Is schizophrenia a neurodevelopmental disorder?

Schizophrenia: a disorder of neurodevelopment?

For the first time, there is a pathogenic hypothesis of schizophrenia based upon reasonable empirical data. The hypothesis is that schizophrenia is a disorder arising from aberrant brain development. The neurodevelopmental view of schizophrenia is supported by neuropathological, epidemiological and clinical findings. Here, the evidence in favour of the model is summarized, together with a consideration of its weaknesses.

Developmental trajectory and disease progression in schizophrenia: the conundrum, and insights from a 12-year prospective study in the Monaghan 101

Though conceptualised originally as a deteriorating disorder, some contemporary studies have been interpreted as challenging these foundations; more radically, it has been proposed that schizophrenia may be a 'static encephalopathy' of neurodevelopmental origin. The argument offered here is that schizophrenia is indeed a neurodevelopmental disorder, but that this is not in itself antithetical to later disease progression. Rather, the onset of psychosis may reflect the maturationally-mediated triggering of an active disease process that is associated with progressive deterioration unless attenuated by antipsychotic drugs. A developmental trajectory is proposed to link first or early second trimester dysplasia to the chronic course of the illness; from this, it is argued that schizophrenia is inherently a progressive disorder but that antipsychotic drugs may act to ameliorate this progressive component and thus confer on the disease course some of the characteristics of a 'static encephalopathy'. The 'true' natural history of an illness cannot be determined from studies in treated populations.

Molecular biological investigations into the role of the NMDA receptor in the pathophysiology of schizophrenia

OBJECTIVE

There is increasing acceptance that schizophrenia is associated with a generalised disorder in cortical neurodevelopment. The aim of this paper is to review the evidence that this disorder may be accounted for by abnormalities in mechanisms mediated by the main family of excitatory neuroreceptors in cortical brain systems, the N-methyl-D-aspartate (NMDA) glutamatergic receptors.

METHOD

The neurobiological evidence is presented for an abnormality in cortical development related to synaptic pathology in schizophrenia. The unique functions of the NMDA receptor in information processing are described, especially its role in learning and memory, and in neural plasticity and brain development. It is argued that the cellular and molecular mechanisms which underlie learning and memory also govern normal brain development. Studies examining abnormalities in glutamatergic transmission in schizophrenia are reviewed.

RESULTS

There is a substantial literature in support of the possibility that NMDA receptor abnormalities may be involved in the neurodevelopmental predisposition to schizophrenia, as well as in symptom production.

CONCLUSIONS

Research to determine the role of the NMDA receptor in the pathophysiology of schizophrenia is warranted and now feasible. To be successful, this research will require the application of molecular biology techniques to postmortem brain tissue studies, in addition to traditional histochemical approaches.

Women and schizophrenia: a review

OBJECTIVE

This is a selective review article which aims to explore current areas of research involving women with schizophrenia and to identify areas requiring future research.

METHOD

Research studies conducted both nationally and internationally are reviewed with an emphasis on a gender-based approach.

RESULTS

The review is divided into three sections. First there is an introduction including a brief consideration of the possible reasons for the noted lack of studies focussing on women with schizophrenia and a summary of the epidemiological evidence that has prompted interest in gender-based schizophrenia research. Second, there is a review of some studies that utilise gender as a paradigm to understand the pathophysiology of schizophrenia, and third, a discussion of the role of gender in management approaches is presented.

CONCLUSIONS

The main conclusion is that women have not been well represented in schizophrenia research. Female-specific management issues and a better understanding of the impact of schizophrenia on women require more gender-based research.

Levels of the growth-associated protein GAP-43 are selectively increased in association cortices in schizophrenia

The pathophysiology of schizophrenia may involve perturbations of synaptic organization during development. The presence of cytoarchitectural abnormalities that may reflect such perturbations in the brains of patients with this disorder has been well-documented. Yet the mechanistic basis for these features of the disorder is still unknown. We hypothesized that altered regulation of the neuronal growth-associated protein GAP-43, a membrane phosphoprotein found at high levels in the developing brain, may play a role in the alterations in brain structure and function observed in schizophrenia. In the mature human brain, GAP-43 remains enriched primarily in association cortices and in the hippocampus, and it has been suggested that this protein marks circuits involved in the acquisition, processing, and/or storage of new information. Because these processes are known to be altered in schizophrenia, we proposed that GAP-43 levels might be altered in this disorder. Quantitative immunoblots revealed that the expression of GAP-43 is increased preferentially in the visual association and frontal cortices of schizophrenic patients, and that these changes are not present in other neuropsychiatric conditions requiring similar treatments. Examination of the levels of additional markers in the brain revealed that the levels of the synaptic vesicle protein synaptophysin are reduced in the same areas, but that the abundance of the astrocytic marker of neurodegeneration, the glial fibrillary acidic protein, is unchanged. In situ hybridization histochemistry was used to show that the laminar pattern of GAP-43 expression appears unaltered in schizophrenia. We propose that schizophrenia is associated with a perturbed organization of synaptic connections in distinct cortical associative areas of the human brain, and that increased levels of GAP-43 are one manifestation of this dysfunctional organization.

Relationship between impairment of prenatal brain growth and family history of psychosis in schizophrenia

Recently McNeil et al. (1993b), showed that schizophrenics had smaller head circumference (HC) at birth than controls. This small head size at birth was observed more commonly among schizophrenics without a family history of psychosis than among familial schizophrenics, suggesting that some prenatal environmental factors, rather than genetic factors, are related to the impaired brain growth in utero. We attempted to replicate this finding in 100 Japanese schizophrenics (DSM-III-R), using contemporaneous data on body measures at birth. Conversely, in the current study, HC at birth was found to be significantly smaller in schizophrenics with a family history of psychosis (N = 19) than those without (N = 81). A multiple regression analysis, controlling for gender, gestational age, maternal age, birth order and year of birth, yielded an overall reduction of about 1 cm in HC at birth among familial schizophrenics compared with non-familial schizophrenics. When HC at birth in family history positive and negative groups was compared separately with the local population norms with adjustment for gender and gestational age, familial and non-familial schizophrenics were both found to have significantly smaller HC at birth, although the difference was less marked for the latter. These results suggest that schizophrenics have delayed cerebral development in utero, and that genes which operate on prenatal neurodevelopment may play an important role in the aetiology of schizophrenia, although it is possible that some environmental factors may also be involved in the impaired brain growth.

Relationship between in utero exposure to influenza epidemics and risk of schizophrenia in Denmark

Several recent epidemiological studies suggest that exposure to influenza during gestation increases the risk of later developing schizophrenia. Inconsistency exists, however, particularly in studies that have examined the relationship between the prevalence of influenza and the monthly number of schizophrenic births, over many years. Our sample (N = 9462) was obtained from a Danish computerized case register, and consisted of schizophrenia patients born between 1915 and 1970, and first admitted to Danish psychiatric hospitals between 1971 and 1991. The study sample was chosen to represent "incidence cases" to allow us to calculate the population attributable risk fraction (PAF). The temporal correlation of fluctuations in the prevalence of influenza and fluctuations in the monthly number of preschizophrenic births was examined using a Poisson regression analysis. Exposure to influenza 4 months prior to birth (i.e., about the 6th month of gestation) was significantly associated with an increased risk of later schizophrenia, especially for narrowly defined schizophrenia. The number of schizophrenic births was found to have risen by 12% (95% confidence interval: 1-24%) for every 100,000 cases of influenza in the 4th month before birth. Our model indicates the PAF to be 1.4%, that is, only 1.4% of the whole schizophrenic sample is attributed to prenatal exposure to influenza. Although maternal exposure to influenza during midgestation is not a major risk factor for schizophrenia, the elucidation of its causal mechanism may open the avenue to understanding the neurodevelopmental origins of the disease.

Schizophrenia and neurological soft signs: gender differences in clinical correlates and antecedent factors

Although it is recognized that patients with schizophrenia demonstrate more neurological soft signs (NSS) than control subjects, the significance and clinical correlates of these signs remain poorly defined. The present study examined 48 patients with DSM-III-R schizophrenia for evidence of NSS. The majority (98%) of patients demonstrated at least one NSS, although the range of scores was wide. There was no relationship between current dosage of neuroleptic medication and NSS score. Among males, there was a significant relationship between NSS and duration of illness. Males whose mothers experienced obstetric complications had higher NSS scores, while females with a family history of schizophrenia exhibited higher scores. These relationships in schizophrenia between NSS and factors of etiological importance wuch as obstetric complications and family history require further evaluation. The present findings are in accord with a body of evidence which suggests that gender may influence the impact of genetic and environmental factors on the neurology of the disorder.

Age-period-cohort analysis of the incidence of schizophrenia in Scotland

Studies examining a possible decline in the incidence of schizophrenia over the last two to three decades have paid little attention to the possible role of birth cohort effects. We collected data on a Scottish national sample of all schizophrenic patients, admitted for the first time between 1966 and 1990 (N = 11348; male = 6301). In an Age-Period-Cohort analysis, a full model, incorporating three factors, had a substantially better fit to the data than other models (especially, an Age-Period model), providing clear evidence of the presence of a cohort effect. After adjustment for the effects of age and period, there was a 55% reduction in the rate of schizophrenia in men and a 39% fall in the number of women over the 50-year birth period from 1923 to 1973. The marked decline in the first admission rates observed in Scotland cannot, however, be attributed entirely to this cohort effect. Rather, a greater proportion of the declining first admission rates (88%) is ascribed to the period effect (i.e. artefactual or causally related cross-sectional effects). Nevertheless, the fact that a birth-cohort effect accounts for part of the declining incidence, suggests that causal environmental factors operating early in life have been diminishing in intensity.

Validation of three dimensions of schizophrenic symptoms in a large unselected sample of patients

A principal components analysis was conducted upon current symptoms and signs rated in a sample of 329 essentially unselected patients with schizophrenia. Three dimensions emerged clearly and closely resembled those previously described in smaller, more selected samples. The clearly defined psychotic dimensions were related in turn to: (i) other mental state variables; (ii) physical treatments administered; (iii) movement disorder; (iv) demographic and historical features; and (v) cognitive function. The correlates of the three dimensions were very different. The clarity of separation achieved in this investigation provides strong support for the view that the three psychotic dimensions of 'poverty', 'hallucinations and delusions' and 'disorganization' are valid and may well have different underlying pathophysiologies.

Small head circumference at birth in schizophrenia

The growing evidence for neurodevelopmental basis to schizophrenia has focused attention on the prenatal development of individuals who later develop the illness. Several previous studies have shown reduced birth weight (BW) in schizophrenics and one recently reported smaller birth head circumference (BHC). The current study compared 67 DSM-III-R schizophrenics and a general population group of 1640, using information obtained from contemporaneous birth records. When gestational age and gender were controlled for, no significant difference was found in BW between the schizophrenics and the comparison population. However, the preschizophrenics showed significantly smaller BHC for gestational age, suggestive of slower fetal brain growth.

Schizophrenia, bacterial toxins and the genetics of redundancy

The hypothesis proposed is that episodes of bacterial toxaemia occurring early in life cause subtle brain damage which predisposes to schizophrenia. The damage is most likely to occur in individuals who have one or more mutations in a large set of genes controlling aspects of the immune response to infection. These genes, numbering several hundreds or even thousands, control a vital but highly redundant system. Schizophrenia, by reducing fertility, causes selective pressure against the mutations which would otherwise accumulate in the genome and degrade our ability to fight infection. This hypothesis is consistent with the key features of the disease which include a strong genetic component, neuroanatomical abnormalities, a seasonal influence, lack of association with HLA subtypes and the observation that the frequency of schizophrenia is similar in widely different populations. If bacterial toxins also have a role in precipitating acute psychosis, then the age incidence of schizophrenia can be explained.

Age-specific neurotoxicity in the rat associated with NMDA receptor blockade: potential relevance to schizophrenia?

Agents that block the N-methyl-D-aspartate (NMDA) subtype of glutamate receptor induce a schizophrenialike psychosis in adult humans and injure or kill neurons in several corticolimbic regions of the adult rat brain. Susceptibility to the psychotomimetic effects of the NMDA antagonist, ketamine is minimal or absent in children and becomes maximal in early adulthood. We examined the sensitivity of rats at various ages to the neurotoxic effects of the powerful NMDA antagonist, MK-801. Vulnerability was found to be age dependent, having onset at approximately puberty (45 days of age) and becoming maximal in early adulthood. This age-dependency profile (onset of susceptibility in late adolescence) in the rat is similar to that for ketamine-induced psychosis or schizophrenia in humans. These findings suggest that NMDA receptor hypofunction, the mechanism underlying the neurotoxic and psychotomimetic actions of NMDA antagonists, may also play a role in schizophrenia.

Psychosis and substance abuse: cause, effect or coincidence?

An association between substance abuse and major psychiatric illness is increasingly well recognised, but most studies have been conducted in the USA and have focussed upon patients with schizophrenia rather than other disorders. We conducted a survey of 38 consecutively admitted patients with DSM-III-R functional psychoses. A semi-structured substance abuse interview was administered and a urine specimen for drug metabolite screening requested. The prevalence of cigarette smoking (63%) and current illicit drug use (26%) were higher than general population norms. The 16 subjects with schizophrenia and related disorders were more likely to smoke cigarettes than the 22 patients with an affective disorder (p = 0.008, odds ratio 8.4, 95% Cl 1.3-69.6), and showed tendencies to more illicit drug and alcohol consumption. Illicit drug users were more likely to have a forensic history and less likely to have entered further education. Substance abuse is common among patients with psychoses, particularly in those with schizophrenia and related disorders. All psychotic patients should have a detailed drug history taken, and therapeutic attempts made to reduce consumption.

The relationship of minor physical anomalies and other putative indices of developmental disturbance in schizophrenia to abnormalities of cerebral structure on magnetic resonance imaging

Minor physical anomalies, together with obstetric complications, family history, and handedness status, were assessed to explore putative neurodevelopmental disturbance(s) in patients with schizophrenia whose cerebral structure had been examined previously by magnetic resonance imaging. Minor physical anomalies were related to negative symptoms in males and to premorbid intellectual function in females, but not to ventricular volume; however, three patients with evident neurodevelopmental anomalies of the ventricular system showed prominent minor physical anomalies. In exploratory analyses, obstetric complications were associated with left ventricular asymmetry, and a positive family history with inverse profiles of asymmetry in males vs. females; non-right-handedness was associated with increased ventricular volume in males but with poorer premorbid intellectual function in females. This nexus of relationships and their gender specificities suggest early dysmorphogenesis in schizophrenia that is related to sexual dimorphism.

A prospective follow-up study of brain morphology and cognition in first-episode schizophrenic patients: preliminary findings

Brain morphological abnormalities have been reported in several independent investigations of chronic schizophrenic patients. The present study is a prospective 4-year follow-up of first-episode schizophrenic patients to determine whether some of these abnormalities may be a consequence of regional brain structural change over time after the onset of a first psychotic episode. Whole hemisphere, temporal lobes, superior temporal gyrus, hippocampus, caudate, corpus callosum, and lateral ventricles were measured in a series of MRI scans taken over a 4-year period in 20 patients and five controls. Total volume reduction was noted in both hemispheres to a greater degree in patients than controls. When adjusted for total brain size, left ventricular enlargement occurred in patients, but not controls, over time. These preliminary data suggest that subtle cortical atrophy may be occurring over time after the onset of illness.

Sequential cross-sectional and 10-year prospective study of severe negative symptoms in relation to duration of initially untreated psychosis in chronic schizophrenia

Current clinical correlates of duration of initially untreated psychotic symptoms were investigated in a cross-sectional analysis followed by a 10-year prospective study among 88 in-patients with a long-standing schizophrenic illness, many of whom had experienced prolonged periods of untreated psychosis due to illness onset and hospital admission in the pre-neuroleptic era. After controlling for the effects of age, and duration and continuity of subsequent neuroleptic treatment, the primary clinical correlate of duration of initially untreated psychosis was muteness. Over the subsequent 10-year-period, no new cases of muteness emerged and some existing cases of muteness partially resolved, though the speech that emerged remained very sparse and revealed generally gross cognitive debility. The pathophysiology underlying active, unchecked psychosis may also constitute an active morbid process that is associated with the further progression of severe negative symptoms and cognitive dysfunction in the long-term.

Low birth weight and schizophrenia

BACKGROUND

Low birth weight has been postulated to be a risk factor for schizophrenia.

METHOD

Obstetric history, premorbid adjustment, and cognitive function during admission were assessed in 167 patients with DSM-III schizophrenia or affective psychosis.

RESULTS

A birth weight of less than 2500 g was significantly more common in patients with schizophrenia than in those with affective psychosis. Schizophrenic patients as a group had significantly lower mean birth weight, a finding which was particularly marked after controlling for sociodemographic confounders. In schizophrenic men, lower birth weight was highly significantly correlated with poorer premorbid social and cognitive ability, and with impairment of adult cognitive function.

CONCLUSIONS

Neurodevelopmental impairment may cause poor foetal growth, and schizophrenia in adult life.

Circumscribed malformation and nerve cell alterations in the entorhinal cortex of schizophrenics. Pathogenetic and clinical aspects

A postmortem histological comparison of 5 selected cases of schizophrenia with 5 non-schizophrenic controls showed a circumscribed malformation of the entorhinal cortex. The cortical alterations consisted mainly of a lack or a change of the characteristic island formations in layer II pre-alpha. Further, there were atypical neurons in layers II and III showing a conspicuous decrease of volume, often a change of the shape. They lay either in clusters or in columnar formations. These cells were considered "young neurons". The changes varied considerably from case to case and sometimes extended to all entorhinal layers. In one case the extension of the changes is described by means of serial sections in steps which extend over the whole rostral entorhinal region. Here, the striking architectural changes were formed in an exactly circumscribed sector and did not extend to the rostral hippocampal formation. On the whole, the changes are regarded as local migrational disturbances that occur during the second trimester of brain development. Neuronal displacements like these could give rise to various aberrant connections within the limbic system and related structures (e.g. the central position of the entorhinal region in circuits such as the entorhino-hippocampal loop, entorhinol-insula and entorhino-orbitofrontal reciprocal connections). Whereas alterations of the genetic programming of cell migrations may be suspected, various environmental influences (e.g. viral infections during the months III-V of pregnancy) appear to play a significant role. The malformations may be a decisive vulnerability factor for the later manifestation of the illness.

Is schizophrenia due to excessive synaptic pruning in the prefrontal cortex? The Feinberg hypothesis revisited

Several lines of evidence support the notion that a substantial reorganization of cortical connections, involving a programmed synaptic pruning, takes place during adolescence in humans. A review of neurobiological abnormalities in schizophrenia indicates that the neurobiological parameters that undergo peripubertal regressive changes may be abnormal in this disorder. An excessive pruning of the prefrontal corticocortical, and corticosubcortical synapses, perhaps involving the excitatory glutamatergic inputs to pyramidal neurons, may underlie schizophrenia. A reciprocal failure of pruning in certain subcortical structures, such as lenticular nuclei, may also occur. Several developmental trajectories, related to early brain insults as well as genetic factors affecting postnatal neurodevelopment, could lead to the illness. These models would have heuristic value and may be consistent with several known facts of the schizophrenic illness, such as its onset in adolescence and the gender differences in its onset and natural course. The relationship between these models and other etiological models of schizophrenia are summarized and approaches to test relevant hypotheses are discussed.

Obstetric complications and schizophrenia. A case-control study

Schizophrenics have been repeatedly found to experience more obstetric complications (OCs) at birth. The meaning of such a finding is debated, and the aim of this study is to contribute to the understanding of OCs' aetiological role in schizophrenia. We compared a group of schizophrenic patients with their siblings and controls, on the basis of obstetric files stemming from the same University Hospital Maternity Ward. Schizophrenic patients had more frequent umbilical cord complications and atypical presentations, as well as higher scores on a scale measuring OCs linked to possible neonatal asphyxia.

Twin concordance for congenital and adult-onset psychosis: a preliminary study of the validity of a novel classification of schizophrenia

As a test of the hypothesis that the psychoses can be divided into congenital and adult-onset forms, we applied operational criteria for these two disorders to the case summaries of 24 monozygotic and 33 dizygotic schizophrenic twin pairs. Our results indicate that the reliability and validity of this novel classification are comparable with the best of the existing systems and support further investigation of the hypothesis.

Evidence for a gender-specific decline in the rate of schizophrenia in rural Ireland over a 50-year period

The issue of whether the incidence rate of schizophrenia may have declined over recent decades has generated considerable controversy. This study sought to ascertain and interview all patients who satisfied contemporary diagnostic criteria for schizophrenia within a defined and unusually homogeneous region of rural Ireland having a total population of 25,178 people; morbid risk for schizophrenia was then examined by quinquennia of birth from 1920-24 to 1965-69. Morbid risk appeared essentially constant for persons born between 1920 and 1939 but fell by 37% for those born between 1940 and 1969, the fall being considerably more prominent in females (-56%) than in males (-19%). Attention is focused on sexual dimorphism in cerebral development and on temporal changes in endogenous or exogenous factors that influence the rate of occurrence of schizophrenia in females.

Regional neuropathology in schizophrenia: where are we? Where are we going?

This paper presents a neurologic formulation for the clinical features of the schizophrenic syndrome, and tests it against a systematic, region by region review of available postmortem neuroanatomical and neuropharmacological data. Based on this review a model is proposed that postulates a developmental lesion affecting the midline neurotransmitter-specific ascending projection systems. Due to the facilitatory role these systems play in the development of the brain regions to which they project, such a lesion is one parsimonious, and testable, explanation for virtually all the clinical, laboratory, and pathological findings reported to date in schizophrenia research. A case is made for establishing a global antemortem-postmortem collaboration using a Latin square design; the alternative may be that, as has happened in the past, the best efforts of dilligent researchers around the world may lead to little improvement in our understanding of schizophrenia.

A comparative study of obstetric history in schizophrenics, bipolar patients and normal subjects

Information on pregnancy and birth complications was collected for 46 patients with DSM-IIIR schizophrenia or bipolar disorder and for 23 normal controls. Pregnancy complications were more frequent and birth complications more frequent and more severe in schizophrenics than in bipolar patients or in normal controls. In contrast with other findings in the literature, more obstetric complications (OCs) were found in female than male schizophrenic patients.

A computerized magnetic resonance imaging study of corpus callosum morphology in schizophrenia

The hypothesis tested was that, in schizophrenia, corpus callosum size would be reduced, particularly in the region responsible for communication between both temporal lobes. This is supported by knowledge of: (a) anatomical homotopicity and functional specialization of fibres within the corpus callosum; (b) evidence linking structural and functional deficits of the corpus callosum and left temporal lobe with schizophrenia; and (c) that temporal lobe neuronal fibres pass through the middle region of the corpus callosum. Brain area and corpus callosum areas, widths and length were measured on mid-sagittal MRI scans using a computer outlining method. Scans from 30 schizophrenics and 44 normal subjects were compared. Mid-sagittal brain area, corpus callosum area, length and anterior widths were reduced in the schizophrenic group compared with controls. A significant area difference between schizophrenics and controls was seen in the mid-corpus callosum which communicates between the temporal lobes, including the superior temporal gyri. In schizophrenics, corpus callosum area reduction was not accounted for by brain area shrinkage alone. Differences between the two groups were accounted for by comparisons between males only. These findings support the hypothesis and the possibility that localized abnormalities of bilaterally connected brain regions might have secondary effects on their homotopically distributed fibres within the corpus callosum.

A case-control study of family history and cerebral cortical abnormalities in schizophrenia

The relationship between family history of psychosis and cortical sulcal widening on CT scans was investigated. Forty-two schizophrenic subjects with a positive family history were individually matched to 42 schizophrenics with no documented family history and 42 healthy controls. Abnormally wide sulci, as defined on the basis of the normal control data, were significantly more common in the family history negative group (9/42) than in the family history positive group (1/42) or the controls (2/36). No significant correlation was found between cerebral cortical ratings and ventricular size.

Schizophrenics with a family history of bipolar disorder. Possible involvement of obstetric complications

The case reports of two DSM III-R schizophrenic patients with a family history of bipolar disorder are presented. The two patients had a history of severe obstetric complications (OCs). These cases are discussed in the light of neurodevelopmental theories of schizophrenia and in the continuum view of psychosis.

Risk of schizophrenia in adults born after obstetric complications and their association with early onset of illness: a controlled study

OBJECTIVE

To determine whether obstetric complications occur to excess in the early histories of individuals who go on to develop schizophrenia when compared with controls, and to seek clinical correlates of any such excess.

DESIGN

Contemporaneous maternity hospital records were identified and extracted verbatim, and these extracts evaluated for obstetric complications by two independent assessors who were blind to subjects' status.

SUBJECTS

65 patients having an ICD-9 diagnosis of schizophrenia, the records of the previous same sex live birth being deemed to be those of a control subject.

MAIN OUTCOME MEASURE

Presence of one or more obstetric complications recorded in maternity notes of patients and controls.

RESULTS

When two recognised scales for specifying obstetric complications were used the patients with schizophrenia were significantly more likely than controls to have experienced at least one obstetric complication (odds ratio 2.44, 95% confidence interval 1.08 to 6.03). Patients also showed a greater number and severity of and total score for obstetric complications, fetal distress being the only complication to occur to significant individual excess (present in five (8%) patients, absent in controls). There was a marked sex effect, male patients being more vulnerable (odds ratio 4.24, 1.39 to 12.90) to such complications. Obstetric complications in patients were unrelated to family history or season of birth but were associated with a significantly younger age at onset of illness (mean difference--4.5 years,--1.2 to--7.8 years).

CONCLUSIONS

Patients with schizophrenia, particularly males, have an excess of obstetric complications in their early developmental histories, and such complications are associated with a younger age at onset of their disease. Though the data are not conclusive, they also suggest that obstetric complications may be secondary to yet earlier events.

Sex and schizophrenia: vive la différence

Epidemiological research in schizophrenia is back in fashion and has taken an iconoclastic turn. Received truths about schizophrenia had a reassuring stability about them, rather like Euclidean geometry. In contrast to, and perhaps in reaction to, the frustrating nebulousness of the disorder itself, its distribution had the attributes of a universal constant: incidence and symptoms unchanging over time and across space–and between the sexes. Dissenting voices were few, but now are growing in number and volume. One sex difference, that of age at onset of schizophrenia, has been accepted since Kraepelin's time, although is still unexplained. But sex differences in incidence, course, and symptoms are now being mooted which hint at sex-dependent differences in aetiology. Much of the re-examination of this issue has sprung from the work of Jill Goldstein and colleagues at Harvard, Robin Murray, David Castle, and colleagues at the Institute of Psychiatry, as well as others, such as Mathias Angermeyer in Mannheim.

From an animal model of an attentional deficit towards new insights into the pathophysiology of schizophrenia

The paper presents an animal model of schizophrenic-like attentional deficit, consisting of an inability to ignore irrelevant stimuli. It is based on the paradigm of latent inhibition (LI), in which animals learn to ignore repeatedly presented stimuli not followed by meaningful consequences. In a series of experiments it was demonstrated that the capacity to ignore irrelevant stimuli is lost in rats treated with systemic or intra-accumbens injections of amphetamine, in normal volunteers given amphetamine, in high "psychosis-prone" persons, in acute schizophrenic patients and in untreated male adult rats that were raised until weaning under conditions of extremely restricted stimulation. In addition, LI is lost following the disruption of the hippocampal input to the nucleus accumbens. In all of the above conditions tested for antagonism by anti-psychotic drugs a loss of LI is reversed. On the basis of these results we propose an animal model which accommodates a neurodevelopmental dysfunction, hippocampal pathology, mesolimbic DA overactivity, vulnerability to stress, and gender differences, all of which have been postulated as factors in the pathophysiology of schizophrenia.

Is the concept of frontal-subcortical dementia relevant to schizophrenia?

A syndrome of subcortical dementia has been described in conditions predominantly affecting the basal ganglia or thalamus, structures that have also been implicated in the pathogenesis of schizophrenia. There are similarities between subcortical dementia and the type II syndrome of schizophrenia, in terms of clinical features, pattern of neuropsychological deficits, pathology, biochemistry and data from brain-imaging studies. These similarities raise the possibility that certain schizophrenic symptoms, particularly negative symptoms and disturbance of movement, may reflect subcortical pathology. Neuropsychological deficits of presumed frontal lobe origin have been reported in some schizophrenic subjects. The occurrence of such deficits in a condition in which frontal lobe pathology has not been clearly demonstrated may be explicable in terms of a subcortical deafferentation of the pre-frontal cortex.

Dermatoglyphic evidence of fluctuating asymmetry in schizophrenia

Fluctuating asymmetry provides a measure of an organism's capacity to buffer adverse factors that could disturb its development. It is estimated from the differences between theoretically identical right- and left-sided structures. Dermatoglyphic fluctuating asymmetry has been recently used to investigate developmental disorders. Fingerprints and palm prints of schizophrenic patients, which had been the subjects of an earlier report of conventional dermatoglyphic trait frequencies, were reanalysed to determine their level of fluctuating asymmetry. A review of the diagnostic protocols and clinical records used in the original study indicated that most of the 482 subjects would have met DSM-III-R criteria for schizophrenia. The schizophrenic sample had significantly higher levels of fluctuating asymmetry on four dermatoglyphic traits, the finger-ridge counts, fingerprint patterns, the palmar atd angles and palmar a-b ridge counts, than controls. This finding supports the results of two earlier studies, and its relevance to the roles of genetics, foetal insults, and developmental anomalies of the brain in the aetiology of schizophrenia is discussed.

A developmental perspective on the pathology and neurochemistry of the temporal lobe in schizophrenia

Neuropathological, neuroimaging, clinical and epidemiological evidence suggests that many cases of schizophrenia are developmental in origin. Dysplastic changes in the medial temporal lobes appear to be of particular importance. However, research implicating a neurodevelopmental origin for schizophrenia has proceeded largely in isolation from knowledge concerning the neurochemistry of the disorder. This paper attempts to integrate these disparate lines of research, and examines the role of trophic mechanisms in the formation of the hippocampus. Those neurotransmitters which have been most consistently found to be abnormal in the temporal lobes of schizophrenics (excitatory amino acids and CCK), are involved in the control of hippocampal development. We suggest that these neurotransmitter findings are the residue of abnormalities in their role as trophic factors in foetal or neonatal life, and that the latter contribute to the developmental aberrations considered fundamental to schizophrenia.

Abnormalities of Cerebral Structure in Schizophrenia on Magnetic Resonance Imaging: Interpretation in Relation to the Neurodevelopmental Hypothesis

The nature of abnormalities of cerebral structure evident in schizophrenia on magnetic resonance imaging is considered in relation to the neurodevelopmental hypothesis of the disorder. While schizophrenic patients showed increased ventricular volume, the extent of increase with age was comparable with that evident in controls and was unrelated to duration of illness. Conversely, cortical atrophy was evident only in patients, and this increased markedly with age and duration of illness. Such findings could be suggestive of two distinct pathophysiological processes in schizophrenia, but a schema for their reconciliation with the neurodevelopmental hypothesis is elaborated.

First onset and early symptomatology of schizophrenia. A chapter of epidemiological and neurobiological research into age and sex differences

In the frame of the ABC (Age, Beginning and Course) Schizophrenia Project we studied the influence of age and sex on first-ever onset, symptom manifestation and early course up to first admission in schizophrenia by using a large, representative sample of first-admitted schizophrenic patients. The results showed that the two variables had surprisingly little bearing upon the core symptoms, particularly on negative and other most frequent symptoms and on first-rank symptoms. In 70% of the cases schizophrenia started solely with negative symptoms, in 20% with negative and positive and in 10% with positive symptoms only. In most of the cases symptoms accumulated exponentially up to the first acute episode with positive symptoms appearing considerably later. The age differences observed concerned secondary phenomena associated with developmental factors. Such phenomena, i.e. anxiety, depression and the cognitive formation of delusions, can be interpreted as responses to the psychosis. Also the sex differences, which culminated in far more frequent socially negative disease behaviour in males, were limited to secondary phenomena. This positive and negative core symptomatology of schizophrenia seems to be astonishingly uniform and fairly independent of age and sex at this early stage of the disease. The only remarkable difference was a three to four years higher mean age of onset in females. We were able to show in animal experiments and to confirm in a clinical study that this finding is attributable to a neuromodulatory effect of estrogens on the sensitivity of D2 receptors in the brain. Apparently, estrogens raise the vulnerability threshold until menopause and have a slight neuroleptic-like effect on the symptomatology in acute schizophrenic episodes.

Low birth weight and a family history of schizophrenia predict poor premorbid functioning in psychosis

Risk factors thought to predispose to schizophrenia, and premorbid functioning, were assessed blind to diagnosis by interviewing the mothers of 73 patients with DSM-III schizophrenia or affective psychosis. Higher risk of schizophrenia in relatives, lower mean birth weight, a more frequent history of obstetric complications, and poorer educational achievement distinguished the patients with schizophrenia from those with affective psychosis. Low birth weight and obstetric complications each predicted childhood schizoid and schizotypal traits. Poor social adjustment between ages 5 and 11 was predicted by low birthweight and by a family history of schizophrenia.

Familial thyroid disease and delayed language development in first admission patients with schizophrenia

One hundred consecutive first admission patients with a DSM-III-R diagnosis of schizophrenia, schizoaffective disorder, or schizophreniform disorder were compared with 100 randomly selected community controls. Childhood histories of physical, medical, and perinatal trauma, as well as physical and cognitive development, were examined by structured interviews with all available mothers of patients and controls. The prevalence of specific psychiatric disorders and several medical illnesses among first degree and more distant relatives was determined by family history questionnaires. The patient group did not have an excess of childhood head injuries, serious infections, or perinatal/birth complications compared with controls. With social class level taken into account, it was found that the acquisition of reading skills occurred significantly later in patients than controls. Family histories of schizophrenia and thyroid disorders were significantly more frequent among patients than controls. These data fail to indicate any childhood physical or medical environmental trauma that could lead to an increased risk for schizophrenia, although patients were substance abusers to a greater extent than controls. This study also confirms the already known contribution of familial factors and suggests an association of the inheritance of thyroid disorders with schizophrenia. Delayed development of reading skills suggests that precursers of illness may appear early in life before psychosis is evident.

The clinical correlates of neurological soft signs in chronic schizophrenia

Among 16 chronic schizophrenic in-patients, all had at least one neurological soft sign (NSS), and 6 (40%) had definite neurodysfunction. NSS and TD scores were highly intercorrelated, and NSS were significantly correlated with neuroleptic drug exposure. NSS correlated positively with both positive and negative symptoms and cognitive impairment but not with cerebral ventricular size on CT. Patients with neurodysfunction had more positive and negative psychopathology, cognitive impairment and TD than those without. Cerebral ventricular sizes and family histories of schizophrenia were similar in both NSS groups. The presence of NSS may be a simple but important way of identifying a subgroup of schizophrenics with neurodevelopmental predisposing abnormalities, and vulnerability to TD.

Perinatal brain injury and cerebellar vermal lobules I-X in schizophrenia

Several studies, including our own, have reported atrophy of the cerebellar vermis in some schizophrenic patients. A recent report by Courchesne et al (1988) of hypoplasia of a developmentally specific region of the cerebellar vermis in autism prompted us to hypothesize that the cerebellar "atrophy" in some schizophrenic patients may also have developmental origins. We measured the area of the vermal lobules in 30 male schizophrenics. Contrary to expectation, the patients as a group had consistently larger cerebellar structures than the controls. Patients with perinatal injury had smaller structures than the nonperinatally injured group, but these measures were still larger than in the control subjects. Patients without perinatal injury differed from controls, having larger lobules VI-VII (p less than 0.03). These preliminary findings tentatively suggest a role for developmental factors for cerebellar structures in schizophrenia. Further research is needed to clarify the cerebellar vermal changes observed in some schizophrenic patients.