Season of birth in psychiatry. A review

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 modulates mood seasonality in humans

We investigate whether mood seasonality is modulated by season of birth. A sample of 1682 university students were administered the Seasonal Pattern Assessment Questionnaire. We found that subjects born during spring or summer months had significantly higher Global Seasonality scores than those born during autumn or winter months.

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.

Season of birth contributes to variation in university examination outcomes

Epidemiological studies show that birth season influences a wide range of biological parameters such as growth, reproduction, mental illnesses, dyslexia, personality, and success in school. The present study is aimed at examining birth season's relationship to examination marks achieved at a university in a very large contemporary sample of male and female undergraduate students. We find that female university students born in spring and summer achieve better marks than those born in autumn and winter. Male students born in spring receive worse marks than those born in other seasons of the year. Furthermore, we find a birth-week periodicity in examination results of female students, with highest examination results for those born in May. We suppose that biological mechanisms might explain part of the observed effects.

Excess in the spring and deficit in the autumn in birth rates of male schizophrenic patients in Italy: potential role of perinatal risk factors

OBJECTIVE

The aim of this study was to evaluate whether there were different seasonal variations of births in an Italian population of patients with schizophrenia, with other psychotic disorders, and with personality disorders than in the general population.

METHODS

Birth dates of 1270 patients admitted to one university psychiatric unit in Rome between 1990 and 2003, with a diagnosis of schizophrenia, other psychotic disorder (OPD) and personality disorder/cluster A (PD) were analyzed according to seasonal variation.

RESULTS

A significant excess of births in spring (with a peak in May) and a deficit in autumn (with a trough in October) was found in the sample of male schizophrenics (n = 506). No statistically significant variations were found in either the sample of female schizophrenics (n = 88) or in the combined sample with OPD and PD (n = 676).

CONCLUSIONS

The findings serve to strengthen the existing hypotheses that schizophrenia is related to environmental factors acting on the development of the central nervous system intrauterinely.

The relation of season of birth to severity of menopausal symptoms

OBJECTIVE

Season of birth influences the rate of several psychiatric disorders. In this study, we investigated whether climacteric symptoms and, in particular, psychological and somatic symptoms of postmenopausal women were influenced by their season of birth.

DESIGN

This retrospective multicenter study was performed on 2,541 women in natural menopause, free of hormone therapy. The score of the Greene Climacteric Scale and of its vasomotor, psychological (anxiety and depression), and somatization subscales were stratified by season of a woman's birth. Data were controlled for possible confounders, such as age, years since menopause, body mass index, education occupation, smoking habits, and season of evaluation.

RESULTS

The Greene Climacteric Scale appeared to be associated with the season of birth, with the lowest scores being observed in women born in autumn and the highest scores in women born in spring (+2.11; 95% CI, 0.67-3.56; P = 0.01), and summer (+2.22; CI, 0.82-3.63; P = 0.01). Lowest scores in autumn and highest scores in spring were also observed for psychological symptoms subscaled as anxiety and depression (+1.43; CI, 0.54-2.32; P = 0.01) and somatic symptoms (+0.59; CI, 0.15-1.04; P = 0.01).

CONCLUSIONS

In this study, we found a relationship between season of birth and some menopause-associated symptoms. Further study is needed to confirm these relationships and examine possible mechanisms.

Effect of month of birth on the risk of suicide

BACKGROUND

Month of birth as a suicide risk factor has not been adequately explored. The findings of published studies are contradictory and inconclusive.

AIMS

To examine the association between suicide and month of birth using suicide data for a 22-year period in England and Wales. The sample size of 26 915 suicides greatly exceeds all previous studies.

METHOD

We analysed all suicides (ICD-9 codes E950-959) and deaths from undetermined injury (E980-989) reported between 1979 and 2001 in England and Wales for persons born between 1955 and 1966, using Poisson and negative binomial generalised linear models with seasonal components.

RESULTS

Birth rates of people who later kill themselves show disproportionate excess for April, May and June compared with the other months. Overall, we found an increase of 17% in the risk of suicide for people born in the peak month (spring-early summer) compared with those born in the trough month (autumn-early winter); this risk increase was larger for women (29.6%) than for men (13.7%).

CONCLUSIONS

The'month of birth'factor in suicide can be interpreted in terms of the foetal origins hypothesis. Our findings might have implications for our understanding of the multifaceted aetiology of suicide and may eventually offer new strategies for research and prevention.

Season-of-birth as a risk factor for the seasonality of suicidal behaviour

Despite implicating the same biological systems, the relationship between suicide seasonality and season-of-birth has not been examined previously. The purpose of this study was to investigate the interaction between season-of-birth and the seasonality of suicidal behaviour. All adult suicides (N = 2923) and deliberate self harm (DSH) hospitalizations (N = 33321) in Western Australia (1970-96) were examined. A variable population at risk approach was used to determine season-of-birth. Seasonality was established by spectral analysis. We found that DSH has a significant season-of-birth (p = 0.047) and seasonality of occurrence, both peaking in spring. Individuals born in the 90 days centred on the peak birth period, however, show no DSH seasonality. In contrast, suicide has no season-of-birth (p = 0.53). We also found a season-of-birth effect among the DSH group that eliminates any seasonality of DSH among the high-risk by birth group. Further work is needed to identify the possible biological and environmental determinants of this interaction.

Is relatively young age within a school year a risk factor for mental health problems and poor school performance? A population-based cross-sectional study of adolescents in Oslo, Norway

Background

Several studies have shown that children who are relatively young within a school year are at greater risk for poorer school performance compared with their older peers. One study also reported that relative age within a school year is an independent risk factor for emotional and behavioral problems. The objective of this study was to test the hypothesis that relatively younger adolescents in the multiethnic population of Oslo have poorer school performance and more mental health problems than their relatively older classmates within the same school year.

Methods

This population-based cross-sectional study included all 10^th-grade pupils enrolled in 2000 and 2001 in the city of Oslo. The participation rate was 88%. Of the 6,752 pupils in the study sample, 25% had a non-Norwegian background. Mental health problems were quantified using the abbreviated versions of Symptom Check List-25 (SCL-10) and the Strength and Difficulties Questionnaire (SDQ). Information on school performances and mental health problems were self-reported. We controlled for confounding factors including parental educational level, social support, gender, and ethnicity.

Results

The youngest one-third of pupils had significantly lower average school grades than the middle one-third and oldest one-third of their classmates (p < 0.001). Of the mental health problems identified in the questionnaires, the groups differed only on peer problems; the youngest one-third reported significantly more problems than the middle and oldest groups (p < 0.05). Age within a school year and gender showed significant interactions with total SDQ score, SDQ peer problems score, SDQ pro social score, and SCL-10 score. After stratifying for gender, the peer problem scores differed significantly between age groups only among boys. The SCL-10 score was significant, but only in girls and in the opposite direction to that expected, with the oldest pupils having significantly higher scores than the other two groups (p < 0.05).

Conclusion

In adolescents from a multicultural city in Norway, relative age within a school year significantly influenced academic performance. In contrast to data from Great Britain, relative age within a school year was not an important risk factor for mental health problems in adolescents in Oslo.

Season of birth in Danish children with language disorder born in the 1958-1976 period

Two preliminary studies have indicated a variation in season of birth in severely language-disordered children. In the current study, the season of birth in 472 Danish children with language disorder born between 1958 and 1976 was compared with the season of birth of all Danish live-born children in the same period. For some part of the period (1964-1969), an excess of boys born in November was found. Particular attention was given to the inconsistent findings also found in language-related disorders like infantile autism and dyslexia and the choice of statistical method to determine seasonality.

Season of birth is related to child retention rates, achievement, and rate of diagnosis of specific LD

A sizable literature has demonstrated that the achievement of children in early elementary school is related to their season of birth: Those born in summer typically perform less well than those born in the fall. A small literature indicates that more children diagnosed with specific learning disabilities (SLD) are born in the summer. We have begun to explore the possibility that the same processes may account for both outcomes. In order to better understand these processes, the standardized achievement levels and rates of diagnosis of SLD for children born during each season were studied in one geographical area of the State of Georgia served by 28 school districts. Standardized achievement scores in reading, mathematics, and science were reliably lower for those born in the summer. Furthermore, there was a strong relationship between season of birth and the rate at which children received a diagnosis of SLD. Summer-born children were diagnosed with SLD at a higher rate than their peers. Four hypotheses for both the lower performance in the general school population and the greater rate of SLD diagnosis among these children are discussed.

The Temperament Scale of Novelty Seeking in adolescents shows an association with season of birth opposite to that in adults

We investigated the relationship between season of birth and the Junior Temperament and Character Inventory of Personality (Junior TCI, JTCI) in adolescents. The Temperament Scale of Novelty Seeking (NS) is significantly higher for females born during October-January as compared to females born otherwise. This association is opposite to that obtained earlier for adults. For both genders pooled, NS is significantly higher for those born during October-March compared to April-September. This association is also found when examining the data for those of age up to 18 years in a third independent study on the age range 11-81 years with the adult TCI. There is a greater tendency for exploration and risk-taking behavior as the child individuates from the family. Our study suggests that the effects of such environmental and developmental changes on personality are different in those born during October-March as compared to those born during April-September. The former show a higher rise in NS during adolescence and a steeper fall in NS during the years of adulthood, compared to the latter. Dopamine turnover is likely associated with NS, and the mutually inhibitory systems of dopamine and melatonin are the paracrine signals of day and night, respectively. Thus, the maternal entrainment of these systems during the prenatal period, or the postnatal environmental influence on these systems, may be different for those born during the short photoperiod of October-March as compared to those born during the long photoperiod part of the year.

Season of birth variations in suicide methods in relation to any history of psychiatric contacts support an independent suicidality trait

BACKGROUND

Due to reports on season of birth variations in suicidal behaviour as well as in cerebrospinal fluid levels of monoamine metabolites, we investigated season of birth variations in suicide methods for completed suicides in relation to any history of psychiatric contacts. Relationships with the psychiatric diagnoses for those with psychiatric contacts were also studied.

METHODS

Sociodemographic variables and suicide methods were examined for all the 693 suicide victims during 1961-1980 in Västerbotten, Sweden. Information on any history of psychiatric contacts was obtained from psychiatric in-patient and out-patient records.

RESULTS

Gender differences in the choice of suicide method were found in the group without any history of psychiatric contacts, but not in those with such a history. Only those without a history of psychiatric contacts showed season of birth variations for suicide methods -- those born during February to April were significantly more likely, and those born during October to January significantly less likely, to have preferred hanging rather than poisoning or petrol gases. These associations were stronger for the determined suicides, for males, and for urban residence. Suicide victims with a history of psychiatric contacts were significantly younger than those without.

LIMITATIONS

No psychological autopsies for those without psychiatric contacts. No information on eventual contacts with general practitioners. No measures of monoamine neurotransmitters were available.

CONCLUSIONS

Season of birth association for suicide methods is likely to be mediated by a suicidality trait independently of specific major psychiatric disorders. Monoamine neurotransmitters, particularly serotonin, are likely to underlie such a trait.

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.

Season of birth variations in the temperament and character inventory of personality in a general population

BACKGROUND

Since several studies show season of birth variations in morbidity, suicidal behavior and CSF (cerebrospinal fluid) monoamine metabolites, we investigated season of birth variations in personality in the population.

METHODS

We analyzed by multiple logistic regressions the Temperament and Character Inventory (TCI) for 2,130 individuals taking part in the Betula prospective random cohort study of Umeå, Sweden.

RESULTS

The personality dimensions were correlated significantly with age and gender. We stratified the data according to age, gender and the season of TCI measurement. By the median split in each stratum, a high-value group and a low-value group were obtained for each of the personality dimensions. Those born during February to April were significantly more likely than those born during October to January to have high NS (novelty seeking) among women, particularly the subscale NS2 (impulsiveness vs. reflection), and to have high PS (persistence) among men. Temperament profiles also showed season of birth variations.

CONCLUSIONS

We discuss the associations in the literature between personality and the monoamines serotonin and dopamine, and suggest that our results are compatible with a hypothesis of season of birth variation in the monoamine turnover. The personality traits are likely to be influenced by several genetic and environmental factors, one of them being the season of birth.

Melatonin production in healthy infants: evidence for seasonal variations

The objective of this study was to determine the normal range of nocturnal urinary excretion of the major melatonin metabolite, 6-sulfatoxymelatonin (6SMT) in a large sample of healthy full-term infants (8 and 16 wk old) and assess whether the endogenous production of melatonin changes with season. 6SMT was assessed in urine samples extracted from disposable diapers removed from full-term, 8- (n = 317) and 16-wk-old (n = 93) infants over the nocturnal period (19:00-08:00 h). In addition, 6SMT was assessed in 8-wk-old (n = 35) healthy infants over the entire 24-h period. 6SMT was determined by an ELISA assay. 6SMT excretion at 8 wk of age exhibited diurnal variations with (mean +/- SD) 61 +/- 18% of the daily production excreted during the nocturnal period regardless of season. The nocturnal 6SMT values in the entire cohort (at 8 as well as 16 wk of age) were found to significantly depart from normal distribution (Kolmogorov-Smirnov test). A normal distribution was obtained using a natural base logarithmic (ln) transformation of the data. The normal range (2.5-97.5 percentile of the ln 6SMT excretion per night) was thus defined as 4.66-8.64 (106-5646 ng/night) for 8-wk-old and 5.19-9.67 (180-15,820 ng/night) for 16-wk-old infants. A significant effect of the month of birth on 6SMT production at the age of 8 wk was found (ANOVA, p < 0.002) with maximal levels produced by infants born in June (summer solstice) and minimal excretion in infants born in December (winter solstice). Short-photoperiod-born infants excreted on average about threefold less 6SMT compared with long-photoperiod-born infants (t test, p = 0. 01). The seasonal variations were no longer present at 16 wk of age. No effect of breast-feeding at the time of sampling on seasonality of 6SMT was found. Normal ranges for the nocturnal urinary excretion of 6SMT in full-term infants at 8 and 16 wk of age are defined. This enables the evaluation of nocturnal 6SMT excretion as a prognostic and diagnostic factor for child development. The strong effect of season on the normal excretion of nocturnal 6SMT at 8 but not 16 wk of age suggests prenatal influence of the photoperiod on the ontogeny of melatonin.

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

BACKGROUND

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

METHOD

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

RESULTS

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

CONCLUSIONS

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

LIMITATIONS

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

Prevention in psychiatry: Australian contributions

OBJECTIVE

To provide a historic context for developing a framework for preventive mental health research in Australia.

METHOD

A literature review was undertaken and references were selected for their relevance to describing the contributions of Australian researchers and clinicians to an epidemiological approach to mental health disorders, particularly schizophrenia.

RESULTS

Australian researchers and clinicians have made major innovative contributions to preventive mental health research.

CONCLUSIONS

Australian mental health services, in collaboration with academic departments, are in a highly favourable position to expand preventive research activities into schizophrenia.

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

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