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

Case-control study of attention-deficit hyperactivity disorder and maternal smoking, alcohol use, and drug use during pregnancy

OBJECTIVE

To address the putative association between attention-deficit hyperactivity disorder (ADHD) and prenatal exposure to maternal cigarette smoking, drugs of abuse, and alcohol attending to potential confounding by familial ADHD, maternal depression, conduct disorder, and indicators of social adversity in the environment.

METHOD

A retrospective, hospital-based, case-control study was conducted with 280 ADHD cases and 242 non-ADHD controls of both genders. The case and control children and their relatives were systematically assessed with structured diagnostic interviews. Logistic regression analysis was used to determine the adjusted effect of prenatal exposure to substance use and ADHD.

RESULTS

ADHD cases were 2.1 times (95% confidence interval = 1.1-4.1;p = .02) more likely to have been exposed to cigarettes and 2.5 times (95% confidence interval = 1.1-5.5; p = .03) more likely to have been exposed to alcohol in utero than were the non-ADHD control subjects. Adjustment by familial psychopathology, Rutter's indicators of social adversity, and comorbid conduct disorder did not account for the effect of prenatal exposure to alcohol or the products of cigarettes.

CONCLUSIONS

ADHD may be an additional deleterious outcome associated with prenatal exposure to alcohol independently of the association between prenatal exposure to nicotine and smoke products and other familial risk factors for the disorder.

A plausible model of schizophrenia must incorporate psychological and social, as well as neuro developmental, risk factors

Subtle alterations in brain development caused by genes or early environmental hazards, such as obstetric complications, play a role in projecting some individuals on a trajectory toward schizophrenia. High-risk and cohort studies demonstrate that children destined to develop schizophrenia tend to have delayed milestones and subtle neuromotor and cognitive impairments (particularly in coordination and language). These neurocognitive problems lead to difficulties in interpersonal relations, and their progressive alienation makes these at-risk children more likely to harbor odd or paranoid ideas. This cascade of increasingly deviant development may then be compounded by brain maturational changes during adolescence with a resultant lability of the dopaminergic response to stress. As a result, the individual is more susceptible to the effects of the abuse of dopamine-releasing drugs, and to other risk factors such as migration or stressful life events; social isolation may be a common pathway underlying several of the social risk factors.

Signs of asphyxia at birth and risk of schizophrenia. Population-based case-control study

BACKGROUND

Previous research has found an association between obstetric complications and schizophrenia, but in many studies the sample size was limited, and no assessment of specific exposures was possible.

AIMS

To assess the role of different complications, and in particular to distinguish between disordered foetal development and hypoxia at birth.

METHOD

From the Stockholm County In-Patient Register and community registers, we identified 524 cases of schizophrenia and 1043 controls, matched for age, gender, hospital and parish of birth. Data on obstetric complications were obtained from birth records.

RESULTS

There was a strong association between signs of asphyxia at birth and schizophrenia (OR 4.4; 95% C11.9-10.3) after adjustment for other obstetric complications, maternal history of psychotic illness and social class.

CONCLUSIONS

Signs of asphyxia at birth are associated with an increased risk of schizophrenia in adults.

Obstetric complications and schizophrenia: prenatal underdevelopment and subsequent neurodevelopmental impairment

BACKGROUND

Many studies have shown an association between obstetric complications and schizophrenia.

AIMS

To investigate the possible relationship between prenatal underdevelopment, neurodevelopmental abnormality and subsequent schizophrenia.

METHOD

The literature was reviewed. In particular, by pooling data from recently published reports, we examined whether low birthweight (< 2500 g) is a risk factor for schizophrenia.

RESULTS

Low birthweight was significantly more common for subjects with schizophrenia than for control subjects: P < 0.00001, odds ratio 2.6 (95% CI 2.0 to 3.3). Individuals born prematurely are at greater risk of perinatal brain damage and subsequent neurodevelopmental abnormalities, which may constitute vulnerability to the development of schizophrenia. Patients with schizophrenia who had low birthweights also tended to have poor premorbid psychosocial adjustment.

CONCLUSIONS

Low birthweight is a modest, but definite, risk factor for schizophrenia. Brain damage associated with prenatal underdevelopment has a role in the pathogenesis of poor premorbid functioning and subsequent neurodevelopmental impairment in some cases of schizophrenia.

Obstetric complications in patients with depression--a population-based case-control study

BACKGROUND

To examine whether sufferers of affective disorders are more likely to be subject to obstetric complications than normal healthy people.

METHOD

Data based on prospectively recorded birth case-notes for patients with a diagnosis of depression (or related disorders) with early onset were compared to those of normal healthy controls, individually matched by gender, time and parity of birth, maternal age and marital status.

RESULTS

Forty-one case-controls pairs born between 1964 and 1978 were compared. No differences between cases and controls in gestational age or birthweight were significant, though depressive patients on average weighed 200 g less than controls at birth. Patients were more likely than controls to be small for their gestational age (22 vs. 1: chi(2)=4.34, P=0.03). They were significantly more likely than controls to have suffered at least one obstetric complication: 35 (85%) vs. 25 (60%), chi(2)=5.03, P=0.02; or more than one (two on average, as opposed to one on average among controls). No obstetric complication was seen significantly more among cases than controls, apart from bleeding during gestation, which was observed for four cases and no controls. The prevalence of complications with a clear brain damaging potential did not differ significantly between cases and controls: 11 (26%) vs. 8 (19%).

CONCLUSIONS

A developmental deficit, as indicated by lower birthweight and gestational age, may contribute to the risk of depressive breakdowns and affective disorders in later life. Severe, brain damaging obstetric complications are unlikely to be a significant risk factor for affective disorders, though some early onset cases may be accounted for by prenatal brain lesions.

LIMITATIONS

Sample size limits statistical power for isolation of a rare, single risk factor.

Risk for obstetric complications and schizophrenia

The goal of this study was to determine whether cases with schizophrenia or related disorders show a history of obstetric complications significantly more often than control subjects and, if so, whether the enhanced risk of a negative pregnancy outcome also extends to the non-schizophrenic offspring of cases. Data based on the obstetric birth case-notes of patients with diagnosed schizophrenia or related disorders were compared to those of normal 'healthy' control subjects; each case/control pair was individually matched by gender, time and parity of birth, maternal age and marital status. Forty-four case/control pairs born in Padova (Italy) between 1964 and 1978 were assessed for prenatal and perinatal complications, including abnormal gestational age or birthweight. No significant differences were observed between cases and control subjects in the general characteristics of birth; gestational age and birthweight in particular were strictly comparable between cases and control subjects. The schizophrenia spectrum patients (75%) were more likely than control subjects (59%) to have experienced at least one definite obstetric complication: odds ratio=2.07 (95% CI: 0.83-5. 15). Cases also suffered more complications per birth than control subjects (average 2:1). In particular, obstetric complications involving a clear damaging potential were seen significantly more often among cases than control subjects: 34% vs. 9%, Fisher's exact test, P=0.008 (odds ratio=5.17, 95% CI: 1.55-17.21). Moreover, severe obstetric complications were noted more often among males (n=13, 41%) than females (n=2, 15%). When any previous pregnancies of the mothers of patients were compared with those of the mothers of control subjects, mothers of cases were seen to have suffered unfavorable pregnancy outcomes significantly more often. In particular mothers of cases were seen to have had more miscarriages (OR=4.66), and pre-term births (OR=2.58) than control subects' mothers. Severe, brain-damaging obstetric complications would seem to be a possible antecedent to a diagnosis of schizophrenia or a related disorder in adulthood. Indeed, some early onset cases may be accounted for by prenatal brain lesions. This enhanced risk of negative pregnancy outcome may be under genetic control, contributing to the persistence of schizophrenia in the general population. The 'healthy' status of control subjects was ascertained indirectly, not by individual assessment of the subjects. The sample size limits the statistical power of calculations.

Labour and delivery complications and schizophrenia. Case-control study using contemporaneous labour ward records

BACKGROUND

Controversy continues regarding an association between obstetric complications and risk of schizophrenia in early adult life.

AIMS

To compare the rate of labour and delivery complications among persons who developed schizophrenia with controls; to establish whether any complication is associated with later schizophrenia.

METHOD

We located the labour ward records of 431 individuals with schizophrenia and of same-gender controls from the same hospital birth series. Mothers were matched by age, socio-economic group and parity. Individual complications were evaluated blindly using two obstetric complication scales.

RESULTS

Overall, the rate of labour and delivery complications for those who developed schizophrenia did not differ from that of controls. Males who had presented to psychiatric services before the age of 30 had a greater frequency of and more severe labour/delivery complications than their matched controls.

CONCLUSIONS

Other than among young-onset males we found no increase in labour and delivery complications among cases.

Labour and delivery complications at birth and later mania. An Irish case register study

BACKGROUND

Several reports postulate that manic depression and schizophrenia share environmental risk factors. Although obstetric adversity has been suggested as a risk factor for schizophrenia, few studies have examined its relationship to bipolar affective disorder.

AIMS

To assess the rate of obstetric complications incurred by patients with mania compared with controls.

METHOD

From the Dublin Psychiatric Case Register we identified individuals with a discharge diagnosis of mania and traced their birth records. Each case was matched with a control of the same gender, born in the same hospital, in the same year, matched for maternal age, parity and social class. Two obstetric complications scales were used to make blind evaluations of labour and delivery data.

RESULTS

Patients with mania did not experience a greater frequency or severity of labour and delivery complications than their matched controls. Rates of obstetric adversity were unrelated to the presence or absence of family history of psychiatric disorder. Obstetric adversity was unrelated to the age at first diagnosis.

CONCLUSIONS

These findings suggest that obstetric adversity is not a risk factor for later mania.

The age of onset of schizophrenia and the theory of anticipation

The clinical phenomenon called anticipation is usually defined as a decrease in age at onset and/or an increase in disease severity in successive generations of afflicted families. The purpose of this study was to examine variables that might influence anticipation in schizophrenia. A total of 380 Austrian patients, born between 1935 and 1964, met criteria for schizophrenia with ICD-8 or ICD-9, SADS-L and DSM-III-R criteria. The inclusion criteria also required medical records of patients to contain information about the year of birth, season of birth, age at onset, accidents or meningoencephalitic diseases during childhood, first- and second-degree relatives afflicted with schizophrenia, sibship size, sib order, education of patient, age of parents, occupation of parents, loss of parents, and place of residence. A Cox multiple-regression analysis showed three factors as having a significant influence on the age of disease onset, including year of birth (which had the largest influence), family history (sporadic cases showed an onset 2 years later than familial cases) and residence (urban dwellers showed psychotic symptoms approximately 1 year sooner than rural ones). A Kaplan-Meier Survival Analysis showed that younger cohorts had onset approximately 10 years earlier in sporadic and familial cases. This cohort effect might be a major source of bias in studies of anticipation.

Early and late environmental risk factors for schizophrenia

Although a high proportion of liability to schizophrenia is under genetic control, a number of environmental risk factors have been identified. The earliest of these are complications of pregnancy and birth, though whether these cause or reflect disturbed brain development is not absolutely clear. Neurodevelopmental deviance is also indicated by neurological dysfunction, social, behavioural and cognitive deficits during childhood. Immigrant status is a significant risk factor, especially prominent among the African Caribbean population in England, though the mechanism is unknown. Later environmental risk factors include adverse life events and substance abuse. An additive model of multiple genetic and environmental risk factors of small effect may be too simplistic and an interactive model where genetic predisposition is compounded by environmental effects is more in keeping with current evidence. The nature of such interactions can be explored more fully when susceptibility genes for schizophrenia are identified.

Premorbid IQ in patients with functional psychosis and their first-degree relatives

Numerous studies have found deficits in premorbid IQ in schizophrenic patients, but it is not clear whether this deficit is shared by (a) patients with other functional psychoses, and (b) relatives of these patients. Ninety-one schizophrenic patients, 66 affective psychotic patients (29 schizoaffective and 37 manic or depressed), and 50 normal control subjects were administered the National Adult Reading Test (NART) which provides an estimate of premorbid IQ. The NART was also completed by 85 first-degree relatives of schizophrenic patients and by 65 first-degree relatives of affective psychotic patients. After adjustments were made for sex, social class, ethnicity and years of education, schizophrenic patients had significantly lower premorbid IQ than their relatives, the affective psychotic patients and controls. Manic and depressed patients had significantly lower NART scores than their first-degree relatives, but schizoaffective patients did not, and neither group differed significantly from controls. There was no significant difference in premorbid IQ between patients who had experienced obstetric complications (OC+) and those who had not (OC-). Both OC+ and OC- schizophrenic patients differed significantly from their relatives, but the disparity was greatest between OC+ patients and their relatives. Relatives of OC+ schizophrenic patients had significantly higher IQ than relatives of OC- schizophrenic patients.

Obstetric complications in schizophrenia, schizoaffective disorder and normal comparison subjects

Previous studies have indicated that obstetric complications (OCs) may be risk factors for schizophrenia, but findings are inconsistent, and data about other diagnostic groups are relatively scarce. We compared the obstetric histories of subjects with schizophrenia, major affective disorder and normal controls. Our subjects included 61 schizophrenia, 26 schizoaffective, 28 major affective disorder patients and 21 normal controls. OCs were rated on the McNeil-Sjöström Scale using data from mothers reports and for a subsample from hospital and birth certificate records. The frequency of OCs did not differ statistically between diagnostic groups at any stage or for the three stages combined. OCs of at least level 4 were found in 69% of schizophrenia patients, 62% of schizoaffective patients, 68% of major affective disorder patients and 71% of the normal comparison group. OCs of at least level 5 were found in 23% of schizophrenia patients, 23% of schizoaffective patients, 21% of the major affective disorder patients and 14% of the normal comparison group. Our findings indicate that the etiologic significance of OCs may not be specific to schizophrenia.

Childhood-onset schizophrenia: rare but worth studying

Childhood-onset schizophrenia (defined by an onset of psychosis by age 12) is a rare and severe form of the disorder that is clinically and neurobiologically continuous with the adult-onset disorder. There is growing evidence for more salient risk or etiologic factors, particularly familial, in this possibly more homogeneous patient population. For the 49 patients with very early onset schizophrenia studied to date at the National Institute of Mental Health, there were more severe premorbid neuro-developmental abnormalities, a higher rate of cytogenetic anomalies, and a seemingly higher rate of familial schizophrenia and spectrum disorders than later onset cases. There was no evidence for increased obstetric complications or environmental stress. These data, while preliminary, suggest that a very early age of onset of schizophrenia may be secondary to greater familial vulnerability. Consequently, genetic studies of these patients may be particularly informative and may provide important etiologic information.

Early cerebro-craniofacial dysmorphogenesis in schizophrenia: a lifetime trajectory model from neurodevelopmental basis to 'neuroprogressive' process

Understanding the temporal origin(s) of schizophrenia, through specifying the earliest identifiable pathology, might indicate when to look for etiological factor(s), what their nature might be, and how course of illness might evolve from these origins. From this premise, earlier formulations are elaborated to offer a rigorously data-driven model that roots schizophrenia in cerebro-craniofacial dysmorphogenesis, particularly along the mid-line but involving other structures, over weeks 9/10 through 14/15 of gestation. However, a brain that has been compromised very early in fetal life is still subject to the normal endogenous programme of developmental, maturational and involutional processes on which a variety of exogenous biological insults and psychosocial stressors can impact adversely over later pregnancy, through infancy and childhood, to maturation and into old age, to sculpt brain structure and function; it should be emphasised that the effects of such endogenous programmes and exogenous insults on such an already developmentally-compromised brain may be different from their effects on a brain whose early fetal origins were unremarkable. From these early origins, a lifetime trajectory model for schizophrenia from developmental basis to 'neuroprogressive' process is constructed. Thereafter, consideration is given to what the model can explain, including cerebral asymmetry and homogeneity, what it cannot explain, what empirical findings would challenge or disprove the model, what cellular and molecular mechanisms might underpin the model, and what are its implications.

Schizophrenic patients and their first-degree relatives show an excess of mixed-handedness

An excess of mixed-handedness in schizophrenia has been reported. However, it is not established whether this excess is manifest in non-schizophrenic psychoses, nor whether the underlying etiology is genetic or environmental. We investigated these issues in a group of patients with schizophrenia (n=94), affective psychosis (n=63), other psychosis (n=26); their respective first-degree relatives (total n=183) and a control group (n=85). A narrow definition of mixed-handedness was used corresponding to groups 5 and 6 as defined by the Annett Handedness Questionnaire. We found an excess of mixed-handedness in the schizophrenic group compared with controls (OR=5.2, 1.4-18.6, p<0.006). There was no difference between the other psychotic groups and controls. There was a trend for an excess of mixed-handedness in the first-degree relatives (n=99) of schizophrenic patients (p=0.055), but not in the relatives of affective or other psychotic patients. There was a striking linear trend in the proportion of mixed-handedness between controls, the relatives and the schizophrenic patients (chi2=7.0, p=0.008). There was no association between mixed-handedness and a history of pregnancy or birth complications in the schizophrenic group. There was some evidence for impaired sociability in the mixed-handed schizophrenic patients. Our results indicate that the excess of mixed-handedness in schizophrenia may have a genetic basis.

Childhood-onset schizophrenia and obstetric complications: a case--control study

Obstetric complications (OCs) may be a risk factor for developing schizophrenia. In a recent study of a meta-analysis, the odds ratio for the development of the disorder in adulthood associated with OCs has been reported to be about 2.0 (i.e., a two-fold increase in risk). However, little attention has been paid to the involvement of OCs in risk of the development of childhood-onset schizophrenia. Therefore, the authors examined the relationship between OCs and childhood-onset schizophrenia. Thirty-three children, aged 8-13 years (average 12.4 years), meeting the DSM-III-R criteria for schizophrenia, were compared with controls (children with anxiety disorder) matched for sex and age. Childhood-onset schizophrenics showed significantly greater scores in all of the three measures of OCs according to Parnas et al.'s scale compared with controls. Moreover, those individuals exposed to OCs were 3.5 times as likely to develop schizophrenia as were those without OCs. The risk association between OCs and the disorder was far greater for male than for female schizophrenics. Our results, together with those in previous studies showing the association between OCs and adult-onset schizophrenia, suggest that childhood- and adult-onset schizophrenia may, at least in part, share a common neuropathogenesis.

The neurodevelopmental basis of schizophrenia: clinical clues from cerebro-craniofacial dysmorphogenesis, and the roots of a lifetime trajectory of disease

A "read-back" analysis of schizophrenia, from chronic illness, through the first psychotic episode, to psychosocial and neurointegrative abnormalities of childhood and infancy, leads to the intrauterine period as a primary focus for etiological events. Evidence for a characteristic topography of cerebro-craniofacial dysmorphology in schizophrenia is reviewed, and interpreted to estimate: (i) the timing of dysmorphic event(s); (ii) the nature of early cellular and molecular mechanisms which might determine that topography of dysmorphogenesis; and (iii) the population homogeneity of these processes. It is argued that early cerebro-craniofacial dysmorphogenesis in schizophrenia should be conceptualized as a first stage not in a static but rather in a dynamic, lifetime trajectory of disease.

Birth insult increases amphetamine-induced behavioral responses in the adult rat

We have previously reported that an apparently uncomplicated Caesarean section birth produces long-term alterations in steady-state levels of dopamine in the central nervous system of the rat. In addition, adult rats that had been born by Caesarean section, either with or without acute global anoxia, showed markedly greater dopamine release from the nucleus accumbens in response to repeated stress, in comparison to vaginally born controls. The aim of the present study was to test whether these birth complications also result in long-term changes in behavior mediated by dopamine systems. For this, we investigated effects of a low dose (0.5 mg/kg) of amphetamine on activity levels in three-month-old rats that had been born vaginally (control), by rapid Caesarean section, or by Caesarean section with 15 min of global anoxia. Amphetamine induced a significantly greater increase in locomotor activity in animals born by Caesarean section or by Caesarean section+ 15 min anoxia, in comparison to the drug's effects in vaginally born controls. Behavioral responses were further analysed from video recordings of the animals' behavior. In confirmation of automated activity counts, both animals born by Caesarean section and by Caesarean section + 15 min anoxia showed a significant increase in the duration and frequency of moving and a decrease in the duration and frequency of standing, in comparison to vaginally born controls. Animals delivered by Caesarean section showed a significant increase in the duration of sniffing and a decrease in the duration and frequency of grooming when compared to vaginally born controls. Animals delivered by Caesarean section + 15 min anoxia showed a significant increase in the duration and frequency of rearing, in comparison to controls. The pattern of behavioral changes observed indicates that, as adults, animals born by Caesarean section and by Caesarean section with added global anoxia both show heightened behavioral responses to amphetamine, in comparison to vaginally born animals. These findings highlight the sensitivity of dopamine pathways to variations in birth procedure and add experimental support to epidemiological evidence implicating birth complications in the pathophysiology of disorders involving central dopaminergic neurons, such as schizophrenia.

Further evidence of an association between maternal smoking during pregnancy and attention deficit hyperactivity disorder: findings from a high-risk sample of siblings

Investigated the role of maternal smoking during pregnancy in the etiology of attention deficit hyperactivity disorder (ADHD). Siblings of ADHD (N = 174) and non-ADHD (N = 129) probands were studied. Information on maternal smoking was obtained from mothers in a standardized manner blind to the sibling's ADHD and high-risk status (i.e., whether a sibling of an ADHD or non-ADHD proband). Fifteen (47%) of the high-risk siblings with ADHD had a history of maternal smoking during pregnancy compared with 33 (24%) of the siblings without ADHD (p = 0.009). This positive association remained significant after adjusting for socioeconomic status, parental IQ, and parental ADHD status. Lower IQ scores were found among those high-risk siblings whose mothers smoked during pregnancy compared with those whose mothers did not smoke. These findings extend our previous findings of an association between maternal smoking during pregnancy and ADHD. Moreover, they highlight the importance of programs aimed at smoking prevention in nonsmoking women and smoking cessation in smoking women of child-bearing age.

Gender and schizophrenia: association of age at onset with antecedent, clinical and outcome features

OBJECTIVE

There is evidence that gender and age at onset may have a bearing on schizophrenia. The extent to which this differential age at onset influences the clinical features of schizophrenia and its outcome in males and females is not clear.

METHOD

One hundred and twenty outpatients with DSM-III-R schizophrenia were studied to determine the association of antecedent, historical, clinical and 13-year outcome features with age at onset in females (n = 64) and in males (n = 56).

RESULTS

Males were significantly younger at illness onset but were not otherwise different from females in antecedent features of illness. For males, age at onset bore little relationship to outcome after 13 years. Females with early onset of illness were more likely to have experienced obstetric complications, to evidence poorer premorbid functioning, and to have a worse clinical, social and functional outcome than females with late onset.

CONCLUSIONS

Even though females may have a more benign illness than males, among females, those with early age at onset may be characterised by neurodevelopmental deviance and worse illness outcome.

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

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

Course of psychopathology, cognition and neurobiological abnormality in schizophrenia: developmental origins and amelioration by antipsychotics?

It is argued that schizophrenia has origins in events occurring during the first or early second trimester that are reflected in minor physical anomalies and which may at least in part predispose to later obstetric complications. This neurodevelopmental basis underlies certain neuromotor and psychosocial abnormalities of infancy and childhood, which are the early manifestations of what will be reconceptualised later as negative symptoms and (particularly frontal) cognitive dysfunction, but gives rise to positive symptoms only on the maturation of other systems necessary for their expression. This later emergence of psychosis may reflect an active morbid process that is associated with increased accrual of negative symptoms and of general (but not frontal) cognitive impairment that may be ameliorated by effective antipsychotic treatment. The psychological or biological basis of this heuristic process is poorly understood. Contemporary re-appraisal of any impact of antipsychotics on the long-term course of schizophrenia must take into account what is known of the origins of the disease process with which such drugs might interact. Much recent work continues to indicate that very early events, during the embryonic/fetal period, are important in, if not fundamental to, the genesis of schizophrenia; i.e. that there is a neurodevelopmental basis to the disorder. The present article seeks to establish a time-line relating early intrauterine adversity and dysmorphogenesis, through the onset of psychosis, to the chronic phase of the illness over adulthood; from this time-line, a schema is elaborated for a beneficial impact of antipsychotics on the course of psychopathology, cognition and, less clearly, neurobiological abnormality.

The membrane phospholipid hypothesis as a biochemical basis for the neurodevelopmental concept of schizophrenia

The neurodevelopmental hypothesis of schizophrenia is becoming an important feature of research in the field. However, its major drawback is that it lacks any biochemical basis which might draw the diverse observations together. It is suggested that the membrane phospholipid hypothesis can provide such a biochemical basis and that the neurodevelopmental phospholipid concept offers a powerful paradigm to guide future research.

The clinical stigmata of aberrant neurodevelopment in schizophrenia

The neurodevelopmental hypothesis of schizophrenia is currently a primary etiopathological model for schizophrenia. Its tenets derive from observations of epidemiological, postmortem, and brain imaging evidence of neurodevelopmental deviance. Clinical stigmata of neurodevelopmental arrest include the presence of obstetric complications, minor physical anomalies, abnormal dermatoglyphics, and childhood neuromotor precursors of adult schizophrenic illness. The relative importance of these stigmata and their relationship to brain imaging findings in schizophrenia are discussed.

Schizophrenia in people with intellectual disability: the role of pregnancy and birth complications

The literature suggests that mental illness is more common in people with intellectual disability than in the general population. Having reviewed the literature, Turner (1989) [Psychological Medicine 19, 301-14] suggested that about 3% of people with intellectual disability also have schizophrenia. As pregnancy and birth complications (PBCs) occur more commonly in people with intellectual disability than in the general population and are also implicated in the aetiology of schizophrenia, it is possible that these conditions share a common aetiology. This study reports on the occurrence of PBCs in those people with intellectual disability who develop schizophrenia. Fifty people with intellectual disability and schizophrenia were matched for age, sex, degree of intellectual disability and presence of epilepsy with a control group who did not suffer from schizophrenia or a schizophreniform psychosis. The obstetric history was obtained and events rated on a scale specifically designed for this study. This PBCs scale consists of six sub-scales covering areas of general maternal health, pregnancy, delivery, medication in labour, total medication score and neonatal score, as well as an overall total score. The study found that people with intellectual disability who develop schizophrenia have significantly higher rates of PBCs than controls. All of the sub-scales on the PBCs scale were significantly higher in people with schizophrenia, with the exception of the medication scales. Only five out of the 50 people with schizophrenia had not had a major obstetric complication, compared to 13 subjects from the control group. A number of abnormalities were specifically higher in people who later developed schizophrenia. These included: abnormally long or short labour; maternal episiotomy; maternal preeclamptic toxaemia; induction of labour; dysmaturity; maternal smoking in pregnancy; and a delay in neonatal crying. The results suggest that PBCs are important in the aetiology of schizophrenia in people with intellectual disability.

Maternal demographic correlates of increased history of obstetric complications in schizophrenia

Evidence that history of obstetric complications (OCs) may contribute to the development of schizophrenia has generated renewed focus on characteristics of mothers of preschizophrenics. We studied the relationship between increased history of obstetric complications (OCs) and maternal age, parity, and social class in 70 Research Diagnosis Criteria schizophrenic patients vs 70 demographically matched controls. The sample has previously been studied concerning OC rates in schizophrenic patients, their relationship to other presumptive etiological factors, as well as head circumference at birth. Parity was the only maternal characteristic significantly associated with increased OCs in mothers of preschizophrenics. As compared with nulliparous control mothers, nulliparous mothers of preschizophrenics had significantly increased rates of total OCs and labour/delivery complications, while primi- and multiparous mothers of preschizophrenics (vs parity-matched control mothers) did not have increased rates of OCs. Abnormal labour length was significantly increased in the nulliparous mothers of preschizophrenics. Previous findings of significantly reduced head circumference at birth in preschizophrenic neonates vs controls were reconfirmed selectively in the nulliparous group.

Influence of perinatal factors on the nucleus accumbens dopamine response to repeated stress during adulthood: an electrochemical study in the rat

Evidence from animal studies suggests that a period of anoxia to the fetus, a consequence common to many birth complications, results in long-term alterations in ventral mesencephalic dopamine function. Long-term functional changes in these dopamine neurons, in particular those that innervate the nucleus accumbens, also occur when animals are repeatedly stressed. In the present study, we examined the possibility that a period of anoxia during a Cesarean section birth can later alter the development of stress-induced sensitization of dopamine transmission in the nucleus accumbens. Dams were decapitated on the last day of gestation and the entire uterus was removed by Cesarean section. Pups were then delivered either immediately (Cesarean section group) or were immersed in a 37 degrees C saline bath for 3.5 or 13.5 min (Cesarean section+anoxia groups) before delivery of the pups. A fourth group of pups that were born vaginally served as controls (Vaginal group). Three to four months postnatally, animals from each group were implanted with monoamine-selective carbon-fiber electrodes into the nucleus accumbens. Voltammetry was used to monitor the dopamine response to each of five consecutive, once daily, 15-min exposures to tail-pinch stress. The results show that the first exposure to stress elicited dopamine signal increases of comparable amplitudes and durations in all animals. However, when compared to the initial stress response, the fourth and fifth exposures to tail-pinch elicited significantly longer-lasting dopamine responses in animals born by Cesarean section, either with or without added anoxia. In contrast, there was no significant day-to-day enhancement of the stress response in control, vaginally born animals. The findings reported here provide experimental support for the idea that birth complications may contribute to the pathophysiology of psychiatric disorders, in particular those that involve central dopamine dysfunction, such as schizophrenia. Specifically, our results suggest that subtle alterations in birth procedure may be sufficient to increase the sensitivity of mesolimbic dopamine neurons to the effects of repeated stress in the adult animal.

Does choice of scale for scoring obstetric complications influence their relationship to other etiological risk factors in schizophrenia?

The relationships between obstetric complications (OCs) and both family history of psychosis and season of birth were investigated among 70 demographically matched pairs of schizophrenic patients and control cases by using OC scores produced by three different OC scales. OCs were studied through blindly assessed hospital records. The particular OC scale had a great influence on the nature of the relationships observed between OCs and both family history and season of birth. Across the three scales, the findings varied from no relationship at all to completely opposite relationships between OCs and both of the other variables. More attention needs to be paid to OC methodological differences as a source of variation in study outcome, and attempts should be made to standardize methods for OC assessment across studies.

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.

Perinatal complications and schizophrenia. Data from the Maternal and Child Health Handbook in Japan

A number of studies have shown that schizophrenics have increased obstetric complications compared with controls, but conflicting negative results have also been reported. Similarly, some studies found that obstetric complications were more frequently observed among male or nonfamilial schizophrenics than their female or familial schizophrenic counterparts, but others reported negative or inverse results. Since 1948 in Japan, every pregnant woman has been assigned a Maternal and Child Health Handbook in which obstetricians have been obliged to fill in obstetric data. In the current study, perinatal complications assessed using the scale of Parnas et al. (1982), based on information from the maternal and child health handbook were compared between DSM-III-R-diagnosed schizophrenics (N = 59), their healthy siblings (N = 31), and controls (N = 108). We found that female schizophrenics had experienced significantly more perinatal complications than siblings and controls. We could not detect any significant association between perinatal complications and family history.

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

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

A case-control study of obstetric complications and later autistic disorder

The precise etiology of autism remains unclear. Obstetric adversity has been described as one factor that may increase the risk for the disorder. We examined the contemporaneous birth records of 49 children satisfying DSM-III-R criteria for autistic disorder, at four Dublin maternity hospitals, using the previous same-sex live birth in that hospital as a control. Data were evaluated blind to subject status using two obstetric complication (OC) rating scales. No significant differences in obstetric adversity were found between index and control groups. Autistic individuals did not differ from controls in terms of previously described risk factors for this disorder (maternal age, maternal parity, birth order, and low birth weight) in autism. These data do not support the view that OCs increase the risk for later autism.

New phenotype definition of attention deficit hyperactivity disorder in relatives for genetic analyses

The goal of the present investigation was to create a phenotype definition in relatives of probands that reflects a more genetic form of attention deficit hyperactivity disorder (ADHD). Logistic regression was applied to the first-degree relatives of ADHD and normal control probands to create a quantitative phenotype that combined information across psychiatric, cognitive, and demographic domains. Models were run separately in mothers, fathers, sisters, and brothers. Although there was some overlap between the variables retained in each model, no two models had exactly the same variables. Our results suggest that the use of fitted logits may be valuable as a potential index of caseness. Since different characteristics were included in different groups of relatives, our results suggest that gender and generation may moderate the expression of ADHD.

Further exploration of a latent class typology of schizophrenia

We previously derived a typology of schizophrenia from a latent class analysis of 447 first-contact non-affective functional psychotic patients from a defined catchment area. Here, using the same sample, we show that the three subtypes, 'neurodevelopmental' (Type A), 'paranoid' (Type B) and 'schizoaffective' (Type C) have different premorbid, phenomenological and treatment response characteristics. A canonical variate analysis of the three subtypes achieved partial separation between the first two subtypes, but the 'schizoaffective' type was less distinct.

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.

Do obstetric complications cause the earlier age at onset in male than female schizophrenics?

We compared the age at onset of 184 patients with functional psychoses with and without a history of obstetric complications (OCs) as defined by the scale of Lewis et al. (1989). OCs had no significant influence on the age at onset in those patients who had affective psychoses or were non-white. There were 73 white patients with a DSM-III-R diagnosis of schizophrenia. The mean age at onset of those 25 who had a history of at least one definite OC was 2.6 years earlier than that of the 48 patients with no history of OCs. This effect was entirely due to the male patients with histories of OCs who had, on average, a 3.5 years earlier age at onset. There were no gender differences in age at onset among schizophrenics without a history of OCs. We suggest that a subgroup of male patients with a history of OCs is responsible for the earlier age at onset in male compared to female schizophrenics.

Obstetric complications and schizophrenia: a case control study based on standardised obstetric records

BACKGROUND

There have been many reports of a higher incidence of 'obstetric complications' in the histories of schizophrenics than of controls, but because of the methodological shortcomings of most of these comparisons the relationship remains controversial.

METHOD

Comprehensive records covering all psychiatric hospital admissions and all hospital deliveries in Scotland since 1971 made it possible to identify the obstetric records of people born in 1971-74 who were subsequently admitted to hospital with a diagnosis of schizophrenia, and then to compare their standardised obstetric records with those of closely matched controls.

RESULTS

One hundred and fifteen schizophrenic/control pairs were compared. The former showed a highly significant (P < 0.001) excess of complications of both pregnancy and delivery. In particular, there was a significant excess of pre-eclampsia (10 v. 2) and of infants detained in hospital for neonatal care (18 v. 6).

CONCLUSION

The raised incidence of obstetric complications often reported in people with schizophrenia is genuine and probably contributes to the aetiology of the condition.

Obstetric complications and schizophrenia: a meta-analysis

BACKGROUND

This systematic review of the association between schizophrenia and obstetric complications (OCs) was performed to assess the degree of heterogeneity between studies and to quantify the increased risk of schizophrenia in exposed subjects.

METHOD

Twenty case-control, one prospective cohort and two historical cohort studies were identified using a MEDLINE search supplemented by a manual search and direct communication with other researchers. Individual odds ratios were calculated for each study and a pooled estimate produced. The effect of methodological variation between studies was further assessed by partitioning studies according to study characteristics.

RESULTS

Overall, there was no significant heterogeneity of effect between studies, and the pooled odds ratio for the exposure to OCs on subsequent development of schizophrenia was 2.0 (95% CI 1.6-2.4). However, partitioning according to study design revealed significant heterogeneity (z = -2.60, P < 0.01) between the pooled estimate from the case-control studies and that from the historical cohort studies. There was a gap on the funnel plot in the region of small studies finding no effect.

CONCLUSIONS

Although the result indicates that subjects exposed to OCs are twice as likely to develop schizophrenia, the analysis suggests that the observed association could be inflated by both selection and publication biases.

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.

Gender-specific changes since 1900 in the season-of-birth effect in schizophrenia

BACKGROUND

It was hypothesised that the size of the season-of-birth effect may have decreased in tandem with the apparent decline in the incidence of schizophrenia.

METHOD

Through the Aberdeen Psychiatric Case Register, subjects were identified who had been diagnosed as schizophrenic and had been born between 1900 and 1969. The ratio of winter/spring to summer/autumn births was compared across the seven decades for both sexes together, for men, and for women.

RESULTS

For the 1935 men, but not for the 1620 women, there was a highly significant increase (P = 0.0009) in season-of-birth effect.

CONCLUSION

Non-seasonal factors have contributed to a declining incidence of schizophrenia in both sexes. 'Seasonal' factors to which female foetuses are more susceptible than male foetuses (such as infection or malnutrition) have also decreased in frequency, severity, or both, but this has not happened with factors affecting males, leading to an increase of their season-of-birth effect.

Antecedents of schizophrenia and affective illness. Obstetric complications

BACKGROUND

This exploratory study seeks to generate new hypotheses about the relationship between obstetric complications and schizophrenia.

METHOD

The British Perinatal Mortality Survey represents 98% of all births during one week in March 1958 in Great Britain. Present State Examination (PSE), Catego diagnoses of narrowly defined schizophrenia (n = 49), broadly defined schizophrenia (n = 79), affective psychosis (n = 44) and neurosis (n = 93) were derived from case notes for all cohort members. The remainder of the cohort, surviving the perinatal period, acted as controls (n = 16 812). Variables in the British Perinatal Mortality Survey were grouped into five categories: the physique/lifestyle of the mother (including demographic characteristics), her obstetric history, the current pregnancy, the delivery and the condition of the baby.

RESULTS

There were 7/17 significant differences in maternal physique/lifestyle and obstetric history between the births of schizophrenics and controls, compared to 4/40 comparisons of somatic variables relating to pregnancy, birth and the condition of the baby. This compares with 4/17 and 7/40 for affective psychotics and a total of 4/57 differences for all categories of variables when neurotics were contrasted with controls.

CONCLUSIONS

The purported increased risk of obstetric complications in schizophrenics may result from the physique/lifestyle of their mothers.

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.

1H-magnetic resonance spectroscopy of the left temporal and frontal lobes in schizophrenia: clinical, neurodevelopmental, and cognitive correlates

Twenty eight schizophrenic patients and 20 normal volunteers underwent proton magnetic resonance spectroscopy (MRS) on the left temporal and frontal lobe regions. Male patients showed a significant reduction in frontal but not temporal n-acetylaspartate (an intraneuronally distributed metabolite) in comparison with either male controls or female patients; frontal choline was raised in male patients relative to these groups. Putative neurodevelopmental indices, including obstetric complications, family history of schizophrenia, and minor physical anomalies, proved unrelated to MRS resonances. However, multiple aspects of memory function in patients were related to temporal but not frontal creatine, a pattern that was not apparent among controls. These MRS findings complement some previous structural MRI studies and much clinical and epidemiological evidence of important gender differences in schizophrenia. The findings also suggest that memory dysfunction in patients with schizophrenia may be associated with a particular pattern of temporal lobe metabolism on MRS.

Obstetric complications as antecedents of schizophrenia: empirical effects of using different obstetric complication scales

The new McNeil-Sjöström Scale for obstetric complications (OCs), as well as scales of Lewis et al. (Schizophrenia: Scientific progress. Oxford University Press, 1989) and Parnas et al. (British Journal of Psychiatry, 140, 416-420, 1982), were applied to the OC histories of 70 singleton schizophrenics and 70 demographically-matched controls from the same hospital delivery series, using blindly assessed hospital pregnancy and birth record information. With the McNeil-Sjöström scale, schizophrenics were found to have significantly increased rates of OCs for the total reproduction, as well as for labor-delivery and the neonatal period but not for pregnancy. Significant increases in OCs in these schizophrenics were also found in scores produced by the Lewis et al. scale but not by the Parnas et al. scale. Further application of these three scales to OC data obtained through parental report for 23 monozygotic (MZ) twin pairs discordant and 10 pairs concordant for schizophrenia, as well as seven normal control MZ pairs, showed a significant difference in OC rates across the different twin pair groups, when assessed by the McNeil-Sjöström and Parnas et al. scales, but not by the Lewis et al. scale. The particular scoring system used in a study is thus of considerable importance not only for findings concerning OC histories of schizophrenics vs. controls, but also for the relationship between OCs and other presumed etiological factors in schizophrenia. Among the three scales, the McNeil-Sjöström scale provided the most sensitive assessment of OC history for schizophrenics.

Age at onset, sex, and familial psychiatric morbidity in schizophrenia. Camberwell Collaborative Psychosis Study

BACKGROUND

Although a genetic component in schizophrenia is well established, it is likely that the contribution of genetic factors is not constant for all cases. Several recent studies have found that the relatives of female or early onset schizophrenic patients have an increased risk of schizophrenia, compared to relatives of male or late onset cases. These hypotheses are tested in the current study.

METHOD

A family study design was employed; the probands were 195 patients with functional psychosis admitted to three south London hospitals, diagnosed using Research Diagnostic Criteria (RDC), and assessed using the Present State Examination (PSE). Information on their relatives was obtained by personal interview of the mother of the proband, and from medical records. Psychiatric diagnoses were made using Family History-Research Diagnostic Criteria (FH-RDC), blind to proband information.

RESULTS

There was a tendency for homotypia in the form of psychosis within families. The lifetime risk of schizophrenia in the first degree relatives of schizophrenic probands, and the risk of bipolar disorder in the first degree relatives of bipolar probands, were 5-10 times higher than reported population risks. Relatives of female and early onset (< 22 years) schizophrenic probands had higher risk of schizophrenia than relatives of male and late onset schizophrenic probands. However, this effect was compensated in part by an excess of non-schizophrenic psychoses in the relatives of male probands.

CONCLUSIONS

These results suggest a high familial, possibly genetic, loading in female and early onset schizophrenia, but do not resolve the question of heterogeneity within schizophrenia.