Winter birth and biological family history in adopted schizophrenics

Revisiting visual dysfunctions in schizophrenia from the retina to the cortical cells: A manifestation of defective neurodevelopment

This review highlights morphological and functional anomalies found along the entire visual pathway in schizophrenia, from the retina to the cortex. Based on the evidence of widespread anatomical and functional visual abnormalities, we posited that a neurodevelopmental anomaly occurring early in life was likely to explain those. Incidentally, support to the neurodevelopmental theory of schizophrenia is strongly emerging from many neurobiological domains. In vertebrates, the first visual structures migrate toward the orbit position at the end of the fourth week of gestation. A neurodevelopmental defect around that time on these embryonic structures could account for the visual anomalies in schizophrenia. Retinol activity might be involved in the process. Future research in schizophrenia should focus on early visual testing, on trials combining multiple visual anomaly assessments and a closer look to retinol activity during the pregnancy.

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.

Birth characteristics and schizotypy: evidence of a potential "second hit"

Schizophrenia is associated with a modest increase in winter births as well as increased odds of being born in more densely populated and midrange latitude regions. It is unclear the degree to which these findings hold for individuals with schizotypy, defined in terms of the personality organization that is a potential precursor to schizophrenia-spectrum disorders. This issue is important for understanding whether birth factors contribute to general schizophrenia vulnerability or whether they reflect a secondary "hit" that increases the likelihood of psychosis onset in vulnerable individuals. The present project examined season of birth, birthplace population and birth location in a large group of young adults from the southeastern United States. Individuals with extreme schizotypy scores did not differ from those without schizotypy in season of birth, birthplace latitude or population. However, 60% of individuals within the schizotypy group who reported a diagnosis of schizophrenia or prior hospitalization were born during winter months; a dramatic difference from other individuals within the schizotypy group. We also found that individuals with negative/schizoid traits showed a birthplace population less than half that of other individuals with schizotypy. Season of birth appears to be a "second hit" that is related to expression of psychopathology onset in vulnerable individuals. This finding, and the unexpected inverse relationship between birthplace population and negative/schizoid traits, is discussed.

Relation of schizophrenia prevalence to latitude, climate, fish consumption, infant mortality, and skin color: a role for prenatal vitamin d deficiency and infections?

Previous surveys found a large (>10-fold) variation in schizophrenia prevalence at different geographic sites and a tendency for prevalence to increase with latitude. We conducted meta-analyses of prevalence studies to investigate whether these findings pointed to underlying etiologic factors in schizophrenia or were the result of methodological artifacts or the confounding of sites' latitude with level of healthcare at those sites. We found that these patterns were still present after controlling for an index of healthcare--infant mortality--and focusing on 49 studies that used similar diagnostic and ascertainment methods. The tendencies for schizophrenia prevalence to increase with both latitude and colder climate were still large and significant and present on several continents. The increase in prevalence with latitude was greater for groups with low fish consumption, darker skin, and higher infant mortality--consistent with a role of prenatal vitamin D deficiency in schizophrenia. Previous research indicates that poor prenatal healthcare and nutrition increase risk for schizophrenia within the same region. These adverse conditions are more prevalent in developing countries concentrated near the equator, but schizophrenia prevalence is lowest at sites near the equator. This suggests that schizophrenia-producing environmental factors associated with higher latitude may be so powerful they overwhelm protective effects of better healthcare in industrialized countries. The observed patterns of correlations of risk factors with prevalence are consistent with an etiologic role for prenatal vitamin D deficiency and exposure to certain infectious diseases. Research to elucidate environmental factors that underlie variations in schizophrenia prevalence deserves high priority.

Month-of-birth effect on further body size in a pig model

Previous studies unanimously confirmed the existence of a dependence of human body size on the month of birth. The cause of the phenomenon has not been identified yet, although some possible causes were proposed e.g. seasonal changes of climatic and nutritional conditions. This study explored the issue in an animal model of 20,513 pigs. We found that body weights of 6-month-old pigs were the highest for subjects born in February, but for 2-month-old pigs the peak fell in May. Any statistical correlation between the month of birth and later body weight may be induced by (1) a long-term effect of the month of birth on further growth potential (LTE), or by (2) a short-term effect of seasonal factors differentiating the growth rate (STE), so we developed a mathematical method to separate the effects. The analysis proved that (1) the observed correlations resulted only from the STE, with May-June being the months of the highest growth tempo, and that (2) there was no significant LTE. The short-term effect was responsible for differences between patterns of weight for 2- and 6-month-old animals by the month of birth: since a pig monthly gain of weight increases with age, it is favorable for it to be born in February to attain the greatest weight at the age of 6 months, whereas 2-month-old piglets are heaviest when born a month or two before the May/June optimum for growth. The lack of a long-term effect of the month of birth on pigs' weight supports the hypothesis of the cultural character of factor(s) responsible for the relationship between the month of birth and later body size in humans.

Effects of prenatal stress on anxiety and social interactions in adult rats

Deficits in social behavior are found in several neuro-psychiatric disorders with a presumed developmental origin. The aim of the present study is to determine if prenatal stress at a given day of gestation alters social behavior in adult offspring. Pregnant rats were exposed to an acute stress (presence of a cat) either at the 10th (S10), the 14th (S14) or the 19th (S19) gestational day. When adult, their offsprings were studied in anxiety, neophobic and social behaviors. The results showed that S10 and S19 rats were more anxious and less aggressive than control rats, while the anxious and aggressive behavior of S14 rats was similar to that of the control ones. It is suggested that day 14 of pregnancy is a hyposensitive period to stressful agents due to an important plasticity of the developing gross nervous structures.

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

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

OBJECTIVE

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

METHOD

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

RESULTS

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

Very mild stress of pregnant rats reduces volume and cell number in nucleus accumbens of adult offspring: some parallels to schizophrenia

Pregnant rats subjected to very mild stress give birth to pups who, when examined as adults, exhibited behavioral and anatomical anomalies that resemble some aspects of schizophrenia. The nucleus accumbens (NAcc) is reduced in volume by 20.7 +/- 3.4% (p = 0.003) in pups born to mothers who were stressed during pregnancy by injections of either saline or amphetamine in saline. The total number of cells is decreased in proportion to the reduction in volume, so the volume cell density of the NAcc is not changed with treatment. The affected volume is localized in the ventral rostral area of the NAcc. Both males and females are affected, but males are slightly more sensitive to the challenge to the mother. Rats born to mothers stressed in mid-pregnancy appear to provide useful parallels to the fetal developmental hypothesis of schizophrenia and to the brain abnormalities seen in this disease.

Month of birth predicted reproductive success and fitness in pre-modern Canadian women

Conditions experienced during early development affect human health and survival in adulthood, but whether such effects have consequences for fitness is not known. One surrogate for early conditions is month of birth, which is known to influence health and survival in many human populations. We show that in nineteenth century Canada, month of birth predicted a woman's fitness measured by the number of grandchildren produced, with the genetic contribution to the following generations by women born in different months differing by over seven grandchildren. This difference was mainly caused by differences in the reproductive rates of both mothers and their offspring, rather than differences in their survival. Women born in the best months of the year had longer reproductive lifespans, larger numbers of live births and raised more offspring to adulthood than those who were born in the worst months. Furthermore, the offspring of those women born in the best months also had greater reproductive rates, suggesting that month of birth also influenced a mother's ability to invest in her offspring. Our results suggest that early conditions may have important consequences for human lifetime reproductive performance within and between generations, and that timing of birth had large effects on fitness in this rural community.

No association between season of birth of patients with schizophrenia and risk of schizophrenia among their siblings

Previous studies on the relationship between the season of birth of patients with schizophrenia and the risk of schizophrenia among their siblings have yielded contradictory results. We investigated whether proband's month of birth affects siblings' risk of developing schizophrenia. We used the Finnish Hospital Discharge Register to identify all patients born in Finland from 1950 to 1976 who had been hospitalized because of schizophrenia at least once between 1969 and 1995. Their siblings were identified from the National Population Register, and data on siblings were linked to the Hospital Discharge Register to obtain information on any hospitalizations. We used logistic regression to investigate a sibling's probability of developing schizophrenia, defining the proband initially as the first sibling in calendar time to develop schizophrenia, then as the affected sibling with lowest onset age. Within-family dependence was taken into account by using robust standard error estimates. Neither models found any association between proband's month of birth and siblings' odds of developing schizophrenia. Our results support those previous studies that found no association between proband's month of birth and family history of schizophrenia, and suggest that the winter-spring excess of births among patients with schizophrenia is not caused by any genetic or environmental risk factor that operates independently of other risk factors.

Month-of-birth effect on height and weight in Polish rural children

This study investigated a hypothesis of dependence of child height and weight on the month of their birth. The sample comprised 1,241 subjects, 568 boys and 673 girls, age 6-20 years, from villages in Olsztyn Province, Northeast Poland. Individuals' height and weight data were standardized by sex and age to allow grouping of individuals born in the same month irrespective of their sex and age at examination. Subjects born in October to March proved to be significantly taller and heavier than those born in April to September. The magnitude of differences between the semiannual groupings equaled 13.1% of a standard deviation (SD) in height (P = 0.03) and 14.2% of SD in weight (P = 0.02). The month-of-birth effect was much stronger for children characterized by high socioeconomic status, where these differences amounted to 39.1% of SD in height (P = 0.02) and 49.4% of SD in weight (P = 0.01). There were no regular changes of the effect with age and no differences between the sexes were found. Fitted cosine functions identified the highest values of examined traits for individuals born in December with the lowest values being found in those born in June. Possible explanations of the month-of-birth effect are considered in terms of age categorizing, seasonal variety of growth rates, as well as birth-related or conception-related global, hemispheric, and local factors. This study rejects the first two possibilities and suggests this effect requires further research to be conducted in various geographical locations, climates, and cultures, on humans as well as on other species.

The "Christmas Effect" and other biometeorologic influences on childbearing and the health of women

OBJECTIVE

To review the body of literature addressing biometeorologic and chronobiologic effects on conception, pregnancy, parturition, and other health conditions.

DATA SOURCES

Computerized searches of MEDLINE, PUBMED, CINAHL, and the World Wide Web.

STUDY SELECTION

Studies, including international research, dating from 1938 to 2001.

DATA EXTRACTION

Data were extracted and information organized under the following categories: influence of leisure time and seasonality on the rate of conception and birth, the relationship of meteorologic changes and lunar cycles to childbearing, the "Christmas Effect" and its impact on other health outcomes, and nursing implications.

DATA SYNTHESIS

Research from the disciplines of biometeorology and chronobiology indicates that there are patterns in the occurrence of conception, pregnancy, and onset of labor that vary in timing and amplitude in different populations and geographic regions. Consideration of these factors should be included in the analysis of birth data when planning and providing maternity care. The Christmas Effect is one of the most predominant seasonal patterns that can be seen in birth data throughout the world.

CONCLUSIONS

Biometeorologic and other cyclic phenomena are underused in the United States in planning and providing maternity care. These phenomena warrant consideration when planning holistic health care.