Maternal exposure to respiratory infections and adult schizophrenia spectrum disorders: a prospective birth cohort study

Prevention of schizophrenia: can it be achieved?

Schizophrenia is a serious mental disorder with a profound impact on patients, their caregivers and society. It is also an expensive disorder to treat, despite being relatively rare. In this paper, prevention of schizophrenia is described in terms of primary, secondary and tertiary prevention. Schizophrenia is regarded as a neurodevelopmental disorder with different phases. Primary prevention essentially involves education programmes about the association of obstetric complications and the increased risk of schizophrenia. Secondary prevention involves intervention at the prodromal phase. We review the literature and discuss the evidence relating to intervention in this phase of the illness. Early intervention could result in reduction in morbidity and better quality of life for the patients and their families. The prodromal phase can now be identified, based on current symptoms, with reliability and predictive validity for the risk of development of schizophrenia in the following year. We also discuss possible risks faced by prodromal patients, such as unnecessary stigmatisation, and the role of drug treatment during intervention at this stage. Any recommendation that anti-psychotic medications be routinely prescribed in this phase should be supported by more research work. Drug and psychosocial intervention is indicated as part of tertiary prevention to prevent further disability in the illness.

Towards an immuno-precipitated neurodevelopmental animal model of schizophrenia

Epidemiological studies have indicated an association between maternal bacterial and viral infections during pregnancy and the higher incidence of schizophrenia in the resultant offspring post-puberty. One hypothesis asserts that the reported epidemiological link is mediated by prenatal activation of the foetal immune system in response to the elevation of maternal cytokine level due to infection. Here, we report that pregnant mouse dams receiving a single exposure to the cytokine-releasing agent, polyriboinosinic-polyribocytidilic acid (PolyI:C; at 2.5, 5.0, or 10.0 mg/kg) on gestation day 9 produced offspring that subsequently exhibited multiple schizophrenia-related behavioural deficits in adulthood, in comparison to offspring from vehicle injected or non-injected control dams. The efficacy of the PolyI:C challenge to induce cytokine responses in naïve non-pregnant adult female mice and in foetal brain tissue when injected to pregnant mice were further ascertained in separate subjects: (i) a dose-dependent elevation of interleukin-10 was detected in the adult female mice at 1 and 6h post-injection, (ii) 12 h following prenatal PolyI:C challenge, the foetal levels of interleukin-1beta were elevated. The spectrum of abnormalities included impairments in exploratory behaviour, prepulse inhibition, latent inhibition, the US-pre-exposure effect, spatial working memory; and enhancement in the locomotor response to systemic amphetamine (2.5 mg/kg, i.p.) as well as in discrimination reversal learning. The neuropsychological parallels between prenatal PolyI:C treatment in mice and psychosis in humans, demonstrated here, leads us to conclude that prenatal PolyI:C treatment represents one of the most powerful environmental-developmental models of schizophrenia to date. The uniqueness of this model lies in its epidemiological and immunological relevance. It is, sui generis, ideally suited for the investigation of the neuropsychoimmunological mechanisms implicated in the developmental aetiology and disease processes of schizophrenia.

Direct and indirect effects of fetal irradiation on cortical gray and white matter volume in the macaque

BACKGROUND

Schizophrenia is associated with reductions in thalamic neuronal number and cortical gray matter volume. Exposure of nonhuman primates to x-irradiation in early gestation has previously been shown to decrease thalamic volume and neuronal number. Here we examine whether early gestational irradiation also results in cortical volume reduction.

METHODS

High-resolution, T1-weighted magnetic resonance scans were collected in adult monkeys 1) exposed to irradiation during the early gestational period (E33-E42) corresponding to thalamic neurogenesis, 2) irradiated in midgestation (E70-81) during neocortical neurogenesis, and 3) not exposed to irradiation. Cortical gray matter and white matter volumes were derived via manual segmentation; frontal and nonfrontal volumes were distinguished via sulcal landmarks.

RESULTS

Monkeys irradiated in early gestation exhibited a trend reduction in nonfrontal gray matter volume (17%) and significant reductions in white matter volume in frontal (26%) and nonfrontal (36%) lobes. Monkeys irradiated in midgestation had smaller gray (frontal: 28%; nonfrontal: 22%) and white matter (frontal: 29%; nonfrontal: 38%) volumes.

CONCLUSIONS

The cortical deficits observed in midgestationally irradiated monkeys are consistent with a reduction in cortical neuronal number. Cortical volume reductions following early gestational irradiation may be secondary to reduced thalamic neuronal number and therefore model the thalamocortical pathology of schizophrenia.

Family structure and risk factors for schizophrenia: case-sibling study

BACKGROUND

Several family structure-related factors, such as birth order, family size, parental age, and age differences to siblings, have been suggested as risk factors for schizophrenia. We examined how family-structure-related variables modified the risk of schizophrenia in Finnish families with at least one child with schizophrenia born from 1950 to 1976.

METHODS

We used case-sibling design, a variant of the matched case-control design in the analysis. Patients hospitalized for schizophrenia between 1969 and 1996 were identified from the Finnish Hospital Discharge Register, and their families from the Population Register Center. Only families with at least two children (7914 sibships and 21059 individuals) were included in the analysis. Conditional logistic regression with sex, birth cohort, maternal schizophrenia status, and several family-related variables as explanatory variables was used in the case-sibling design. The effect of variables with the same value in each sibship was analyzed using ordinary logistic regression.

RESULTS

Having a sibling who was less than five years older (OR 1.46, 95% CI 1.29-1.66), or being the firstborn (first born vs. second born 1.62, 1.87-1.4) predicted an elevated risk, but having siblings who were more than ten years older predicted a lower risk (0.66, 0.56-0.79).

CONCLUSIONS

Several family-structure-related variables were identified as risk factors for schizophrenia. The underlying causative mechanisms are likely to be variable.

Maternal poly I:C exposure during pregnancy regulates TNF alpha, BDNF, and NGF expression in neonatal brain and the maternal-fetal unit of the rat

Maternal infection during pregnancy is associated with increased risk for neurodevelopmental disorders. Polyriboinosinic-polyribocytidilic acid (poly I:C) or saline was administered to rats to model maternal infection; levels of TNFalpha, brain-derived neurotrophic factor (BDNF), and nerve growth factor (NGF) were determined by ELISA. TNFalpha was significantly increased in maternal plasma, placenta, and amniotic fluid, while it was significantly decreased in fetal liver/spleen and neonatal brain. NGF and BDNF were significantly decreased in the placenta and fetal liver/spleen. There was no change in BDNF or NGF in the fetal or neonatal brain. Changes in TNFalpha, BDNF, and NGF after maternal exposure to poly I:C represent a potential mechanism through which maternal infection increases risk for neurodevelopmental disorders.

Early maternal stress and health behaviours and offspring expression of psychosis in adolescence

OBJECTIVE

It has been suggested that influences operating early in life may affect the risk of postpubertal psychosis outcomes. This hypothesis was tested using a broad outcome of psychotic symptoms expressed in adolescence (prevalence: 15.6%).

METHOD

Findings are based on a longitudinal, population-based cohort study of 963 adolescents aged 15-20 years and their parents in the area of Munich, Germany. Trained psychologists assessed adolescents with the Munich-Composite International Diagnostic Interview. Independently, direct diagnostic interviews were conducted with the parents.

RESULTS

A range of medical complications of pregnancy and delivery, including lower birth weight, were not associated with the psychosis outcome. However, a number of maternal health behaviours and experiences did show associations, independent of confounders.

CONCLUSION

Not maternally reported medical complications of pregnancy and delivery, but maternal prenatal health behaviours predicted expression of psychosis along a continuum in adolescence. This effect may either be direct or constitute a proxy for later postnatal maternal behaviours associated with psychosis risk in the offspring.

Disruption of neurogenesis on gestational day 17 in the rat causes behavioral changes relevant to positive and negative schizophrenia symptoms and alters amphetamine-induced dopamine release in nucleus accumbens

Gestational disruption of neurodevelopment has been proposed to lead to pathophysiological changes similar to those underlying schizophrenia. We induced such disruption by treating pregnant rat dams with methylazoxymethanol acetate (MAM) on gestational day 17 (GD17). Total brain size and that of the prefrontal cortex and hippocampus were reduced in adult rats exposed prenatally to MAM. When locomotor activity was assessed in an open field, MAM-exposed rats were hyper-responsive to a mild stress and to amphetamine (2 mg/kg, s.c.). They also engaged in less social interaction than controls. We studied, by microdialysis, the effect of amphetamine on extracellular dopamine in the nucleus accumbens and the medial prefrontal cortex of freely moving control and MAM-exposed rats. Amphetamine (2 mg/kg, s.c.) induced an increase in dopamine release that was larger in the nucleus accumbens of MAM-exposed rats than in controls, whereas no difference was seen in the medial prefrontal cortex. In controls, amphetamine infused into the medial prefrontal cortex (50 microM) led to a slight decrease in extracellular dopamine in the nucleus accumbens. This effect was absent in MAM-exposed rats, where a transient increase in nucleus accumbens dopamine levels was seen after amphetamine infusion. These results show that the late gestational disruption of neurogenesis in the rat leads to behavioral changes that mimic positive and negative schizophrenia symptoms, and also to a dysregulation of subcortical dopamine neurotransmission. This study contributes to the evaluation of the validity of the prenatal MAM GD17 treatment in rats as an animal model for schizophrenia.

Prenatal infection and risk for schizophrenia: IL-1beta, IL-6, and TNFalpha inhibit cortical neuron dendrite development

Prenatal exposure to infection increases risk for schizophrenia, and we have hypothesized that inflammatory cytokines, generated in response to maternal infection, alter neuron development and increase risk for schizophrenia. We sought to study the effect of cytokines generated in response to infection-interleukin-1beta (IL-1beta), tumor necrosis factor-alpha (TNFalpha), and interleukin-6 (IL-6)-on the dendritic development of cortical neurons. Primary mixed neuronal cultures were obtained from E18 rats and exposed to 0, 100, or 1000 units (U)/ml of IL-1beta, TNFalpha, IL-6, or IL-1beta+TNFalpha for 44 h. MAP-2-positive neurons were randomly identified for each condition and the number of primary dendrites, nodes, and total dendrite length was determined. We found that 100 U of TNFalpha significantly reduced the number of nodes (27%, p=0.02) and total dendritic length (14%, p=0.04), but did not affect overall neuron survival. A measure of 100 U IL-1beta+TNFalpha significantly reduced the number of primary dendrites (17%, p=0.006), nodes (32%, p=0.001), and total dendritic length (30%, p<0.0001), although it did not affect overall neuron survival. At 1000 U, each cytokine significantly reduced the number of primary dendrites (14-24%), nodes (28-37%), as well as total dendritic length (25-30%); neuron survival was reduced by 14-21%. These results indicate that inflammatory cytokines can significantly reduce dendrite development and complexity of developing cortical neurons, consistent with the neuropathology of schizophrenia. These findings also support the hypothesis that cytokines play a key mechanistic role in the link between prenatal exposure to infection and risk for schizophrenia.

Animal models of obstetric complications in relation to schizophrenia

Epidemiological studies have provided strong evidence that exposure to obstetric complications is associated with an increased risk for later development of schizophrenia. These human studies have now begun to tease out which specific pregnancy, labor/delivery or neonatal complications might confer greatest risk for schizophrenia. Animal modeling can be a useful tool to directly ask if a particular obstetric complication can actually cause changes in brain function or behavior resembling changes in schizophrenia. This review describes currently available animal models for some of the obstetric complications with greatest effect size for schizophrenia, including maternal diabetes, preeclampsia, infection and stress during pregnancy, intrauterine growth retardation and fetal/neonatal hypoxia. Where available, evidence that these types of obstetric complications in animals produce alterations in CNS function or behavior, related to features of schizophrenic pathology, is presented. Animal models might provide insights into the mechanisms by which specific obstetric complications have long-term influence on brain development leading to increased risk for schizophrenia. Factors common to several obstetric complications associated with schizophrenia may also be discerned. In this way, animal modeling may provide the framework for human studies to ask further more refined questions concerning the role of specific obstetric factors contributing to schizophrenia, and may provide clues to prevention.

Maternal exposure to bacterial endotoxin during pregnancy enhances amphetamine-induced locomotion and startle responses in adult rat offspring

An increased incidence of schizophrenia has been associated with several perinatal insults, most notably maternal infection during pregnancy and perinatal hypoxia. This study used a rat model to directly test if maternal exposure to bacterial endotoxin (lipopolysaccharide, LPS) during pregnancy alters behaviors relevant to schizophrenia, in offspring at adulthood. The study also tested if postnatal anoxia interacted with gestational LPS exposure to affect behavior. At adulthood, offspring from dams administered LPS on days 18 and 19 of pregnancy showed significantly increased amphetamine-induced locomotion, compared to offspring from saline-treated dams. A period of anoxia on postnatal day 7 had no effect on amphetamine-induced locomotion and there was no interaction between effects of gestational LPS and postnatal anoxia on this behavior. Offspring from LPS-treated dams also showed enhanced acoustic startle responses as adults, compared to offspring from saline-treated dams. In offspring tested for pre-pulse inhibition (PPI) of acoustic startle and for apomorphine modulation of PPI, no effects of either gestational LPS or of postnatal anoxia and no interactions between LPS and anoxia were observed. It is concluded that maternal LPS exposure during pregnancy in the rat may be a useful model to study mechanisms responsible for effects of maternal infection on behaviors relevant to schizophrenia, in offspring.

Prenatal lead exposure, delta-aminolevulinic acid, and schizophrenia

Schizophrenia is a severe mental disorder of unknown etiology. Recent reports suggest that a number of environmental factors during prenatal development may be associated with schizophrenia. We tested the hypothesis that environmental lead exposure may be associated with schizophrenia using archived serum samples from a cohort of live births enrolled between 1959 and 1966 in Oakland, California. Cases of schizophrenia spectrum disorder were identified and matched to controls. A biologic marker of lead exposure, delta-aminolevulinic acid (delta-ALA), was determined in second-trimester serum samples of 44 cases and 75 controls. delta-ALA was stratified into high and low categories, yielding 66 subjects in the high category, corresponding to a blood lead level (BPb) greater than or equal to 15 micro g/dL, and 53 in the low category, corresponding to BPb less than 15 micro g/dL. Using logistic regression, the odds ratio (OR) for schizophrenia associated with higher delta-ALA was 1.83 [95% confidence interval (CI), 0.87-3.87; p = 0.1]. Adjusting for covariates gave an OR of 2.43 (95% CI, 0.99-5.96; p = 0.051). This finding suggests that the effects of prenatal exposure to lead and/or elevated delta-ALA may extend into later life and must be further investigated as risk factors for adult psychiatric diseases.

Endotoxin exposure in utero increases ethanol consumption in adult male offspring

Epidemiological studies have suggested that adverse experiences in utero predispose individuals to neurobehavioral disorders including drug abuse in adulthood. The present study was designed to examine the hypothesis that maternal endotoxin exposure during pregnancy increases ethanol consumption in adult offspring. Pregnant Sprague-Dawley rats were subjected to lippopolysaccharide (LPS, 1.0 mg/kg, s.c.) treatment on alternate days throughout pregnancy. Adult male offspring were tested for ethanol consumption by using a free-access and two bottle choice paradigm. The animals exposed to LPS showed increased ethanol intake and preference as well as decreased rearing activity in the open field test. These data suggest that maternal infection during pregnancy might precipitate alcohol drinking behavior in adult offspring and this effect might be due, at least in part, to elevated levels of anxiety.

Association between IL-1beta -511C/T and IL-1RA (86bp)n repeats polymorphisms and schizophrenia

It has been established that cytokines play a critical role in the regulation of the CNS and recent studies have suggested that dysfunctions of both pro-inflammatory (IL-1beta, IL-6, and TNF-alpha) and anti-inflammatory (IL-1RA and IL-10) cytokines could be involved in the pathophysiology of schizophrenia. Previous studies have reported that functional polymorphisms in some cytokines genes may have important regulatory effects on such system. Therefore, the aim of the present study was to explore the possible role of the IL-1beta -511C/T and IL-1RA (86bp)(n) repeats polymorphisms in schizophrenia. A case control association study comparing genotype and allele frequencies in 346 northen Italian subjects (169 schizophrenic patients and 177 unrelated healthy volunteers) was performed. The frequencies of IL-1beta -511C and IL-1RA allele 1 (86bp)(4) are significantly higher in schizophrenic patients compared to controls (IL-1beta -511 P=0.047; IL-1RA (86bp)(n) P=0.002). Moreover our data show a protective effect of the IL-1RA allele 2 (86bp)(2) against schizophrenia (OR=0.59 95%CI:0.388-0.910; P=0.016) and this effect is enhanced by the concomitant presence of IL-1beta -511T (OR=0.48 95%CI:0.30-0.76; P=0.002). Our findings support the hypothesis that genetically determined changes in IL-1 metabolism regulation may contribute to the pathogenesis of schizophrenia confirming a role of IL-1 gene cluster in disease susceptibility.

Immune activation during pregnancy in rats leads to a postpubertal emergence of disrupted latent inhibition, dopaminergic hyperfunction, and altered limbic morphology in the offspring: a novel neurodevelopmental model of schizophrenia

Prenatal exposure to infection is associated with increased liability to schizophrenia, and it is believed that such an association is mediated by the maternal immune response, in particular, the proinflammatory cytokines released by the maternal immune system, which may disrupt fetal brain development. Impaired capacity to ignore irrelevant stimuli is one of the central deficits in schizophrenia, and is manifested, among others, in loss of latent inhibition (LI), a phenomenon whereby repeated inconsequential pre-exposure to a stimulus impairs its subsequent capacity to signal significant consequences. We tested the effects of prenatal immune activation induced by peripheral administration of the synthetic cytokine releaser polyriboinosinic-polyribocytidilic acid (poly I : C) to pregnant dams, on LI in juvenile and adult offspring. Consistent with the characteristic maturational delay of schizophrenia, prenatal immune activation did not affect LI in the juvenile offspring, but led to LI disruption in adulthood. Both haloperidol (0.1 mg/kg) and clozapine (5 mg/kg) reinstated LI in the adult offspring. In addition, prenatal immune activation led to a postpubertal emergence of increased sensitivity to the locomotor-stimulating effects of amphetamine and increased in vitro striatal dopamine release, as well as to morphological alterations in the hippocampus and the entorhinal cortex in the adult offspring, consistent with the well-documented mesolimbic dopaminergic and temporolimbic pathology in schizophrenia. These results suggest that prenatal poly I : C administration may provide a neurodevelopmental model of schizophrenia that reproduces a putative inducing factor; mimics the temporal course as well as some central abnormalities of the disorder; and predicts responsiveness to antipsychotic drugs. Neuropsychopharmacology (2003) 28, 1778-1789. advance online publication, 16 July 2003; doi:10.1038/sj.npp.1300248

The "two-headed" latent inhibition model of schizophrenia: modeling positive and negative symptoms and their treatment

RATIONALE

Latent inhibition (LI), namely, poorer performance on a learning task involving a previously pre-exposed non-reinforced stimulus, is disrupted in the rat by the dopamine (DA) releaser amphetamine which produces and exacerbates psychotic (positive) symptoms, and this is reversed by treatment with typical and atypical antipsychotic drugs (APDs) which on their own potentiate LI. These phenomena are paralleled by disrupted LI in normal amphetamine-treated humans, in high schizotypal humans, and in schizophrenia patients in the acute stages of the disorder, as well as by potentiated LI in normal humans treated with APDs. Consequently, disrupted LI is considered to provide an animal model of positive symptoms of schizophrenia with face, construct and predictive validity.

OBJECTIVES

To review most of the rodent data on the neural substrates of LI as well as on the effects of APDs on this phenomenon with an attempt to interpret and integrate these data within the framework of the switching model of LI; to show that there are two distinct LI models, disrupted and abnormally persistent LI; to relate these findings to the clinical condition.

RESULTS

The nucleus accumbens (NAC) and its DA innervation form a crucial component of the neural circuitry of LI, and are involved at the conditioning stage. There is a clear functional differentiation between the NAC shell and core subregions whereby damage to the shell disrupts LI and damage to the core renders LI abnormally persistent under conditions that disrupt LI in normal rats. The effects of shell and core lesions parallel those produced by lesions to the major sources of input to the NAC: entorhinal cortex lesion, like shell lesion, disrupts LI, whereas hippocampal lesion, like core lesion, produces persistent LI with changes in context, and basolateral amygdala (BLA) lesion, like core lesion, produces persistent LI with extended conditioning. Systemically induced blockade of glutamatergic as well as DA transmission produce persistent LI via effects exerted at the conditioning stage, whereas enhancement of DA transmission disrupts LI via effects at the conditioning stage. Serotonergic manipulations can disrupt or potentiate LI via effects at the pre-exposure stage. Both typical and atypical APDs potentiate LI via effects at conditioning whereas atypical APDs in addition disrupt LI via effects at pre-exposure. Schizophrenia patients can exhibit disrupted or normal LI as a function of the state of the disorder (acute versus chronic), as well as persistent LI.

CONCLUSIONS

Different drug and lesion manipulations produce two poles of abnormality in LI, namely, disrupted LI under conditions which lead to LI in normal rats, and abnormally persistent LI under conditions which disrupt it in normal rats. Disrupted and persistent LI are differentially responsive to APDs, with the former reversed by both typical and atypical APDs and the latter selectively reversed by atypical APDs. It is suggested that this "two-headed LI model" mimics two extremes of deficient cognitive switching seen in schizophrenia, excessive and retarded switching between associations, mediated by dysfunction of different brain circuitries, and can serve to model positive symptoms of schizophrenia and typical antipsychotic action, as well as negative symptoms of schizophrenia and atypical antipsychotic action.

DNA stability and schizophrenia in twins

The goal of these experiments was to understand DNA changes relevant to schizophrenia. This work compared DNA of monozygotic (MZ) twins surrounding (CAG)(n) repeating sequences, and characterized the relationship between fragile sites and schizophrenia. Twelve twin-pairs, previously classified as MZ and 18 unrelated sib-pairs, from seven families were studied. Eight twin-pairs were affected by schizophrenia, four concordantly and four discordantly. DNA comparisons were made using profiles of electrophoretic size fractionations of PCR amplified (CAG)(n) containing genomic fragments. These profiles were generated by a new method, developed by us, called targeted genomic differential display (TGDD). Surprisingly, the number of peak profile differences in MZ twin-pairs discordant for schizophrenia was greater than the concordantly ill twins and the well twins and, in some cases, overlapped the range of sib-pairs. These results might mean that some twins were not MZ but it was not possible to definitively test these samples for zygosity. Alternatively, the results might be explained as an increased mutation rate (or genomic instability) around (CAG)(n) sites in individuals afflicted with schizophrenia. Also, we uncovered an association of schizophrenia (i.e., a linkage of chromosomal abnormalities and gene localizations) with fragile sites spread throughout the genome (chi(2), P = 0.001). Furthermore, it appears that an increasing number of genes linked to schizophrenia are associated with (CAG)(n) sequences. Fragile sites and (CAG)(n) repeat sequences are known to be unstable. We speculate the association of genomic instability with schizophrenia accounts for seemingly disparate biological and environmental factors that influence disease occurrence.

Maternal infection regulates BDNF and NGF expression in fetal and neonatal brain and maternal-fetal unit of the rat

Maternal infection during pregnancy is associated with increased risk for neurodevelopmental disorders. Lipopolysaccharide (LPS) or saline was administered to rats to model maternal infection, and levels of brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) in maternal plasma, placenta, amniotic fluid, fetal liver/spleen, fetal brain, and cerebral cortex after birth were determined by ELISA or semiquantitative Western blot analysis. BDNF expression was significantly increased in the fetal brain (p=0.039); NGF expression was significantly increased in neonatal cortex (p=0.0009). Neurotrophic factor expression was also altered in other tissues of the maternal-fetal unit. Abnormal expression of neurotrophic factors represents a potential mechanism through which maternal infection increases risk for neurodevelopmental disorders.

Childhood developmental abnormalities in schizophrenia: evidence from high-risk studies

According to cohort studies, individuals who develop schizophrenia in adulthood show developmental abnormalities in childhood. These include delays in attainment of speech and motor milestones, problems in social adjustment, and poorer academic and cognitive performance. Another method of investigating developmental abnormalities associated with schizophrenia is the high-risk (HR) method, which follows up longitudinally the development of children at high risk for schizophrenia. Most HR studies have investigated children who have a parent with schizophrenia. This review summarizes findings concerning childhood and adolescent development from 16 HR studies and compares them with findings from cohort, conscript, and family studies. We specifically addressed two questions: (1) Does the development of HR children differ from that of control children? (2) Which developmental factors, if any, predict the development of schizophrenia-spectrum disorders in adulthood? While the answer to the first question is affirmative, there may be other mechanisms involved in addition to having a parent with schizophrenia. Factors which appear to predict schizophrenia include problems in motor and neurological development, deficits in attention and verbal short-term memory, poor social competence, positive formal thought disorder-like symptoms, higher scores on psychosis-related scales in the MMPI, and severe instability of early rearing environment.

Maternal influenza infection causes marked behavioral and pharmacological changes in the offspring

Maternal viral infection is known to increase the risk for schizophrenia and autism in the offspring. Using this observation in an animal model, we find that respiratory infection of pregnant mice (both BALB/c and C57BL/6 strains) with the human influenza virus yields offspring that display highly abnormal behavioral responses as adults. As in schizophrenia and autism, these offspring display deficits in prepulse inhibition (PPI) in the acoustic startle response. Compared with control mice, the infected mice also display striking responses to the acute administration of antipsychotic (clozapine and chlorpromazine) and psychomimetic (ketamine) drugs. Moreover, these mice are deficient in exploratory behavior in both open-field and novel-object tests, and they are deficient in social interaction. At least some of these behavioral changes likely are attributable to the maternal immune response itself. That is, maternal injection of the synthetic double-stranded RNA polyinosinic-polycytidylic acid causes a PPI deficit in the offspring in the absence of virus. Therefore, maternal viral infection has a profound effect on the behavior of adult offspring, probably via an effect of the maternal immune response on the fetus.

Chorioamnionitis and brain injury

The limited available evidence supports a strong association of chorioamnionitis with neonatal encephalopathy and CP in the term infant. The association of chorioamnionitis with depressed Apgar scores or neonatal seizures and with CP is equivocal in the preterm infant. Different study results may be related to differences in study populations, perhaps specifically to differences in susceptibility by stages of neurologic development as well as differences in gene frequencies associated with inflammation and thrombophilia. We require further understanding of the normal roles of cytokines in brain development, pregnancy, and inflammatory homeostasis before clinical interventions directed at cytokines, their receptors, or the inflammatory process are considered.

Birth month and suicidal and depressive symptoms in Australians born in the Southern vs. the Northern hemisphere

To test whether Australians in utero during the Southern hemisphere flu peak would show increased suicidal and depressive symptoms, as would those born in the Northern hemisphere and who were in utero during the Northern hemisphere flu peak. A sample of 2514 adolescents and young adults presenting to general practitioners completed measures of depressive and suicidal symptoms. Patients' date and country of birth were recorded. Those born in the Southern hemisphere in September-November showed the highest suicidal and depressive symptoms, as did those born in the Northern hemisphere in March-May. Season of birth may be a risk factor for depressive and suicidal symptoms.

Corticosteroids, immune suppression, and psychosis

The role of the immune system in psychiatric symptoms has been an area of much interest for many years. This review discusses medications and medical illnesses associated with immune system dysfunction, and their relationship to psychiatric symptoms, particularly psychosis. Medical illnesses including HIV infection, systemic lupus erythematosus (SLE), and Cushing's disease are all associated with psychiatric symptoms. In addition, high dosages of prescription corticosteroids (eg, prednisone and dexamethasone) are associated with mood changes, cognitive deficits, and even psychosis. However, the role of the immune system in mediating the psychiatric disturbances with each of these conditions is not clear. Directions for further research and treatment considerations are discussed.

In utero infection and adult schizophrenia

We review emerging evidence indicating that in utero exposure to infection is a risk factor for schizophrenia. It is hypothesized that a prenatal infection increases the liability to schizophrenia in adulthood by adversely affecting the maturation of critical brain structural and functional components implicated in the pathogenesis and pathophysiology of the disorder. Early evidence for a role of in utero infection includes investigations linking schizophrenia with birth during the winter and in urban regions, and ecologic studies demonstrating associations between influenza epidemics and births of pre-schizophrenic patients. The findings of the latter studies are, however, equivocal. To more rigorously address this question, our group has used increasingly sophisticated research designs that incorporate more refined measures of exposure and outcome, and continuous follow-up of treated cases. This work has already yielded several intriguing findings, including associations between schizophrenia and two in utero infections--rubella and respiratory infection. We also describe our ongoing birth cohort investigations that are expected to advance this work further, including studies that utilize maternal serum samples drawn during pregnancy of offspring who were later diagnosed with schizophrenia.

Maternal infection: window on neuroimmune interactions in fetal brain development and mental illness

Direct viral infection of the developing brain can have disastrous consequences for the fetus. More subtle and perhaps more insidious are viral infections of the pregnant mother, which can have long-lasting effects such as an increased risk of schizophrenia in the offspring. A recent mouse model has shown that respiratory infection in the pregnant mother leads to marked behavioral and pharmacological abnormalities in the offspring, some of which are relevant for schizophrenia and autism. This effect on fetal brain development might be caused by the maternal antiviral immune response, possibly mediated by cytokines.

Maternal cytokine levels during pregnancy and adult psychosis

We investigated levels of maternal cytokines in late pregnancy in relation to the subsequent development of adult schizophrenia and other psychoses in their offspring. The sample included the mothers of 27 adults with schizophrenia and other psychotic illnesses and 50 matched unaffected controls from the Providence cohort of the Collaborative Perinatal Project. Serum samples were analyzed for interleukin 1 beta (IL-1-beta), interleukin 2 (IL-2), interleukin 6 (IL-6), interleukin 8 (IL-8), and tumor necrosis factor alpha (TNF-alpha) by enzyme immunoassay. Maternal levels of TNF-alpha were significantly elevated among the case series (t = 2.22, p =.04), with evidence of increasing odds of psychosis in relation to higher cytokine levels. We did not find significant differences between case and control mothers in the serum levels of IL-1, IL-2, IL-6, or IL-8. These data support previous clinical investigations reporting maternal infections during pregnancy as a potential risk factor for psychotic illness among offspring.

Cytokine effects on cortical neuron MAP-2 immunoreactivity: implications for schizophrenia

BACKGROUND

Cytokines demonstrate diverse actions in the brain and modulate systemic and central nervous system (CNS) responses to injury, infection, and inflammation. Cytokines in the CNS are elevated during infection and ischemia, two neurodevelopmental insults associated with increased schizophrenia risk. We hypothesize that cytokine-mediated neuronal injury during development may contribute to schizophrenia pathophysiology, causing subtle alterations in neuronal number and density.

METHODS

We examined cytokine regulation of neuronal number in embryonic day 18 rat cortical cultures using MAP-2 immunohistochemistry. Mixed cultures derived from frontal cortex were fixed and stained after 48-hour exposure to the proinflammatory interleukin-1beta (IL-1beta), interleukin-6 (IL-6), or tumor necrosis factor-alpha (TNF-alpha; 0, 10, 100, or 1000 units/mL).

RESULTS

IL-1beta (maximum effect 35%) and IL-6 (maximum effect 29%) produced dose-dependent decreases in the number of cells (neurons) immunoreactive for MAP-2 antibody, suggesting decreased neuronal survival. TNF-alpha also tended to decrease MAP-2 immunostaining at the highest dose tested.

CONCLUSIONS

Our data suggest a role for cytokines in the modulation of neuronal survival during neurodevelopment, a finding potentially relevant to schizophrenia pathophysiology. If cytokine-mediated neuronal injury proves to be a common response to gestational insults associated with increased schizophrenia risk, the pharmacologic modulation of these molecules may have clinical utility.

Schizophrenia and viral infection during neurodevelopment: a focus on mechanisms

The task of defining schizophrenia pathogenesis has fascinated and frustrated researchers for nearly a century. In recent years, unprecedented advances from diverse fields of study have given credence to both viral and developmental theories. This review considers possible mechanisms by which viral and developmental processes may interact to engender schizophrenia. Many of the current controversies in schizophrenia pathogenesis are reviewed in light of the viral hypothesis, including: epidemiological findings and the role of a genetic diathesis, phenotype heterogeneity, abnormalities in excitatory and inhibitory neurotransmitter systems, anomalous cerebral latereralization, and static vs progressive disease. The importance of animal models in elucidating the impact of viral infections on developing neurons is illustrated by recent studies in which neonatal rats are infected with lymphocytic choriomeningitis virus in order to examine alterations in hippocampal circuitry. Finally, consideration is given to a new hypothesis that some cases of schizophrenia could be instigated by a viral infection that disrupts developing inhibitory circuits, consequently unleashing glutamatergic neurotransmission leading to selective excitotoxicity, and a degenerative disease course.

Prenatal exposure to maternal infection alters cytokine expression in the placenta, amniotic fluid, and fetal brain

Prenatal exposure to infection appears to increase the risk of schizophrenia and other neurodevelopmental disorders. We have hypothesized that cytokines, generated in response to maternal infection, play a key mechanistic role in this association. E16 timed pregnancy rats were injected i.p. with Escherichia coli lipopolysaccharide (LPS) to model prenatal exposure to infection. Placenta, amniotic fluid and fetal brains were collected 2 and 8h after LPS exposure. There was a significant treatment effect of low-dose (0.5mg/kg) LPS on placenta cytokine levels, with significant increases of interleukin (IL)-1beta (P<0.0001), IL-6 (P<0.0001), and tumor necrosis factor-alpha (TNF-alpha) (P=0.0001) over the 2 and 8h time course. In amniotic fluid, there was a significant effect of treatment on IL-6 levels (P=0.0006). Two hours after maternal administration of high-dose (2.5mg/kg) LPS, there were significant elevations of placenta IL-6 (P<0.0001), TNF-alpha (P<0.0001), a significant increase of TNF-alpha in amniotic fluid (P=0.008), and a small but significant decrease in TNF-alpha (P=0.035) in fetal brain. Maternal exposure to infection alters pro-inflammatory cytokine levels in the fetal environment, which may have a significant impact on the developing brain.

A classification of sociomedical health indicators: perspectives for health administrators and health planners

The conceptualization and operationalization of measures of health status are considered. Health indicators are conceived as a subset of social indicators, and therefore, as any social indicator, they are viewed as derivative from social issues. The interrelationships of different frames of reference for defining and measuring health that have accompained three distinct health problem patterns in the United States are viewed from a developmental perspective. Mortality and morbidity rates, the traditional health indicators, by themselves no longer serve to assess health status in developed nations. Their deficiencies as indicators serve as background for a classification schema for sociomedical health status indicators that relates health definition frames of reference, measures of health status, and health problems. The role of a group of health indicators-sociomedical heath indicators-in the current formulation of health status measures is assessed.