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

Season of birth and eating disorders: patterns across diagnoses in a specialized eating disorders service

OBJECTIVE

In view of inconsistent findings from previous studies, the aim was to investigate possible seasonal variation in month of birth in patients with anorexia nervosa, bulimia nervosa, and eating disorder not otherwise specified.

METHOD

We examined the month of birth in a cohort of 1,305 adult patients with a DSM-IV eating disorder diagnosis at first presentation to a specialized eating disorders service.

RESULTS

When compared to general population data, we found no evidence of significant variation in month or season of birth in anorexia nervosa, bulimia nervosa, or eating disorder not otherwise specified.

CONCLUSION

The authors question whether people who develop eating disorders differ from the general population in their season of birth. Caution is expressed about further speculation regarding the etiological significance of season of birth in eating disorders.

Schizophrenia and neural tube defects: comparisons from an epidemiological perspective

In this review, we examine and compare epidemiological studies of schizophrenia and neural tube defects (NTDs). Although there is no apparent link between these 2 disparate disorders in terms of clinical manifestation or phenotypes, overlapping patterns in the variation of incidence of schizophrenia with that of NTDs indicate the existence of one or more shared etiological risk factors. Evidence in support of such a phenomenon may enhance our understanding of underlying pathological mechanisms and may guide future studies of etiology and prevention. The similarities that occur in a number of epidemiological observations for these disorders are in keeping with a hypothesis of nutritional deficiencies in utero acting as a risk factor for both schizophrenia and NTDs. Programes of periconceptual folate and multivitamin supplementation aimed to reduce the risk of NTDs are already in place in many countries. Nevertheless, evidence of additional effects of specific maternal micronutrient deficiency on risk of schizophrenia may not only increase enthusiasm for expansion of such programes but also enhance understanding of etiology of this disorder and offer the potential for targeted interventions in high-risk groups.

Premorbid adjustment in schizophrenia--an important aspect of phenotype definition

Schizophrenia is a heterogeneous disorder, and early signs of disorder such as poor premorbid adjustment (PMA) are often present before the onset of diagnosable illness. Differences in PMA between patients may be suggestive of differing aetiological pathways. Poor PMA in schizophrenia has repeatedly been reported to be associated with male sex, earlier age at onset, illness severity, negative symptoms, and poor outcome. Studies of schizophrenia patients systematically assessed for PMA have used small patient samples and have rarely used controls.

OBJECTIVE

To investigate possible correlations of PMA, as measured with the Cannon-Spoor Premorbid Adjustment Scale (PAS), with such meaningful clinical characteristics as sex, age at onset, negative symptoms etc. using one of the largest samples of schizophrenia inpatients as well as controls characterised for PMA to date.

METHOD

PMA, diagnosis and lifetime symptoms were assessed in 316 inpatients with schizophrenia and 137 population based controls using the PAS and the Structured Clinical Interview for DSM.

RESULTS

Controls demonstrated better PAS scores than inpatients with schizophrenia. Earlier age at onset and negative symptoms were found to be associated with poorer PAS scores. There was no difference in PAS ratings between males and females in patients with schizophrenia. Among the control probands, females showed significantly better PAS scores than males.

CONCLUSION

PAS scores are worse in individuals who eventually develop schizophrenia, and the distribution of these scores among schizophrenia inpatients is correlated with specific clinical features. Earlier findings, which had reported an association with age at onset and negative symptoms in small patient samples, were substantiated. The widely reported association of poor PMA with male sex, if genuinely present, does not appear to be disease specific. Our findings suggest that PMA is in itself a valuable phenotype characteristic and that it may represent a specific biological phenotype which may be of value in sub-sample selection.

Antibodies to Toxoplasma gondii in patients with schizophrenia: a meta-analysis

Recent studies have linked infectious agents to schizophrenia. The largest number of studies has involved the analysis of Toxoplasma gondii; these studies were subjected to a meta-analysis. Published articles and abstracts were identified by searches of MEDLINE, Ovid, and Google Scholar; by a search of Chinese publications; through letters to researchers; and by visiting China. Published and unpublished controlled studies that used serological methods for measuring T. gondii antibodies to assess inpatients and/or outpatients diagnosed with schizophrenia were selected for analysis, and source documents were translated as needed. Forty-two studies carried out in 17 countries over 5 decades were identified; 23 of these (6 unpublished) met selection criteria. The combined odds ratio (OR) was 2.73 (95% confidence interval, 2.10 to 3.60; chi-square with 1 df 263; P < .000001). Seven studies that included only patients with first-episode schizophrenia (OR 2.54) did not differ significantly from 16 studies that included patients in all clinical phases (OR 2.79). The results suggest that individuals with schizophrenia have an increased prevalence of antibodies to T. gondii. This association is consistent with other epidemiological studies as well as with animal studies. Although the OR of 2.73 is modest, it exceeds that for genetic or other environmental factors identified to date and suggests that Toxoplasma is in some way associated with a large number of cases of schizophrenia. If an etiological association can be proven, it would have implications for the design of measures for the prevention and treatment of this disease.

Stress during development: Impact on neuroplasticity and relevance to psychopathology

Development represents a critical moment for shaping adult behavior and may set the stage to disease vulnerability later in life. There is now compelling evidence that stressful experiences during gestation or early in life can lead to enhanced susceptibility for mental illness. In this paper we review the data from experimental studies aimed at investigating behavioral, hormonal, functional and molecular consequences of exposure to stressful events during prenatal or early postnatal life that might contribute to later psychopathology. The use of the newest methodology in the field and the intensive efforts produced by researchers have opened the possibility to reveal the complex, finely tuned and previously unappreciated sets of molecular interactions between different factors that are critical for neurodevelopment thus leading to important discoveries regarding perinatal life. The major focus of our work has been to revise and discuss data from animal studies supporting the role of neuronal plasticity in the long-term effects produced by developmental adversities on brain function as well as the possible implications for disease vulnerability. We believe these studies might prove useful for the identification of novel targets for more effective pharmacological treatments of mental illnesses.

Cytomegalovirus and schizophrenia

Several lines of evidence suggest that cytomegalovirus (CMV) may play an aetiological role in schizophrenia. Epidemiologically, both have a worldwide distribution and an increased prevalence in lower socioeconomic groups. Studies have reported that some patients experiencing initial episodes of schizophrenia have increased levels of IgG antibodies against CMV, but not other herpes viruses, in their sera and CSF. Treatment with antipsychotic medications may result in a decrease in CMV antibodies, while treatment with anti-herpes virus and anti-inflammatory medications may reduce symptoms in some individuals with schizophrenia. There is also some overlap in the genes that are thought to operate in CMV infections and schizophrenia. The strongest argument against the role of CMV in schizophrenia is the absence of the traditional CMV neuropathological changes in the brains of individuals with schizophrenia; however, neuropathological studies of CMV have mostly been conducted in immune-compromised individuals. Further studies on CMV and schizophrenia are needed and may lead to improved treatments for schizophrenia.

Brain morphological changes associated with exposure to HSV1 in first-episode schizophrenia

Infectious agents have been proposed as one of the risk factors for schizophrenia. However, the data on the association of infectious agents with in vivo brain changes are scant. We evaluated the association of serological evidence of exposure to herpes simplex virus 1 (HSV1) with in vivo brain structural variations among first-episode antipsychotic-naive schizophrenia/schizoaffective disorder patients and control subjects. We assayed HSV1 immunoglobulin G (IgG) antibody in serum samples from 30 patients and 44 healthy subjects and obtained structural magnetic resonance imaging scans from the same individuals. There were proportionately more patients with elevated HSV1 antibody ratios than healthy comparison subjects (chi2=3.98, 1 df, P=0.046) and patients had significantly higher HSV1 IgG antibody ratios compared with healthy subjects. Using optimized voxel-based morphometry, we examined diagnosis by HSV1 serological status interaction followed by within- and between-group comparison across the serological status. We observed a diagnosis by HSV1 serological status interaction and a significant main effect of HSV1 serological status in the prefrontal gray matter. Patients exposed to HSV1 had decreased gray matter in Brodmann area 9 (dorsolateral prefrontal cortex) and 32 (anterior cingulate cortex) compared with patients without serological evidence of exposure to HSV1. HSV1-associated differences in brain structure were not detected among healthy subjects. These findings suggest that HSV1 exposure in schizophrenia is associated with specific regional gray matter differences that may not be attributable to medications, illness chronicity or comorbid substance use. This study provides suggestive evidence for a link between HSV1 exposure and some of the cerebral morphological changes often reported in schizophrenia.

Cerebrospinal fluid monoamine metabolite levels in human newborn infants born in winter differ from those born in summer

An earlier study has shown significant differences in the CSF monoamine metabolite levels in adults born during different seasons of the year. We study here the relationship between season of birth and CSF monoamine metabolite levels in 283 newborn febrile infants without neurological abnormalities, with an age distribution ranging from birth to about 3 months, adjusting for the confounding variables age and time at lumbar puncture, weight at birth, estimated gestational age at birth, gender, race, and medicaid status. Each of the three metabolite levels as well as their ratios HVA/5-HIAA and 5-HIAA/MHPG showed significant month-of-birth variations, but not the ratio HVA/MHPG. For HVA and MHPG levels, the maximum was obtained around the winter birth months November-December, whereas for 5-HIAA level, the maximum was obtained around the summer birth months June-July. The correlations between HVA and 5-HIAA were, in general, significantly positive within the different birth seasons and races. Among summer-born Caucasian infants, MHPG was significantly positively correlated with HVA and with 5-HIAA, whereas among winter-born Black infants, MHPG was significantly positively correlated with HVA. Season of birth is an unspecific environmental factor that may be proxy for several possible seasonally varying environmental circumstances such as the length of photoperiod, temperature, infections, nutrition, stress and lifestyle. Studies relating season of birth to monoaminergic turnover at different stages of life may yield important clues about the gestational and perinatal origins of neurodevelopment.

Season of birth interacts with measures of inbreeding in multiplex schizophrenia pedigrees: evidence from genetic isolates in Daghestan

While the season-of-birth effect is one of the most consistent epidemiological features of schizophrenia, there is a lack of consistency with respect to the interaction between season of birth and family history of schizophrenia. Apart from family history, measures related to consanguinity can be used as proxy markers of genomic heterogeneity. Thus, these measures may provide an alternate, indirect index of genetic susceptibility. We had the opportunity to explore the interaction between season of birth and measure of consanguinity in well-described genetic isolates in Daghestan, some of which are known for their relatively high prevalence of schizophrenia. Our previous population-genetic study showed Daghestan has an extremely high genetic diversity between the ethnic populations and a low genetic diversity within them. The isolates selected for this study include some with more than 200 and some with less than 100 generations of demographical history since their founding. Based on pedigrees of multiply-affected families, we found that among individuals with schizophrenia, the measure of consanguinity was significantly higher in the parents of those born in winter/spring compared to those born in summer/autumn. Furthermore, compared to summer/autumn born, winter/spring born individuals with schizophrenia had an earlier age-of-onset, and more prominent auditory hallucinations. Our results suggest that the offspring of consanguineous marriages, and thus those with reduced allelic heterogeneity, may be more susceptible to the environmental factor(s) underpinning the season-of-the effect in schizophrenia.

A birth-season/DRD4 gene interaction predicts weight gain and obesity in women with seasonal affective disorder: A seasonal thrifty phenotype hypothesis

We have recently described an association between the hypofunctional 7-repeat allele (7R) of the dopamine-4 receptor gene (DRD4), weight gain, and obesity in women with seasonal affective disorder (SAD). In the current study, we examined whether season-of-birth might interact with the 7R allele to influence body weight regulation in SAD. In 182 female probands with SAD, we performed an analysis of covariance predicting maximum lifetime body mass index (BMI) with both the exon-3 variable number of tandem repeat polymorphism of DRD4 and season-of-birth as independent variables, and age as the covariate. The overall model was highly significant (F = 4.42, df = 8, 173, p < 0.0001) with season-of-birth predicting maximal lifetime BMI both on its own and in its interaction with the 7R allele. The latter finding was attributable to 7-repeat carriers born in the spring (N = 17), who had a mean maximal lifetime BMI of 33.7 kg/m2 (SD 8.6), compared to 26.7 kg/m2 (SD 5.4) for all other probands combined (N = 165) (F = 20.01, df = 1, 179, p < 0.0001). The lifetime rate of obesity (maximal BMI > 30 kg/m2) was also significantly higher in the 7R/spring birth group (9/17=52.9% vs 32/165=19.4%; chi2 = 9.94, df = 1, p = 0.002; odds ratio = 4.68, 95% CI = 1.67-13.07). These data may reflect a novel gene-environment interaction, during early brain development, which establishes an increased risk for obesity in women with SAD. Although the mechanism for season-of-birth effects in psychiatric disorders is unknown, a characteristic pattern of melatonin exposure during the second and third trimesters may be of particular relevance in this study population. We speculate that these data may reflect the vestigial expression of a seasonal thrifty phenotype that contributed to the positive selection of the 7R allele over the past 40,000 years.

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

Although the association of schizophrenia and winter birth has been replicated many times in the Northern hemisphere, studies in the Southern hemisphere have been less consistent in their findings. A study from NE Brazil indicated the period between May and July, 3 months after the peak in rainfall, as a risk period for schizophrenia birth. We report findings from a random selection of charts (N = 1789) from the only public inpatient psychiatric facility in Ceará, Brazil (2 degrees to 5 degrees S). We compared the seasonality of birth in the schizophrenia group (N = 406) to multiple control groups: (1) psychosis not otherwise specified (N = 868), (2) other psychiatric diagnoses (N = 515), and (3) the average monthly birth rate in the general population. Patients with schizophrenia had a significantly greater risk of being born in the risk period compared with any of the control groups. There is a significant association between rainfall in a month and schizophrenia births 3 (p = 0.03) and 4 months (p = 0.01) later. This study corroborates findings of a significant seasonality in schizophrenia births in northeast Brazil.

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.

Developmental vitamin D deficiency alters MK 801-induced hyperlocomotion in the adult rat: An animal model of schizophrenia

BACKGROUND

Developmental vitamin D (DVD) deficiency has been proposed as a risk factor for schizophrenia. The behavioral phenotype of adult rats subjected to transient low prenatal vitamin D is characterized by spontaneous hyperlocomotion but normal prepulse inhibition of acoustic startle (PPI). The aim of this study was to examine the impact of selected psychotropic agents and one well-known antipsychotic agent on the behavioral phenotype of DVD deplete rats.

METHODS

Control versus DVD deplete adult rats were assessed on holeboard, open field and PPI. In the open field, animals were given MK-801 and/or haloperidol. For PPI, the animals were given apomorphine or MK-801.

RESULTS

DVD deplete rats had increased baseline locomotion on the holeboard task and increased locomotion in response to MK-801 compared to control rats. At low doses, haloperidol antagonized the MK-801 hyperactivity of DVD deplete rats preferentially and, at a high dose, resulted in a more pronounced reduction in spontaneous locomotion in DVD deplete rats. DVD depletion did not affect either baseline or drug-mediated PPI response.

CONCLUSIONS

These results suggest that DVD deficiency is associated with a persistent alteration in neuronal systems associated with motor function but not those associated with sensory motor gating. In light of the putative association between low prenatal vitamin D and schizophrenia, the discrete behavioral differences associated with the DVD model may help elucidate the neurobiological correlates of schizophrenia.

Schizophrenia, autoimmunity and immune system dysregulation: A comprehensive model updated and revisited

Recent investigation suggests a strong relationship between immunological effects and the pathophysiology of schizophrenia. Two prevalent approaches exist to this association. First, is more empirical a-priori research investigating immunological changes prevalent in schizophrenia and the second approach is more hypothesis-driven with analysis of immunological changes in schizophrenia based on known irregularities of the illness. The former approach is based upon three predominant lines of investigation including observations of a diffuse non-specific overactivation of the immunological response system, of a T-helper cell type 1 immune activation and of a T-helper cell type 2 immune activation in subgroups of schizophrenia patients. These last two theories suggest that a subgroup of patients with schizophrenia may demonstrate features of an autoimmune process, a theory supported by a growing database of investigation. The latter approach notes that many observations of immune dysregulation in schizophrenia overlap with central etiopathophysiological mechanisms as well as with clinical manifestations of the illness. Immunotherapy offers the opportunity to modify or re-balance the immune system and may become useful in management of the illness. Given that autoimmune mechanisms could interrupt neurotransmission, any process interfering with this disruption including therapeutic antibodies to involved cytokines, or with various other natural autoantibodies or immune system regulators, may become useful in the augmentative management of the illness.

Season of birth, age and negative symptoms in a Xhosa schizophrenia sample from the Southern Hemisphere

OBJECTIVES

Seasonality of birth, more specifically winter/spring births, has been implicated as a risk factor for the development of schizophrenia. The primary aim of this study was to determine whether schizophrenia patients of Xhosa ethnicity born in autumn/winter have different symptom profiles to those born in spring/summer. The secondary aim was to determine whether the autumn/winter and spring/summer birth rates for schizophrenia patients of Xhosa ethnicity were similar to that of the general Xhosa population.

METHOD

Individuals with a diagnosis of schizophrenia, born in the Western and Eastern Cape Provinces of South Africa (n = 386), were categorized as autumn/winter-born (March to August) patients or summer/spring-born (September to February) patients. Negative global scores of the schedules for the assessment of negative symptoms were categorized as normal (rating of 0 and 1) or positive (rating of 2 to 5).

RESULTS

Patients born in autumn/winter were more likely to have avolition/apathy than those born in summer/spring. The results also showed that the age of the patients played a significant role in modifying the effect of the season of birth on symptoms of schizophrenia. Especially older people (more than 30 years old) born in autumn/winter had a higher incidence of avolition/apathy than those born in summer/spring (p = 0.026). Furthermore, in the relationship of birth season and avolition/apathy, the marital status of the patient was a significant independent explanatory variable, while gender was not. The study also showed a spring excess of 4% in birth rate compared with the general Xhosa population.

CONCLUSION

The results from our study support the existence of a seasonal birth pattern in an African schizophrenia population and suggest that avolition/apathy may underpin this seasonal pattern.

Winter birth in association with a risk of brain tumor among a Finnish patient population

The aim of this study was to analyze whether winter birth is related to risk of brain tumor in a clinical sample of patients from northern Finland. The study group comprised 101 patients suffering from a primary brain tumor. When comparing births in winter to births in other seasons, a 1.39-fold (95% CI 1.01-1.77) excess of winter births among patients was observed compared to respective births in the general population (p = 0.026). Especially patients with pituitary adenomas exhibited a 2.5-fold (95% CI 1.5-4.4) excess of winter births. The authors conclude that the season-of-birth effect in brain tumor patients should not be neglected when the actual and important tumorigenesis is investigated.

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.

Enduring effects of photoperiod on affective behaviors in Siberian hamsters (Phodopus sungorus)

The effects of perinatal and postweaning photoperiods on subsequent affective behaviors were examined in adult Siberian hamsters (Phodopus sungorus). Hamsters exposed perinatally to short days (8 hr light/day) exhibited mixed results for adult anxiety-like behaviors and increased some depressive-like behaviors compared with hamsters exposed to long days (16 hr light/day). Postweaning exposure to short days increased depressive- and anxiety-like behaviors compared with long days. Sex differences in affective behaviors were observed. These results suggest that anxiety-like behaviors are organized early in life and endure throughout adulthood, and anxiety- and depressive-like behaviors are modified by postweaning photoperiod. The persistence of photoperiod-induced affective behaviors in rodents supports the hypothesis that symptoms of human affective disorders may reflect ancestral adaptations to seasonal environments.

Schizophrenia as an inflammation-mediated dysbalance of glutamatergic neurotransmission

This overview tries to bridge the gap between psychoneuroimmunological findings and recent results from pharmacological, neurochemical and genetic studies in schizophrenia. Schizophrenia is a disorder of dopaminergic neurotransmission, but modulation of the dopaminergic system by glutamatergic neurotransmission seems to play a key role. This view is supported by genetic findings of the neuregulin- and dysbindin genes, which have functional impact on the glutamatergic system. Glutamatergic hypofunction, however, is mediated by the N-methyl-D-aspartate (NMDA)-receptor antagonism. The only endogenous NMDA receptor antagonist identified up to now is kynurenic acid (KYNA). Despite the NMDA receptor antagonism, KYNA also blocks, in lower doses, the nicotinergic acetycholine receptor, i.e., increased KYNA levels can explain psychotic symptoms and cognitive deterioration. KYNA levels are described to be higher in the cerebrospinal fluid (CSF) and in critical central nervous system (CNS) regions of schizophrenics as compared to controls. Another line of evidence suggests that a (prenatal) infection is involved in the pathogenesis of schizophrenia. Due to an early sensitization process of the immune system or to a (chronic) infection, which is not cleared through the immune response, an immune imbalance between the type-1 and the type-2 immune responses takes place in schizophrenia. The type-1 response is partially inhibited, while the type-2 response is over-activated. This immune constellation is associated with inhibition of the enzyme indoleamine dioxygenase (IDO), because IDO - located in astrocytes and microglial cells - is inhibited by type-2 cytokines. IDO catalyzes the first step in tryptophan metabolism, the degradation from tryptophan to kynurenine, as does tryptophan 2,3-dioxygenase (TDO). Due to the inhibition of IDO, tryptophan-kynurenine is predominantly metabolized by TDO, which is located in astrocytes, not in microglial or other CNS cells. In schizophrenia, astrocytes in particular are activated, as increased levels of S100B appear. Additionally, they do not have the enzymatic equipment for the normal metabolism-route of tryptophan. Due to the lack of kynurenine hydroxylase (KYN-OHase) in astrocytes, KYNA accumulates in the CNS, while the metabolic pathway in microglial cells is blocked. Accordingly, an increase of TDO activity has been observed in critical CNS regions of schizophrenics. These mechanisms result in an accumulation of KYNA in critical CNS regions. Thus, the immune-mediated glutamatergic-dopaminergic dysregulation may lead to the clinical symptoms of schizophrenia. Therapeutic consequences, e.g., the use of anti-inflammatory cyclo-oxygenase-2 inhibitors, which can also decrease KYNA directly, are discussed.

Seasonality effects on schizophrenic births in multiplex families in a tropical island

Many studies have found that individuals with schizophrenia have been born in winter months in disproportionately high numbers. Temperature and weather effects, such as hot summers or cold winters, have been among the suggested explanations for this seasonality effect. We studied the relationship between schizophrenia and season of birth in Puerto Rico, a tropical island with mild seasonal variation of temperature and virtually no cold periods. Our sample consisted of 132 subjects (57 with schizophrenia, 75 without) from 24 multiplex families. Schizophrenic family members were significantly more likely to be born during the winter months (21/57; 36.8%) than their unaffected relatives (16/75; 21.3%). These results suggest that extreme temperatures are not a sufficient explanation for the seasonality effect and that other factors associated with seasonality may have an effect on the later development of schizophrenia. The fact that a seasonality effect was found in a group likely to have an increased genetic loading for schizophrenia suggests that seasonality may be associated with a second, environmental "hit" in a "two-hit hypothesis" of schizophrenia.

Seasonality of birth in patients with schizophrenia in Japan

Although most Western studies have found a birth excess during winter or early spring among patients with schizophrenia, this has not been found in Japanese samples. The purpose of the present paper was to investigate this finding using a large Japanese sample. Distributions of monthly birth numbers of patients with schizophrenia were compared to those of the general population. Patients were from the governmental data, numbering 88 788. A significant birth excess during winter to early spring was found in male and female subjects with schizophrenia compared to the general population. There is a significant birth excess during winter to early spring for schizophrenia in Japan. The authors consider that the discrepancy between the current study and the previous Japanese studies was caused by small sample size and selection bias in the previous Japanese studies.

The role of the phosphatidylinositide 3-kinase–protein kinase B pathway in schizophrenia

Neuroanatomical studies of brains from schizophrenic patients report evidence for neuronal dystrophy, while in genetic studies in schizophrenia there is evidence for mutations in growth factors and the downstream enzymes phosphatidylinositide 3-kinase (PI3K) and protein kinase B (PKB). Since the PI3K-PKB pathway is involved in cellular growth and proliferation, reduced activity of this cascade in schizophrenia could at least partly explain the neuronal dystrophy. Risk factors for schizophrenia, such as corticosteroids and cannabis, suppress the activity of the PI3K-PKB pathway. Conversely, estrogen and vitamin D, 2 factors with a moderate protective activity in schizophrenia, electroconvulsive shock therapy, and chronic treatment with antipsychotic compounds stimulate the pathway. Reduced activity of the PI3K-PKB pathway makes the brain more susceptible to virus infections, anoxia, and obstetric complications (recognized risk factors for schizophrenia), whereas a diminution of growth factor levels towards the end of puberty could contribute to an increase in schizophrenia symptoms observed around that time. On the other hand, constitutive (over)activation of the PI3K-PKB pathway increases cancer risk. Consequently, the presumed hypoactivity of the PI3K-PKB cascade might provide a partial explanation for the remarkable epidemiological finding of a reduced cancer rate in schizophrenic patients. Recognition of the role of a dysfunctional PI3K-PKB pathway in schizophrenia might help in the discovery of hitherto undetected causative gene mutations and could also lead to novel therapeutic approaches. However, a major challenge that remains to be solved is how the PI3K-PKB pathway can be activated without increasing the risk of cancer.

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.

Environmental risk factors for psychosis

Genetic factors are clearly important in the etiology of schizophrenia, but the environment in which an individual's genes find expression is also crucial to the development of the illness. In this review of environmental risk factors for schizophrenia, we consider risks operating prenatally and perinatally, during childhood, and then later in life prior to illness onset. Some of these risk factors have been well documented, for example, early hazards causing fetal growth retardation or hypoxia, and hazards nearer the onset of illness like drug abuse and migration. Others are much less certain. The importance of interaction between genetic and environmental risk is, however, undoubtedly important and there is emerging evidence for this from a range of sources. As the etiology of schiz-ophrenia is unraveled, the picture becomes more complex, but also more obviously relevant to the plight of the individual patient.

Variations in the incidence of schizophrenia: data versus dogma

The schizophrenia research community has shared a belief that the incidence of schizophrenia shows little variation. This belief is related to the dogma that schizophrenia affects all individuals equally, regardless of sex, race, or nationality. However, there is now robust evidence that the incidence of schizophrenia is characterized by substantial variability. There is prominent variation in the incidence of schizophrenia between sites. The incidence of schizophrenia is significantly higher in males than in females (male:female ratio = 1.4). Migrants and those living in urban areas have a higher incidence of schizophrenia. The incidence of schizophrenia has fluctuations across time. In addition, the prevalence of schizophrenia is also characterized by prominent variation. The realization that schizophrenia is characterized by rich and informative gradients will serve as a catalyst for future research.

Madness explained: Why we must reject the Kraepelinian paradigm and replace it with a ‘complaint-orientated’ approach to understanding mental illness

This article is a synopsis of the argument outlined in my book Madness explained: Psychosis and human nature, in which I describe a new paradigm (which might be called a 'complaint-orientated' approach) for understanding the psychotic disorders, the most disabling forms of psychiatric illness. Despite extensive efforts to study the genetics, pathophysiology and neuropsychology of the psychoses, replicable findings have been rare. I argue that this is because the phenomena concerned have been poorly defined. Since the end of the 19th century, research into the psychoses has been dominated by the system of classification first proposed by the German psychiatrist Emil Kraepelin, which assumes that the severe mental illnesses fall into discrete types such as 'schizophrenia' and 'manic depression', and that there is a clear dividing line between madness and normal functioning. However, Kraepelinian diagnoses fail all empirical tests of their validity. For example, they do not identify patients with common symptoms, with common aetiologies, who respond to specific treatments. I suggest that we therefore need to abandon psychiatric diagnoses altogether and must instead attempt to explain the specific complaints ('symptoms') that patients bring to our attention. These include hallucinations, delusional beliefs, thought and communication disorders, which are much more widely experienced than was previously thought (for example, about 10% of the population have experienced hallucinations). I show that recent psychological research has revealed much about the mechanisms underlying each of these complaints. For example, auditory hallucinations occur when the individual mistakes inner speech for an external stimulus, and delusions appear to be the product of abnormal inferential processes. The new approach has implications for aetiology. For example, researchers working within the Kraepelinian paradigm have often assumed that the psychoses are endogenous. However, there is compelling evidence that the risk of experiencing psychotic complaints is influenced by adverse environmental factors such as insecure attachment relations and exposure to sexual and other kinds of trauma. These associations are relatively easy to understand once the psychological mechanisms leading to specific complaints are known. When all of the psychotic complaints have been explained, there will be no 'schizophrenia' or 'manic depression' left behind awaiting explanation. The approach that I advocate is not only more scientific than the Kraepelinian approach, but also more humane. In contrast to the Kraepelinian approach, which has encouraged disrespect for patients' experiences, it encourages us to treat patients as rational agents and to take what they say seriously.

Solar cycles and their relationship to human disease and adaptability

In this paper, we show that 11-year solar cycle peaks predispose humans to disease, but also endow creativity and adaptability. We give several examples of diseases that are modulated by light and present evidence for an effect of intensity and variation in sunlight, primarily ultraviolet radiation (UVR), on the human genome. The birth dates of nearly 237,000 unique clients in the Maine Medicaid database collected from 1995 to 2004, inclusive, were related to solar cycle irradiance for the past seventy-one years, encompassing seven solar cycles. The sample was divided into four general categories of disease: mental/behavioral illnesses; metabolic diseases; autoimmune diseases; neoplasms. The birth months for those clients born in any given year were arranged in the form of a winter/summer ratio in order to more clearly appreciate the seasonality inherent in each disease category. Solar cycles were separated into chaotic (approximately three times as irradiant) or non-chaotic according to the Gutenberg-Richter power law and the uncertainty inherent in predicting solar storms. The results show that radiation peaks in solar cycles and particularly in chaotic solar cycles (CSCs) are associated with a higher incidence of mental disorders, suggesting the sensitivity of ectodermal embryonic tissues to UVR. Autoimmune diseases have intermediate sensitivity, while the neoplasms in the study, primarily of endoderm, appear suppressed by peak UVR intensity. The ratio of the number of clients born in CSC cycles to non-CSC cycles was highest for the more genetic mental diseases, like schizophrenia and bipolar disorder, but as that ratio decreased, the clients with diseases like multiple sclerosis and rheumatoid arthritis showed more environmental features manifested as a greater winter/summer birth month ratio that was significantly different than that of the average client in the whole data set. The paper presents evidence that latitude, e.g., variation in light, is an added stress to the immune system (especially at 53-54 degrees N. latitude) that is involved in nearly all human disease. We hypothesize that introns, the presumptive engenderers of gene control, modulate the effects of UVR, particularly for the neoplasms studied. We conclude that intermittent and largely unpredictable peak solar cycle radiation has been the fundamental engine of evolution, forcing organisms to adapt to mutagenic UVR and producing enough damage to instigate genetic variation. Probably a chance genetic mutation over 80,000 years ago produced a human brain capable of abstract thought and consciousness. The slight genetic instability that favored an adaptable, creative brain also produced other somatic variations that present phenotypically as disease, but largely expressed after natural selection (reproduction) and associated with the inexorable entropy of aging.

Season of birth is associated with anthropometric and neurocognitive outcomes during infancy and childhood in a general population birth cohort

The 'season of birth' effect is one of the most consistently replicated associations in schizophrenia epidemiology. In contrast, the association between season of birth and development in the general population is relatively poorly understood. The aim of this study was to explore the impact of season of birth on various anthropometric and neurocognitive variables from birth to age seven in a large, community-based birth cohort. A sample of white singleton infants born after 37 weeks gestation (n = 22,123) was drawn from the US Collaborative Perinatal Project. Anthropometric variables (weight, head circumference, length/height) and various measures of neurocognitive development, were assessed at birth, 8 months, 4 and 7 years of age. Compared to summer/autumn born infants, winter/spring born infants were significantly longer at birth, and at age seven were significantly heavier, taller and had larger head circumference. Winter/spring born infants were achieving significantly higher scores on the Bayley Motor Score at 8 months, the Graham-Ernhart Block Test at age 4, the Wechsler Intelligence Performance and Full Scale scores at age 7, but had significantly lower scores on the Bender-Gestalt Test at age 7 years. Winter/spring birth, while associated with an increased risk of schizophrenia, is generally associated with superior outcomes with respect to physical and cognitive development.

Schizophrenia: An Update and Review

Schizophrenia is a common complex disorder characterized by psychosis, cognitive dysfunction and negative symptoms, whose etiology involves interactions between both genetic and environmental vulnerability factors. Recently, ongoing research attempting to elucidate the nature of these vulnerability factors has been generating exciting findings. The advances in understanding of environmental risk factors for mental illnesses and in genetic research into mental illnesses will be reviewed. Limitations of the findings and implications of these advances for genetic counseling practice will also be discussed.

Human endogenous retrovirus expression profiles in samples from brains of patients with schizophrenia and bipolar disorders

The detection and identification of retroviral transcripts in brain samples, cerebrospinal fluid, and plasma of individuals with recent-onset schizophrenia and schizoaffective disorders suggest that activation or upregulation of distinct human endogenous retroviruses (HERVs) may play a role in the etiopathogenesis of neuropsychiatric diseases. To test this hypothesis, we performed a comprehensive microarray-based analysis of HERV transcriptional activity in human brains. We investigated 50 representative members of 20 HERV families in a total of 215 brain samples derived from individuals with schizophrenia or bipolar disorders and matched controls. A characteristic brain-specific retroviral activity profile was found that consists of members of the class I families HERV-E, HERV-F, and ERV9 and members of HERV-K taxa. In addition to these constitutively expressed HERVs, a number of differentially active HERV elements were identified in all brain samples independent of the disease pattern that may reflect differences in the genetic background of the tested individuals. Only a subgroup of the HML-2 family (HERV-K10) was significantly overrepresented in both bipolar-disorder- and schizophrenia-associated samples compared to healthy brains, suggesting a potential association with disease. Real-time PCR analysis of HERV env transcripts with coding capacity potentially involved in neuroinflammatory conditions revealed that env expression of HERV-W, HERV-FRD, and HML-2 remains unaffected regardless of the clinical picture. Our data suggest that HERV transcription in brains is weakly correlated with schizophrenia and related diseases but may be influenced by the individual genetic background, brain-infiltrating immune cells, or medical treatment.

Transient prenatal vitamin D deficiency is associated with subtle alterations in learning and memory functions in adult rats

Based on clues from epidemiology, low prenatal vitamin D has been proposed as a candidate risk factor for schizophrenia. Recent animal experiments have demonstrated that transient prenatal vitamin D deficiency is associated with persistent alterations in brain morphology and neurotrophin expression. In order to explore the utility of the vitamin D animal model of schizophrenia, we examined different types of learning and memory in adult rats exposed to transient prenatal vitamin D deficiency. Compared to control animals, the prenatally deplete animals had a significant impairment of latent inhibition, a feature often associated with schizophrenia. In addition, the deplete group was (a) significantly impaired on hole board habituation and (b) significantly better at maintaining previously learnt rules of brightness discrimination in a Y-chamber. In contrast, the prenatally deplete animals showed no impairment on the spatial learning task in the radial maze, nor on two-way active avoidance learning in the shuttle-box. The results indicate that transient prenatal vitamin D depletion in the rat is associated with subtle and discrete alterations in learning and memory. The behavioural phenotype associated with this animal model may provide insights into the neurobiological correlates of the cognitive impairments of schizophrenia.

Do maternal folate and homocysteine levels play a role in neurodevelopmental processes that increase risk for schizophrenia?

OBJECTIVE

Evidence from many different lines of research supports the hypothesis that schizophrenia is a disorder of development with etiological factors implicated as early as the second trimester in utero. We suggest that low maternal folate, acting to increase homocysteine levels, may provide a functional link between many of the identified prenatal risk factors and the hypothesized mechanisms whereby neurodevelopmental patterning deviates toward a schizophrenic potential.

METHODS

PubMed was searched from the present back to 1963, when elevated homocysteine was identified as a pathogen in homocystinuria as first described by Carson and colleagues (Arch Dis Child 1963;38:425-36). All articles for homocystinuria, homocysteine, folate, and development with schizophrenia were evaluated.

RESULTS

The findings from this review support the hypothesis that maternal low folate and high homocysteine levels may provide a potential teratogenic mechanism that increases the risk for developing schizophrenia.

CONCLUSION

The potential role of maternal folate deficiency and hyperhomocystinemia in the genesis of schizophrenia would extend the range of their known teratogenic effects. Given the potential for preventive treatment offered by this hypothesis, we believe further investigation into this mechanism is warranted.

Seasonality of schizophrenia births in the Japanese population: increased winter births possibly confined to the north area

A number of North American and European studies have observed a higher proportion of winter births in schizophrenia patients. Thus, seasonal fluctuation of unknown environmental factors may affect brain development in ways that alter susceptibility to schizophrenia. Specification of these factors may help elucidate the etiopathological mechanism of the disease, about which little is certain. A small number of studies have investigated this issue in Asian populations, and the findings are not as consistent as those of Western populations. No remarkable excess of winter births has been observed in Japanese or Korean studies, while some studies have reported a significant decrease of summer births. We further investigated the issue in Japanese patients with schizophrenia (n=3927). No significant excess of winter births was observed, but a decrease in the summer births was found in male subjects. This is largely consistent with previous Japanese studies; however, when the subjects were confined to those born in a colder and higher latitude area of Japan (n=1338), a consistent trend for both a winter increase, and a summer decrease, was found. However, the results did not consistently reach statistical significance, possibly due to the lack of statistical power. Environmental factors that correlate with latitude might play a role in the development of the seasonality of births in schizophrenia. Further studies in a larger sample size are required to test these possibilities.

Linkage analysis of a completely ascertained sample of familial schizophrenics and bipolars from Palau, Micronesia

We report on linkage analysis of a completely ascertained population of familial psychosis derived from the oceanic nation of Palau. Palau, an archipelago of islands in the Southern Pacific, currently has a population of approximately 23,000 individuals. The peoples of Palau populated these islands recently in human history, approximately 2,000 years ago. As both historical and genetic evidence suggest, the population is far more homogeneous than most other populations undergoing genetic studies, and should therefore prove quite useful for mapping genetic variants having a meaningful impact on susceptibility to psychotic disorders. Moreover, for our study, essentially all on-island schizophrenics (150) and individuals with other psychotic disorders (25) participated. By analysis of narrow (only schizophrenia) and broad (all psychosis) diagnostic schemes, two-point linkage analyses suggest that two regions of the genome harbor genetic variants affecting liability in most families, 3q28 (LOD = 3.03) and 17q32.2 (LOD = 2.80). Results from individual pedigrees also support 2q37.2, 2p14, and 17p13 as potentially harboring important genetic variants. Most of these regions have been implicated in other genetic studies of psychosis in populations physically quite distant from this Oceanic population, although some (e.g., 3q28) appear to be novel results for schizophrenia linkage analyses.

The potential impact of genetic counseling for mental illness

Mental disorders are relatively highly heritable, yet complex with important interactions between genetic risk and environmental factors in determining illness expression. Due to the high prevalence of these complex disorders, steady increase in knowledge about genetic contributions, and increasing public awareness, this area may come to represent a significant proportion of all genetic counseling. The potential impact of genetic counseling in mental illness is broad. As well as the conventional expectations, genetic counseling may have the positive outcomes of reducing the guilt, shame, and stigma associated with mental illness, even within families. However, like many interventions in medicine, genetic counseling for mental disorders could potentially have unintended consequences resulting in increased stigma, guilt, and shame. The potential impacts of genetic education and providing recurrence risks on stigma are reviewed, as well as the role of education about the environment as a way of modifying family members' guilt. The review allows a preliminary formulation of a series of suggestions for genetic counseling in mental illness.

Vitamin D receptor variants in 192 patients with schizophrenia and other psychiatric diseases

Intriguing parallels have been noted previously between the biology of Vitamin D and the epidemiology of schizophrenia. We have scanned the Vitamin D receptor (VDR) gene by DOVAM-S (Detection of Virtually All Mutations-SSCP), a robotically enhanced multiplexed scanning method. In total, 100 patients with schizophrenia (86 Caucasians and 14 African-Americans) were scanned. In addition, pilot experiments were performed in patients with bipolar disorder (BPD) (24), autism (24), attention deficit hyperactivity disorder (ADHD) (24), and alcoholism (20). A total of 762 kb of the VDR genomic sequence was scanned. R208N and V339I were each found in one African-American patient, while absent in 35 African-American controls without schizophrenia (2/14 versus 0/35, P=0.08). Within the power of the study (> or =1.6-fold relative risk), the common M1T variant is not associated with schizophrenia. In the 92 scanned patients with other psychiatric diseases, R173S was found in a single patient with bipolar disorder. In conclusion, we describe three novel structural variants of the Vitamin D receptor. Further study is required to clarify their role, if any, in psychiatric disease.

Pineal attrition, loss of cognitive plasticity, and onset of puberty during the teen years: is it a modern maladaptation exposed by evolutionary displacement?

Cognitive plasticity, a developmental trait that promotes acquisition of complex skills such as language or playing musical instruments, diminishes substantially during puberty. The loss of plasticity has been attributed to surge of sex steroids during adolescence, but the phenomenon remains poorly understood. We hypothesize that pineal involution during puberty may contribute to plasticity decay. The pineal gland produces melatonin, the level of which declines dramatically during onset of puberty. Emerging evidence suggest that melatonin may modulate cognitive plasticity, independent of the effects of sex steroids, and low sex steroids and high melatonin may be simultaneously required to maintain cognitive plasticity. Potential mechanisms by which melatonin may modulate plasticity are examined within the sleep and hippocampal long-term potentiation frameworks. Implications for psychiatric conditions that involve sleep disorders and learning dysfunctions such as schizophrenia and autism are discussed, and the potential adaptive roles of postprandial and postcoital sleep are explored. From the Darwinian perspective, development and reproductive maturity may represent distinct phases that require tailored cognitive strategies to maximize fitness. While cognitive flexibility and susceptibility to new skills may be paramount during development, reduced cognitive flexibility and increased cognitive determinism may enable more efficient responses to stimuli during adulthood. Thus, cognitive plasticity and cognitive determinism may represent trade-off adaptations and different dimensions of intelligence. The decline of plasticity and emergence of puberty during the second decade may be relics of prehistoric times when the human lifespan was short and the environment was relatively simple and static. Today, when the environment is more complex and dynamic, and humans are living far longer, the early obsolescence of plasticity during puberty may represent a Darwinian inefficiency exposed by evolutionary displacement. Regulation of plasticity may be a systemic phenomenon, as exemplified by the association of learning disability with allergic conditions, a form of immune plasticity dysfunction. Ramifications for other plastic functions that decline during puberty such as wound healing and hyaline cartilage regeneration are explored. Like the plasticity of immunity and cognition, the plasticity of hyaline cartilage during youth may enable hosts to respond to ecologic opportunities and generate the optimally adapted adult phenotype. Pineal involution may represent a potential target for therapeutic extension or restoration of plasticity after puberty. Extending plasticity may have far-reaching consequences for human evolution.

Theories of schizophrenia: a genetic-inflammatory-vascular synthesis

BACKGROUND

Schizophrenia, a relatively common psychiatric syndrome, affects virtually all brain functions yet has eluded explanation for more than 100 years. Whether by developmental and/or degenerative processes, abnormalities of neurons and their synaptic connections have been the recent focus of attention. However, our inability to fathom the pathophysiology of schizophrenia forces us to challenge our theoretical models and beliefs. A search for a more satisfying model to explain aspects of schizophrenia uncovers clues pointing to genetically mediated CNS microvascular inflammatory disease.

DISCUSSION

A vascular component to a theory of schizophrenia posits that the physiologic abnormalities leading to illness involve disruption of the exquisitely precise regulation of the delivery of energy and oxygen required for normal brain function. The theory further proposes that abnormalities of CNS metabolism arise because genetically modulated inflammatory reactions damage the microvascular system of the brain in reaction to environmental agents, including infections, hypoxia, and physical trauma. Damage may accumulate with repeated exposure to triggering agents resulting in exacerbation and deterioration, or healing with their removal. There are clear examples of genetic polymorphisms in inflammatory regulators leading to exaggerated inflammatory responses. There is also ample evidence that inflammatory vascular disease of the brain can lead to psychosis, often waxing and waning, and exhibiting a fluctuating course, as seen in schizophrenia. Disturbances of CNS blood flow have repeatedly been observed in people with schizophrenia using old and new technologies. To account for the myriad of behavioral and other curious findings in schizophrenia such as minor physical anomalies, or reported decreased rates of rheumatoid arthritis and highly visible nail fold capillaries, we would have to evoke a process that is systemic such as the vascular and immune/inflammatory systems.

SUMMARY

A vascular-inflammatory theory of schizophrenia brings together environmental and genetic factors in a way that can explain the diversity of symptoms and outcomes observed. If these ideas are confirmed, they would lead in new directions for treatments or preventions by avoiding inducers of inflammation or by way of inflammatory modulating agents, thus preventing exaggerated inflammation and consequent triggering of a psychotic episode in genetically predisposed persons.

Site-specific cytosine methylation in S-COMT promoter in 31 brain regions with implications for studies involving schizophrenia

The catechol-o-methyltransferase (COMT) gene on chromosome 22q11 has been considered a strong candidate gene for schizophrenia (SZ) susceptibility. A functional Val/Met polymorphism in exon 4, with potential to affect COMT activity has been implicated in SZ, but the results remain inconclusive. We hypothesized that the association of COMT gene with SZ is not strictly a genetic alteration but could involve DNA methylation, as an epigenetic alteration. Thus, we chose to examine the cytosine DNA methylation profile of the human COMT promoter regions, which partially overlaps with the MB-COMT coding region and covers a total of 56 cytosines. Our analysis of 31 brain regions and 51 individual blood samples suggests that the cytosine methylation in his region is restricted to the CpG dinucleotides only. Also, the methylation pattern is nearly identical in the brain and blood with few exceptions. One cytosine (#27) is partially methylated in 5 brain regions and another cytosine (#23) is partially methylated in 81 of 82 samples studied. The exception being the blood DNA from a single SZ patient with prominent extreme negative symptoms, which was completely methylated. Interestingly, there was no difference in methylation at these sites in the blood DNA from three pairs of monozygotic twins discordant for SZ. The results support the use of blood DNA in methylation studies and rule out S-COMT promoter methylation as a common cause of SZ. The unique observation of a completely methylated cytosine 23 in one patient with SZ may have the potential to affect COMT mRNA transcription and gene activity, but remains to be evaluated.

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.

Timing of birth and risk of multiple sclerosis: population based study

OBJECTIVES

To determine if risk of multiple sclerosis (MS) is associated with month of birth in countries in the northern hemisphere and if factors related to month of birth interact with genetic risk.

DESIGN

Population based study with population and family based controls and a retrospective cohort identified from death certificates. A post hoc pooled analysis was carried out for large northern datasets including Sweden and Denmark.

SETTING

19 MS clinics in major cities across Canada (Canadian collaborative project on the genetic susceptibility to multiple sclerosis); incident cases of MS from a population based study in the Lothian and Border regions of Scotland; and death records from the UK Registrar General.

POPULATIONS

17,874 Canadian patients and 11,502 British patients with multiple sclerosis.

MAIN OUTCOME MEASURE

Diagnosis of multiple sclerosis.

RESULTS

In Canada (n = 17,874) significantly fewer patients with MS were born in November compared with controls from the population census and unaffected siblings. These observations were confirmed in a dataset of British patients (n = 11, 502), in which there was also an increase in the number of births in May. A pooled analysis of datasets from Canada, Great Britain, Denmark, and Sweden (n = 42,045) showed that significantly fewer (8.5%) people with MS were born in November and significantly more (9.1%) were born in May. For recent incident data, the effect of month of birth was most evident in Scotland, where MS prevalence is the highest.

CONCLUSIONS

Month of birth and risk of MS are associated, more so in familial cases, implying interactions between genes and environment that are related to climate. Such interactions may act during gestation or shortly after birth in individuals born in the northern countries studied.