Does prenatal influenza divert susceptible females from later affective psychosis to schizophrenia?

Neuropsychiatric outcomes in offspring after fetal exposure to maternal influenza infection during pregnancy: A systematic review

Increasing evidence suggests that influenza infection in pregnancy may disrupt fetal neurodevelopment. The impact of maternal influenza infection on offspring neuropsychiatric health has not been comprehensively reviewed. We systematically reviewed comparative studies evaluating associations between maternal influenza infection and neuropsychiatric health outcomes in offspring. We searched MEDLINE, EMBASE, CINAHL, and Web of Science for articles published until January 7, 2022. Included were English studies evaluating neuropsychiatric outcomes in offspring aged > 6 months born to women with and without influenza during pregnancy, defined as clinical or laboratory-confirmed influenza illness, or being pregnant during pandemics/epidemics. Of 12,010 records screened, 42 studies were included. Heterogeneity in study design, exposures, and outcome definitions precluded meta-analyses. Four of 14 studies assessing schizophrenia reported adjusted ratio estimates from 0.5 to 8.2; most 95% CIs contained the null value; study quality was high in three of four. Two studies reported an increased risk of schizophrenia with influenza exposure any time during pregnancy (adjusted incidence rate ratio 8.2, 95% CI: 1.4-48.8; adjusted odds ratio 1.3, 95% CI: 1.2-1.5); another reported a reduced risk with first-trimester exposure (adjusted risk ratio 0.5, 95% CI: 0.3-0.9). Seven studies of autism spectrum disorder reported adjusted ratio estimates from 0.9 to 4.0; all 95% CIs included the null value; study quality was high in four. No conclusions could be drawn about the association between exposure to maternal influenza and neuropsychiatric outcomes due to the limited quantity and quality of available research. Large observational studies with long-term follow-up are required to investigate these associations.

The fetal origins of mental illness

The impact of infections and inflammation during pregnancy on the developing fetal brain remains incompletely defined, with important clinical and research gaps. Although the classic infectious TORCH pathogens (ie, Toxoplasma gondii, rubella virus, cytomegalovirus [CMV], herpes simplex virus) are known to be directly teratogenic, emerging evidence suggests that these infections represent the most extreme end of a much larger spectrum of injury. We present the accumulating evidence that prenatal exposure to a wide variety of viral and bacterial infections-or simply inflammation-may subtly alter fetal brain development, leading to neuropsychiatric consequences for the child later in life. The link between influenza infections in pregnant women and an increased risk for development of schizophrenia in their children was first described more than 30 years ago. Since then, evidence suggests that a range of infections during pregnancy may also increase risk for autism spectrum disorder and depression in the child. Subsequent studies in animal models demonstrated that both pregnancy infections and inflammation can result in direct injury to neurons and neural progenitor cells or indirect injury through activation of microglia and astrocytes, which can trigger cytokine production and oxidative stress. Infectious exposures can also alter placental serotonin production, which can perturb neurotransmitter signaling in the developing brain. Clinically, detection of these subtle injuries to the fetal brain is difficult. As the neuropsychiatric impact of perinatal infections or inflammation may not be known for decades after birth, our construct for defining teratogenic infections in pregnancy (eg, TORCH) based on congenital anomalies is insufficient to capture the full adverse impact on the child. We discuss the clinical implications of this body of evidence and how we might place greater emphasis on prevention of prenatal infections. For example, increasing uptake of the seasonal influenza vaccine is a key strategy to reduce perinatal infections and the risk for fetal brain injury. An important research gap exists in understanding how antibiotic therapy during pregnancy affects the fetal inflammatory load and how to avoid inflammation-mediated injury to the fetal brain. In summary, we discuss the current evidence and mechanisms linking infections and inflammation with the increased lifelong risk of neuropsychiatric disorders in the child, and how we might improve prenatal care to protect the fetal brain.

Does Prenatal Exposure to Maternal Inflammation Causes Sex Differences in Schizophrenia-Related Behavioral Outcomes in Adult Rats?

Highlighted Research Paper:Maternal Immune Activation during Pregnancy Alters the Behavior Profile of Female Offspring of Sprague Dawley Rats, by Brittney R. Lins, Wendie N. Marks, Nadine K. Zabder, Quentin Greba, and John G. Howland

Sex-Dependent Effects of Perinatal Inflammation on the Brain: Implication for Neuro-Psychiatric Disorders

Individuals born preterm have higher rates of neurodevelopmental disorders such as schizophrenia, autistic spectrum, and attention deficit/hyperactivity disorders. These conditions are often sexually dimorphic and with different developmental trajectories. The etiology is likely multifactorial, however, infections both during pregnancy and in childhood have emerged as important risk factors. The association between sex- and age-dependent vulnerability to neuropsychiatric disorders has been suggested to relate to immune activation in the brain, including complex interactions between sex hormones, brain transcriptome, activation of glia cells, and cytokine production. Here, we will review sex-dependent effects on brain development, including glia cells, both under normal physiological conditions and following perinatal inflammation. Emphasis will be given to sex-dependent effects on brain regions which play a role in neuropsychiatric disorders and inflammatory reactions that may underlie early-life programming of neurobehavioral disturbances later in life.

Maternal inflammation during pregnancy and offspring psychiatric symptoms in childhood: Timing and sex matter

OBJECTIVE

Maternal infection during pregnancy has been associated with increased risk of offspring psychopathology, including depression. As most infections do not cross the placenta, maternal immune responses to infection have been considered as potentially contributing to this relationship. This study examined whether gestational timing of maternal inflammation during pregnancy is associated with offspring internalizing and/or externalizing symptoms during childhood and, further, whether fetal sex moderated this relationship.

METHOD

Participants were 737 pregnant women and their offspring who were continuously followed through late childhood. Archived first and second trimester sera were analyzed for markers of inflammation [interleukin 8 (IL-8), IL-6, IL-1 receptor antagonist (IL-1ra), and soluble tumor necrosis factor receptor-II (sTNF-RII)]. When offspring were aged 9-11, mothers completed a questionnaire assessing psychological symptoms.

RESULTS

Multivariate regression analyses indicated that elevated IL-8 in the first trimester was associated with significantly higher levels of externalizing symptoms in offspring. Higher IL-1ra in the second trimester was associated with higher offspring internalizing symptoms. Further, second trimester IL-1ra was associated with increased internalizing symptoms in females only.

CONCLUSION

These findings demonstrate that elevated maternal inflammation during pregnancy is associated with the emergence of separate psychological phenotypes and that timing of exposure and fetal sex matter for offspring outcomes. Given that internalizing and externalizing symptoms in childhood increase risk for a variety of mental disorders later in development, these findings potentially have major implications for early intervention and prevention work.

Maternal infection and stress during pregnancy and depressive symptoms in adolescent offspring

Maternal infection during pregnancy has been linked to increased risk of offspring depression. Additionally, maternal stress during pregnancy has been consistently linked with adverse offspring outcomes associated with depression. Relatedly, stress has been associated with increased risk of infection; however no study has investigated stress-infection interactions during pregnancy and risk for offspring depression. Participants were drawn from the Child Health and Development Studies (CHDS), a prospective, longitudinal study that enrolled pregnant women from 1959 to 1966. Maternal health and birth outcome information were collected, as well as open-ended interviews about worrisome events during pregnancy. The present study included participants from a subsample of women whose offspring (n = 1711) completed self-reports of depressive symptoms during adolescence. Results indicated that maternal infection during only the second trimester was associated with higher scores on adolescent offspring depressive symptoms, while controlling for maternal education at birth, adolescent age, and maternal depressive symptoms at adolescence. Maternal experiences of daily stress during pregnancy moderated this association, such that mothers diagnosed with second trimester infection and who experienced daily stress had offspring with significantly higher depression scores than mothers of adolescents diagnosed with an infection alone. Findings have potential implications for prevention and intervention strategies.

Prenatal immune programming of the sex-dependent risk for major depression

Maternal immune functioning during pregnancy contributes to sex-dependent deficits in neurodevelopment and to behaviors associated with affective traits in preclinical studies, and has been indirectly associated with offspring depression in epidemiologic studies. We therefore investigated the association between immune activity during pregnancy and the risk of depression among male and female offspring. We conducted a case-control study of depression (n=484 cases and n=774 controls) using data from the New England Family Study, a pregnancy cohort enrolled between 1959 and 1966 that assessed psychiatric outcomes in adult offspring (mean age=39.7 years). We assayed concentrations of three pro-inflammatory cytokines, interleukin (IL)-1β, IL-6 and tumor necrosis factor (TNF)-α, and the anti-inflammatory cytokine, IL-10, in maternal serum collected at the end of the second and beginning of the third trimesters. High maternal TNF-α was associated with reduced odds of depression among both male and female offspring (odds ratio (OR)=0.68; confidence interval (CI)=0.48, 0.98). However, when considering the TNF-α to IL-10 ratio, a measure of the ratio of pro- to anti-inflammatory loading, maternal immune effects on offspring depression differed significantly by sex (χ(2)=13.9, degrees of freedom=4, P=0.008). Among females, higher maternal TNF-α:IL-10 was associated with reduced odds of depression (OR=0.51; CI=0.32, 0.81), whereas, among males, high maternal TNF-α:IL-10 was associated with elevated odds of depression (OR=1.86; CI=1.02, 3.39). Thus, the balance between TNF-α and IL-10 in maternal prenatal serum was associated with depression in a sex-dependent manner. These findings are consistent with the role of TNF-α in the maturation of the sexually dimorphic fetal brain circuitry that regulates stress and affective responses, and support a prenatal stress-immune model of depression pathogenesis.

Association Between Prenatal Exposure to Maternal Infection and Offspring Mood Disorders: A Review of the Literature

The purpose of this article is to provide a systematic review of studies that have examined the association between prenatal exposure to maternal infection and development of mood disorders across the life course. Drawing from both human- and animal-based studies, we give an overview of hypothesized biological mechanisms by which exposure to maternal infection during critical periods of gestation may contribute to fetal programming of mood disorders in offspring. We discuss studies examining the association between prenatal exposure to maternal infection with pathogens including influenza as well as other respiratory viruses, herpesviruses, hepatitis viruses, and Toxoplasma gondii and mood disorders in human populations. Moreover, we outline strengths and limitations of the current body of evidence and make recommendations for future research. We also discuss findings in the context of well-documented gender and socioeconomic disparities in the prevalence and severity of mood disorders, particularly major depression, and the role that early exposure to infection may play in explaining the perpetuation of such disparities across generations. Overall, this review of the current knowledge on this topic has important implications for determining future research directions, designing interventions as well as prenatal care guidelines targeted at prevention or treatment of infection during pregnancy, and clinical practice for the identification of individuals that may be at increased risk for mood disorders beginning early in life. Importantly, such efforts may not only lower the overall burden of mood disorders but also serve to address social disparities in these adverse mental health conditions in the U.S.

The poly(I:C)-induced maternal immune activation model in preclinical neuropsychiatric drug discovery

Increasing epidemiological and experimental evidence implicates gestational infections as one important factor involved in the pathogenesis of several neuropsychiatric disorders. Corresponding preclinical model systems based upon maternal immune activation (MIA) by treatment of the pregnant female have been developed. These MIA animal model systems have been successfully used in basic and translational research approaches, contributing to the investigation of the underlying pathophysiological mechanisms at the molecular, cellular and behavioral levels. The present article focuses on the application of a specific MIA rodent paradigm, based upon treatment of the gestating dam with the viral mimic polyinosinic-polycytidilic acid (Poly(I:C)), a synthetic analog of double-stranded RNA (dsRNA) which activates the Toll-like receptor 3 (TLR3) pathway. Important advantages and constraints of this animal model will be discussed, specifically in light of gestational infection as one vulnerability factor contributing to the complex etiology of mood and psychotic disorders, which are likely the result of intricate multi-level gene×environment interactions. Improving our currently incomplete understanding of the molecular pathomechanistic principles underlying these disorders is a prerequisite for the development of alternative therapeutic approaches which are critically needed in light of the important drawbacks and limitations of currently available pharmacological treatment options regarding efficacy and side effects. The particular relevance of the Poly(I:C) MIA model for the discovery of novel drug targets for symptomatic and preventive therapeutic strategies in mood and psychotic disorders is highlighted in this review article.

The environment and susceptibility to schizophrenia

In the present article the putative role of environmental factors in schizophrenia is reviewed and synthesized. Accumulating evidence from recent studies suggests that environmental exposures may play a more significant role in the etiopathogenesis of this disorder than previously thought. This expanding knowledge base is largely a consequence of refinements in the methodology of epidemiologic studies, including birth cohort investigations, and in preclinical research that has been inspired by the evolving literature on animal models of environmental exposures. This paper is divided into four sections. In the first, the descriptive epidemiology of schizophrenia is reviewed. This includes general studies on incidence, prevalence, and differences in these measures by urban-rural, neighborhood, migrant, and season of birth status, as well as time trends. In the second section, we discuss the contribution of environmental risk factors acting during fetal and perinatal life; these include infections [e.g. rubella, influenza, Toxoplasma gondii (T. gondii), herpes simplex virus type 2 (HSV-2)], nutritional deficiencies (e.g., famine, folic acid, iron, vitamin D), paternal age, fetal/neonatal hypoxic and other obstetric insults and complications, maternal stress and other exposures [e.g. lead, rhesus (Rh) incompatibility, maternal stress]. Other putative neurodevelopmental determinants, including cannabis, socioeconomic status, trauma, and infections during childhood and adolescence are also covered. In the third section, these findings are synthesized and their implications for prevention and uncovering biological mechanisms, including oxidative stress, apoptosis, and inflammation, are discussed. Animal models, including maternal immune activation, have yielded evidence suggesting that these exposures cause brain and behavioral phenotypes that are analogous to findings observed in patients with schizophrenia. In the final section, future studies including new, larger, and more rigorous epidemiologic investigations, and research on translational and clinical neuroscience, gene-environment interactions, epigenetics, developmental trajectories and windows of vulnerability, are elaborated upon. These studies are aimed at confirming observed risk factors, identifying new environmental exposures, elucidating developmental mechanisms, and shedding further light on genes and exposures that may not be identified in the absence of these integrated approaches. The study of environmental factors in schizophrenia may have important implications for the identification of causes and prevention of this disorder, and offers the potential to complement, and refine, existing efforts on explanatory neurodevelopmental models.

Prenatal infection and schizophrenia: a review of epidemiologic and translational studies

An emerging literature from epidemiologic, clinical, and preclinical investigations has provided evidence that gestational exposure to infection contributes to the etiology of schizophrenia. In recent years, these studies have moved from ecologic designs, which ascertain infection based on epidemics in populations, to investigations that have capitalized on reliable biomarkers in individual pregnancies. These studies have documented specific candidate infections that appear to be associated with an elevated risk of schizophrenia. Animal models of maternal immune activation inspired by this work have revealed intriguing findings indicating behavioral, neurochemical, and neurophysiologic abnormalities consistent with observations in schizophrenia. In parallel studies in humans and animals, investigators are working to uncover the cellular and molecular mechanisms by which in utero exposure to infection contributes to schizophrenia risk. In this review, the authors discuss and critically evaluate the epidemiologic literature on in utero exposure to infection and schizophrenia, summarize emerging animal models of maternal immune activation, and discuss putative unique and common mechanisms by which in utero exposure to infection alters neurodevelopment, potentially increasing susceptibility to schizophrenia. The promise of this work for facilitating the identification of susceptibility loci in genetic studies of schizophrenia is illustrated by examples of interaction between in utero exposure to infection and genetic variants. The authors then elaborate on possible implications of this work, including the use of preventive measures for reducing the incidence of schizophrenia. Finally, they discuss new approaches aimed at addressing current challenges in this area of research.

Neurodevelopmental basis of bipolar disorder: a critical appraisal

Neurodevelopmental factors have been implicated in the pathophysiology of mental disorders. However, the evidence regarding their role in bipolar disorder is controversial. We reviewed the pertinent literature searching for evidence regarding a neurodevelopmental origin of bipolar disorder. Findings from clinical, epidemiological, neuroimaging, and post-mortem studies are discussed, as well as the implications of the available data for a better understanding of the mechanisms involved in the genesis of bipolar disorder. While some evidence exists for developmental risk factors in bipolar disorder, further research is needed to determine the precise extent of their contribution to pathogenesis. The timing and course of such developmentally mediated neurobiological alterations also need to be determined. Of particular importance for further study is the possibility that bipolar disorder may be mediated by an abnormal maturation of brain structures involved in affect regulation.

Season of birth, clinical manifestations and Dexamethasone Suppression Test in unipolar major depression

BACKGROUND

Reports in the literature suggest that the season of birth might constitute a risk factor for the development of a major psychiatric disorder, possibly because of the effect environmental factors have during the second trimester of gestation. The aim of the current paper was to study the possible relationship of the season of birth and current clinical symptoms in unipolar major depression.

METHODS

The study sample included 45 DSM-IV major depressive patients and 90 matched controls. The SCAN v. 2.0, Hamilton Depression Rating Scale (HDRS) and Hamilton Anxiety Scale (HAS) were used to assess symptomatology, and the 1 mg Dexamethasone Suppression Test (DST) was used to subcategorize patients.

RESULTS

Depressed patients as a whole did not show differences in birth season from controls. However, those patients born during the spring manifested higher HDRS while those born during the summer manifested the lowest HAS scores. DST non-suppressors were almost exclusively (90%) likely to be born during autumn and winter. No effect from the season of birth was found concerning the current severity of suicidal ideation or attempts.

DISCUSSION

The current study is the first in this area of research using modern and rigid diagnostic methodology and a biological marker (DST) to categorize patients. Its disadvantages are the lack of data concerning DST in controls and a relatively small size of patient sample. The results confirm the effect of seasonality of birth on patients suffering from specific types of depression.

Exposure to obstetric complications and subsequent development of bipolar disorder: Systematic review

BACKGROUND

Research has suggested an association between obstetric complications and bipolar disorder. However, no quantitative evaluation has been made of the pooled data from existing studies.

AIMS

To systematically review studies comparing exposure to obstetric complications in cases of bipolar disorder v. non-psychiatric controls, and in cases of bipolar disorder v. cases of other mental disorders.

METHOD

Publications were identified by computer searches of seven databases, by hand searches of reference lists and from raw data received from researchers.

RESULTS

Forty-six studies were identified, of which 22 met the inclusion criteria. The pooled odds ratio for exposure to obstetric complications and subsequent development of bipolar disorder was 1.01 (95% CI 0.76-1.35) compared with healthy controls, 1.13 (95% CI 0.64-1.99) compared with cases of unipolar disorder and 0.61 (95% CI 0.39-0.95) compared with those who developed schizophrenia.

CONCLUSIONS

There is no robust evidence that exposure to obstetric complications increases the risk of developing bipolar disorder. However, the range of events regarded as obstetric complications and methodological inadequacies make definitive conclusions difficult.

Risk factors in relation to an emergence of bipolar disorder: a systematic review

OBJECTIVE

There is a consensus that genetic factors are important in the causation of bipolar disorder (BPD); however, little is known about other risk factors in the aetiology of BPD. Our aim was to review the literature on such risk factors - risk factors other than family history of affective disorders - as predictors for the initial onset of BPD.

METHODS

We conducted a literature search using the MEDLINE, PsycINFO and EMBASE databases. We selected factors of interest including demographic factors, factors related to birth, personal, social and family backgrounds, and history of medical conditions. The relevant studies were extracted systematically according to a search protocol.

RESULTS

We identified approximately 100 studies that addressed the associations between antecedent environmental factors and a later risk for BPD. Suggestive findings have been provided regarding pregnancy and obstetric complications, winter-spring birth, stressful life events, traumatic brain injuries and multiple sclerosis. However, evidence is still inconclusive. Childbirth is likely to be a risk factor. The inconsistency across studies and methodological issues inherent in the study designs are also discussed.

CONCLUSION

Owing to a paucity of studies and methodological issues, risk factors of BPD other than family history of affective disorders have generally been neither confirmed nor excluded. We call for further research.

Mood disorders and influenza epidemics in Japan

The finding that influenza epidemics are associated with an increased risk of adult mood disorder has been controversial. In this study, data were collected from governmental statistics, the Patient Survey in Japan, in 1996. Index years were defined as 1957/58, 1962, and 1965, and comparison years were defined as 2 years before and 2 years after the index year. The subjects were 361 patients with mood disorders who were born in the index years of influenza epidemics. In order to isolate patients exposed to an influenza epidemic during their second prenatal trimester, the months of birth 5 months after the influenza epidemics were defined as risk exposure months. The proportions of patients born during the exposure period in the index years were compared with those of patients born in the corresponding months in the comparison years. The same procedures were conducted for the periods 2 and 8 months after the epidemics. For female inpatients only, the proportion of patients born in the A2 influenza-exposure months in 1965 with second-trimester exposure was smaller than that of patients born in the corresponding months in the comparison years; the same phenomenon was observed for third-trimester exposure in 1957-58. However, no differences were observed in other comparisons. These findings suggest that prenatal exposure to influenza might decrease the risk for adult mood disorders in females. However, whether there is a causal relationship is still unproven.

Maternal exposure to influenza and paranoid schizophrenia

Previous research has suggested that schizophrenics exposed to influenza in the second trimester have more delusions of jealousy, delusions of reference and suspiciousness. We therefore hypothesised that the risk-increasing effect of in utero exposure to influenza would be particularly demonstrable in paranoid schizophrenia. We studied patients with an ICD diagnosis of schizophrenia in England and Wales who were born each month between 1923 and 1965 (N = 17,247. Chi-square test for trend showed that an increase in influenza exposure level during the fifth month of gestation was accompanied by an increase in the proportion of patients with paranoid schizophrenia. However, logistic regression analysis including sex, seasonality and birth period in the model resulted in the loss of any significant association between in utero exposure to influenza and the development of paranoid schizophrenia, the loss of this significance being mainly accounted for by birth period. Therefore, the association in utero exposure to influenza and subsequent development of paranoid schizophrenia we hypothesised was not supported by our data.

Season of birth and schizophrenia: sex difference

1. A statistically significant increased risk of schizophrenia for individuals born in winter has been reported. The increase risk is of the order of 5-15 percent. The seasonal effect is more marked among females. This winter birth effect suggests some environmental agents, probably a neuropathogen one, acting on the foetus. 2. The present study sought to test the environmental damage hypothesis by application of the family history of psychiatric disorder distinction to season of birth data divided according to sex and using a control population. 3. From computer records, all patients admitted to the psychiatric department of Marseilles Timone hospital between January 1984 and December 1989 who satisfied DSM III, DSM III R criteria for schizophrenia were identified. Patients were then classified into two groups: family history of psychiatric disorder versus no family history. Division according to the sex was carried on after two groups were formed. 4. The data show (I) a significant excess of births in the early months of the year (p < 0.05) for all patients with no family history of psychiatric disorder, (2) a significant excess of births for females (p < 0.05) with no family history. 5. These results provide indirect support for the neurodevelopmental theory of schizophrenia.

New directions in the prevention and treatment of schizophrenia: a biological perspective

Our current treatments for schizophrenia are, at best, palliative. With the exception of counseling those families with a known high risk for having schizophrenic offspring, no preventive measures are currently available. The not too distant future, however, promises to bring improvements in somatic treatments as well as the possible introduction of preventive measures. We are fully aware that current biological treatments work best when they are combined with psychosocial intervention, and expect that future biological treatments and preventions will also involve appropriate nonbiological considerations. Psychosocial treatments are covered elsewhere in this issue. Here we look at how modern genetics, pre- and perinatal factors, early and sustained intervention, and new medications are likely to decrease both the number of individuals with schizophrenia and the severity of the illness.

Maternal exposure to influenza and risk of schizophrenia: a 22 year study from The Netherlands

We investigated any effect of prenatal exposure to influenza during gestation on subsequent risk of schizophrenia using a national sample from The Netherlands. Dates of births of all Dutch-born schizophrenia (ICD-9) patients (n = 10,630) admitted to hospitals for the first time between 1970 and 1992 were examined in relation to the occurrence of influenza epidemics between 1947 and 1969. As a measure of prevalence of influenza, the number of deaths from influenza per month in The Netherlands was used. A Poisson regression analysis revealed that an increase in the prevalence of influenza 3 months prior to birth was followed by an increase in births of preschizophrenics, although this fell outside statistical significance (p = .11). However, the effect became marked in typical schizophrenics (n = 4726), but not in less typical cases (n = 5389). For typical schizophrenics, the parameter estimate derived from the regression model indicates that there was a 10% increase (95% confidence interval: -1 to 22%) in preschizophrenic births for every 500 deaths from influenza 3 months before birth.

No association between prenatal exposure to influenza and autism

We examined the relationship between the number of autistic patients, obtained from the register of the National Autism Society (NAS), born each month between January 1953 and December 1988 in England, and the occurrence of influenza epidemics one to nine months before birth. The relative risk of developing autism, for exposure to influenza during gestation, was assessed by a Poisson regression model. Our results indicate that exposure to influenza epidemics during gestation is not associated with autism.

Prenatal exposure to influenza epidemics and risk of mental retardation

This study was undertaken to determine whether prenatal exposure to influenza epidemics increases the risk of mental handicap. The monthly birth frequencies of 827 first-admission individuals (mean age at admission 13 years) with a primary diagnosis of non-specific mental retardation, discharged from psychiatric hospitals in England and Wales, were examined in relation to the monthly death rates from influenza over the period 1953-1980. The relative risk of developing mental handicap when exposed to influenza epidemics during mid-gestation was assessed by a generalized linear model. Increased death rates from influenza, a measure of prevalence of the infection, were significantly associated with an increase in births of mentally handicapped individuals 6 months later. For every 1000 female deaths from influenza there was a 17% increase in births of mentally handicapped individuals 6 months later. Maternal exposure to influenza at approximately the third to fourth month of gestation may be risk factor for developing mental handicap.

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.