying mechanism.

A Translational Perspective of Maternal Immune Activation by SARS-CoV-2 on the Potential Prenatal Origin of Neurodevelopmental Disorders: The Role of the Cholinergic Anti-inflammatory Pathway

The emergent Coronavirus Disease 2019 (COVID-19) caused by the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) could produce a maternal immune activation (MIA) via the inflammatory response during gestation that may impair fetal neurodevelopment and lead to postnatal and adulthood mental illness and behavioral dysfunctions. However, so far, limited evidence exists regarding long-term physiological, immunological, and neurodevelopmental modifications produced by the SARS-CoV-2 in the human maternal-fetal binomial and, particularly, in the offspring. Relevant findings derived from epidemiological and preclinical models show that a MIA is indeed linked to an increased risk of neurodevelopmental disorders in the offspring. We hypothesize that a gestational infection triggered by SARS-CoV-2 increases the risks leading to neurodevelopmental disorders of the newborn, which can affect childhood and the long-term quality of life. In particular, disruption of either the maternal or the fetal cholinergic anti-inflammatory pathway (CAP) could cause or exacerbate the severity of COVID-19 in the maternal-fetal binomial. From a translational perspective, in this paper, we discuss the possible manifestation of a MIA by SARS-CoV-2 and the subsequent neurodevelopmental disorders considering the role of the fetal-maternal cytokine cross-talk and the CAP. Specifically, we highlight the urgent need of preclinical studies as well as multicenter and international databanks of maternal-fetal psychophysiological data obtained pre-, during, and post-infection by SARS-CoV-2 from pregnant women and their offspring.

Season-of-birth phenomenon in health and longevity: epidemiologic evidence and mechanistic considerations

In many human populations, especially those living in regions with pronounced climatic differences between seasons, the most sensitive (prenatal and neonatal) developmental stages occur in contrasting conditions depending on the season of conception. The difference in prenatal and postnatal environments may be a factor significantly affecting human development and risk for later life chronic diseases. Factors potentially contributing to this kind of developmental programming include nutrition, outdoor temperature, infectious exposures, duration of sunlight, vitamin D synthesis, etc. Month of birth is commonly used as a proxy for exposures which vary seasonally around the perinatal period. Season-of-birth patterns have been identified for many chronic health outcomes. In this review, the research evidence for the seasonality of birth in adult-life disorders is provided and potential mechanisms underlying the phenomenon of early life seasonal programming of chronic disease and longevity are discussed.

The fetal origins of mental illness

The impact of infections and inflammation during pregnancy on the developing fetal brain remains incompletely defined, with important clinical and research gaps. Although the classic infectious TORCH pathogens (ie, Toxoplasma gondii, rubella virus, cytomegalovirus [CMV], herpes simplex virus) are known to be directly teratogenic, emerging evidence suggests that these infections represent the most extreme end of a much larger spectrum of injury. We present the accumulating evidence that prenatal exposure to a wide variety of viral and bacterial infections-or simply inflammation-may subtly alter fetal brain development, leading to neuropsychiatric consequences for the child later in life. The link between influenza infections in pregnant women and an increased risk for development of schizophrenia in their children was first described more than 30 years ago. Since then, evidence suggests that a range of infections during pregnancy may also increase risk for autism spectrum disorder and depression in the child. Subsequent studies in animal models demonstrated that both pregnancy infections and inflammation can result in direct injury to neurons and neural progenitor cells or indirect injury through activation of microglia and astrocytes, which can trigger cytokine production and oxidative stress. Infectious exposures can also alter placental serotonin production, which can perturb neurotransmitter signaling in the developing brain. Clinically, detection of these subtle injuries to the fetal brain is difficult. As the neuropsychiatric impact of perinatal infections or inflammation may not be known for decades after birth, our construct for defining teratogenic infections in pregnancy (eg, TORCH) based on congenital anomalies is insufficient to capture the full adverse impact on the child. We discuss the clinical implications of this body of evidence and how we might place greater emphasis on prevention of prenatal infections. For example, increasing uptake of the seasonal influenza vaccine is a key strategy to reduce perinatal infections and the risk for fetal brain injury. An important research gap exists in understanding how antibiotic therapy during pregnancy affects the fetal inflammatory load and how to avoid inflammation-mediated injury to the fetal brain. In summary, we discuss the current evidence and mechanisms linking infections and inflammation with the increased lifelong risk of neuropsychiatric disorders in the child, and how we might improve prenatal care to protect the fetal brain.

Seasonality of births in horizontal strabismus: comparison with birth seasonality in schizophrenia and other disease conditions

Recent work has implicated one type of horizontal strabismus (exotropia) as a risk factor for schizophrenia. This new insight raises questions about a potential common developmental origin of the two diseases. Seasonality of births is well established for schizophrenia. Seasonal factors such as light exposure affect eye growth and can cause vision abnormalities, but little is known about seasonality of births in strabismus. We examined birth seasonality in people with horizontal strabismus in a retrospective study in Washoe County, Nevada, and re-examined similar previously obtained data from Osaka, Japan. We then compared seasonal patterns of births between strabismus, refractive error, schizophrenia and congenital toxoplasmosis. Patients with esotropia had a significant seasonality of births, with a deficit in March, then increasing to an excess in September, while patients with exotropia had a distinctly different pattern, with an excess of births in July, gradually decreasing to a deficit in November. These seasonalities were statistically significant with either χ2 or Kolmogorov-Smirnov-type statistics. The birth seasonality of esotropia resembled that for hyperopia, with an increase in amplitude, while the seasonality for myopia involved a phase-shift. There was no correlation between seasonality of births between strabismus and congenital toxoplasmosis. The pattern of an excess of summer births for people with exotropia was remarkably similar to the well-established birth seasonality of one schizophrenia subtype, the deficit syndrome, but not schizophrenia as a whole. This suggests a testable hypothesis: that exotropia may be a risk factor primarily for the deficit type of schizophrenia.

Season of birth: A predictor of ADHD symptoms in early midlife

OBJECTIVE

In this longitudinal study, we applied linear regression analyses to examine season of birth as related to symptoms of attention deficit/hyperactivity disorder (ADHD) in early midlife.

METHOD

We gathered longitudinal data on a prospective cohort of community-dwelling men and women (N = 548) followed from adolescence to early midlife.

FINDINGS

The findings indicate that, as compared with participants who were born in the summer, those who were born in the spring (Beta = 0.34; t-statistic = 3.59; p < 0.001) had significantly more ADHD symptoms. In addition, exposure to maternal cigarette smoking in adolescence significantly intensified (p < 0.01) the association between season of birth and ADHD symptoms in early midlife.

CONCLUSION

These findings suggest that exposure to greater maternal maladaptive behaviors, such as cigarette smoking, may result in a greater vulnerability to other environmental risk factors, such as season of birth.

Season of birth and depression in adulthood: Revisiting historical forerunner evidence for in-utero effects

Evidence showing a relationship between season of birth and adult well-being is long-standing, but is now largely overlooked or dismissed. In light of increasingly compelling evidence for the effects of in-utero conditions on adult health, however, it is instructive to revisit the relationship, with an eye toward resolving the reasons for skepticism. This study uses data from the first National Health and Nutritional Examination Survey to examine the effects of month of birth on adult depression. The data correspond to an important time in history and the analysis points to one reason why enthusiasm for birth seasonality in depression has faded: although there was a strong relationship between month of birth and depression in the early 20th century, with spring and summer month births corresponding to significantly more depression, the relationship was largely eliminated by the 1940 birth cohort. Few adults alive today would be subject to this effect, but when it was apparent it was enormously consequential. Population attributable risk scenarios indicate that among those born between 1900 and 1920 the prevalence of major depression would have been reduced by approximately 22% if all births had been confined to November through March. The percent rises to 26% among those born between 1900 and 1910, and was likely even higher in earlier cohorts. Additional analyses point to the importance of nutritional deficits in explaining these effects. In the early 20th century, the relationship between month of birth and depression was weaker in circumstances where the food supply was less seasonally sensitive. For this reason, the turn-of-the-century relationship between month of birth and depression was much weaker among the well-educated, in Southern states, and in urban areas. Although birth seasonality in depression can be regarded as a historical artefact of diet and nutrition, evidence for its prior existence nonetheless speaks to the significance of other in-utero effects, both past and present.

The association between season of birth, age at onset, and clozapine use in schizophrenia

OBJECTIVE

This study aimed to determine whether the rate of clozapine use, an indicator of refractoriness in schizophrenia, is associated with the season of birth and age at onset in patients with schizophrenia based on nationwide data.

METHODS

Patients with schizophrenia (n = 114 749) who received prescriptions for antipsychotic medication between 2008 and 2014 were retrospectively identified from the Korean National Health Insurance Service database. The study population was divided into three groups based on their age at the onset of schizophrenia (early, middle, and late onset). We assessed differences in the month of birth between patients and the general population. In addition, the cumulative clozapine use was calculated.

RESULTS

Compared to the late-onset schizophrenia group, the early- and middle-onset groups showed a higher probability of birth during the winter season. In addition, the early-onset group showed the highest cumulative clozapine use rate. In the middle-onset group, the initiation of clozapine use was significantly earlier for patients born in winter compared to those born in summer.

CONCLUSION

Our results indicate that the age at onset is an important factor in predicting the prognosis of schizophrenia patients. The season of birth also affects the prognosis, but with less robustness. Specifically, it appears that early disease onset and winter birth might be associated with poor outcomes in Korean patients with schizophrenia.

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.

Interaction Effects of Season of Birth and Cytokine Genes on Schizotypal Traits in the General Population

Literature suggests that the effect of winter birth on vulnerability to schizophrenia might be mediated by increased expression of proinflammatory cytokines due to prenatal infection and its inadequate regulation by anti-inflammatory factors. As the response of the immune system depends on genotype, this study assessed the interaction effects of cytokine genes and season of birth (SOB) on schizotypy measured with the Schizotypal Personality Questionnaire (SPQ-74). We searched for associations of IL1B rs16944, IL4 rs2243250, and IL-1RN VNTR polymorphisms, SOB, and their interactions with the SPQ-74 total score in a sample of 278 healthy individuals. A significant effect of the IL4 X SOB interaction was found, p = 0.007 and η² = 0.028. We confirmed this effect using an extended sample of 373 individuals. Homozygotes CC born in winter showed the highest SPQ total score and differed significantly from winter-born T allele carriers, p = 0.049. This difference was demonstrated for cognitive-perceptual and disorganized but not interpersonal dimensions. The findings are consistent with the hypothesis that the cytokine genes by SOB interaction can influence variability of schizotypal traits in the general population. The IL4 T allele appeared to have a protective effect against the development of positive and disorganized schizotypal traits in winter-born individuals.

Birth seasonality in rural areas of Iran, analysis of 5,536,262 births from 1992 to 2007

PURPOSE

We conducted this study to investigate birth seasonality in rural parts of Iran.

METHODS

In this study, patterns of 5,536,262 live births in rural parts of Iran between 1992 and 2007 were studied. Information about birth numbers, environmental factors, and sociocultural status of participants was obtained from previous works. Visually inspecting the seasonal variation of birth, studying its trend using autocorrelation analysis, examining the trend of birth seasonality using the seasonality coefficient, a newly introduced index, studying correlations between birth seasonality and possible associated factors, and analyzing associations between these variables and birth seasonality using multiple regression model were performed in this study.

RESULTS

In this study, we showed birth seasonality in rural parts of Iran, with the highest births in the first two seasons, winter and spring, mostly before the year of 2002. Latitude and mean temperature of districts, wealth status of families, education of women, and mothers' ages were associated with birth seasonality. However, latitude, temperature, and mothers' ages lost their associations after adjusting for sociocultural factors in the regression model.

CONCLUSIONS

Birth numbers in rural areas of Iran follow a rhythmic seasonal pattern; however, the ordering of seasons changes in the last years of the study period.

Season of birth and population schizotypy: Results from a large sample of the adult general population

Although the last years have seen an increasing interest in schizotypy and its pathogenesis, there exist only a handful of studies examining the possible interaction between season of birth (SOB) and schizotypic personality structure. Available research used differing screening instruments, rendering comparisons between studies difficult, and sample sizes in adult populations may have been too small to detect a mild effect. The current study examined the association between SOB and psychometric schizotypy in the so far single-largest sample from the adult general population (N=8114), balanced for men and women, and utilizing a valid and reliable instrument for the assessment of schizotypy. Using the 12 most informative items of the Schizotypal Personality Questionnaire Brief, we obtained evidence of a small, but significant, effect of late winter and early spring births (February/March) on psychometric schizotypy. The effect was not constrained to women, but affected men and women alike. The observed association between SOB and schizotypy appears compatible with seasonal variations of temperature and influenza prevalence, and with recent evidence on seasonal variability in the activity of the human immune system. Our findings lend support to the continuum hypothesis of schizotypy and schizophrenia, for which SOB effects have been previously established.

Association of adoptive child's thought disorders and schizophrenia spectrum disorders with their genetic liability for schizophrenia spectrum disorders, season of birth and parental Communication Deviance

Joint effects of genotype and the environment have turned out to be significant in the development of psychotic disorders. The purpose of the present study was to assess the association of an adoptive child׳s thought and schizophrenia spectrum disorders with genetic and environmental risk indicators and their interactions. A subgroup of the total sample used in the Finnish Adoptive Family Study was considered in the present study. The subjects were 125 adoptees at a high (n=53) or low (n=72) genetic risk of schizophrenia spectrum disorders and their adoptive parents. The risk factors evaluated were the adoptive child's genetic risk for schizophrenia spectrum disorders, winter or spring birth and parental Communication Deviance (CD). Thought disorders in the adoptees were assessed using the Thought Disorder Index and diagnoses were made according to DSM-III-R criteria. The adoptive child׳s Thought Disorder Index was only associated with parental Communication Deviance. The adoptive child's heightened genetic risk or winter or spring birth or parental CD or their interactions did not predict the adoptee's schizophrenia spectrum disorder. The results suggest that studies taking several risk indicators and their interactions into account may change views on the mutual significance of well-known risk factors.

Neuroimmunological aberrations and cerebral asymmetry abnormalities in schizophrenia: select perspectives on pathogenesis

Within the wide-ranging gamut of factors that comprise gene-environment interactions postulated to underlie schizophrenia, the crosstalk between environmental factors and feto-maternal immune components has been put forth as one of the important mechanisms that increase the risk towards schizophrenia in the offspring. Interestingly, immune factors have been shown to critically modulate the brain development during the prenatal stages. Moreover the past many decades, influential theoretical propositions and evidence base (albeit not unequivocally) have compellingly linked prenatal sex hormonal status to critically provoke long lasting immunological changes and subsequently affect developmental programming of cerebral asymmetry in schizophrenia. In this review, we summarize the select perspectives emphasizing the role of neuroimmunoendocrine pathways in anomalous cerebral asymmetry in contemporary understanding of schizophrenia pathogenesis.

Peptide sharing between influenza A H1N1 hemagglutinin and human axon guidance proteins

Epidemiologic data suggest that maternal microbial infections may cause fetal neurodevelopmental disorders, potentially increasing susceptibility to heavy psychopathologies such as schizophrenia, schizophreniform disorder, autism, pervasive developmental disorders, bipolar disorders, psychosis, epilepsy, language and speech disorders, and cognitive impairment in adult offspring. However, the molecular pathomechanisms underlying such a relationship are not clear. Here we analyze the potential role of the maternal immune response to viral infection in determining fetal brain injuries that increase the risk of neurological disorders in the adult. We use influenza infection as a disease model and human axon guidance pathway, a key process in the formation of neural network during midgestation, as a potential fetal target of immune insults. Specifically, we examined influenza A H1N1 hemagglutinin (HA), an antigenic viral protein, for amino acid sequence similarity to a random library of 188 axon guidance proteins. We obtain the results that (1) contrary to any theoretical expectations, 45 viral pentapeptide matches are distributed throughout a subset of 36 guidance molecules; (2) in 24 guidance proteins, the peptide sharing with HA antigen involves already experimentally validated influenza HA epitopes; and (3) most of the axon guidance vs HA peptide overlap is conserved among influenza A viral strains and subsets. Taken together, our data indicate that immune cross-reactivity between influenza HA and axon guidance molecules is possible and may well represent a pathologic mechanism capable of determining neurodevelopmental disruption in the fetus.

Alterations of white matter integrity related to the season of birth in schizophrenia: a DTI study

In schizophrenia there is a consistent epidemiological finding of a birth excess in winter and spring. Season of birth is thought to act as a proxy indicator for harmful environmental factors during foetal maturation. There is evidence that prenatal exposure to harmful environmental factors may trigger pathologic processes in the neurodevelopment, which subsequently increase the risk of schizophrenia. Since brain white matter alterations have repeatedly been found in schizophrenia, the objective of this study was to investigate whether white matter integrity was related to the season of birth in patients with schizophrenia. Thirty-four patients with schizophrenia and 33 healthy controls underwent diffusion tensor imaging. Differences in the fractional anisotropy maps of schizophrenia patients and healthy controls born in different seasons were analysed with tract-based spatial statistics. A significant main effect of season of birth and an interaction of group and season of birth showed that patients born in summer had significantly lower fractional anisotropy in widespread white matter regions than those born in the remainder of the year. Additionally, later age of schizophrenia onset was found in patients born in winter months. The current findings indicate a relationship of season of birth and white matter alterations in schizophrenia and consequently support the neurodevelopmental hypothesis of early pathological mechanisms in schizophrenia.

Season of Birth and Later Outcomes: Old Questions, New Answers

Season of birth is associated with later outcomes; what drives this association remains unclear. We consider a new explanation: variation in maternal characteristics. We document large changes in maternal characteristics for births throughout the year; winter births are disproportionally realized by teenagers and the unmarried. Family background controls explain nearly half of season-of-birth's relation to adult outcomes. Seasonality in maternal characteristics is driven by women trying to conceive; we find no seasonality among unwanted births. Prior seasonality-in-fertility research focuses on conditions at conception; here expected conditions at birth drive variation in maternal characteristics while conditions at conception are unimportant.

Season of birth effect on psychotic-like experiences in Japanese adolescents

A number of studies have investigated seasonality of birth in schizophrenia. Most of the studies have consistently observed an excess of winter births, often associated with decreased summer births. We postulated that psychotic-like experiences (PLEs), subclinical hallucinatory and delusional experiences, may also be affected by birth season. In the present study, we assessed the season of birth effect on the prevalence of PLEs using data from the cross-sectional survey of 19,436 Japanese adolescents. As a result, significant excess of winter births was observed in the prevalence of PLEs, accompanied by a decreased proportion of summer births. The odds ratios for the prevalence of PLEs were estimated to be 1.11, which was on the same order with those for the development of schizophrenia in the previous meta-analytic studies. To our knowledge, this is the first to show the seasonality of birth in the prevalence of PLEs and implicate the winter birth effect on subclinical stage of schizophrenia.

Seasonal variations of neuromotor development by 14 months of age: Hamamatsu Birth Cohort for mothers and children (HBC Study)

The present study aimed at investigating whether neuromotor development, from birth to 14 months of age, shows seasonal, cyclic patterns in association with months of birth. Study participants were 742 infants enrolled in the Hamamatsu Birth Cohort (HBC) Study and followed-up from birth to the 14th month of age. Gross motor skills were assessed at the ages of 6, 10, and 14 months, using Mullen Scales of Early Learning. The score at each assessment was regressed onto a trigonometric function of months of birth, with an adjustment for potential confounders. Gross motor scores at the 6th and 10th months showed significant 1-year-cycle variations, peaking among March- and April-born infants, and among February-born infants, respectively. Changes in gross motor scores between the 10th and 14th months also showed a cyclic variation, peaking among July- and August-born infants. Due to this complementary effect, gross motor scores at the 14th month did not show seasonality. Neuromotor development showed cyclic seasonality during the first year of life. The effects brought about by month of birth disappeared around 1 year of age, and warmer months seemed to accelerate the neuromotor development.

[Environmental risk factors for schizophrenia: a review]

BACKGROUND

Evidence of variations in schizophrenia incidence rates has been found in genetically homogenous populations, depending on changes within time or space of certain environmental characteristics. The consideration of the impact of environmental risk factors in etiopathogenic studies has put the environment in the forefront of research regarding psychotic illnesses. Various environmental factors such as urbanicity, migration, cannabis, childhood traumas, infectious agents, obstetrical complications and psychosocial factors have been associated with the risk of developing schizophrenia. These risk factors can be biological, physical, psychological as well as social and may operate at different times in an individual's life (fetal period, childhood, adolescence and early adulthood). Whilst some of these factors act on an individual level, others act on a populational level, modulating the individual risk. These factors can have a direct action on the development of schizophrenia, or on the other hand act as markers for directly implicated factors that have not yet been identified.

LITERATURE FINDINGS

This article summarizes the current knowledge on this subject. An extensive literature search was conducted via the search engine Pubmed. Eight risk factors were selected and developed in the following paper: urbanicity (or living in an urban area), cannabis, migration (and ethnic density), obstetrical complications, seasonality of birth, infectious agents (and inflammatory responses), socio-demographic factors and childhood traumas. For each of these factors, we provide information on the importance of the risk, the vulnerability period, hypotheses made on the possible mechanisms behind the factors and the level of proof the current research offers (good, medium, or insufficient) according to the amount, type, quality and concordance of the studies at hand. Some factors, such as cannabis, are "unique" in their influence on the development of schizophrenia since it labels only one risk factor. Others, such as obstetrical complications, are grouped (or "composed") in that they include various sub-factors that can influence the development of schizophrenia.

DISCUSSION

The data reviewed clearly demonstrates that environmental factors have an influence on the risk of developing schizophrenia. For certain factors - cannabis, migration, urbanicity, obstetrical complications, seasonality - there is enough evidence to establish an association with the risk of schizophrenia. This association, however, remains weak (especially for seasonality). With the exception of cannabis, no direct link can yet be established. Concerning the three remaining factors - childhood traumas, infectious agents, socio-demographic factors - the available proof is insufficient. One main limitation concerning all environmental factors is the generalization of results due to the fact that the studies were conducted on geographically limited populations. The current state of knowledge does not allow us to determine the mechanisms by which these factors may act.

CONCLUSION

Further research is needed to fill the gaps in our understanding of the subject. In response to this need, a collaborative European project (European Study of Gene-Environment Interactions [EU GEI]) was set-up. This study proposes the analysis of those environmental factors that influence the incidence of schizophrenia in various European countries, in both rural and urban settings, migrant and native populations, as well as their interaction with genetic factors.

Relationships of Un and Gi seasons of birth to clinical symptoms and signs

OBJECTIVES

Season of birth (SOB) is a medical term used to describe the relationship between the season in which one is born and his or her physiologic and pathological characteristics. In East Asian medicine, the Un-Gi SOB is based on the Yin-yang-Five Phases theory. The purpose of this study is to examine the relationship between Un-Gi SOB and a multitude of clinical symptoms and signs, and to examine which of the Un and Gi seasons has the greatest impact on these symptoms and signs.

METHODS

Using the Delphi method, three Un-Gi experts formulated a 26-item questionnaire consisting of clinical symptoms and signs, with each item rated on a Likert 7-point scale. A total of 1057 Korean adolescents (583 males, 474 females) completed the 26-item questionnaire. After identifying the Un and Gi seasons of all subjects, item scores were evaluated to determine whether there was a difference between Un and Gi seasons.

RESULTS

For Un seasons, males born in the Wood season had greater indigestion and were less physically active, whereas females born in the Earth season were better able to concentrate but had slower rates of growth. For Gi seasons, males born in the Fire season had greater indigestion and morning fatigue, and males born in the Earth season had higher tension. There was no relationship between symptoms, signs, and the Gi SOB in females. This indicates that males born in Wood Un and Gi seasons are susceptible to Earth-related clinical problems, whereas females born in the Earth Un season are susceptible to Earth-related clinical problems.

CONCLUSIONS

The study results suggest that Un-Gi seasons based on the Yin-yang-Five Phases are related to clinical symptoms and signs, with significant differences between genders.

Mapping brain regions in which deep brain stimulation affects schizophrenia-like behavior in two rat models of schizophrenia

BACKGROUND AND OBJECTIVES

The development of more efficient treatment remains a major unmet need in the realm of schizophrenia disease. Using the maternal immune stimulation and the pubertal cannabinoid administration rat model of schizophrenia, the present study aimed at testing the hypothesis that deep brain stimulation (DBS) serves as a novel therapeutic technique for this disorder.

METHODS

Adult offspring of dams, treated with the immune activating agent poly I:C (4 mg/kg, n = 50) or saline (n = 50), underwent bilateral stereotactic electrode implantation into one of the following brain regions: subthalamic nucleus (STN, n = 12/10), entopeduncularis nucleus (EP, n = 10/11), globus pallidus (GP, n = 10/10), medial prefrontal cortex (mPFC, n = 8/8), or dorsomedial thalamus (DM, n = 10/11). Adult rats treated with the CB1 receptor agonist WIN 55,212-2 (WIN, n = 16) or saline (n = 12) during puberty were bilaterally implanted with electrodes into either the mPFC (n = 8/6) or the DM (n = 8/6). After a post-operative recovery period of one week, all rats were tested on a well-established cross-species phenomenon that is disrupted in schizophrenia, the pre-pulse inhibition (PPI) of the acoustic startle reflex (ASR) under different DBS conditions.

RESULTS

Poly I:C induced deficits in PPI of the ASR were normalized upon DBS. DBS effects depended on both stimulation target and stimulation parameters. Most prominent effects were found under DBS at high frequencies in the mPFC and DM. These effects were replicated in the pubertal WIN administration rat model of schizophrenia.

CONCLUSIONS

Brain regions, in which DBS normalized PPI deficits, might be of therapeutic relevance to the treatment of schizophrenia. Results imply that DBS could be considered a plausible therapeutic technique in the realm of schizophrenia disease.

Influence of relative age on diagnosis and treatment of attention-deficit/hyperactivity disorder in children

BACKGROUND

The annual cut-off date of birth for entry to school in British Columbia, Canada, is Dec. 31. Thus, children born in December are typically the youngest in their grade. We sought to determine the influence of relative age within a grade on the diagnosis and pharmacologic treatment of attention-deficit/hyperactivity disorder (ADHD) in children.

METHODS

We conducted a cohort study involving 937 943 children in British Columbia who were 6-12 years of age at any time between Dec. 1, 1997, and Nov. 30, 2008. We calculated the absolute and relative risk of receiving a diagnosis of ADHD and of receiving a prescription for a medication used to treat ADHD (i.e., methylphenidate, dextroamphetamine, mixed amphetamine salts or atomoxetine) for children born in December compared with children born in January.

RESULTS

Boys who were born in December were 30% more likely (relative risk [RR] 1.30, 95% confidence interval [CI] 1.23-1.37) to receive a diagnosis of ADHD than boys born in January. Girls born in December were 70% more likely (RR 1.70, 95% CI 1.53-1.88) to receive a diagnosis of ADHD than girls born in January. Similarly, boys were 41% more likely (RR 1.41, 95% CI 1.33-1.50) and girls 77% more likely (RR 1.77, 95% CI 1.57-2.00) to be given a prescription for a medication to treat ADHD if they were born in December than if they were born in January.

INTERPRETATION

The results of our analyses show a relative-age effect in the diagnosis and treatment of ADHD in children aged 6-12 years in British Columbia. These findings raise concerns about the potential harms of overdiagnosis and overprescribing. These harms include adverse effects on sleep, appetite and growth, in addition to increased risk of cardiovascular events.

Short and long term variation in ultraviolet radiation and multiple sclerosis

We examined the role of ultraviolet radiation (UVR) in persons diagnosed with multiple sclerosis (MS) in four different populations, Italians, Danish, White and African Americans. We tested whether variation in UVR as determined by seasons (short term variation) and solar cycles (long term variation) is related to MS birth month and to survival as measured by lifespan. Cases were selected from three Italian MS Case Registries (2,737); from the United States National Center for Health Statistics (56,020); and from the Danish Multiple Sclerosis registry (15,900). Chi-square tests were used to study the pattern of month of birth distribution in patients with MS comparing with general population data. T-tests were employed to study solar cycles association with lifespan. A surplus of births was observed in June for White Americans. A decrease of births in October and November, though not significant after multiple testing correction, was observed in the three populations. In White American with MS overall, males and females, we found that solar cycle is associated with lifespan. We found that season and solar cycles have some role in MS susceptibility and life duration. However, this is an exploratory analysis and further work is needed to discern the association.

Relationships between season of birth, schizotypy, temperament, character and neurocognition in a non-clinical population

While schizophrenia has been associated with a slight excess of winter/early spring birth, it is unclear whether there is such an association in relation to schizotypal personality traits. Season of birth has also been reported to relate to temperament and character personality dimensions and cognitive functioning. Moreover, non-clinical schizotypy has been shown to be associated with mild cognitive impairment, although its precise nature is yet to be elucidated. Here we examined the relationships between season of birth, schizotypal traits, temperament and character, and cognitive function. Four hundred and fifty-one healthy adults completed the Schizotypal Personality Questionnaire (SPQ). The Temperament and Character Inventory (TCI) and a neuropsychological test battery consisting of full versions of the Wechsler Memory Scale-Revised and the Wechsler Adult Intelligence Scale-Revised, and the Wisconsin Card Sorting Test, were also administered to most of the participants. The total SPQ score of those born in winter was significantly higher than that of the remaining participants. Season of birth was not significantly associated with any of the TCI dimensions or cognitive test results. Significant but mild relationships between higher SPQ scores and lower scores on some aspects of IQ were observed. These results support the notion that schizotypy and schizophrenia are neurodevelopmental conditions on the same continuum.

Associations between season of birth and the risk of lung cancer: epidemiological findings from Hungary

Lung cancer is the leading cause of cancer deaths worldwide. Both incidence and mortality of lung cancer are especially high in Hungary. Several investigations suggested recently that month of birth (MOB) is associated with the risks of several nonmalignant disorders as well as some malignant disorders. Only a few studies investigated previously the association between MOB and risk of lung cancer, but they provided inconsistent results. We, therefore, decided to investigate this issue in a large sample of individuals who died from lung cancer. Accordingly, we determined the MOB-associated risk of death by lung cancer between the years 1970 and 2009 among all individuals born in Hungary between 1925 and 1934. The final sample included about two million people. A total of 61,904 deaths by lung cancer occurred in this sample during the period investigated. Using analysis of variance (ANOVA), we did not find significant association between MOB and risk of lung cancer death, either in the whole population investigated (F = 1.492; p = .145) or in the female subpopulation (F = 1.535; p = .129). However, those males born in late spring (May-June) had a lower risk of lung cancer development (F = 2.577; p = .006). Results of the Edwards test also did not suggest consistent association between MOB and risk of lung cancer death in the whole investigated period (1925-1934) in any populations (i.e., whole population or male and female subpopulations). In conclusion, we did not find significant association between MOB and risk of lung cancer in our total sample (although results alluded to a weak association between MOB and risk of lung cancer development among males). The possible associations between MOB and the risk of lung cancer development (or smoking) would require confirmation (or refutation) in large studies from other populations.

Cognitive and emotional processing associated with the Season of Birth and dopamine D4 receptor gene

The 7-repeats variant of the dopamine D4 receptor (7R) VNTR polymorphism has been associated with higher novelty seeking (NS) and disadvantageous decision making in the Iowa Gambling Task (IGT). Season of Birth (SOB) is a significant determinant of NS. SOB and L-DRD4 genetic polymorphism may independently and interactively influence similar behaviors through their common effects on the dopaminergic system. Two hundred and twenty-seven healthy males grouped in summer-born/4-repeats (4R) (n=75), winter-born/4R (n=90), summer-born/7R (n=31) and winter-born/7R (n=31) groups, completed multimodal assessment for personality, planning for problem solving and decision making. Winter-born/7R subjects had significantly worse IGT performance throughout the task compared to 4R individuals, while summer-born 7R subjects had intermediate, although not significantly different performance. Moreover, winter-born/7R subjects had increased behavioral approach to reward without parallel reduction in sensitivity to fear or to social approval cues. The DRD4-by-SOB groups did not differ in planning for problem solving. These results suggest that a DRD4-by-SOB interaction is associated with increased behavioral approach to reward and risk taking but efficient problem solving. In addition, these results further support the hypothesis that SOB modifies the behavioral expression of dopaminergic genetic polymorphism. SOB should be included in future studies of risky behaviors and behavioral genetic studies of the dopamine system.

Prenatal Factors in Schizophrenia

The purpose of this review is to summarize the current state of knowledge on how nongenetic factors occurring before, during, or soon after birth are related to schizophrenia. Schizophrenia is a complex psychiatric illness with a varied clinical presentation that has both environmental and genetic origins and that may result from insults to the nervous system that occur throughout development. In line with this, several endogenous (internal) and exogenous (external) nongenetic factors of pregnancy and birth have been related to an increased risk for schizophrenia in later life. These factors include maternal diabetes, low birth weight, older paternal age, winter birth, and prenatal maternal stress, among others. Although each of these nongenetic factors alone slightly increases the risk for schizophrenia, risk increases when these factors combine with each other and with other risk factors. The mechanisms that link each specific risk factor with the occurrence of schizophrenia remain largely unknown. In order to build better models of the illness, researchers will have to address the question of how environmental and genetic risk factors work together in increasing risk and explore to what extent certain underlying risk factors may explain different aspects of the disease.

Season of birth is significantly associated with the risk of completed suicide

BACKGROUND

Previous studies have provided somewhat inconsistent results about the effects of season of birth on the risk of suicidal behavior. Therefore, we decided to investigate this question in a large sample of suicide completers.

METHODS

We determined the season of birth-associated risk of completed suicide between the years 1970 and 2008 among all individuals who were born in the area of today's Hungary between 1930 and 1939, 1941 and 1942, and 1944 and 1969.

RESULTS

The final sample of participants included around six and a half million people. About 80,000 completed suicides occurred among participants during the period investigated (the number of suicide completers in our study greatly exceeds the number of suicide completers in any previous studies). A significantly (p < .05) elevated risk of completed suicide was found among those individuals who were born in the high-risk period (spring and summer). Quantitatively, the biggest increase (7.6% [95% confidence interval: 5.4-9.9]) in suicide risk was detected among those who were born in July compared with the average risk of suicide in the population investigated. The associations between season of birth and the risk of completed suicide were stronger among male subjects than among female subjects and among those who committed suicide using violent methods than among those who chose nonviolent methods.

CONCLUSIONS

Our results from a large sample of suicide completers from Hungary--a country with one of the highest suicide rates in the world over the last century--strongly support the concept that the season of birth is significantly associated with the risk of completed suicide.

Classical and Bayesian estimation in the logistic regression model applied to diagnosis of child attention deficit hyperactivity disorder

The limitations inherent to classical estimation of the logistic regression models are known. The Bayesian approach in statistical analysis is an alternative to be considered, given that it makes it possible to introduce prior information about the phenomenon under study. The aim of the present work is to analyze binary and multinomial logistic regression simple models estimated by means of a Bayesian approach in comparison to classical estimation. To that effect, Child Attention Deficit Hyperactivity Disorder (ADHD) clinical data were analyzed. The sample included 286 participants of 6-12 years (78% boys, 22% girls) with ADHD positive diagnosis in 86.7% of the cases. The results show a reduction of standard errors associated to the coefficients obtained from the Bayesian analysis, thus bringing a greater stability to the coefficients. Complex models where parameter estimation may be easily compromised could benefit from this advantage.

Neuroanatomic and cognitive abnormalities related to herpes simplex virus type 1 in schizophrenia

Herpes simplex virus 1 (HSV-1) tends to replicate in the temporal cortex and can damage the limbic system. The presence of serum antibodies to HSV-1 is associated with cognitive impairment in adults with schizophrenia, suggesting that cerebral gray matter abnormalities might distinguish patient subgroups defined by HSV-1 exposure. We assessed 43 adult outpatients with schizophrenia. The assessment included clinical interviews, neurocognitive testing, anatomic brain magnetic resonance imaging and measures of serum IgG antibodies specific to herpes simplex viruses 1 and 2. We then compared 25 patients who tested positive for antibodies to HSV-1 with 15 who were seronegative for both HSV-1 and HSV-2. The seropositive patients performed significantly worse than the seronegative patients on four neuropsychological measures of psychomotor speed, executive functioning, and explicit verbal memory. Voxel-based morphometric analyses revealed that the same patients showed reduced gray matter volume in the anterior cingulate and areas of the cerebellum. Finally, performance on the test of psychomotor speed and executive functioning that showed the largest between- group effect size correlated with reduced gray matter volume in some of the same brain regions (cingulate and cerebellum) that distinguished the two HSV-1 subgroups. In these outpatients with schizophrenia, HSV-1 seropositivity and performance on a cognitive test that is highly sensitive to it co-localize to closely overlapping brain regions.

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.

Risk of developing schizophrenia among Japanese high-risk offspring of affected parent: outcome of a twenty-four-year follow up

AIMS

Prospective follow-up studies of high-risk children may help clarify the etiological factors in schizophrenia. While studies from North America, Europe and Israel have estimated the risk of schizophrenia at 7-16% in the offspring of an affected parent, no data have been reported for Asian populations.

METHOD

We started a follow up of the offspring of Japanese schizophrenia patients in 1978. We investigated the estimated risk of schizophrenia in 51 high-risk offspring at the 24-year follow up. The effects of the parents' status, including history of psychiatric hospitalization and social functioning, on the risk in the offspring were also investigated.

RESULTS

The cumulative incidence of schizophrenia was 13.7 % and the lifetime prevalence was estimated to be 13.5 +/- 4.8%. The association between the psychiatric hospitalization in the probands and the risk of schizophrenia in the offspring was not significant, and the Global Assessment of Functioning score was significantly lower in the probands with a history of psychiatric hospitalization than in those without such a history.

CONCLUSIONS

The risk of developing schizophrenia in Japanese high-risk offspring might be comparable with the Western results. The present study suggests that the severity of the disease or the level of social functioning may not significantly affect the risk in Japanese offspring.

Environmental studies of schizophrenia through the prism of epigenetics

Traditionally, etiological research of schizophrenia has been focused on elucidating predisposing genes and environmental risk factors. While numerous putative environmental hazards have been suggested, inconsistencies and methodological limitations of epidemiological studies have made it difficult to identify even a single exogenous cause of schizophrenia. Furthermore, there is increasing evidence that environmental risk factors may not play as much of a significant role in schizophrenia as previously suspected. In this article, we argue that molecular epigenetic studies can overcome the complexities of traditional epidemiological studies and may become a productive line of research in understanding the nongenetic mechanisms of schizophrenia.

Peaks of solar cycles affect the gender ratio

In this study, we report that the gender ratio (GR) at death [where GR=(N(males)/N(males)+N(females))] of those born (and likely conceived) in solar cycle peaks (about a 3-year period occurring on average every approximately 11 years), is inversely related to mean male age at death; e.g., the higher the GR(at death) the lower the mean lifespan, while the GR(at death) of those born in non-peak years has no relation to mean male lifespan. Although changes in the GR are small and may be of little clinical significance, the GR is a sensitive indicator of environmental effects, and therefore is pertinent to epigenetics. This paper supports the hypothesis that solar radiation, probably in the ultraviolet spectrum, by some manner interacts with chromosomal DNA (genes) and produces the genetic variety that not only fosters adaptation, but also produces the diseases that reduce lifespan. This paper also proposes that sunlight is more effective in modifying genomes at the time of conception than later in gestation or infancy. Referring to the work of others, this study also reveals that geographic latitude also affects the GR, suggesting that the variation in light is probably as important as the intensity of light in modifying genomes. This study finds that men sustain more genetic variation, producing 28% more disease than women, as well as a 2% decrease in GR from birth to death, and a shorter life (in Maine) by 7 years.

Month of birth and offspring count of women: data from the Southern hemisphere

BACKGROUND

Several studies indicate that the month of birth affects later reproductive output of women in the Northern hemisphere.

METHODS

To investigate whether a comparable but time-shifted effect is also present in the Southern hemisphere where the seasonal variation of the environment is reversed, we analysed the association between birth month and offspring count in post-reproductive New Zealand women. We further examined whether this association differed with the hemisphere of birth as well as the socio-economic background.

RESULTS

We find that the association between birth month and offspring count of New Zealand women born in the Southern, albeit not Northern, hemisphere is a mirror image of the pattern reported from Austrian women: on average, women born during the Southern hemisphere summer months have fewer children than women born in winter. This association is highly significant within the lowest family income category but insignificant within higher family income categories.

CONCLUSIONS

This study provides evidence for a causal link between the seasonality of the environment during the pre- and perinatal period and offspring count of women. It further indicates that the main contribution of the birth month effect found in the present study comes from the lowest family income category.

Birth months and vulnerability to juvenile delinquency

BACKGROUND

Birth months have been shown to affect susceptibility to schizophrenia and other mental disorders, thus this factor could also affect predisposition to delinquency through biological effects on brain development and personality and/or through relative age effects at school. This study aimed to examine the relationship between birth-season and relative age at school on the risk of delinquency.

METHODS

We investigated the ratio of observed and expected births in winter/summer and that in the first/last months of the Japanese school year in 5008 young male Japanese delinquents.

RESULTS

No significant difference was found between observed and expected numbers of births in winter/summer or those in the first/last months of the school year.

CONCLUSIONS

The present study did not provide evidence for any effect from season of birth or a relative age effect within the school year on the risk of delinquency in Japanese male teenagers.

Maternal immune activation alters fetal brain development through interleukin-6

Schizophrenia and autism are thought to result from the interaction between a susceptibility genotype and environmental risk factors. The offspring of women who experience infection while pregnant have an increased risk for these disorders. Maternal immune activation (MIA) in pregnant rodents produces offspring with abnormalities in behavior, histology, and gene expression that are reminiscent of schizophrenia and autism, making MIA a useful model of the disorders. However, the mechanism by which MIA causes long-term behavioral deficits in the offspring is unknown. Here we show that the cytokine interleukin-6 (IL-6) is critical for mediating the behavioral and transcriptional changes in the offspring. A single maternal injection of IL-6 on day 12.5 of mouse pregnancy causes prepulse inhibition (PPI) and latent inhibition (LI) deficits in the adult offspring. Moreover, coadministration of an anti-IL-6 antibody in the poly(I:C) model of MIA prevents the PPI, LI, and exploratory and social deficits caused by poly(I:C) and normalizes the associated changes in gene expression in the brains of adult offspring. Finally, MIA in IL-6 knock-out mice does not result in several of the behavioral changes seen in the offspring of wild-type mice after MIA. The identification of IL-6 as a key intermediary should aid in the molecular dissection of the pathways whereby MIA alters fetal brain development, which can shed new light on the pathophysiological mechanisms that predispose to schizophrenia and autism.

Season of birth and dopamine receptor gene associations with impulsivity, sensation seeking and reproductive behaviors

Background

Season of birth (SOB) has been associated with many physiological and psychological traits including novelty seeking and sensation seeking. Similar traits have been associated with genetic polymorphisms in the dopamine system. SOB and dopamine receptor genetic polymorphisms may independently and interactively influence similar behaviors through their common effects on the dopaminergic system.

Methodology/Principal Findings

Based on a sample of 195 subjects, we examined whether SOB was associated with impulsivity, sensation seeking and reproductive behaviors. Additionally we examined potential interactions of dopamine receptor genes with SOB for the same set of traits. Phenotypes were evaluated using the Sociosexual Orientation Inventory, the Barratt Impulsivity Scale, the Eysenck Impulsivity Questionnaire, the Sensation Seeking Scale, and the Delay Discounting Task. Subjects were also asked about their age at first sex as well as their desired age at the birth of their first child. The dopamine gene polymorphisms examined were Dopamine Receptor D2 (DRD2) TaqI A and D4 (DRD4) 48 bp VNTR. Primary analyses included factorial gender×SOB ANOVAs or binary logistic regression models for each dependent trait. Secondary analysis extended the factorial models by also including DRD2 and DRD4 genotypes as independent variables. Winter-born males were more sensation seeking than non-winter born males. In factorial models including both genotype and season of birth as variables, two previously unobserved effects were discovered: (1) a SOB×DRD4 interaction effect on venturesomeness and (2) a DRD2×DRD4 interaction effect on sensation seeking.

Conclusion

These results are consistent with past findings that SOB is related to sensation seeking. Additionally, these results provide tentative support for the hypothesis that SOB modifies the behavioral expression of dopaminergic genetic polymorphism. These findings suggest that SOB should be included in future studies of risky behaviors and behavioral genetic studies of the dopamine system.

No evidence for a preferential transmission of the methylenetetrahydrofolate reductase 677T allele in families with schizophrenia offspring

The methylenetetrahydrofolate reductase (MTHFR) 677C > T polymorphism has been associated with an increased risk of schizophrenia in various case-control studies. However, case-control studies are sensitive to population stratification, which is not an issue in family-based studies. We conducted a family-based study comprising 120 families with a schizophrenic family member to explore the association between the parental MTHFR 677C > T polymorphism and schizophrenia risk in offspring. In addition, a meta-analysis was performed using the available studies with data on this subject. Transmission Disequilibrium Test (TDT) analysis showed no preferential transmission of the 677T allele from parents heterozygous for the MTHFR 677C > T polymorphism to schizophrenia offspring (P = 0.27). The genotype relative risks were 1.43 (95% CI: 0.83-2.47) for the 677TT and 1.42 (95% CI: 0.54-3.78) for the 677CT genotype, relative to the 677CC genotype. A meta-analysis using data from family-based studies comprising a total of 416 parent-child triads yielded no evidence implicating the 677T allele in schizophrenia risk (P = 0.58). By applying a log-linear model, we found no asymmetry within parental mating type. Our data provided no evidence that transmission of the MTHFR 677T allele is associated with schizophrenia risk. In addition, we found no evidence that the maternal genotype influences the risk of having schizophrenia offspring substantially.

Season of birth in siblings of patients with seasonal affective disorder. A test of the parental conception habits hypothesis

Recently we have published a report on seasonally varying birth rates in 553 patients with seasonal affective disorder (SAD). The present study is aimed to test the hypothesis of an idiosyncratic seasonal conception pattern of the parents of these patients to explain this phenomenon. We conducted a telephone interview with the patients to obtain information on the birth data of their siblings. Using the method of chart review to acquire information on the family history of our patients, we excluded those siblings with psychiatric disorders. We first compared the birth months and the quarters of birth of 435 healthy siblings with the general population. Secondly, we compared the birth distribution of the index SAD patients with that of their siblings. There was a significant deviation between the birth distribution of the siblings and the general population calculated on a monthly basis (p = 0.044). When comparing quarters we found less births than expected in the first (-14.1%) and fourth quarter of the year (-15.1%) and an excess of births in the second (+7.7%) and third quarter (+21.1%; p = 0.018). There were no significant differences between the group of SAD patients and their siblings regarding their birth patterns as calculated by months (p = 0.848) or quarters (p = 0.320). Our study provides support for the hypothesis of specific parental conception habits underlying the birth seasonality in SAD. Further research could be conducted in non-seasonal depression as there is still a lack of studies on seasonality of birth in affective disorders.

Is there seasonal variation in risk of Parkinson's disease?

Recent studies suggest that, for many adult-onset neurological diseases, persons born at a certain time of year are at higher risk of the disease. Small-scale studies have suggested that persons born in the spring may be at higher risk of developing Parkinson's disease (PD) late in life. There have also been suggestions that there are clusters of PD birth dates in the years of major influenza pandemics. To determine whether there is any seasonal variation in the birth dates of PD patients, we examined birth dates of 8,168 PD patients collected from subspecialty movement disorder clinics across Canada. Patterns of seasonality of birth were examined and compared with the general Canadian population. In addition, we compared counts of patients born in the years of major influenza pandemics with the number born in the surrounding years. We found no evidence of systematic seasonal variation in PD incidence by birth date, or of clustering of birth dates during influenza pandemic years in PD patients.