In utero infection and adult schizophrenia

Evaluating early preventive antipsychotic and antidepressant drug treatment in an infection-based neurodevelopmental mouse model of schizophrenia

Current pharmacotherapy of schizophrenia remains unsatisfactory with little hope for complete functional restoration in patients once the disease has developed. A preventive approach based on intervention in the prodromal stage of the disease aiming to preserve functional integrity by halting the progress of the disease is therefore extremely attractive. Here, we investigated the effects of preventive antipsychotic or antidepressant drug treatment in a well-established neurodevelopmental mouse model of multiple schizophrenia-related abnormalities. Pregnant mice on gestation day 9 were exposed to the viral mimic polyriboinosinic-polyribocytidylic acid (2 mg/kg, intravenously) or corresponding vehicle treatment, and the resulting offspring from both prenatal treatment conditions were subjected to chronic antipsychotic (haloperidol or clozapine), antidepressant (fluoxetine), or placebo treatment during the periadolescent stage of development. The effects of the preventive pharmacotherapy on behavioral and pharmacological functions were then investigated in adulthood using paradigms relevant to schizophrenia, namely prepulse inhibition, latent inhibition, and sensitivity to psychostimulant drugs. We show that periadolescent treatment with the reference antipsychotic and antidepressant drugs can successfully block the emergence of multiple psychosis-related behavioral and pharmacological abnormalities in subjects predisposed to adult brain pathology by exposure to prenatal immune challenge. At the same time, however, our study reveals numerous negative influences of the early pharmacological intervention on normal behavioral development in control subjects. Hence, even though preventive pharmacotherapy may be beneficial in individuals with predisposition to psychosis-related brain dysfunctions, chronic antipsychotic or antidepressant drug treatment in false-positive subjects is associated with substantial risk for long-term behavioral disturbances in adulthood.

Ontogeny of sensorimotor gating and immune impairment induced by prenatal immune challenge in rats: implications for the etiopathology of schizophrenia

It has been hypothesized that the maternal immune response to infection may influence fetal brain development and lead to schizophrenia. Animal experimentation has supported this notion by demonstrating altered sensorimotor gating (prepulse inhibition, PPI) in adult rats prenatally exposed to an immune challenge. In the present study, pregnant rats were exposed to the bacterial endotoxin lipopolysaccharide (LPS) throughout gestation and the offspring were examined by evaluating the PPI, dopaminergic function, brain protein expression and cytokine serum levels from weaning to late adulthood. Prenatal LPS exposure induced a deficit in PPI that emerged at 'puberty' and that persisted throughout adult life. This prenatal insult caused age-specific changes in accumbal dopamine levels and in synaptophysin expression in the frontal cortex. Moreover, serum cytokine levels were altered in an age- and cytokine-dependent manner. Here we show that prenatal LPS administration throughout pregnancy causes maturation-dependent PPI deficits and age-dependent alterations in dopamine activity, as well as in synaptophysin expression and cytokine levels.

Chronic clozapine treatment improves prenatal infection-induced working memory deficits without influencing adult hippocampal neurogenesis

BACKGROUND

Converging evidence indicates that prenatal exposure to immune challenge can induce long-term cognitive deficits relevant to schizophrenia. Such cognitive impairments may be related to deficient hippocampal neurogenesis at adult age.

OBJECTIVES

In the present study, we sought evidence for the possibility that chronic treatment with the reference atypical antipsychotic drug clozapine may improve prenatal infection-induced cognitive dysfunctions by stimulating adult hippocampal neurogenesis.

METHODS

This hypothesis was tested in a well-established mouse model of prenatal immune challenge which is based on prenatal administration of the viral mimic, polyriboinosinic-polyribocytidilic acid (PolyI:C).

RESULTS

We found that maternal PolyI:C (5 mg/kg, i.v.) exposure on gestation day 17 led to significant spatial working memory impairment and reduced hippocampal neurogenesis in the resulting offspring at adult age. The latter effect was apparent in postmortem immunohistochemical analyses of the cell proliferation marker bromodeoxyuridine and the microtubule-associated protein doublecortin, a marker of newborn neuronal cells. Chronic (3 weeks) administration of clozapine (5 mg/kg/day, i.p.) significantly improved the prenatal PolyI:C-induced working memory deficits, while at the same time, it negatively affected working memory performance in adult offspring born to control mothers. These bidirectional cognitive effects of clozapine were not paralleled by concomitant effects on adult hippocampal neurogenesis.

CONCLUSIONS

Our findings do not support the hypothesis that the atypical antipsychotic drug clozapine may influence cognitive functions by acting on adult neurogenesis in the hippocampus, regardless of whether the drug is administered to subjects with or without a neurodevelopmental predisposition to adult neuropathology.

Models of neurodevelopmental abnormalities in schizophrenia

The neurodevelopmental hypothesis of schizophrenia asserts that the underlying pathology of schizophrenia has its roots in brain development and that these brain abnormalities do not manifest themselves until adolescence or early adulthood. Animal models based on developmental manipulations have provided insight into the vulnerability of the developing fetus and the importance of the early environment for normal maturation. These models have provided a wide range of validated approaches to answer questions regarding environmental influences on both neural and behavioral development. In an effort to better understand the developmental hypothesis of schizophrenia, animal models have been developed, which seek to model the etiology and/or the pathophysiology of schizophrenia or specific behaviors associated with the disease. Developmental models specific to schizophrenia have focused on epidemiological risk factors (e.g., prenatal viral insult, birth complications) or more heuristic models aimed at understanding the developmental neuropathology of the disease (e.g., ventral hippocampal lesions). The combined approach of behavioral and neuroanatomical evaluation of these models strengthens their utility in improving our understanding of the pathophysiology of schizophrenia and developing new treatment strategies.

Prenatal exposure to infection: a primary mechanism for abnormal dopaminergic development in schizophrenia

RATIONALE

Prenatal exposure to infection is a notable environmental risk factor in the development of schizophrenia. One prevalent hypothesis suggests that infection-induced disruption of early prenatal brain development predisposes the organism to long-lasting structural and functional brain abnormalities. Many of the prenatal infection-induced functional brain abnormalities appear to be closely associated with imbalances in the mesocorticolimbic dopamine system in adult life, suggesting that disruption of functional and structural dopaminergic development may be at the core of the developmental neuropathology associated with psychosis-related abnormalities induced by prenatal exposure to infection.

OBJECTIVES

In this review, we integrate recent findings derived from experimental models in animals with parallel research in humans which supports this hypothesis. We thereby highlight the developmental perspective of abnormal DA functions following in-utero exposure to infection in relation to the developmental and maturational mechanisms potentially involved in schizophrenia.

RESULTS

Experimental investigations show that early prenatal immune challenge can lead to the emergence of early structural and functional alterations in the mesocorticolimbic DA system, long before the onset of the full spectrum of psychosis-associated behavioral and cognitive abnormalities in adulthood.

CONCLUSIONS

Dopaminergic mal-development in general, and following prenatal immune activation in particular, may represent a primary etiopathological mechanism in the development of schizophrenia and related disorders. This hypothesis differs from the view that dopaminergic abnormalities in schizophrenia may be secondary to abnormalities in other brain structures and/or neurotransmitter systems. The existence of primary dopaminergic mechanisms may have important implications for the identification and early treatment of individuals prodromally symptomatic for schizophrenia.

A review of the fetal brain cytokine imbalance hypothesis of schizophrenia

Maternal infection during pregnancy increases the risk of schizophrenia and other brain disorders of neurodevelopmental origin in the offspring. A multitude of infectious agents seem to be involved in this association. Therefore, it has been proposed that factors common to the immune response to a wide variety of bacterial and viral pathogens may be the critical link between prenatal infection and postnatal brain and behavioral pathology. More specifically, it has been suggested that the maternal induction of pro-inflammatory cytokines may mediate the neurodevelopmental effects of maternal infections. Here, we review recent findings from in vitro and in vivo investigations supporting this hypothesis and further emphasize the influence of enhanced anti-inflammatory cytokine signaling on early brain development. Disruption of the fetal brain balance between pro- and anti-inflammatory cytokine signaling may thus represent a key mechanism involved in the precipitation of schizophrenia-related pathology following prenatal maternal infection and innate immune imbalances.

Effects of prenatal immune activation on hippocampal neurogenesis in the rat

Maternal infection during pregnancy has been associated with an increased risk for the development of schizophrenia, a disorder characterized by abnormalities in hippocampal morphology and function. Neurogenesis occurs in the hippocampus throughout development into adulthood and is believed to modulate hippocampal function. This study used a rat model in which bacterial endotoxin, lipopolysaccharide (LPS), is administered to pregnant dams, to test if prenatal immune activation has acute and/or long term effects on various phases of neurogenesis (proliferation, survival, differentiation) in the hippocampal dentate gyrus of offspring. When LPS was administered to dams on gestation days (GD) 15 and 16, there was decreased proliferation of dentate cells at postnatal day (PD) 14 and decreased survival of cells generated at PD14 in offspring. When prenatal exposure to LPS was later in pregnancy (GD 18 and 19), offspring showed decreased survival of cells generated both at the time of LPS exposure and at PD14. There was no change in cell proliferation or survival in adult offspring at PD60, with prenatal LPS exposure. Co-administration of the cyclo-oxygenase inhibitor, ibuprofen (IBU), together with prenatal LPS on GD 15 and 16, was unable to prevent the deficit in neuronal survival at PD14. IBU blocked LPS-induced fever but did not block LPS-induced increases in plasma cytokines and corticosterone in the pregnant dam. This indicates that deficits in neurogenesis caused by prenatal LPS are not mediated by LPS-induced fever or eicosanoid induction, but could be mediated by LPS-induced increases in maternal cytokines or corticosterone.

Prevalence of self-reported infection during pregnancy among control mothers in the National Birth Defects Prevention Study

BACKGROUND

Although specific maternal infections during pregnancy have been associated with birth defects and other adverse pregnancy outcomes, the prevalence of infections during pregnancy has not been well described.

METHODS

We estimated the prevalence of self-reported infection among 4967 women with live-born infants without major birth defects. We assessed the prevalence of reported infections and fever by type of infection, specific illness, and maternal characteristics including race and age.

RESULTS

Overall, 63.6% of women reported at least one infection during pregnancy. Reports of infections were more common during pregnancy than in the 3 months before pregnancy. Nearly half (49.6%) of women reported a respiratory infection, 20.5% reported a fever, 17.1% reported a urinary tract infection, 4.2% reported a yeast infection, and 3.4% reported a sexually transmitted disease. A subanalysis of self-reported infection and preterm delivery was performed among primiparous mothers with singleton pregnancies, but no statistically significant differences in infection prevalence were found. Women younger than 35 years reported nonrespiratory infections more frequently than women aged 35 years or older (prevalence ratio [PR] 1.41; 95% confidence interval [CI]: 1.21-1.64). Prevalence of nonrespiratory infections was also higher among those who smoked than among those who did not (PR 1.33; 95% CI: 1.20-1.47).

CONCLUSIONS

Reported infections during pregnancy are common, implying that a small increase in risk for birth defects or other adverse pregnancy outcomes could have a significant public health effect and underscoring the importance of understanding the effects of prenatal infections.

The antecedents of schizophrenia: a review of birth cohort studies

BACKGROUND

Birth cohort (BC) studies demonstrate that individuals who develop schizophrenia differ from the general population on a range of developmental indices. The aims of this article were to summarize key findings from BC studies in order to identify areas of convergence and to outline areas requiring further research.

METHOD

We define BC studies as studies based on general population BCs where data are collected prospectively from birth or childhood and which identify schizophrenia or related disorders as an outcome. To identify such studies, we searched various electronic databases using the search parameters (schizo* OR psych*) AND (birth cohort). We also checked the references of relevant articles and previous reviews.

RESULTS

We identified 11 BCs from 7 countries that have examined schizophrenia as an outcome in adulthood. There is relatively consistent evidence that, as a group, children who later develop schizophrenia have behavioral disturbances and psychopathology, intellectual and language deficits, and early motor delays. Evidence with respect to alterations in language, educational performance, and physical growth has also been identified in some studies. BC studies have also contributed evidence about a wide range of putative risk factors for schizophrenia.

CONCLUSIONS

BC studies have provided important, convergent insights into how the developmental trajectory of individuals who develop schizophrenia differs from their peers. The combination of new paradigms and larger cohorts, with the tools of modern epidemiology and biomedical science, is advancing our understanding of the developmental pathways to schizophrenia.

Prenatal immune activation leads to multiple changes in basal neurotransmitter levels in the adult brain: implications for brain disorders of neurodevelopmental origin such as schizophrenia

Maternal infection during pregnancy enhances the offspring's risk for severe neuropsychiatric disorders in later life, including schizophrenia. Recent attempts to model this association in animals provided further experimental evidence for a causal relationship between in-utero immune challenge and the postnatal emergence of a wide spectrum of behavioural, pharmacological and neuroanatomical dysfunctions implicated in schizophrenia. However, it still remains unknown whether the prenatal infection-induced changes in brain and behavioural functions may be associated with multiple changes at the neurochemical level. Here, we tested this hypothesis in a recently established mouse model of viral-like infection. Pregnant dams on gestation day 9 were exposed to viral mimetic polyriboinosinic-polyribocytidilic acid (PolyI:C, 5 mg/kg i.v.) or vehicle treatment, and basal neurotransmitter levels were then compared in the adult brains of animals born to PolyI:C- or vehicle-treated mothers by high-performance liquid chromatography on post-mortem tissue. We found that prenatal immune activation significantly increased the levels of dopamine and its major metabolites in the lateral globus pallidus and prefrontal cortex, whilst at the same time it decreased serotonin and its metabolite in the hippocampus, nucleus accumbens and lateral globus pallidus. In addition, a specific reduction of the inhibitory amino acid taurine in the hippocampus was noted in prenatally PolyI:C-exposed offspring relative to controls, whereas central glutamate and gamma-aminobutyric acid (GABA) content was largely unaffected by prenatal immune activation. Our results thus confirm that maternal immunological stimulation during early/middle pregnancy is sufficient to induce long-term changes in multiple neurotransmitter levels in the brains of adult offspring. This further supports the possibility that infection-mediated interference with early fetal brain development may predispose the developing organism to the emergence of neurochemical imbalances in adulthood, which may be critically involved in the precipitation of adult behavioural and pharmacological abnormalities after prenatal immune challenge.

Associations between indoor environmental factors and parental-reported autistic spectrum disorders in children 6-8 years of age

Potential contributions of environmental chemicals and conditions to the etiology of Autism Spectrum Disorders are the subject of considerable current research and speculation. The present paper describes the results of a study undertaken as part of a larger project devoted to the connection between properties of the indoor environment and asthma and allergy in young Swedish children. The larger project, The Dampness in Buildings and Health (DBH) Study, began in the year 2000 with a questionnaire distributed to parents of all children 1-6 years of age in one Swedish county (DBH-I). A second, follow-up questionnaire (DBH-III) was distributed in 2005. The original survey collected information about the child, the family situation, practices such as smoking, allergic symptoms, type of residence, moisture-related problems, and type of flooring material, which included polyvinyl chloride (PVC). The 2005 survey, based on the same children, now 6-8 years of age, also asked if, during the intervening period, the child had been diagnosed with Autism, Asperger's syndrome, or Tourette's syndrome. From a total of 4779 eligible children, 72 (60 boys, 12 girls) were identified with parentally reported autism spectrum disorder. A random sample of 10 such families confirmed that the diagnoses had been made by medical professionals, in accordance with the Swedish system for monitoring children's health. An analysis of the associations between indoor environmental variables in 2000 as well as other background factors and the ASD diagnosis indicated five statistically significant variables: (1) maternal smoking; (2) male sex; (3) economic problems in the family; (4) condensation on windows, a proxy for low ventilation rate in the home; (5) PVC flooring, especially in the parents' bedroom. In addition, airway symptoms of wheezing and physician-diagnosed asthma in the baseline investigation (2000) were associated with ASD 5 years later. Results from the second phase of the DBH-study (DBH-II) indicate PVC flooring to be one important source of airborne phthalates indoors, and that asthma and allergy prevalence are associated with phthalate concentrations in settled dust in the children's bedroom. Because these associations are among the few linking ASD with environmental variables, they warrant further and more extensive exploration.

Activation of the maternal immune system alters cerebellar development in the offspring

A common pathological finding in autism is a localized deficit in Purkinje cells (PCs). Cerebellar abnormalities have also been reported in schizophrenia. Using a mouse model that exploits a known risk factor for these disorders, maternal infection, we asked if the offspring of pregnant mice given a mid-gestation respiratory infection have cerebellar pathology resembling that seen in these disorders. We also tested the effects of maternal immune activation in the absence of virus by injection of the synthetic dsRNA, poly(I:C). We infected pregnant mice with influenza on embryonic day 9.5 (E9.5), or injected poly(I:C) i.p. on E12.5, and assessed the linear density of PCs in the cerebellum of adult or postnatal day 11 (P11) offspring. To study granule cell migration, we also injected BrdU on P11. Adult offspring of influenza- or poly(I:C)-exposed mice display a localized deficit in PCs in lobule VII of the cerebellum, as do P11 offspring. Coincident with this are heterotopic PCs, as well as delayed migration of granule cells in lobules VI and VII. The cerebellar pathology observed in the offspring of influenza- or poly(I:C)-exposed mice is strikingly similar to that observed in autism. The poly(I:C) findings indicate that deficits are likely caused by the activation of the maternal immune system. Finally, our data suggest that cerebellar abnormalities occur during embryonic development, and may be an early deficit in autism and schizophrenia.

Cytokines and perinatal brain damage

Perinatal brain damage has been implicated in the pathogenesis of neurodevelopmental impairments and psychiatric illnesses. This article reviews evidence that infection outside of the brain can damage the brain, and discusses specific cytokines and pathomechanisms that probably mediate the putative effect of remote infection on the developing brain. Events associated with increased circulating inflammatory cytokines, chemokines, and immune cells are described. Finally, studies of genetic variation in susceptibility to cytokine-related brain damage are reviewed.

Deficient maternal care resulting from immunological stress during pregnancy is associated with a sex-dependent enhancement of conditioned fear in the offspring

Activation of maternal stress response systems during pregnancy has been associated with altered postpartum maternal care and subsequent abnormalities in the offspring’s brain and behavioral development. It remains unknown, however, whether similar effects may be induced by exposure to immunological stress during pregnancy. The present study was designed to address this issue in a mouse model of prenatal immune activation by the viral mimic polyriboinosinic–polyribocytidilic acid (PolyI:C). Pregnant mice were exposed to PolyI:C-induced immune challenge or sham treatment, and offspring born to PolyI:C- and sham-treated dams were simultaneously cross-fostered to surrogate rearing mothers, which had either experienced inflammatory or vehicle treatment during pregnancy. We evaluated the effects of the maternal immunological manipulation on postpartum maternal behavior, and we assessed the prenatal and postnatal maternal influences on anxiety- and fear-related behavior in the offspring at the peri-adolescent and adult stage of development. We found that PolyI:C treatment during pregnancy led to changes in postpartum maternal behavior in the form of reduced pup licking/grooming and increased nest building activity. Furthermore, the adoption of neonates by surrogate rearing mothers, which had experienced PolyI:C-induced immunological stress during pregnancy, led to enhanced conditioned fear in the peri-adolescent and adult offspring, an effect that was exclusively seen in female but not male subjects. Unconditioned (innate) anxiety-related behavior as assessed in the elevated plus maze and open field explorations tests were not affected by the prenatal and postnatal manipulations. Our results thus highlight that being raised by gestationally immune-challenged surrogate mothers increases the vulnerability for specific forms of fear-related behavioral pathology in later life, and that this association may be mediated by deficits in postpartum maternal care. This may have important implications for the identification and characterization of early-life risk factors involved in the developmental etiology of fear-related neuropsychiatric disorders.

Results from a hypothesis generating case-control study: herpes family viruses and schizophrenia among military personnel

BACKGROUND

Herpes family viruses can cause central nervous system inflammatory changes that can present with symptoms indistinguishable from schizophrenia and therefore are of interest in schizophrenia research. Most existing studies of herpes viruses have used small populations and postdiagnosis specimens. As part of a larger research program, we conducted a hypothesis-generating case-control study of selected herpes virus antibodies among individuals discharged from the US military with schizophrenia and pre- and postdiagnosis sera.

METHODS

Cases (n = 180) were servicemembers hospitalized and discharged from military service with schizophrenia. Controls, 3:1 matched on several factors, were members not discharged. The military routinely collects and stores members' serum specimens. We used microplate enzyme immunoassay to measure immunoglobulin G (IgG) antibody levels to 6 herpes viruses in pre- and postdiagnosis specimens. Conditional logistic regression was used, and the measure of association was the hazard ratio (HR).

RESULTS

Overall, we found a significant association between human herpes virus type 6 and schizophrenia, with an HR of 1.17 (95% confidence interval [CI] = 1.04, 1.32). Women and blacks had significant negative associations with herpes simplex virus type 2 and cytomegalovirus; among blacks, there was a significant positive association with herpes simplex virus type 1. Among men, there was a HHV-6 temporal effect with an HR of 1.41 (95% CI = 1.02, 1.96) for sera drawn 6-12 months before diagnosis.

DISCUSSION

Findings from previous studies of herpes family viruses and schizophrenia have been inconsistent. Our study is based on a larger population than most previous studies and used serum specimens collected before onset of illness. This study adds to the body of knowledge and provides testable hypotheses for follow-on studies.

Gene-environment interaction and covariation in schizophrenia: the role of obstetric complications

While genetic factors account for a significant proportion of liability to schizophrenia, a body of evidence attests to a significant environmental contribution. Understanding the mechanisms through which genetic and environmental factors coalesce in influencing schizophrenia is critical for elucidating the pathways underlying psychotic illness and for developing primary prevention strategies. Although obstetric complications (OCs) remain among the most well-documented environmental indicators of risk for schizophrenia, the pathogenic role they play in the etiology of schizophrenia continues to remain poorly understood. A question of major importance is do these factors result from a genetic diathesis to schizophrenia (as in gene-environment covariation), act additively or interactively with predisposing genes for the disorder in influencing disease risk, or independently cause disease onset? In this review, we evaluate 3 classes of OCs commonly related to schizophrenia including hypoxia-associated OCs, maternal infection during pregnancy, and maternal stress during pregnancy. In addition, we discuss several mechanisms by which OCs impact on genetically susceptible brain regions, increasing constitutional vulnerability to neuromaturational events and stressors later in life (ie, adolescence), which may in turn contribute to triggering psychosis.

Increased tumor necrosis factor-alpha concentrations with interleukin-4 concentrations in exacerbations of schizophrenia

Several studies have indicated that cytokines may be involved in the pathophysiology of schizophrenia. Previous studies, however, have yielded contradictory results; in this study we assess the plasma levels of both T-helper-1 (Th1) and T-helper-2 (Th2) cytokines in patients with acute exacerbations of schizophrenia. Plasma concentrations of interleukin-4 (IL-4), interleukin-6 (IL-6), interleukin-8 (IL-8), interleukin-10 (IL-10), tumor necrosis factor-alpha (TNF-alpha) and soluble receptor of interleukin-6 (sIL-6R) were measured with high sensitivity, enzyme-linked immunosorbent assays (ELISA) in patients with acute exacerbations of schizophrenia as compared with healthy controls. Patients with an acute exacerbation of schizophrenia had significantly increased production of TNF-alpha and significantly reduced production of IL-4 as compared with healthy subjects. No significant difference was observed in IL-6, sIL-6R, IL-8 and IL-10. Acute exacerbations of schizophrenia are associated with increased TNF-alpha concentrations (Th1) with concomitantly reduced concentrations of IL-4 (Th2) and a resulting increased TNF-alpha/IL-4 ratio.

Dysthymia in male adolescents is associated with increased risk of later hospitalization for psychotic disorders: a historical-prospective cohort study

AIM

Retrospective studies indicate that patients with psychotic disorders and schizophrenia often suffer from depressive symptoms before the onset of psychosis. In a historical-prospective design, we studied the association between dysthymia in adolescence and later hospitalization for psychotic disorders and schizophrenia.

METHODS

The Israeli Draft Board screens the entire, unselected population of 16-17 years old male adolescents for psychiatric disorders. These adolescents were followed for hospitalization for psychotic disorders and schizophrenia using the Israeli National Psychiatric Hospitalization Case Registry. Of 275,705 male adolescents screened, 1267 (0.5%) were hospitalized for psychotic disorders (International Classification of Diseases [ICD]-10 20.0-29.9), and 757 (0.3%) were hospitalized for schizophrenia (ICD-10 20.0-20.9) over the next 1-10 years.

RESULTS

Of 275,705 male adolescents screened, 513 (0.2%) were diagnosed as suffering from dysthymia by the Draft Board. Of these adolescents, 10/513 (2.0%) were later hospitalized for psychotic disorders (including schizophrenia, HR=3.967, 95%CI (confidence intervals): 2.129-7.390), and 4/513 (0.8%) were later hospitalized for schizophrenia (HR=2.664, 95%CI: 0.997-7.116).

CONCLUSIONS

In this population-based cohort of male adolescents, dysthymia was associated with increased risk for future psychotic disorders. Dysthymia in some adolescents might be a prodromal symptom, while in others it might be a risk factor for later psychosis. Clinicians assessing dysthymic adolescents should be aware that these symptoms might be part of the prodrome.

Adult brain and behavioral pathological markers of prenatal immune challenge during early/middle and late fetal development in mice

Maternal infection during pregnancy increases the risk for neurodevelopmental disorders such as schizophrenia and autism in the offspring. This association appears to be critically dependent on the precise prenatal timing. However, the extent to which distinct adult psychopathological and neuropathological traits may be sensitive to the precise times of prenatal immune activation remains to be further characterized. Here, we evaluated in a mouse model of prenatal immune challenge by the viral mimic, polyriboinosinic-polyribocytidilic acid (PolyIC), whether prenatal immune activation in early/middle and late gestation may influence the susceptibility to some of the critical cognitive, pharmacological, and neuroanatomical dysfunctions implicated in schizophrenia and autism. We revealed that PolyIC-induced prenatal immune challenge on gestation day (GD) 9 but not GD17 significantly impaired sensorimotor gating and reduced prefrontal dopamine D1 receptors in adulthood, whereas prenatal immune activation specifically in late gestation impaired working memory, potentiated the locomotor reaction to the NMDA-receptor antagonist dizocilpine, and reduced hippocampal NMDA-receptor subunit 1 expression. On the other hand, potentiation of the locomotor reaction to the dopamine-receptor agonist amphetamine and reduction in Reelin- and Parvalbumin-expressing prefrontal neurons emerged independently of the precise times of prenatal immune challenge. Our findings thus highlight that prenatal immune challenge during early/middle and late fetal development in mice leads to distinct brain and behavioral pathological symptom clusters in adulthood. Further examination and evaluation of in utero immune challenge at different times of gestation may provide important new insight into the neuroimmunological and neuropathological mechanisms underlying the segregation of different symptom clusters in heterogeneous neuropsychiatric disorders such as schizophrenia and autism.

Immunologic and neurodevelopmental susceptibilities of autism

Symposium 5 focused on research approaches that are aimed at understanding common patterns of immunological and neurological dysfunction contributing to neurodevelopmental disorders such as autism and ADHD. The session focused on genetic, epigenetic, and environmental factors that might act in concert to influence autism risk, severity and co-morbidities, and immunological and neurobiological targets as etiologic contributors. The immune system of children at risk of autism may be therefore especially susceptible to psychological stressors, exposure to chemical triggers, and infectious agents. Identifying early biomarkers of risk provides tangible approaches toward designing studies in animals and humans that yield a better understanding of environmental risk factors, and can help identify rational intervention strategies to mitigate these risks.

Maternal exposure to herpes simplex virus and risk of psychosis among adult offspring

BACKGROUND

Viral exposure during gestation is thought to be a risk factor for schizophrenia. Previous studies have indicated that prenatal exposure to herpes simplex virus type 2 (HSV-2) may be a risk for the subsequent development of schizophrenia in some populations. In this investigation, we tested a large and diverse population to assess the risk of psychoses among offspring of mothers with serological evidence of HSV-2 infection.

METHODS

We conducted a nested case-control study of 200 adults with psychoses and 554 matched control subjects (matched for city and date of birth, race/ethnicity, gender, and parent history of treatment for mental disorder) from three cohorts of the Collaborative Perinatal Project (Boston, Providence, and Philadelphia). We analyzed stored serum samples that had been obtained from these mothers at the end of pregnancy for antibodies directed at HSV-2, using type-specific solid-phase enzyme immunoassay techniques.

RESULTS

Offspring of mothers with serologic evidence of HSV-2 infection were at significantly increased risk for the development of psychoses (odds ratio [OR] = 1.6; 95% confidence interval [CI] = 1.1-2.3). This risk was particularly elevated among women with high rates of sexual activity during pregnancy (OR = 2.6; 95% CI = 1.4-4.6).

CONCLUSIONS

Maternal exposure to herpes simplex virus type 2 is associated with an increased risk for psychoses among adult offspring. These results are consistent with a general model of risk resulting from enhanced maternal immune activation during pregnancy.

Inflammatory cytokine alterations in schizophrenia: a systematic quantitative review

BACKGROUND

Cytokines play an important role in infection and inflammation and are crucial mediators of the cross-talk between the brain and the immune system. Schizophrenia would be associated with an imbalance in inflammatory cytokines, leading to a decrease in Th1 and an increase in Th2 cytokine secretion. However, data published so far have been inconsistent. The primary objective of the present meta-analysis was to verify whether the cytokine imbalance hypothesis of schizophrenia is substantiated by evidence.

METHODS

Cross-sectional studies were included if they assessed in vivo plasma or serum cytokine concentrations and/or in vitro secretion of cytokines by peripheral blood leukocytes from schizophrenia patients and healthy volunteers.

RESULTS

Data from 62 studies involving a total sample size of 2298 schizophrenia patients and 1858 healthy volunteers remained for analysis. Ten cytokines were assessed, including the prototypic Th1 and Th2 cytokines gamma interferon (IFN-gamma) and interleukin 4 (IL-4) as well as IL-2, soluble IL-2 receptor (sIL-2R), IL-1beta, IL-1 receptor antagonist (IL-1RA), tumor necrosis factor-alpha (TNF-alpha), IL-6, soluble IL-6 receptor (sIL-6R), and IL-10. The results show that an increase occurs in in vivo IL-1RA, sIL-2R, and IL-6 and a decrease occurs in in vitro IL-2 in schizophrenia. No significant effect sizes were obtained for the other cytokines.

CONCLUSIONS

These findings provide the first evidence of establishment of an inflammatory syndrome in schizophrenia, which refutes the current hypothesis of a Th2 slant. Caveats are presented to data interpretation, including the role of stress and the effect of weight gain that develops in schizophrenia.

Prenatal exposures to persistent and non-persistent organic compounds and effects on immune system development

Immune system development, particularly in the prenatal period, has far-reaching consequences for health during early childhood, as well as throughout life. Environmental disturbance of the complex balances of Th1 and Th2 response mechanisms can alter that normal development. Dysregulation of this process or an aberrant trajectory or timing of events can result in atopy, asthma, a compromised ability to ward off infection, or other auto-immune disease. A wide range of chemical, physical and biological agents appear to be capable of disrupting immune development. This MiniReview briefly reviews developmental milestones of the immune system in the prenatal period and early life, and then presents examples of environmentally induced alterations in immune markers. The first example involves a birth cohort study linked to an extensive programme of air pollution monitoring; the analysis shows prenatal ambient polycyclic aromatic hydrocarbons (PAH) and fine particle (PM2.5) exposures to be associated with altered lymphocyte immunophenotypic distributions in cord blood and possible changes in cord serum immunoglobulin E levels. The second example is a study of prenatal-polychlorinated biphenyl (PCB) exposures and the foetal development of the thymus, the organ responsible for lymphocyte maturation. Mothers with higher serum concentrations of PCBs gave birth to neonates having smaller indices of thymus size. Finally, this report underscores the tight connection between development of the immune system and that of the central nervous system, and the plausibility that disruption of critical events in immune development may play a role in neurobehavioural disorders.

Adult behavioral and pharmacological dysfunctions following disruption of the fetal brain balance between pro-inflammatory and IL-10-mediated anti-inflammatory signaling

Maternal infections during pregnancy increase the risk for schizophrenia and related disorders of putative neurodevelopmental origin in the offspring. This association has been attributed to enhanced expression of pro-inflammatory cytokines in the fetal environment in response to maternal immunological stimulation. In contrast, the specific roles of anti-inflammatory cytokines are virtually unknown in this context. Here, we demonstrate that genetically enforced expression of the anti-inflammatory cytokine interleukin (IL)-10 by macrophages attenuates the long-term behavioral and pharmacological consequences of prenatal immune activation in a mouse model of prenatal viral-like infection by polyriboinosinic-polyribocytidilic acid (PolyI:C; 2 mg/kg, intravenously). In the absence of a discrete prenatal inflammatory stimulus, however, enhanced levels of IL-10 at the maternal-fetal interface by itself also precipitates specific behavioral abnormalities in the grown offspring. This highlights that in addition to the disruptive effects of excess pro-inflammatory molecules, a shift toward enhanced anti-inflammatory signaling in prenatal life can similarly affect cognitive and behavioral development. Hence, shifts of the balance between pro- and anti-inflammatory cytokine classes may be a critical determinant of the final impact on neurodevelopment following early life infection or innate immune imbalances.

Relative prenatal and postnatal maternal contributions to schizophrenia-related neurochemical dysfunction after in utero immune challenge

Prenatal exposure to infections represents a risk factor for the emergence of neuropsychiatric disorders in later life, including schizophrenia and autism. However, it remains essentially unknown whether this association is primarily attributable to prenatal and/or postnatal maternal effects on the offspring. Here, we addressed this issue by dissecting the relative contributions of prenatal inflammatory events and postnatal maternal factors in an animal model of prenatal viral-like infection. Pregnant mice were exposed to the inflammatory agent polyriboinosinic-polyribocytidilic acid (PolyI:C; 5 mg/kg, i.v.) or vehicle treatment on gestation day 9, and offspring born to PolyI:C- and vehicle-treated dams were cross fostered to surrogate rearing mothers that had either experienced inflammatory or sham treatment during pregnancy. We demonstrate that a variety of dopamine- and glutamate-related pharmacological and neuroanatomical disturbances emerge after prenatal immune challenge regardless of whether neonates were raised by vehicle- or PolyI:C-exposed surrogate mothers. However, the adoption of prenatal control animals to immune-challenged surrogate mothers was also sufficient to induce specific pharmacological and neuroanatomical abnormalities in the fostered offspring. Multiple schizophrenia-related dysfunctions emerging after prenatal immune challenge are thus mediated by prenatal but not postnatal maternal effects on the offspring, but immunological stress during pregnancy may affect postpartum maternal factors in such a way that being reared by an immune-challenged surrogate mother can confer risk for distinct forms of psychopathology in adult life.

Obstetric conditions and risk of first admission with schizophrenia: a Danish national register based study

A range of complications of pregnancy, abnormal fetal growth and development, and complications of delivery have been associated with increased risk of schizophrenia. Few studies have been able to adjust for a broad range of potential confounding factors. A national population nested case-control study based on Danish longitudinal registers was conducted to investigate the risk of schizophrenia associated with exposure to a range of obstetric events. The sample included 1039 first admissions to, or contacts with Danish psychiatric services with an ICD-8 or ICD-10 diagnosis of schizophrenia and 24, 826 individually matched controls. Adjusting for the other obstetric factors, family psychiatric history, and socio-economic and demographic factors, risk of schizophrenia was associated with maternal non-attendance at antenatal appointments (Incidence Rate Ratio (IRR) 2.08, 95% CI: 1.0, 4.4), gestational age of 37 weeks or below (IRR 1.51, 95% CI: 1.0, 2.2), maternal influenza (IRR 8.2, 95% CI: 1.4, 48.8), preeclampsia (IRR 2.72, 95% CI: 1.0, 7.3), threatened premature delivery (IRR 2.39, 95% CI: 1.4, 4.1), haemorrhage during delivery (IRR 2.43, 95% CI: 1.1, 5.6), manual extraction of the baby (IRR 2.15, 95% CI: 1.1, 4.4), and maternal sepsis of childbirth and the puerperium (IRR 2.91, 95% CI: 1.1, 7.9). There was no significant interaction between the obstetric factors and either sex or family psychiatric history. The data suggest a modest association between prematurity, indicators of hypoxia, maternal infections, and maternal behaviours and risk of the later development of schizophrenia after adjusting for a number of possible confounding factors.

Maternal immune activation alters fetal brain development through interleukin-6

Schizophrenia and autism are thought to result from the interaction between a susceptibility genotype and environmental risk factors. The offspring of women who experience infection while pregnant have an increased risk for these disorders. Maternal immune activation (MIA) in pregnant rodents produces offspring with abnormalities in behavior, histology, and gene expression that are reminiscent of schizophrenia and autism, making MIA a useful model of the disorders. However, the mechanism by which MIA causes long-term behavioral deficits in the offspring is unknown. Here we show that the cytokine interleukin-6 (IL-6) is critical for mediating the behavioral and transcriptional changes in the offspring. A single maternal injection of IL-6 on day 12.5 of mouse pregnancy causes prepulse inhibition (PPI) and latent inhibition (LI) deficits in the adult offspring. Moreover, coadministration of an anti-IL-6 antibody in the poly(I:C) model of MIA prevents the PPI, LI, and exploratory and social deficits caused by poly(I:C) and normalizes the associated changes in gene expression in the brains of adult offspring. Finally, MIA in IL-6 knock-out mice does not result in several of the behavioral changes seen in the offspring of wild-type mice after MIA. The identification of IL-6 as a key intermediary should aid in the molecular dissection of the pathways whereby MIA alters fetal brain development, which can shed new light on the pathophysiological mechanisms that predispose to schizophrenia and autism.

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.

Neurobehavioral and immunological consequences of prenatal immune activation in rats. Influence of antipsychotics

Increasing evidence suggests that pre- or perinatal events that influence the immune system contribute to the development of behavioral or neuropsychiatric disorders. For instance, exposure of pregnant rats to the bacterial endotoxin lipopolysaccharide (LPS) disrupts sensorimotor information processing, as assessed by the prepulse inhibition test (PPI), and also the immune function in adult offspring, which might be of particular relevance as regards schizophrenia. However, the consequences of maternal LPS exposure during pregnancy on synaptic functioning in adult offspring and, more importantly, the therapeutic opportunity to re-establish PPI and immune function have still to be demonstrated. In this work, we analyzed the consequences of prenatal LPS exposure on dopaminergic neurotransmission and presynaptic markers in adult brain areas related to PPI circuitry. In addition, we tested whether oral treatment with the typical antipsychotic drug haloperidol (HAL) could reinstate PPI performances and cytokine serum levels in six-month-old male rats with prenatal LPS exposure. Both sensory information processing deficits and immune anomalies induced by prenatal exposure to LPS were accompanied by changes in dopaminergic neurotransmission and synaptophysin expression. It is important to note that PPI disruption and serum increases in cytokines induced by prenatal LPS exposure were both reversed by HAL. Taken together, these results demonstrate the critical influence of prenatal immune events on the functioning of adult nervous and immune systems, in association with the putative role of the immune system in the development of behavior relevant to schizophrenia.

The effects of genetic liability for schizophrenia and maternal smoking during pregnancy on obstetric complications

The purpose of this study was to determine whether a genetic vulnerability for schizophrenia and/or health-risk behaviors among schizophrenic pregnant women were associated with an increased incidence of obstetric complications (OCs).

METHOD

A high-risk birth cohort was formed by searching the Finnish Perinatal Register for all births from 1991-2000 with arterial cord pH values below 7.20, an indication of fetal asphyxia. This database was merged with national hospital discharge registries to determine psychiatric morbidity of the mothers and the mothers' first-degree relatives. Mothers were divided into 3 groups: women diagnosed with schizophrenia/schizoaffective disorder (n=53), mothers with a first-degree relative with schizophrenia/schizoaffective disorder (n=590) and healthy controls (n=36,895).

RESULT

Schizophrenic women had significantly more OCs than mothers with a first-degree schizophrenic relative and controls. These women had significantly increased rates of eclampsia, premature delivery, prenatal hospitalizations, and marginally significant increases in high blood pressure. Offspring of schizophrenic mothers had significantly decreased APGAR scores and birth weight and increased medical complications after birth. In contrast, women with a schizophrenic first-degree relative had no significant increases in OCs compared to controls. Schizophrenic mothers also smoked more than the other groups and smoking was found to mediate the relationship between maternal schizophrenic status and decreased birth weight among offspring.

CONCLUSIONS

Maternal schizophrenia during pregnancy leads to an increased risk of OCs, possibly due to engagement in health-risk behaviors during pregnancy, such as smoking, whereas genetic susceptibility to schizophrenia, by itself, does not appear to be related to incidence of OCs.

Distinct roles of protein kinase R and toll-like receptor 3 in the activation of astrocytes by viral stimuli

Impaired immune surveillance and constitutive immunosuppressive properties make the central nervous system (CNS) a particular challenge to immune defense, and require that CNS-resident cells be capable of rapidly recognizing and responding to infection. We have previously shown that astrocytes respond to treatment with a TLR3 ligand, poly I:C, with the upregulation of innate immune functions. In the current study, we examine the activation of innate immune functions of astrocytes by Theiler's murine encephalomyelitis virus (TMEV), a picornavirus, which establishes a persistent infection in the CNS of susceptible strains of mice and leads to the development of an autoimmune demyelinating disease that resembles human multiple sclerosis. Astrocytes infected with TMEV are activated to produce type I interferons, the cytokine IL-6, and chemokines CCL2 and CXCL10. We further examined the mechanisms that are responsible for the activation of astrocytes in response to direct viral infection and treatment with poly I:C. We found that the cytoplasmic dsRNA-activated kinase PKR is important for innate immune responses to TMEV infection, but has no role in their induction by poly I:C delivered extracellularly. In contrast, we found that TLR3 has only a minor role in responses to TMEV infection, but is important for responses to poly I:C. These results highlight the differences between responses induced by direct, nonlytic virus infection and extracellular poly I:C. The activation of astrocytes through these different pathways has implications for the initiation and progression of viral encephalitis and demyelinating diseases such as multiple sclerosis.

Cerebral palsy and fetal inflammatory response syndrome: a review

Cerebral palsy (CP) is the most common cause of severe physical disability in childhood. The precise etiological factor for the development of the majority of cases of CP has not been identified, however, prematurity is considered to be the leading identifiable risk factor. During the last decade, intrauterine infection/inflammation has been identified as the most common cause of preterm delivery and neonatal complications. When microorganisms or their products gain access to the fetus they stimulate the production of cytokines and a systemic response termed FIRS (Fetal Inflammatory Response Syndrome). Subsequently, FIRS was implicated as a cause of fetal or neonatal injury that leads to CP and chronic lung disease. Several authors found an increase in the risk for CP in infants born to mothers with clinical chorioamnionitis, especially in preterm neonates. A relationship between CP and intra-amniotic inflammation was demonstrated, intrauterine infection may lead to activation of the cytokine network which in turn can cause white matter brain damage and preterm delivery, as well as the future development of CP. This white matter insult is identified clinically as periventricular leucomalacia (PVL) which is associated with the subsequent development of impaired neurological outcomes of variable severity including CP.

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.

Neurobiology of schizophrenia

With its hallucinations, delusions, thought disorder, and cognitive deficits, schizophrenia affects the most basic human processes of perception, emotion, and judgment. Evidence increasingly suggests that schizophrenia is a subtle disorder of brain development and plasticity. Genetic studies are beginning to identify proteins of candidate genetic risk factors for schizophrenia, including dysbindin, neuregulin 1, DAOA, COMT, and DISC1, and neurobiological studies of the normal and variant forms of these genes are now well justified. We suggest that DISC1 may offer especially valuable insights. Mechanistic studies of the properties of these candidate genes and their protein products should clarify the molecular, cellular, and systems-level pathogenesis of schizophrenia. This can help redefine the schizophrenia phenotype and shed light on the relationship between schizophrenia and other major psychiatric disorders. Understanding these basic pathologic processes may yield novel targets for the development of more effective treatments.

Maternal infection and white matter toxicity

Studies examining maternal infection as a risk factor for neurological disorders in the offspring have suggested that altered maternal immune status during pregnancy can be considered as an adverse event in prenatal development. Infection occurring in the mother during the gestational period has been implicated in multiple neurological effects. The current manuscript will consider the issue of immune/inflammatory conditions during prenatal development where adverse outcomes have been linked to maternal systemic infection. The discussions will focus primary on white matter and oligodendrocytes as they have been identified as target processes. This white matter damage occurs in very early preterm infants and in various other human diseases currently being examined for a linkage to maternal or early developmental immune status. The intent is to draw attention to the impact of altered immune status during pregnancy on the offspring for the consideration of such contributing factors to the general assessment of developmental neurotoxicology.

Immune activation during pregnancy in mice leads to dopaminergic hyperfunction and cognitive impairment in the offspring: a neurodevelopmental animal model of schizophrenia

BACKGROUND

Maternal viral infection is associated with increased risk for schizophrenia. It is hypothesized that the maternal immune response to viruses may influence fetal brain development and lead to schizophrenia.

METHODS

To mimic a viral infection, the synthetic double strand RNA polyriboinosinic-polyribocytidilic acid (poly I:C) was administered into pregnant mice. Behavioral evaluations (thigmotaxis, methamphetamine [MAP]-induced hyperactivity, novel-object recognition test [NORT]), sensorimotor gating (prepulse inhibition [PPI]), and biochemical evaluation of the dopaminergic function of the offspring of phosphate-buffered saline (PBS)-treated dams (PBS-mice) and that of poly I:C-treated dams (poly I:C-mice) were examined.

RESULTS

In juveniles, no difference was found between the poly I:C-mice and PBS-mice. However, in adults, the poly I:C-mice exhibited attenuated thigmotaxis, greater response in MAP-induced (2 mg/kg) hyperlocomotion, deficits in PPI, and cognitive impairment in NORT compared with the PBS-mice. Cognitive impairment in the adult poly I:C-mice could be improved by subchronic administration of clozapine (5.0 mg/kg) but not haloperidol (.1 mg/kg). Increased dopamine (DA) turnover and decreased receptor binding of D2-like receptors, but not D1-like receptors, in the striatum were found in adult poly I:C-mice.

CONCLUSIONS

Prenatal poly I:C administration causes maturation-dependent increased subcortical DA function and cognitive impairment in the offspring, indicating a neurodevelopmental animal model of schizophrenia.

10-year research update review: the epidemiology of child and adolescent psychiatric disorders: II. Developmental epidemiology

OBJECTIVE

To describe the growth of developmental epidemiology in the past decade and to illustrate it with examples of recent studies.

METHOD

A review of publications on developmental epidemiology in the past 10 years and a discussion of some key examples.

RESULTS

The authors describe how the interaction between developmental psychopathology and psychiatric epidemiology has produced developmental epidemiology, the study of patterns of distribution of psychiatric disorders in time as well as in space. They give two examples of the kinds of questions that developmental epidemiology can help to answer: (1) Is the prevalence of autism increasing? Does the use of vaccines explain the increase? (2) Is there an epidemic of child and adolescent depression? Finally, they describe two areas of science that are beginning to inform developmental epidemiology: molecular genetics and the use of biological measures of stress.

CONCLUSIONS

While child and adolescent psychiatric epidemiology continues, as described in the first of these reviews, to address questions of prevalence and burden, it has also expanded into new areas of research in the past decade. In the next decade, longitudinal epidemiological data sets with their rich descriptive data on psychopathology and environmental risk over time and the potential to add biological measures will provide valuable resources for research into gene-environment correlations and interactions.

Investigating the neurodevelopmental hypothesis of schizophrenia

1. An optimal intra-uterine environment is critical for normal development of the brain. It is now thought that abnormal development in a compromised prenatal and/or early postnatal environment may be a risk factor for several neurological disorders that manifest postnatally, such as cerebral palsy, schizophrenia and epilepsy. 2. The present review examines some of the effects of abnormal prenatal brain development and focuses on one disorder that has been hypothesized to have, at least in part, an early neurodevelopmental aetiology: schizophrenia. 3. The key neuropathological alterations and changes in some of the neurotransmitter systems observed in patients with schizophrenia are reviewed. Evidence in support of a neurodevelopmental hypothesis for schizophrenia is examined. 4. A summary of the animal models that have been used by researchers in an attempt to elucidate the origins of this disorder is presented. Although no animal model of a complex human disorder is ever likely to emulate deficits in all aspects of structure and function observed in patients with a neuropsychiatric illness, our findings and those of others give support to the early neurodevelopmental hypothesis. 5. Thus, it is possible that an adverse event in utero disrupts normal brain development and creates a vulnerability of the brain that predisposes an already at-risk individual (e.g. genetic inheritance) to develop the disorder later in life.

Maternal infection and adverse fetal and neonatal outcomes

Adverse pregnancy outcomes can follow direct placental, fetal, or neonatal infection, or preterm birth associated with vaginal, cervical, intrauterine, or even nonpelvic infections. These latter infections appear to be associated with the majority of very early preterm births, and may explain some of the long-term neurologic damage associated with preterm birth. Bacterial vaginosis and its associated intrauterine infections likely contribute far more to the overall burden of adverse pregnancy outcomes than the more classical perinatal infections such as rubella and syphilis.

Maternal influenza infection is likely to alter fetal brain development indirectly: the virus is not detected in the fetus

Epidemiological studies have shown that maternal infection can increase the risk for mental illness in the offspring. In a mouse model of maternal respiratory infection with influenza virus, the adult offspring display striking behavioral, pharmacological and histological abnormalities. Although influenza primarily infects the respiratory system, there are reports of viral mRNA and protein in the fetus of infected pregnant animals. To determine the extent of viral spread following maternal respiratory infection, we used RT-PCR to assay various maternal and fetal tissues for influenza A mRNAs coding for neuraminidase, non-structural protein 2, nuclear protein and matrix protein. While infected maternal lungs exhibit uniformly very strong signals, placentae are only rarely positive, and viral RNAs are not detectable in fetal brains from infected mothers. Thus, the effects of maternal infection on fetal brain development are likely to be indirect, probably involving the maternal inflammatory response.

Practitioner review: early adversity and developmental disorders

BACKGROUND

Knowledge of genetic influences, on developmental disorders such as autism spectrum, attention deficit/hyperactivity disorder and learning disabilities, has increased the opportunities for understanding the influences of the early environment.

METHODS

This paper provides a selective, narrative review for clinicians of the effects of factors such as exposure to toxins and stresses in utero and in postnatal life; brain injuries and perinatal compromise; neglect, malnutrition and selective food deficiencies. It also considers what is known about the mechanisms through which early adversities operate.

RESULTS

Gaps in the research are identified and suggestions made about clinical investigations. Several types of environmental adversity have associations with later disorders that suggest a causal role. The effects are often on a broad range of psychological processes, and are not always quickly reversible. Several adversities often coexist, calling for skilled judgement about priorities in treatment.

CONCLUSIONS

Individuals vary considerably in their exposure to adversity and their vulnerability to its effects, and genetic inheritance can influence both.

The neurodevelopmental model of schizophrenia: update 2005

Neurodevelopmental models of schizophrenia that identify longitudinal precursors of illness have been of great heuristic importance focusing most etiologic research over the past two decades. These models have varied considerably with respect to specificity and timing of hypothesized genetic and environmental 'hits', but have largely focused on insults to prenatal brain development. With heritability around 80%, nongenetic factors impairing development must also be part of the model, and any model must also account for the wide range of age of onset. In recent years, longitudinal brain imaging studies of both early and adult (to distinguish from late ie elderly) onset populations indicate that progressive brain changes are more dynamic than previously thought, with gray matter volume loss particularly striking in adolescence and appearing to be an exaggeration of the normal developmental pattern. This supports an extended time period of abnormal neurodevelopment in schizophrenia in addition to earlier 'lesions'. Many subtle cognitive, motor, and behavioral deviations are seen years before illness onset, and these are more prominent in early onset cases. Moreover, schizophrenia susceptibility genes and chromosomal abnormalities, particularly as examined for early onset populations (ie GAD1, 22q11DS), are associated with premorbid neurodevelopmental abnormalities. Several candidate genes for schizophrenia (eg dysbindin) are associated with lower cognitive abilities in both schizophrenic and other pediatric populations more generally. Postmortem human brain and developmental animal studies document multiple and diverse effects of developmental genes (including schizophrenia susceptibility genes), at sequential stages of brain development. These may underlie the broad array of premorbid cognitive and behavioral abnormalities seen in schizophrenia, and neurodevelopmental disorders more generally. Increased specificity for the most relevant environmental risk factors such as exposure to prenatal infection, and their interaction with susceptibility genes and/or action through phase-specific altered gene expression now both strengthen and modify the neurodevelopmental theory of schizophrenia.

Neurodevelopment, neuroplasticity, and new genes for schizophrenia

Schizophrenia is a complex, debilitating neuropsychiatric disorder. Epidemiological, clinical, neuropsychological, and neurophysiological studies have provided substantial evidence that abnormalities in brain development and ongoing neuroplasticity play important roles in the pathogenesis of the disorder. Complementing these clinical studies, a range of cytoarchitectural, morphometric, ultrastructural, immunochemical, and gene expression methods have been applied in investigations of postmortem brain tissues to characterize the cellular and molecular profile of putative developmental and plastic abnormalities in schizophrenia. While findings have been diverse and many are in need of replication, investigations focusing on higher cortical and limbic brain regions are increasingly demonstrating abnormalities in the structural and molecular integrity of the synaptic complex as well as glutamate-related receptors and signal transduction pathways that play critical roles in brain development, synaptogenesis, and synaptic plasticity. Most exciting have been recent associations of schizophrenia with specific genes, such as neuregulin-1, dysbindin-1, and AKT-1, which are vital to synaptic development, neurotransmission, and plasticity.

Influenza Vaccine Programs and Pregnancy: A Need for More Evidence

Influenza viruses are the most common cause of seasonal respiratory morbidity in the world. Annual influenza vaccination is recommended for persons at high risk for serious disease. In the United States, in 2004, the Advisory Committee on Immunization Practices added all pregnant women to its high-risk list. In Canada, the National Advisory Committee on Immunization only includes pregnant women who have other underlying risk factors in the high-priority category for influenza immunization. This commentary provides an overview of maternal morbidity in pandemic and nonpandemic influenza seasons as well as a list of research questions whose answers are needed for evidence-based public health policy in this area.

Ethical issues in the use of genetic information

Advances in molecular genetics promise to deepen our understanding of the biological basis of human behavior and shed light on the pathophysiology of mental illness. Genetic research is likely to improve our ability to develop somatic treatments for psychiatric syndromes as well as to identify targets for environmental intervention. However, population-screening tests for disorders with multifactorial inheritance may offer little clinical benefit to outweigh their potential for misuse. Relevant legal issues surrounding the use of genetic information in psychiatry include the perceived need for laws to prevent insurance and employment discrimination, and concerns about genetic status as a possible excuse for criminal behavior. Relevant ethical issues include threats to patient privacy and confidentiality and the importance of fairly distributing the benefits and burdens of genetic advances.