Seasonality, birth complications and schizophrenia in a high risk sample

Impact of respiratory viral infections during pregnancy on the neurological outcomes of the newborn: current knowledge

Brain development is a complex process that begins during pregnancy, and the events occurring during this sensitive period can affect the offspring's neurodevelopmental outcomes. Respiratory viral infections are frequently reported in pregnant women, and, in the last few decades, they have been related to numerous neuropsychiatric sequelae. Respiratory viruses can disrupt brain development by directly invading the fetal circulation through vertical transmission or inducing neuroinflammation through the maternal immune activation and production of inflammatory cytokines. Influenza virus gestational infection has been consistently associated with psychotic disorders, such as schizophrenia and autism spectrum disorder, while the recent pandemic raised some concerns regarding the effects of severe acute respiratory syndrome coronavirus 2 on neurodevelopmental outcomes of children born to affected mothers. In addition, emerging evidence supports the possible role of respiratory syncytial virus infection as a risk factor for adverse neuropsychiatric consequences. Understanding the mechanisms underlying developmental dysfunction allows for improving preventive strategies, early diagnosis, and prompt interventions.

Minimal brain damage and seasonality of birth in schizophrenic disorders

A minimal brain damage examination was carried out in 73 schizophrenic patients divided into three groups according to their season of birth. Results showed no statistically significant difference among groups in the prevalence of neurological soft signs.

Obstetric complications in distinct schizophrenic subgroups

In 55 chronic DSM III-R schizophrenics the occurrence of obstetric complications (OCs) was investigated using the familial/sporadic strategy and Leonhard's unsystematic/systematic distinction. The overall frequency and severity of OCs did not differ between patients and controls. A sub-sample of patients, whose genetic risk was supposed to be high in both classification systems (diagnosis of unsystematic and familial schizophrenia), had significantly fewer OCs than controls on the Lewis and Murray scale (P< 0.05). With reference to previous reports of increased mortality rates in the offspring of schizophrenics, high genetic risk and additional perinatal stressors may increase perinatal mortality. In contrast, patients whose genetic risk was supposed to be low in both systems (diagnosis of systematic and sporadic schizophrenia) showed a trend to an increased frequency of OCs in the Fuchs scale. In the context of the recently reported highly significantly increased rate of maternal infections during midgestation in these patients, it was supposed that perinatal complications may be of some aetiological importance in schizophrenics with low genetic risk.

Common or distinct pathways to psychosis? A systematic review of evidence from prospective studies for developmental risk factors and antecedents of the schizophrenia spectrum disorders and affective psychoses

BACKGROUND

Identifying the unique and shared premorbid indicators of risk for the schizophrenia spectrum disorders (SSD) and affective psychoses (AP) may refine aetiological hypotheses and inform the delivery of universal versus targeted preventive interventions. This systematic review synthesises the available evidence concerning developmental risk factors and antecedents of SSD and AP to identify those with the most robust support, and to highlight remaining evidence gaps.

METHODS

A systematic search of prospective birth, population, high-risk, and case-control cohorts was conducted in Medline and supplemented by hand searching, incorporating published studies in English with full text available. Inclusion/exclusion decisions and data extraction were completed in duplicate. Exposures included three categories of risk factors and four categories of antecedents, with case and comparison groups defined by adult psychiatric diagnosis. Effect sizes and prevalence rates were extracted, where available, and the strength of evidence synthesised and evaluated qualitatively across the study designs.

RESULTS

Of 1775 studies identified by the search, 127 provided data to the review. Individuals who develop SSD experience a diversity of subtle premorbid developmental deficits and risk exposures, spanning the prenatal period through early adolescence. Those of greatest magnitude (or observed most consistently) included obstetric complications, maternal illness during pregnancy (especially infections), other maternal physical factors, negative family emotional environment, psychopathology and psychotic symptoms, and cognitive and motor dysfunctions. Relatively less evidence has accumulated to implicate this diversity of exposures in AP, and many yet remain unexamined, with the most consistent or strongest evidence to date being for obstetric complications, psychopathology, cognitive indicators and motor dysfunction. Among the few investigations affording direct comparison between SSD and AP, larger effect sizes and a greater number of significant associations are commonly reported for SSD relative to AP.

CONCLUSIONS

Shared risk factors for SSD and AP may include obstetric complications, childhood psychopathology, cognitive markers and motor dysfunction, but the capacity to distinguish common versus distinct risk factors/antecedents for SSD and AP is limited by the scant availability of prospective data for AP, and inconsistency in replication. Further studies considering both diagnoses concurrently are needed. Nonetheless, the prevalence of the risk factors/antecedents observed in cases and controls helps demarcate potential targets for preventative interventions for these disorders.

Multiple 'hits' during postnatal and early adulthood periods disrupt the normal development of sensorimotor gating ability in rats

In the present study, we evaluated a multiple-hit animal model of schizophrenia in an attempt to capture the complex interactions among various adverse developmental factors in schizophrenia. Sprague-Dawley rats were assigned to receive either repeated daily 3-h maternal separation for eight days (first 'hit') on postnatal days (PND) 3 to 10, and/or avoidance conditioning for six days (second 'hit') on PND 49-56, and/or repeated phencyclidine treatment (third 'hit', 3.0 mg/kg, sc) immediately after each daily avoidance conditioning. Prepulse inhibition (PPI) of acoustic startle reflex was assessed at late adolescence (PND 41-43) and early adulthood (PND 62-63). The change in %PPI from the adolescence phase to adulthood phase was used to index the maturation-related improvement of sensorimotor gating ability. Maternal separation, avoidance conditioning and PCP treatment had a complex three-way interaction on the functional improvement of sensorimotor gating. Maternal separation impaired PPI improvement preferentially in the saline rats that were not subjected to avoidance conditioning. Avoidance conditioning had no effect on PPI improvement in the non-maternally separated rats, but restored the maternal separation-induced disruption. However, this restoration effect was abolished by PCP treatment. The present study also identified a number of behavioral, emotional and learning abnormalities caused by these three developmental insults which may precede their interactive disruption of normal development of sensorimotor gating ability.

Progressive and interrelated functional and structural evidence of post-onset brain reduction in schizophrenia

CONTEXT

Progressive brain abnormalities in schizophrenia remain controversial. Evidence of interrelated progressive functional impairment would buttress the case for structural progression. Mismatch negativity (MMN) is reduced in chronic but not first-hospitalized schizophrenia and may index progressive structural changes.

OBJECTIVE

To determine whether MMN shows associations with underlying auditory cortex gray matter at first hospitalization and progressive reduction longitudinally.

DESIGN

Cross-sectional (first hospitalization) and longitudinal (1.5-year follow-up).

SETTING

A private psychiatric hospital.

PARTICIPANTS

Protocol entrance: MMN and magnetic resonance imaging at first hospitalization in 20 subjects with schizophrenia, 21 subjects with bipolar disorder with psychosis, and 32 control subjects. Longitudinal electrophysiologic testing: MMN in 16 subjects with schizophrenia, 17 subjects with bipolar disorder, and 20 control subjects. Longitudinal electrophysiologic testing and magnetic resonance imaging: MMN and magnetic resonance imaging in 11 subjects with schizophrenia, 13 subjects with bipolar disorder, and 13 control subjects. At each time point, reported samples were group matched for age, handedness, and parental socioeconomic status.

INTERVENTIONS

Electrophysiologic testing and high-resolution structural magnetic resonance imaging.

MAIN OUTCOME MEASURES

Mismatch negativity amplitude and Heschl gyrus and planum temporale gray matter volumes.

RESULTS

Initially, groups did not differ in MMN amplitude. Subjects with schizophrenia showed associations between MMN and Heschl gyrus (r=-0.52; P=.02) not present in the other groups. At longitudinal MMN testing, schizophrenia showed MMN reduction (P=.004). Only schizophrenia evinced longitudinal left hemisphere Heschl gyrus reduction (P=.003), highly correlated with MMN reduction (r=0.6; P=.04).

CONCLUSIONS

At first hospitalization for schizophrenia, MMN indexed left hemisphere Heschl gyrus gray matter volume, consistent with variable progression of pre-hospitalization cortical reduction. Longitudinally, the interrelated progressive reduction of functional and structural measures suggests progressive pathologic processes early in schizophrenia. An active process of progressive cortical reduction presents a potential therapeutic target. Mismatch negativity may be a simple, sensitive, and inexpensive index not only of this progressive pathologic process but also of successful intervention.

Role of calcium regulation in pathophysiology model of schizophrenia and possible interventions

Recent advances into the neuroscience research related to pathophysiology of schizophrenia have been impressive. While some are based on pre-existing theories and models, others have explored on a molecular level attempting to integrate the concepts of the past and present. However, given the complex multifactorial etiology of schizophrenia attempts to improve the current treatment modalities raise more questions than answers. In the cascade model of the hypotheses, the focus will be on a common factor/marker for the disease, to address the possible stepwise correlation between the various theories. Homeostasis of calcium, its relation to the release of glutamate, dopamine and nitric oxide will be discussed in detail with the potential for interventions aimed at every stage. Although this hypothesis emphasizes the role of calcium as a common factor, other potential causes such as autoantibodies to the receptors, such as NMDA (and GABA) cannot be ruled out.

Perinatal characteristics and schizophrenia: electrodermal activity as a mediating link in a vulnerability-stress perspective

Vulnerability-stress models of schizophrenia assert that the disorder results from an interaction between genetic or biologically acquired vulnerability and unfavourable environmental conditions. As our knowledge of early environmental factors for schizophrenia evolves, the question of links between early factors and a development of schizophrenia becomes more important. In this article, we analyse the relationship between obstetrical complications (OCs) and adult schizophrenia and methodological concerns in the search for pre- and perinatal risk factors. We review findings of aberrant electrodermal activity in schizophrenic patients and suggest that OCs may induce insults to cerebral structures that are critically involved in the control of orienting and of autonomic responses.

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

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

Relationship of birth season to clinical features, family history, and obstetric complication in schizophrenia

Birth in late winter and spring has been consistently shown to be a risk factor of schizophrenia. The relationship of late winter/spring birth to clinical characteristics and other putative risk factors, such as family history and obstetric complications, may provide clues to etiology. Data relating to season of birth, clinical features, family history, and obstetric complications were analyzed for 192 patients with schizophrenia as defined by Research Diagnostic Criteria (including schizoaffective disorder). There was no significant association of season of birth with any of the psychopathological dimensions nor was there a significant association with obstetric variables or family history. However, winter-born schizophrenic patients who had a negative family history were more likely to have a history of obstetric complications. These findings suggest that obstetric complications associated with schizophrenia are perhaps the result of some seasonal risk factors important in those without a family history of the disorder.

No difference found between winter- and non-winter-born schizophrenic cases

The distinction between winter-born (WBS) and non-winter born (NWBS) schizophrenic cases has been proposed as a strategy to identify distinct etiologic subtypes within schizophrenia, the WBS subgroup being a predominantly environmental subtype. The goal of this paper is to empirically test the validity of this strategy by comparing WBS and NWBS groups on a broad array of clinical and biological variables. DSM-III-R schizophrenic, schizoaffective and schizophreniform subjects were comprehensively assessed using (i) the Comprehensive Assessment of Symptoms and History; (ii) a comprehensive neurological exam; (iii) a neuropsychological battery, including IQ and the Continuous Performance Test and (iv) an MRI scanning. The patients were divided into WBS and NWBS, using five alternative sets of definitions of winter birth. These comparisons yielded no differences between the groups on any of the 23 variables. The results suggest that the distinction between winter-born and non-winter-born cases has very limited power to identify distinct schizophrenic subtypes, and that better delineation of the correlates of environmental risk factors in schizophrenia will require a better identification of these factors.

The relationship of the skin conductance and finger pulse amplitude components of the orienting response to season of birth in schizophrenia and depression

Schizophrenia is said to be associated with a modest excess of winter births. We examined relations of season of birth (SOB) to the skin conductance response (SCR) and finger pulse amplitude response (FPAR) components of the orienting response (OR) in 83 schizophrenic patients, 59 depressed patients, and 81 normal controls. SCR-OR nonresponding was more prevalent among depressed patients regardless of SOB, whereas only winter-born schizophrenics showed significantly more frequent electrodermal nonresponding than controls. However, this latter relation was not confirmed with log linear analysis. No other relations of SOB to SCR-OR or FPAR-OR nonresponding were significant. Our data do not support the view that nonresponding in the SCR or FPAR components of the OR is associated with winter birth either in schizophrenia or depression.

Fall conception increases the risk of neurodevelopmental disorder in offspring

Hormonal imbalances in utero may render males more vulnerable to neurodevelopmental disorder (ND) than females. Since hormonal activity can be influenced by photoperiod, the relationship between season of conception and incidence of ND in offspring was examined within 11,578 mother/child pairs. Fall conception significantly elevated the odds for mental retardation, reading, arithmetic disability, or performance aptitude deficits (but not seizures, articulation disorder, cerebral palsy, or verbal aptitude deficits), and decreased the odds for reading talent (even when socioeconomic class, prenatal visits, infections, fever, vomiting, edema, anemia, and weight loss were covaried). Since the seasonality effect was not stronger in males, and was not specific to those NDs caused by left hemisphere dysfunction, the predictions of Geschwind and Galaburda (1985a, 1985b, 1985c) were not confirmed.

Can environmental factors explain the epidemiology of schizophrenia in immigrant groups?

Recent evidence suggests that high rates of schizophrenia in first- and second-generation immigrants could be due to exposure to environmental factors such as viral infections in the host country. These findings are discussed alongside parallel data relating to other diseases such as multiple sclerosis and diabetes mellitus. It is argued that in each case the interaction between the environmental agent and constitutional factors related to the immune system need to be considered.

Gestational and neonatal factors in the etiology of schizophrenia

This study evaluates research on gestational and neonatal factors implicated as causes of schizophrenia. These include obstetrical complications (particularly gestational hypoxia), viral infections, autoimmune agents, developmental deficits, and maternal stress. Evidence strongly suggests that these factors are importantly connected to the onset of adult schizophrenia.

Seasonality in psychiatry--a review

This paper reviews the literature pertaining to seasonal patterns in psychiatric illnesses. Evidence on the season of birth phenomenon suggests that a greater risk of pre-, peri-, or post-natal damage is associated with the winter months. There is currently insufficient evidence to pinpoint the exact mechanism involved or to ascertain whether the mechanism is common to each condition. Studies of seasonal patterns of incidence of psychiatric disorders have highlighted the role of seasonally regulated environmental factors on internal biological processes. There is growing evidence that serotonin is involved in a variety of psychiatric disorders. Seasonal patterns have been observed in processes involving serotonergic functioning. Furthermore, it has been postulated that these processes may be influenced by photoperiod, suggesting that the seasonal patterns of incidence of several psychiatric conditions may share a common neurophysiological substrate.

The relationship between schizophrenia and immigration. Are there alternatives to psychosocial hypotheses?

Several recent studies have found markedly increased rates of schizophrenia among West Indian immigrants to the UK. Almost exclusively, authors have sought psychosocial explanations for these findings. This paper hypothesises that environmental causes, notably obstetric complications and perinatal infections, provide more plausible aetiological models, especially for the raised rates of schizophrenia among second-generation West Indian immigrants.

Estimating effects of proband characteristics on familial risk: II. The association between age at onset and familial risk in the Maryland schizophrenia sample

In this report we apply methods outlined in the companion paper [Liang, Genet Epidemiol 8:329-338, 1991] to study the association between proband age at onset and familial risk among first-degree relatives of 374 schizophrenic probands. The analyses take into consideration the potential problems of censoring and correlation of age at onset within families. All analyses were done by gender of the proband; age at onset was dichotomized. The results of the analyses of the male probands suggest that there is an increased risk of schizophrenia among the relatives of male probands who have an onset prior to age 17 when compared to relatives of male probands who have an onset later than 16. We did not find an association between age at onset and familial risk among the female probands, but this may be due to the smaller number of female probands and the lower power associated with the analyses.

Season of birth and electrodermal unresponsiveness in male schizophrenics

The present study was designed to examine differences in the electrodermal activity of schizophrenics born in the season of excessive risk (January-April), and those born in the season of nonexcessive risk (May-December). Thirty-two male schizophrenics were presented with a series of orienting tones (1000 Hz, 80dB, 2 sec duration) while electrodermal activity was monitored. They were subdivided according to season of birth and compared in three electrodermal variables, and also in some background and clinical parameters. We found that schizophrenics born in the season of excessive risk were characterized by significantly lower electrodermal activity and more negative symptoms than those born in the season of nonexcessive risk.