Gender-specific changes since 1900 in the season-of-birth effect in schizophrenia

Gender differences in the association between environment and psychosis

Various environmental exposures have been associated with psychosis spectrum disorder. However, the role of gender in this association has received little attention. Therefore, we conducted a systematic review to evaluate gender-related differences and identified 47 research articles investigating the associations of psychosis with childhood adversity, substance use, urbanicity, migration, season of birth, and obstetric complication in the PubMed database. The findings suggest that childhood abuse may be more strongly associated with a risk to develop psychosis and an earlier age at onset of illness in women than in men. Furthermore, childhood adversity has been associated with the severity of different symptom dimensions in men and women. Growing up in an urban environment and immigration are more strongly associated with psychosis risk in men than in women. Despite a higher prevalence of substance abuse comorbidity in men diagnosed with psychotic disorders, it appears that the association between substance use and psychosis risk may be stronger in women. These findings should be evaluated with caution considering several methodological limitations, limited number of studies, and lack of consistency across results. Overall, although further investigation is needed, our review shows that gender-related differences in the associations of environmental exposures with psychosis expression may exist.

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

OBJECTIVE

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

METHOD

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

RESULTS

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

CONCLUSIONS

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

The role of environmental influences on schizophrenia admissions in Israel

OBJECTIVE

The role of environmental factors in hospitalization of patients with schizophrenia is incompletely understood. This study attempts to relate the pattern of hospital admissions to environmental variables such as season and to social factors such as nationally celebrated holidays.

METHODS

Charts of all adults (n = 4,331) with a discharge diagnosis of schizophrenia admitted to the Abarbanel Mental Health Centre (Bat Yam, Israel) between 1 January 2001 and 31 December 2005 were reviewed. Hospitalizations were classified by gender, first or repeat admission, month and season of admission, and whether or not the admission coincided with a major Jewish holiday period.

RESULTS

There was a significant reduction (p < 0.05) in first admissions for men during April, the month corresponding to Passover, the most widely celebrated holiday in Israel. This pattern was not seen for women or for repeat admissions. There was no significant effect of the season upon admission rates, using two different methods of defining the season.

CONCLUSIONS

This study demonstrated significant monthly variability in admission rates and a possible protective effect of a widely celebrated public religious holiday. A consistent effect of season upon rates of admission was not found. Future studies need to identify which specific social factors exert a protective or harmful effect and study how knowledge of these effects can be translated into clinical practice.

Season of birth and prevalence of overweight and obesity in Canada

BACKGROUND

The contexts of prenatal life, such as one's season of birth, have been shown to influence health later in life. For example, research has shown a disproportionate number of schizophrenic patients are born during the late winter and early spring. The purpose of this study was to examine season of birth as a possible risk for overweight and obesity.

METHODOLOGY

Utilizing cycle 2.1 of the Canadian Community Health Survey, birth data of respondents 12 to 64 years old were examined. The risk associated with season of birth was compared to risks previously identified for overweight and obesity (e.g. physical inactivity, low socioeconomic status etc.).

RESULTS

Overall, among the 20-64 year olds, those in the obese III (BMI> or =40 kg/m(2)) category were 1.54 times more likely to be born in the winter (95% CI: 1.21-1.95). This effect appears largely due to a winter/spring season of birth effect among the obese II/III (BMI> or =35) 20-29 y cohort (Winter OR: 1.53, 95% CI: 1.08-2.18; Spring OR: 1.55, 95% CI: 1.10-2.18). A summer season of birth effect was observed for the obese II/III 40-49 y cohort (OR: 1.59, 95% CI: 1.21-2.11). No season of birth effects were observed among any BMI categories for those 12-19 years, or among those 20 y and over in the overweight BMI category.

CONCLUSION

A greater proprtion of class III obese Canadians are born during the winter/spring, particularly in the 20-29 y age cohort. However, other factors (e.g. physical inactivity) represent greater risks for obesity than season of birth.

Dates of birth and seasonal changes in well-being among 4904 subjects completing the seasonal pattern assessment questionnaire

BACKGROUND

Abnormal distributions of birthdates, suggesting intrauterine aetiological factors, have been found in several psychiatric disorders, including one study of out-patients with Seasonal Affective Disorder (S.A.D.). We investigated birthdate distribution in relation to seasonal changes in well-being among a cohort who had completed the Seasonal Pattern Assessment Questionnaire (SPAQ).

METHOD

A sample of 4904 subjects, aged 16 to 64, completed the SPAQ. 476 were cases of S.A.D. on the SPAQ and 580 were cases of sub-syndromal S.A.D. (S-S.A.D.). 92 were interview confirmed cases of S.A.D. Months and dates of birth were compared between S.A.D. cases and all others, between S.A.D. and S-S.A.D. cases combined and all others, and between interview confirmed cases and all others. Seasonality, as measured through seasonal fluctuations in well-being on the Global Seasonality Scores (GSS) of the SPAQ, was compared for all subjects by month and season of birth.

RESULTS

There was no evidence of an atypical pattern of birthdates for subjects fulfilling criteria for S.A.D., for the combined S.A.D./S-S.A.D. group or for interview confirmed cases. There was also no relationship between seasonality on the GSS and month or season of birth.

LIMITATIONS

Diagnoses of S.A.D. made by SPAQ criteria are likely to be overinclusive.

CONCLUSION

Our findings differ from studies of patients with more severe mood disorders, including psychiatric out-patients with S.A.D. The lack of association between seasonality and birthdates in our study adds credence to the view that the aetiology of S.A.D. relates to separable factors predisposing to affective disorders and to seasonality.

Season of birth in Japanese patients with schizophrenia

A number of North American and European studies have observed a higher proportion of winter births in schizophrenia patients. Fewer studies have investigated this issue in Asian populations, and the findings are not as consistent as in the studies of Western populations. A statistically significant excess of winter births has not been observed in Japanese or Korean studies, while some of the studies found a decreased number of summer births among their patients. We further investigated the issue in Japanese patients with schizophrenia (n=2985). No significant excess of winter births was observed. Spearman correlation between schizophrenia births and ambient temperature was not significant. However, a decrease in the summer births was found, consistent with most of the previous Japanese studies. When analyzed by gender, a decrease in summer births was found in males, but not in females. In addition, a trend towards an increase in winter births was observed and Spearman correlation between low ambient temperature and schizophrenia births was significant in male subjects. More significant seasonality of birth in male patients than in female patients might be related to more susceptibility to pre- or perinatal disturbances in neurodevelopment in males than in females.

Season of birth, gender and negative symptoms in schizophrenia

The aim of this study was to ascertain whether the symptom profile distinguishes between schizophrenic patients born in the winter and early spring and those born in other seasons. The sample consisted of 204 patients with a DSM-III-R diagnosis of schizophrenia who had been hospitalized for acute psychotic decompensation. Symptom ratings were based on the Positive and Negative Syndrome Scale (PANSS). The use of demographic and anamnestic data as dependent variables did not detect any season-of-birth effect. In contrast, clear gender-specific differences emerged from the comparison focusing on symptom dimensions and clinical subtype. Female patients born in the winter and early spring had higher scores on the PANSS negative scale and anergia factor whereas male patients born in other seasons had higher scores on the PANSS anergia factor. In addition, we found a gender-specific association between season of birth and clinical subtype. Most paranoid female patients were born in the non-winter months whereas, among men, a slightly higher percentage of paranoid patients were born in winter months. These results suggest that gender plays a role in modulating the effect of the season of birth on symptoms of schizophrenia.

Season of birth in females with anorexia nervosa in Northeast Scotland

OBJECTIVE

To determine whether patients with anorexia nervosa exhibit an abnormal pattern in their season of birth.

METHOD

Case records of female patients presenting to secondary services in Northeast Scotland from 1965 to 1997 who received a clinical diagnosis of anorexia nervosa were examined. The months of birth of the 446 anorexic patients with a confirmed diagnosis were compared with 5,766 female control subjects born locally in 1951, 1961, 1971, and 1981.

RESULTS

Patients with anorexia nervosa had an excess of births in the first 6 months of the year (p =.013). The greatest excess was from March to June.

DISCUSSION

This provides further evidence that birth dates of anorexics peak in the late spring and early summer. There are parallels with the epidemiology of schizophrenia. The evidence suggests that a seasonally fluctuating factor, most plausibly an intrauterine effect of common infectious agents during the winter months, is of etiological significance.

Seasonal influences on admissions in schizophrenia and affective disorder in Ireland

Although the seasonal patterns of admissions of affective disorder have been extensively studied, less attention has been given to the seasonal admission patterns of schizophrenia. The traditional method of aggregating the data over a study period, rather than analysing by year of admission may obscure potentially relevant fluctuations in the seasonal pattern. We examined the year-to-year variation in the admission patterns of schizophrenia and affective disorder in Ireland. Using the National Psychiatric Inpatient Reporting System (NPIRS), individuals admitted with an ICD-9/10 diagnosis of a first episode of schizophrenia or affective disorder during the 6-year period 1989-1994 were identified. Seasonal variations in their admission patterns were examined statistically and graphically. There was a significant seasonal variation in the monthly admission patterns of both schizophrenia and affective disorder. This pattern was more marked for individuals with affective disorder. However, the seasonal pattern was not constant from year to year, particularly for schizophrenia.

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

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

Gender-specific decline and seasonality of births in operationally defined schizophrenics in Italy

All clinical records of schizophrenic patients included in the period 1979-1995 in the South Verona Psychiatric Case Register were reviewed and diagnoses operationally defined according to ICD-10 criteria using OPCRIT 3.1. Among the 335 scrutinized, 205 patients met the ICD-10 criteria for paranoid or undifferentiated schizophrenia. No seasonality of birth was found in these patients using a log-linear equiprobability model. The incidence and seasonality of birth were then analysed on the subsample of 106 patients born in 1947-1974 for whom corresponding data for the Verona general population were available. Schizophrenic males displayed a significant excess of birth in November-January with respect to the Verona population (chi 2 = 10.93, p = 0.012). The time series of the incidence of schizophrenia by cohort of birth 1947-1974 had a linearly decreasing trend, steeper in males than in females. The significant increase in age at first ever psychiatric contact, observed in both males and females throughout the period considered, cannot completely account for the gender-specific decline of birth of schizophrenics.

Season of birth and schizophrenia in Tasmania

OBJECTIVE

The purpose of the present study was to determine whether there was a significant seasonal variation in the birth dates of patients with schizophrenia born in Tasmania.

METHOD

The season of birth in Tasmanian-born patients with schizophrenia (n = 1412), born between 1919-1970, was compared with general population data.

RESULTS

No significant variation in month or quarter of birth was detected for the subjects with schizophrenia. Neither was there any significant seasonal excess when data from different decades were analysed separately, nor for subsidiary analyses of gender or paranoid/non paranoid subtype.

CONCLUSION

These results are compared with those of six other published studies of Australasian-born subjects identified through registers in different States. While both positive and negative results are reported, no clear pattern emerges. The relevance of season of birth to the development of schizophrenia in Australia remains an open question.