Season of birth and schizophrenia in Northeast Brazil: relationship to rainfall

Systematic review and meta-analysis: Season of birth and schizophrenia risk

OBJECTIVE

Winter birth has been hypothesized to be associated with increased schizophrenia risk for nearly a century. Major hypotheses regarding the potential etiological risk factors for schizophrenia such as vitamin D deficiency and virus exposure in utero are predicated based on the observation that risk of schizophrenia is higher in children born in winter months.

METHODS

We conducted a systematic review and meta-analysis to examine the association between season and month of birth and risk of schizophrenia. We further investigated this relationship stratified by hemisphere.

RESULTS

Forty-three studies spanning 30 countries and territories and 440,039 individuals with schizophrenia were included in this meta-analysis. Winter births were associated with a small but statistically significant increased risk of schizophrenia (OR 1.05, 95 % CI 1.03-1.07, p < 0.0001) and summer births were associated with a small but statistically significant decreased risk of schizophrenia (OR 0.96, 95 % CI 0.94-0.98, p = 0.0001). Stratified subgroup analysis demonstrated no significant difference between hemispheres in the risk of schizophrenia for either winter or summer births.

CONCLUSIONS

Analysis using birth month data demonstrated a clear seasonal trend towards increased risk of schizophrenia being associated with winter birth months and decreased risk of schizophrenia in summer-to-fall months in the Northern but not Southern Hemisphere. These data suggest a small-but-substantial increased risk of schizophrenia in winter birth month. Further research needs to examine potential etiologic causes for this association.

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.

Need for Ethnic and Population Diversity in Psychosis Research

This article aims to evaluate "racial", ethnic, and population diversity-or lack thereof-in psychosis research, with a particular focus on socio-environmental studies. Samples of psychosis research remain heavily biased toward Western, Educated, Industrialized, Rich, and Democratic (WEIRD) societies. Furthermore, we often fail to acknowledge the lack of diversity, thereby implying that our findings can be generalized to all populations regardless of their social, ethnic, and cultural background. This has major consequences. Clinical trials generate findings that are not generalizable across ethnicity. The genomic-based prediction models are far from being applicable to the "Majority World." Socio-environmental theories of psychosis are solely based on findings of the empirical studies conducted in WEIRD populations. If and how these socio-environmental factors affect individuals in entirely different geographic locations, gene pools, social structures and norms, cultures, and potentially protective counter-factors remain unclear. How socio-environmental factors are assessed and studied is another major shortcoming. By embracing the complexity of environment, the exposome paradigm may facilitate the evaluation of interdependent exposures, which could explain how variations in socio-environmental factors across different social and geographical settings could contribute to divergent paths to psychosis. Testing these divergent paths to psychosis will however require increasing the diversity of study populations that could be achieved by establishing true partnerships between WEIRD societies and the Majority World with the support of funding agencies aspired to foster replicable research across diverse populations. The time has come to make diversity in psychosis research more than a buzzword.

Impact of Season of Birth on Psychiatric Disorder Susceptibility and Drug Abuse Incidence in a Population from the Köppen Tropical Savanna Region of Brazil

BACKGROUND

Despite much evidence that season of birth (SOB) my influence the vulnerability to psychiatric disorders, divergence has been reported, in particular between populations born in the northern and southern hemispheres. We analyzed the potential modified risk by SOB to psychiatric disorder or drug addiction comorbidity in a population born in the Triângulo Mineiro region, a southern hemisphere Köppen tropical savanna region in Brazil.

METHOD

We accessed the records of 98,457 of patients and healthy controls of the National Datacenter of Medical Promptuary to evaluate the influence of SOB as a modifying factor on the occurrence of mental disorders and drug abuse conditions among individuals born from the year 2000 to 2016.

RESULTS

The data revealed significant modification of the relative incidence of major depressive disorder (MDD) (F11, 72 = 2.898; p = 0.003; eta-squared, ES = 0.313; ⍺ = 0.97), anxiety-related disorder (ARD) (F11, 81 =2.389; p = 0.013; ES = 0.241; ⍺ = 0.932), and schizophrenia (SZ) (F11, 83 = 2.764; p = 0.005; ES = 0.303; α = 0.963), while there was no increase in the number of healthy controls born in any month of the year (F11, 71 = 1.469; p = 0.163). Post hoc analyses indicated a significant higher vulnerability to MDD or ARD if the patient was born in August, or October to December, respectively. A relative increase in the incidence of SZ was also observed in patients born from August to October, compared to patients born from November to January.

CONCLUSIONS

SOB may influence the risk for psychiatric disorders in the TMR population. Regional particularities associated with the climatic regime may account for the apparent divergence between studies.

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.

Misreporting Month of Birth: Diagnosis and Implications for Research on Nutrition and Early Childhood in Developing Countries

A large literature has used children’s birthdays to identify exposure to shocks and estimate their impacts on later outcomes. Using height-for-age z scores (HAZ) for more than 990,000 children in 62 countries from 163 Demographic and Health Surveys (DHS), we show how random errors in birth dates create artifacts in HAZ that can be used to diagnose the extent of age misreporting. The most important artifact is an upward gradient in HAZ by recorded month of birth (MOB) from start to end of calendar years, resulting in a large HAZ differential between December- and January-born children of –0.32 HAZ points. We observe a second artifact associated with round ages, with a downward gradient in HAZ by recorded age in months, and then an upward step after reaching ages 2, 3, and 4. These artifacts have previously been interpreted as actual health shocks. We show that they are not related to agroclimatic conditions but are instead linked to the type of calendar used and arise mainly when enumerators do not see the child’s birth registration cards. We explain the size of the December–January gap through simulation in which 11 % of children have their birth date replaced by a random month. We find a minor impact on the average stunting rate but a larger impact in specific error-prone surveys. We further show how misreporting MOB causes attenuation bias when MOB is used for identification of shock exposure as well as systematic bias in the impact on HAZ of events that occur early or late in each calendar year.

Investigating the effect of climatic parameters on mental disorder admissions

The main objective of this study was to evaluate the role of climatic parameters and phenomena including the monthly number of dusty/rainy/snowy/foggy days, cloudiness (Okta), horizontal visibility, and barometric pressure (millibar) on major depressive disorder, bipolar, schizophrenia, and schizoaffective admissions. The monthly data related to the number of admissions in Farshchian hospital and climatic parameters from March 2005 to March 2017 were extracted. Random forest regression and dynamic negative binomial regression were used to examine the relationship between variables; the statistical significance was considered as 0.05. The number of dusty/rainy/snowy/foggy days, cloudiness, and the number of days with vision less than 2 km had a significant positive relationship with admissions due to schizophrenia (p < 0.05). Barometric pressure had a negative effect on schizophrenia admissions (p < 0.001). The number of dusty/rainy/snowy/foggy days and cloudiness had a significant effect on schizoaffective admissions (p < 0.05). Bipolar admissions were negatively associated with rainy days and positively associated with dusty days and cloudiness (p < 0.05). The number of rainy/dusty/snowy days and cloudiness had a positive significant effect on major depressive disorder admissions. The results of the present study confirmed the importance of climatic parameter variability for major depressive disorder, bipolar, schizophrenia, and schizoaffective admissions.

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.

Modeling month-season of birth as a risk factor in mouse models of chronic disease: from multiple sclerosis to autoimmune encephalomyelitis

Month-season of birth (M-SOB) is a risk factor in multiple chronic diseases, including multiple sclerosis (MS), where the lowest and greatest risk of developing MS coincide with the lowest and highest birth rates, respectively. To determine whether M-SOB effects in such chronic diseases as MS can be experimentally modeled, we examined the effect of M-SOB on susceptibility of C57BL/6J mice to experimental autoimmune encephalomyelitis (EAE). As in MS, mice that were born during the M-SOB with the lowest birth rate were less susceptible to EAE than mice born during the M-SOB with the highest birth rate. We also show that the M-SOB effect on EAE susceptibility is associated with differential production of multiple cytokines/chemokines by neuroantigen-specific T cells that are known to play a role in EAE pathogenesis. Taken together, these results support the existence of an M-SOB effect that may reflect seasonally dependent developmental differences in adaptive immune responses to self-antigens independent of external stimuli, including exposure to sunlight and vitamin D. Moreover, our documentation of an M-SOB effect on EAE susceptibility in mice allows for modeling and detailed analysis of mechanisms that underlie the M-SOB effect in not only MS but in numerous other diseases in which M-SOB impacts susceptibility.-Reynolds, J. D., Case, L. K., Krementsov, D. N., Raza, A., Bartiss, R., Teuscher, C. Modeling month-season of birth as a risk factor in mouse models of chronic disease: from multiple sclerosis to autoimmune encephalomyelitis.

Birth month and risk of atopic dermatitis: a nationwide population-based study

BACKGROUND

An individual's birth month has been associated with allergic diseases, but little is known about the association between birth month and atopic dermatitis (AD).

OBJECTIVE

The aim of this study was to investigate the risk of AD in children born in various months.

METHODS

Using Taiwan's National Health Insurance Research Database, we conducted a case-control study that included 31 237 AD cases and 124 948 age- and gender-matched controls without AD. Data regarding sociodemographic factors and coexisting medical conditions were collected and controlled in the multivariate logistic regression to determine the adjusted odds ratios and 95% confidence intervals for AD associated with the participant's birth month.

RESULTS

Compared with people born in May, people born in December had the highest risk of AD (OR 1.17, 95% CI 1.10-1.25), followed by people born in October (OR 1.15, 95% CI 1.08-1.22) and November (OR 1.13, 95% CI 1.06-1.20). Low income (OR 1.28), asthma (OR 1.88), allergic rhinitis (OR 1.70), psoriasis (OR 2.36), vitiligo (OR 1.99), urticaria (OR 2.14), and systemic lupus erythematosus (OR 1.91) were significant coexisting medical conditions associated with AD.

CONCLUSION

Being born in December, October, or November may be associated with an increased risk of AD. Future investigations are needed to evaluate the possible mechanism behind the association between birth month and AD.

Evidence for phenotypic plasticity in response to photic cues and the connection with genes of risk in schizophrenia

Numerous environmental factors have been identified as influential in the development of schizophrenia. Some are byproducts of modern life, yet others were present in our evolutionary past and persist to a lesser degree in the current era. The present study brings together published epidemiological data for schizophrenia and data on variables related to photic input for places of residence across geographical regions, using rainfall as an inverse, proxy measure for light levels. Data were gathered from the literature for two countries, the former Yugoslavia and Ireland, during a time in the early 20th century when mobility was relatively limited. The data for Yugoslavia showed a strong correlation between hospital census rates for schizophrenia (by place of birth) and annual rain (r = 0.96, p = 0.008). In Ireland, the hospital census rates and first admissions for schizophrenia (by place of permanent residence) showed a trend for correlation with annual rain, reaching significance for 1st admissions when the rainfall data was weighted by the underlying population distribution (r = 0.71, p = 0.047). In addition, across the years 1921-1945, birth-year variations in a spring quarter season-of-birth effect for schizophrenia in Ireland showed a trend for correlation with January-March rainfall (r = 0.80, p ≤ 0.10). The data are discussed in terms of the effect of photoperiod on the gestation and behavior of offspring in animals, and the premise is put forth that vestigial phenotypic plasticity for such photic cues still exists in humans. Moreover, genetic polymorphisms of risk identified for psychotic disorders include genes modulated by photoperiod and sunlight intensity. Such a relationship between phenotypic plasticity in response to a particular environmental regime and subsequent natural selection for fixed changes in the environmentally responsive genes, has been well studied in animals and should not be discounted when considering human disease.

Viral infection, inflammation and schizophrenia

Schizophrenia is a severe neurodevelopmental disorder with genetic and environmental etiologies. Prenatal viral/bacterial infections and inflammation play major roles in the genesis of schizophrenia. In this review, we describe a viral model of schizophrenia tested in mice whereby the offspring of mice prenatally infected with influenza at E7, E9, E16, and E18 show significant gene, protein, and brain structural abnormalities postnatally. Similarly, we describe data on rodents exposed to bacterial infection or injected with a synthetic viral mimic (PolyI:C) also demonstrating brain structural and behavioral abnormalities. Moreover, human serologic data has been indispensible in supporting the viral theory of schizophrenia. Individuals born seropositive for bacterial and viral agents are at a significantly elevated risk of developing schizophrenia. While the specific mechanisms of prenatal viral/bacterial infections and brain disorder are unclear, recent findings suggest that the maternal inflammatory response may be associated with fetal brain injury. Preventive and therapeutic treatment options are also proposed. This review presents data related to epidemiology, human serology, and experimental animal models which support the viral model of schizophrenia.

[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.

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.