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

The Pittsburgh Oral-Facial Cleft study: expanding the cleft phenotype. Background and justification

The Pittsburgh Oral-Facial Cleft study was begun in 1993 with the primary goal of identifying genes involved in nonsyndromic orofacial clefts in a variety of populations worldwide. Based on the results from a number of pilot studies and preliminary genetic analyses, a new research focus was added to the Pittsburgh Oral-Facial Cleft study in 1999: to elucidate the role that associated phenotypic features play in the familial transmission patterns of orofacial clefts in order to expand the definition of the nonsyndromic cleft phenotype. The purpose of this paper is to provide a comprehensive review of phenotypic features associated with nonsyndromic orofacial clefts. These features include fluctuating and directional asymmetry, non-right-handedness, dermatoglyphic patterns, craniofacial morphology, orbicularis oris muscle defects, dental anomalies, structural brain and vertebral anomalies, minor physical anomalies, and velopharyngeal incompetence.

Quantitative craniofacial anomalies in a racially mixed schizophrenia sample

BACKGROUND

The observation that some patients with schizophrenia display subtly anomalous craniofacial features dates back to the early 1900s and has recently been hypothesized to reflect disrupted prenatal development also involving the brain. Most studies to date have used observer ratings rather than physical measurements and have studied only Caucasian samples. Our objective was to determine whether schizophrenia is associated with craniofacial anomalies applying quantitative methods in Caucasian and African American subjects.

METHODS

Participants were 32 Caucasian and 20 African American outpatients aged 18 to 60, meeting Structured Clinical Interview for DSM-IV (SCID) confirmed criteria for schizophrenia/schizoaffective disorder, recently discharged from a psychiatric hospital in Queens, New York. The healthy control subjects were recruited through local advertisements and were individually matched to the patient sample on gender, race, and age.

RESULTS

Thirty-two measurements of the head and face reflecting all regions of potential developmental significance were taken according to published methods and validated for this study. Significantly greater skull base width [F(1,51) = 13.11, p = .0005] and greater height of the cutaneous lower lip [F(1,51) = 7.90, p = .0059] were found among patients after applying multiplicity correction. Statistical correction for group differences in body weight did not alter the findings.

CONCLUSIONS

Findings agree with the two major anthropometric studies in schizophrenia.

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

OBJECTIVE

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

METHOD

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

RESULTS

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

CONCLUSION

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

Longitudinal assessment of psychopathological domains over late-stage schizophrenia in relation to duration of initially untreated psychosis: 3-year prospective study in a long-term inpatient population

There remains uncertainty regarding any progressive nature of psychopathology and cognitive dysfunction in late-stage schizophrenia, and whether duration of initially untreated psychosis (DUP) might be associated with such 'progression'. This study examines longitudinally, over 3 years, the psychopathology and neuropsychology in 82 inpatients with DSM-IV schizophrenia, many of whom were admitted in the pre-neuroleptic era. Increase in executive dysfunction exceeded that in general cognitive impairment. Positive but not negative symptom severity decreased modestly; the primary predictor of negative symptom severity was DUP. On index assessment, psychopathology evidenced a three-factor structure; at follow-up, psychomotor poverty evidenced greater prominence and cohesion, and was on both occasions predicted primarily by DUP, while reality distortion was altered and disorganisation disassembled into alternative elements. It would appear that as years of chronic, refractory illness accrue, psychomotor poverty becomes more sharply delineated and dominant within the overall structure of psychopathology, and its prominence is predicted enduringly by DUP.

3D morphometrics of craniofacial dysmorphology reveals sex-specific asymmetries in schizophrenia

Over early fetal life cerebral and craniofacial morphogenesis proceed in embryological intimacy. Therefore, craniofacial shape differences between schizophrenia patients and controls are informative of developmental disturbance(s) in cerebral-craniofacial morphogenesis. 3D craniofacial coordinates were calculated from interlandmark distances for 169 patients with DSM-III-R schizophrenia and 78 matched normal controls. These were analysed using geometric morphometrics with visualisation of the resultant statistical models. Patients of both sexes were characterised by an intricate topography of 3D shape change involving lengthened lower mid-facial height, shortened upper mid-facial height, nasion located posteriorly and a wider face posteriorly; there was sex-specific rotation of the midface such that the base of the nose is more anterior in female patients but more posterior in male patients. Importantly, there were sex-specific asymmetries: in males, controls evidenced marked directional asymmetry while patients showed reduced directional asymmetry; conversely, in females controls evidenced little directional asymmetry while patients showed marked directional asymmetry. In schizophrenia, the topography of craniofacial dysmorphology appears to reflect subtle disruption to a critical 3D trajectory of embryonic-fetal craniofacial growth, particularly along the midline, with disturbance to the establishment of normal asymmetries in a sex-related manner.

Schizophrenia, schizoaffective and bipolar disorder within an epidemiologically complete, homogeneous population in rural Ireland: small area variation in rate

While a controversy has endured as to whether schizophrenia evidences the geographical variations in rate that characterise essentially all medical conditions, even less is known of such fundamental aspects of the epidemiology of schizoaffective and bipolar disorder. Within an ethnically and socioeconomically homogeneous region of rural Ireland, population 29,542, several methodological refinements were adopted to seek an epidemiologically complete population of 'all' cases of these disorders, with each potential case interviewed and diagnosed. Prevalence and morbid risk were calculated over the region as a whole and for each of the 39 constituent District Electoral Divisions [DEDs], by place at birth and by place at onset. Using multiple sources of information, 115 cases of schizophrenia, 33 of schizoaffective disorder and 77 of bipolar disorder were identified. Unremarkable overall prevalence and morbid risk values obscured marked variation between District Electoral Divisions for schizophrenia. No such variation was observed for bipolar disorder. These data indicate, using improved methodology, that what is often interpreted as an invariant overall rate of schizophrenia across countries and cultures may not apply to spatial microstructure; macroscopic rates can obscure small area variations when ethnic and socioeconomic diversity are minimised and effects of urbanicity are absent. Under these conditions, small area variations in bipolar disorder may be limited.

The causes of schizophrenia: neurodevelopment and other risk factors

Understanding the etiology of schizophrenia has been a considerable challenge. The neurodevelopmental hypothesis has held sway in recent years, focusing our attention on biological causes acting in early life. Much evidence supports this hypothesis and risk factors operating in early life (e.g., obstetric complications) have been shown to be associated with the later development of schizophrenia. Indicators of abnormal neurodevelopment that characterize individuals vulnerable to later developing schizophrenia have also been identified. For example, as a group, children who will later develop schizophrenia subtly differ from their peers in terms of their motor, cognitive, and social functioning. However, there is much that cannot be explained in purely neurodevelopmental terms. There is growing evidence of associations between the risk of schizophrenia and factors such as drug misuse, ethnicity/migration, life events, and urbanicity. A multifactorial model of causation that encompasses biological, social, and psychological elements is arguably both a better representation of current research findings and a more appropriate model for clinical practice.

Mouse genetic models for prepulse inhibition: an early review

Prepulse inhibition (PPI) is the phenomenon in which a weak prepulse stimulus attenuates the response to a subsequent startling stimulus. Patients with schizophrenia and some other neuropsychiatric disorders have impaired PPI. Impaired PPI in these patient populations is thought to reflect dysfunctional sensorimotor gating mechanisms. Recently, various inbred mouse strains and genetically modified mouse lines have been examined to investigate the potential genetic basis of sensorimotor gating. This review provides a synopsis of the use of mouse models to explore genetic and neurochemical influences on PPI. Studies describing the PPI responses of various inbred strains of mice, mice with genetic mutations, and mice treated with various drugs prior to July 2001 are reviewed. The continuous nature of the distribution of PPI responses among inbred strains of mice indicates that PPI is a polygenic trait. Findings from spontaneous and gene-targeted mutants suggest that mutant mice are important tools for dissecting and studying the role of single genes and their products, and chromosomal regions in regulating PPI. Pharmacological studies of PPI have typically confirmed effects in mice that are similar to those reported previously in rats, with some important exceptions. The use of mice to study PPI is increasing at a dramatic rate and is helping to increase our understanding of the biological basis for sensorimotor gating.

Sex differences in psychosis: normal or pathological?

BACKGROUND

Schizophrenia first appears in adolescence, in boys at an earlier age than girls. The interpretation of this key epidemiological finding crucially depends on whether similar age-related sex differences exist in the expression of associated, subclinical psychosis-like experiences.

METHODS

Findings are based on a population sample of 2548 adolescents and young adults aged 17-28. Subjects were assessed with the core psychosis sections on delusions and hallucinations of the Munich-Composite International Diagnostic Interview.

RESULTS

The risk of subclinical psychotic experiences was significantly higher for males in the younger half of the cohort (17-21 years), but similar in the older half (22-28 years).

CONCLUSIONS

These findings suggest that normal maturational changes in adolescence with differential age of onset in boys and girls cause the expression of psychosis, the extreme of which is schizophrenia.

Prospective analysis of premature mortality in schizophrenia in relation to health service engagement: a 7.5-year study within an epidemiologically complete, homogeneous population in rural Ireland

While premature death in schizophrenia is well recognised, mortality risk has received little longitudinal study in relation to population representativeness and patient engagement with health services. Within a rural Irish catchment area of socioeconomic, ethnic and geographical homogeneity and low residential mobility, an epidemiologically complete population of 72 patients with schizophrenia was followed up over 7.5 years in order to quantify mortality prospectively. Information was obtained in relation to 99% of the cohort, with 94% of those surviving retained in engagement with psychiatric care. There were 25 deaths (35% of cohort). A relative risk of 2.06 (95% CI, 1.40-2.80; P < 0.001) among this epidemiologically complete population may constitute an estimate of risk for mortality inherent to schizophrenia when disengagement from health services, residential mobility and socioeconomic, ethnic and geographical diversity are minimised. On long-term prospective evaluation, risk for death in schizophrenia was doubled on a background of enduring engagement in psychiatric care with increasing provision of community-based services and introduction of second-generation antipsychotics.

Craniofacial dysmorphogenesis in fetally irradiated nonhuman primates: implications for the neurodevelopmental hypothesis of schizophrenia

BACKGROUND

Craniofacial abnormalities arising from gestational disturbances have been documented in some schizophrenic patients. Reduction of thalamic neurons, a key feature of the neuropathology of schizophrenia, could also have a prenatal origin via disruption of thalamic neurogenesis. This study investigates whether craniofacial dysmorphology and thalamic neuron loss might be associated manifestations of a disruption in embryonic development.

METHODS

Thalamic neurons were deleted by exposing fetal macaques to x-rays during thalamic genesis (E33-42). Another group of macaques was irradiated after thalamic genesis (E70-81). Body, head, and facial measurements were obtained from the early irradiated (EX), late irradiated (LX), and control animals at adulthood.

RESULTS

Head width, distance between outer eye edges, and ear width were smaller in EX macaques compared with control animals. The LX macaques exhibited only reduced ear width compared with control animals.

CONCLUSIONS

These findings indicate that certain features of thalamic neuropathology and craniofacial dysmorphogenesis observed in schizophrenic patients may have a common etiology.

3D laser surface scanning and geometric morphometric analysis of craniofacial shape as an index of cerebro-craniofacial morphogenesis: initial application to sexual dimorphism

BACKGROUND

Over early fetal life, when disturbances in schizophrenia have been posited and craniofacial dysmorphogenesis reported, cerebral morphogenesis proceeds in embryological intimacy with craniofacial morphogenesis. Digitization technologies now allow 3D recording of craniofacial surface landmarks and modeling of craniofacial shape differences using geometric morphometrics.

METHODS

Using normal sexual dimorphism as an exemplar, facial surfaces of 131 Medical School employees [82 females, 49 males] were recorded in 3D using a portable, hand-held laser scanner; 3D coordinate data were then analyzed using geometric morphometrics.

RESULTS

Males and females differed markedly on an omnibus test of craniofacial shape. Logistic regression analysis of 16 principal components of shape variability, explaining 84.9% of the overall sample variance, generated 8 principal components as significant and independent discriminators. On visualization, the female face is wider and flatter; the eyes are more lateral, anterior and are further apart, and nasal bridge is posterior; the nose is smaller; the lips are fuller and the chin more forward. These findings are complementary to sexual dimorphism in cerebral structures.

CONCLUSIONS

This technique reliably discriminates geometric features of craniofacial morphology that are associated with aspects of cerebral morphology, and may inform on putative neurodevelopmental disorders characterised by dysmorphogenesis.

Patterns of dysmorphic features in schizophrenia

Congenital dysmorphic features are prevalent in schizophrenia and may reflect underlying neurodevelopmental abnormalities. A cluster analysis approach delineating patterns of dysmorphic features has been used in genetics to classify individuals into more etiologically homogeneous subgroups. In the present study, this approach was applied to schizophrenia, using a sample with a suspected genetic syndrome as a testable model. Subjects (n = 159) with schizophrenia or schizoaffective disorder were ascertained from chronic patient populations (random, n = 123) or referred with possible 22q11 deletion syndrome (referred, n = 36). All subjects were evaluated for presence or absence of 70 reliably assessed dysmorphic features, which were used in a three-step cluster analysis. The analysis produced four major clusters with different patterns of dysmorphic features. Significant between-cluster differences were found for rates of 37 dysmorphic features (P < 0.05), median number of dysmorphic features (P = 0.0001), and validating features not used in the cluster analysis: mild mental retardation (P = 0.001) and congenital heart defects (P = 0.002). Two clusters (1 and 4) appeared to represent more developmental subgroups of schizophrenia with elevated rates of dysmorphic features and validating features. Cluster 1 (n = 27) comprised mostly referred subjects. Cluster 4 (n = 18) had a different pattern of dysmorphic features; one subject had a mosaic Turner syndrome variant. Two other clusters had lower rates and patterns of features consistent with those found in previous studies of schizophrenia. Delineating patterns of dysmorphic features may help identify subgroups that could represent neurodevelopmental forms of schizophrenia with more homogeneous origins.

The early stages of schizophrenia: speculations on pathogenesis, pathophysiology, and therapeutic approaches

Schizophrenia is commonly considered a neurodevelopmental disorder that is associated with significant morbidity; however, unlike other neurodevelopmental disorders, the symptoms of schizophrenia often do not manifest for decades. In most patients, the formal onset of schizophrenia is preceded by prodromal symptoms, including positive symptoms, mood symptoms, cognitive symptoms, and social withdrawal. The proximal events that trigger the formal onset of schizophrenia are not clear but may include developmental biological events and environmental interactions or stressors. Treatment with antipsychotic drugs clearly ameliorates psychotic symptoms, and maintenance therapy may prevent the occurrence of relapse. The use of atypical antipsychotic agents may additionally ameliorate the pathophysiology of schizophrenia and prevent disease progression. Moreover, if treated properly early in the course of illness, many patients can experience a significant remission of their symptoms and are capable of a high level of recovery following the initial episode. Because the clinical deterioration that occurs in schizophrenia may actually begin in the prepsychotic phase, early identification and intervention may favorably alter the course and outcome of schizophrenia.

The origin and course of schizophrenia: implications for clinical practice

The authors first review current evidence concerning abnormalities of brain structure and function in schizophrenia and interpret them within a "network" pathophysiological model of the disorder. This information is then placed within a contemporary neurodevelopmental framework that "roots" the illness in adverse events during early pregnancy, which result in a developmentally compromised nervous system. They then consider the controversy as to whether the subsequent expression of psychosis reflects an active morbid process and, in a more general sense, whether the disorder is characterized by subsequent progression and clinical deterioration. The authors argue that the developmental and progressive models should not be considered in an either-or manner, since this perspective is not logical and favors nihilistic approaches to intervention and treatment, but rather should be integrated within a lifetime trajectory model. Finally, implications for current psychiatric practice are considered.

Relationship of the factor structure of psychopathology in schizophrenia to the timing of initial intervention with antipsychotics

Timing of intervention with antipsychotic medication may influence long-term outcome in schizophrenia in a manner that is poorly understood. This study evaluated psychopathology, its factor structure, and cognitive dysfunction in older patients with chronic schizophrenia in relation to the intervals from onset of psychosis to initiation of treatment with antipsychotics, and from initiation of antipsychotic treatment to current assessments. The subjects were 129 patients with schizophrenia, many of whom became ill in the preneuroleptic era. Their current psychopathology was assessed using the Positive and Negative Syndrome Scale, and its factor structure examined using principal component analysis. Current general and executive cognitive function was evaluated using the Mini-Mental State Examination and the Executive Interview, respectively. Using multiple regression modelling, increasing duration of initially unmedicated psychosis, but not the much longer duration of subsequently treated illness, was the primary predictor of psychomotor poverty (negative symptoms) but not of reality distortion or disorganisation over the three domains of psychopathology resolved; duration of initially unmedicated psychosis marginally predicted the severity of general, but not of executive, cognitive dysfunction. Delayed intervention with antipsychotics appears associated with poorer long-term course in terms of increased severity of psychopathology in the psychomotor poverty domain.

Paternal factors and schizophrenia risk: de novo mutations and imprinting

There is a strong genetic component for schizophrenia risk, but it is unclear how the illness is maintained in the population given the significantly reduced fertility of those with the disorder. One possibility is that new mutations occur in schizophrenia vulnerability genes. If so, then those with schizophrenia may have older fathers, because advancing paternal age is the major source of new mutations in humans. This review describes several neurodevelopmental disorders that have been associated with de novo mutations in the paternal germ line and reviews data linking increased schizophrenia risk with older fathers. Several genetic mechanisms that could explain this association are proposed, including paternal germ line mutations, trinucleotide repeat expansions, and alterations in genetic imprinting in one or several genes involved in neurodevelopment. Animal models may be useful in exploring these and other explanations for the paternal age effect and they may provide a novel approach for gene identification. Finally, it is proposed that environmental exposures of the father, as well as those of the mother and developing fetus, may be relevant to the etiology of schizophrenia.

Coupling of dopamine receptor subtypes to multiple and diverse G proteins

The family of five dopamine receptors subtypes activate cellular effector systems through G proteins. Historically, dopamine receptors were thought to only stimulate or inhibit adenylyl cyclase, by coupling to either G(s)alpha or G(i)alpha, respectively. Recent studies in transfected cells, reviewed here, have shown that multiple and highly diverse signaling pathways are activated by specific dopamine receptor subtypes. This multiplicity of signaling responses occurs through selective coupling to distinct G proteins and each of the receptors can interact with more than one G protein. Although some of the multiple coupling of dopamine receptors to different G proteins occurs from within the same family of G proteins, these receptors can also couple to G proteins belonging to different families. Such multiple interactions between receptors and G proteins elicits functionally distinct physiological effects which acts to enhance and subsequently suppress the original receptor response, and to activate apparently distinct signaling pathways. In the brain, where coexpression of functionally distinct receptors in heterogeneous cells further adds to the complexity of dopamine signaling, minor alterations in receptor/G protein coupling states during either development or in adults, may underlie the imbalanced signaling seen in dopaminergic-linked diseases such as schizophrenia, Parkinson's disease and attention deficit hyperactivity disorder.

Long-term adaptive life functioning in relation to initiation of treatment with antipsychotics over the lifetime trajectory of schizophrenia

BACKGROUND

There is evidence that the stage of illness at which antipsychotic treatment is initiated in schizophrenia may have consequences for its subsequent course. How this might relate to impaired adaptive life functioning in the long-term is poorly understood.

METHODS

Thirty-eight inpatients, many of whom had been admitted in the preneuroleptic era, were assessed using the Social-Adaptive Functioning Evaluation (SAFE); constituent clinical and medication phases of the lifetime trajectory of their illnesses were then analyzed to identify predictors of SAFE score using multiple regression modeling.

RESULTS

The primary, independent predictor of SAFE score was duration of initially unmedicated psychosis, which accounted for 22% of variance (p<.001) therein. Conversely, duration of subsequently treated illness, although decades longer, failed to predict SAFE score.

CONCLUSIONS

These findings are consistent with some form of "progressive" process, particularly over the first several years following the emergence of psychosis, which is associated with accrual of deficits in adaptive life functioning.

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.

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

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