Course of schizophrenia: neuropsychological evidence for a static encephalopathy

Age and neuropsychologic function in schizophrenia: a decline in executive abilities beyond that observed in healthy volunteers

BACKGROUND

Kraepelin originally conceptualized schizophrenia as a degenerative brain disorder. It remains unclear whether the illness is characterized by a static encephalopathy or a deterioration of brain function, or periods of each condition. Assessments of cognitive function, as measured by neuropsychologic assessment, can provide additional insight into this question. Few studies of patients with schizophrenia have investigated the effect of aging on executive functions, in an extensive neuropsychologic battery across a wide age range, compared to healthy volunteers.

METHODS

We examined the interaction of aging and neuropsychologic function in schizophrenia through a cross-sectional study in patients (n = 87) and healthy control subjects (n = 94). Subjects were divided into three age groups (20-35, 36-49, and 50-75), and performance on an extensive neuropsychologic battery was evaluated.

RESULTS

Compared to control subjects, patients with schizophrenia demonstrated similar age-related declines across most neuropsychologic functions, with the exception of abstraction ability, in which significant evidence of a more accelerated decline was observed.

CONCLUSIONS

These results are consistent with previous reports indicating similar age effects on most aspects of cognition in patients with schizophrenia and healthy adults, but they support the hypothesis that a degenerative process may result in a more accelerated decline of some executive functions in older age in schizophrenia.

Declining of memory functions of normal elderly persons

Two studies examined the declining of memory functions in normal elderly persons using the Yokota memory test (YMT), which includes 15 items concerning verbal and non-verbal memory functions. In the first study, 552 subjects over 40 years of age in five age groups were examined. Factor analysis revealed that YMT consisted of two factors pertaining to short-term/working memory, and two factors pertaining to long-term memory. It is suggested that the former was more affected than the latter, with aging. In the second study, YMT was examined in relation to the revised version of Hasegawa dementia scale (HDS-R), which was the most popular intelligence scale for the elderly in Japan. As a result, memory functions differentially declined with the decreasing score of HDS-R, which suggests that memory functions differentially declined with progressive risk of dementia.

Memory and organizational strategies in chronic and acute schizophrenic patients

The memory profile of acute and chronic schizophrenic patients was examined according to the information processing model, with which encoding, retention and retrieval processes of these patients were compared. The effects of an external organizational strategy on their verbal learning and memory were also examined. Twenty chronic and 20 acute schizophrenic patients were tested with a list learning task consisting of a random (i.e., words presented randomly) and a blocked (i.e., words presented in clusters) word-list. The schizophrenic patients, as compared with age- and education-matched normal control subjects, demonstrated impaired learning, and the duration of their illness was not a significant factor in the severity of their learning impairment. However, the acute and chronic schizophrenic patients seem able to retain most of the newly acquired materials, regardless of the presentation format, after 30 min. In addition, the learning and subjective organizational strategy of the chronic patients, but not that of the acute patients, improved significantly by the blocked presentation. However, semantic organization could facilitate both the chronic and acute schizophrenic patients to retain more newly learned items.

Why does postpsychotic IQ decline in childhood-onset schizophrenia?

OBJECTIVE

The authors' goal was to examine whether the postpsychotic decline in full scale IQ during adolescence for patients with childhood-onset schizophrenia is due to a dementing process or simply failure to acquire new information and skills.

METHOD

Linear regression was used to determine the rate of change for scaled and raw scores on subtests of 31 patients with childhood-onset schizophrenia. The resulting slopes were examined and related to changes in the patients' brains determined by magnetic resonance imaging.

RESULTS

Three postpsychotic subtest scaled scores declined significantly: picture arrangement, information, and block design. In contrast, there was no decline in the non-age-corrected (raw) scores for any subtest. A significant correlation was found between decrease in hippocampal volume and a smaller increase in raw score on the information subtest.

CONCLUSIONS

The decline during adolescence in the full-scale IQ of patients with childhood-onset schizophrenia does not reflect dementia but, rather, an inability to acquire new information and abilities.

Use of the cognitive abilities screening instrument to assess elderly persons with schizophrenia in long-term care settings

This article presents data evaluating the cognitive status of elderly persons with schizophrenia using the Cognitive Abilities Screening Instrument (CASI). Comparisons between the Mini-Mental State Exam (MMSE) and the CASI demonstrate greater specificity of the CASI in determining level of cognitive function. The authors argue that the CASI provides a comprehensive profile including nine cognitive domains. Therefore, for this understudied population in nursing homes, CASI is a more useful outcome measure for psychiatric nursing interventions designed to improve cognitive function in elderly residents with schizophrenia. Psychiatric nurses cannot hope to understand and improve what they cannot accurately assess.

Cognitive and functional changes with aging in schizophrenia

The variation in functional outcome in schizophrenia appears to be exaggerated in late life. The cognitive and functional deficits commonly seen in younger schizophrenic patients appear to worsen in some cases in late life, while others patients appear to have a stable course of illness without functional decline, and still other patients have been reported to have essentially no residual symptoms in their later years. Cognitive and functional deficits appear to worsen more significantly in patients with a lifetime course of severe functional deficit. Despite the profound functional and cognitive deficits in these patients, neuropathologic studies have found no evidence of typical causes of severe cognitive impairments. This paper reviews the current findings on cognitive and functional changes in aging in schizophrenia, with a specific focus on patients with a poor lifetime functional outcome.

Memory impairment in schizophrenia: a meta-analysis

OBJECTIVE

Memory impairment is well documented in schizophrenia. Less is known, however, about the exact magnitude, pattern, and extent of the impairment. The effect of potential moderator variables, such as medication status and duration of illness, is also unclear. In this article, the authors presented meta-analyses of the published literature on recall and recognition memory performance between patients with schizophrenia and normal comparison subjects.

METHOD

Meta-analyses were conducted on 70 studies that reported measures of long-term memory (free recall, cued recall, and recognition of verbal and nonverbal material) and short-term memory (digit span). Tests of categorical models were used in analyses of potential moderators (clinical variables and study characteristics).

RESULTS

The findings revealed a significant and stable association between schizophrenia and memory impairment. The composite effect size for recall performance was large. Recognition showed less, but still significant, impairment. The magnitude of memory impairment was not affected by age, medication, duration of illness, patient status, severity of psychopathology, or positive symptoms. Negative symptoms showed a small but significant relation with memory impairment.

CONCLUSIONS

This meta-analysis documented significant memory impairment in schizophrenia. The impairment was stable, wide ranging, and not substantially affected by potential moderating factors such as severity of psychopathology and duration of illness.

Longitudinal study of cognitive function in first-episode and recent-onset schizophrenia

OBJECTIVE

Whether cognitive function in schizophrenia deteriorates, improves, or remains stable is a crucial question. Few studies have examined the longitudinal stability of cognitive function and the relationship between cognitive performance and clinical symptoms over time in a cohort of well-treated patients with schizophrenia.

METHOD

In the present study, 54 patients with first-episode and recent-onset schizophrenia completed a comprehensive cognitive test battery and were rated on symptom measures at index hospitalization and again after 5 years.

RESULTS

Performance IQ and full-scale IQ significantly improved, whereas verbal IQ did not change. Group performance improved on some of the neuropsychological tests, including the Circle A letter-cancellation task, free recall of logical memory test score, and the Wisconsin Card Sorting Test. Mean finger-tapping performance worsened over time, whereas performance on other neuropsychological tests did not change. Negative, psychotic, and disorganized symptoms significantly improved over the time period. Changes in negative symptoms were correlated with performance changes in verbal IQ and full-scale IQ but not performance IQ. Improvement in verbal cognition was observed when negative symptoms improved. Psychotic and disorganized symptom dimensions were not correlated with any IQ measure.

CONCLUSIONS

These results indicate that in a cohort of young patients receiving neuroleptic treatment early in their illness, cognitive performance does not deteriorate--and may improve. Only one of the three symptom dimensions--negative--was associated with change in cognitive performance. This study supports the view that negative symptoms are associated with a poor long-term cognitive outcome and may be closely related to the primary cognitive deficit in schizophrenia.

Evidence for activation of microglia in patients with psychiatric illnesses

Activation of microglia/macrophages is a key event in response to pathological changes in the CNS. HLA-DR is a valuable immunohistochemical marker that specifically reacts with activated microglia cells. In order to elucidate a potential role of microgliosis in severe psychiatric illnesses, post-mortem frontal cortex and hippocampus of patients with schizophrenia (n = 14) and affective disorder (n = 6) and control specimens (n = 13) were studied. Additionally Alzheimer's disease cases (n = 8) were included as a human model system with typical neurodegenerative alterations and microglia activation. All patient groups revealed subjects with abundant microglia immunostaining (schizophrenia, three patients; affective disorder, one patient; Alzheimer's disease, four patients) in both gray and white matter. This finding provides evidence for distinct neuropathological changes in brains of patients with schizophrenia and affective disorder. The activation of microglia cells, which represent a major part of the brain immune response, may help to unravel the pathophysiological processes in severe psychiatric illnesses.

Can excellent school performance be a precursor of schizophrenia? A 28-year follow-up in the Northern Finland 1966 birth cohort

OBJECTIVE

Poor scholastic performance is known to pre-date adult schizophrenia. We studied the 1966 North Finland general population birth cohort (n = 11017) in order to determine whether excellent school performance was a risk or protective factor.

METHOD

Data on school marks at the age of 16 years were linked to data on psychiatric morbidity. In total, 89 subjects (58 boys) developed DSM-III-R schizophrenia between the ages of 16 and 28 years.

RESULTS

Six (11%) of the pre-schizophrenic boys (6/54) had excellent mean school marks, compared to only 3% (166/5245) of the comparison group (OR 3.8; 95% CI 1.6-9.3, adjusted for parental social class, place of residence and birth order).

CONCLUSION

These results may be a chance phenomenon and require replication. However, adult schizophrenia may be linked to excellent school performance. This result may be relevant both to the preservation of schizophrenia in the population, and to mechanisms of developing schizophrenia.

The neuropathology of schizophrenia. A critical review of the data and their interpretation

Despite a hundred years' research, the neuropathology of schizophrenia remains obscure. However, neither can the null hypothesis be sustained--that it is a 'functional' psychosis, a disorder with no structural basis. A number of abnormalities have been identified and confirmed by meta-analysis, including ventricular enlargement and decreased cerebral (cortical and hippocampal) volume. These are characteristic of schizophrenia as a whole, rather than being restricted to a subtype, and are present in first-episode, unmedicated patients. There is considerable evidence for preferential involvement of the temporal lobe and moderate evidence for an alteration in normal cerebral asymmetries. There are several candidates for the histological and molecular correlates of the macroscopic features. The probable proximal explanation for decreased cortical volume is reduced neuropil and neuronal size, rather than a loss of neurons. These morphometric changes are in turn suggestive of alterations in synaptic, dendritic and axonal organization, a view supported by immunocytochemical and ultrastructural findings. Pathology in subcortical structures is not well established, apart from dorsal thalamic nuclei, which are smaller and contain fewer neurons. Other cytoarchitectural features of schizophrenia which are often discussed, notably entorhinal cortex heterotopias and hippocampal neuronal disarray, remain to be confirmed. The phenotype of the affected neuronal and synaptic populations is uncertain. A case can be made for impairment of hippocampal and corticocortical excitatory pathways, but in general the relationship between neurochemical findings (which centre upon dopamine, 5-hydroxytryptamine, glutamate and GABA systems) and the neuropathology of schizophrenia is unclear. Gliosis is not an intrinsic feature; its absence supports, but does not prove, the prevailing hypothesis that schizophrenia is a disorder of prenatal neurodevelopment. The cognitive impairment which frequently accompanies schizophrenia is not due to Alzheimer's disease or any other recognized neurodegenerative disorder. Its basis is unknown. Functional imaging data indicate that the pathophysiology of schizophrenia reflects aberrant activity in, and integration of, the components of distributed circuits involving the prefrontal cortex, hippocampus and certain subcortical structures. It is hypothesized that the neuropathological features represent the anatomical substrate of these functional abnormalities in neural connectivity. Investigation of this proposal is a goal of current neuropathological studies, which must also seek (i) to establish which of the recent histological findings are robust and cardinal, and (ii) to define the relationship of the pathological phenotype with the clinical syndrome, its neurochemistry and its pathogenesis.

No evidence for astrogliosis in brains of schizophrenic patients. A post-mortem study

Schizophrenia is clinically and neuropsychologically characterized by severe cognitive and functional impairment suggesting the presence of a neurodegenerative process in the brains of affected individuals. A variety of neuroanatomical changes have been described such as loss and disorientation of neurons in grey and white matter and cortical atrophy. However, the neuropathological basis for schizophrenia is still unclear. In the present study we monitored the density of GFAP-positive astrocytes in brains of 33 schizophrenic patients and 26 healthy controls. Both grey matter (entorhinal cortex and subiculum) and white matter (premotor cortex, subventricular zone of the third ventricle and next to inferior horn) structures were measured bilaterally. The overall finding was that there is no evidence for increased astrogliosis in brains of schizophrenic patients vs healthy controls. Therefore, degeneration is unlikely to be the main neuropathological mechanism in schizophrenic brains.

Cognitive decline in late-life schizophrenia: a longitudinal study of geriatric chronically hospitalized patients

BACKGROUND

Geriatric schizophrenic patients with a chronic course of institutionalization manifest cognitive and functional impairments that implicate decline at some time point after the onset of illness. The rate of change in cognitive and functional status in these patients has not yet been identified with a longitudinal study.

METHODS

Three hundred and twenty-six schizophrenic patients entered a 30-month follow-up study with two separate assessments of the patients. Overall functional and cognitive status was indexed with the Clinical Dementia Rating (CDR). Survival analysis was used to examine changes in cognitive and functional status, including worsening for the less impaired patients and improvements on the part of more impaired patients.

RESULTS

Approximately 30% of the patients who had baseline scores in the less impaired range manifested a worsening of their CDR ratings to a score of 2.0 (moderate) or more severe, whereas only 7% of the sample with lower scores at baseline appeared to improve in their functioning. Several characteristics of the patients at baseline assessment predicted increased risk for cognitive and functional decline, including lower levels of education, older age, and more severe positive symptoms.

CONCLUSIONS

Cognitive and functional decline can be detected in a short-term follow-up in a subset of geriatric long-stay patients with schizophrenia. This decline appears distributed across patients and not due to the presence of progressive degenerative dementing conditions. Later research will have to identify the causes of this decline, possibly on the basis of the risk factors identified in this study.

Late paraphrenia: a variant of schizophrenia manifest in late life or an organic clinical syndrome? A review of recent evidence

A large amount of research has been devoted during the past 15 years to the clinical and neurobiological aspects of the disorder named as 'late paraphrenia' (LP) in 1955. The symptomatology and diagnosis of the disorder, its prognosis, the cognitive functioning of those affected, the structural changes in the brain as revealed by modern techniques of brain imaging and its postmortem neuropathology have all been submitted to investigation. The results have been widely regarded as consistent with the concept of LP as an organic disease of the brain, but increased knowledge of the neurobiology of schizophrenia and of the age-related changes that occur in the brains of elderly people casts doubt on the validity of this interpretation. The findings are consistent with the view that LP is the form in which schizophrenia is manifest in old age. The proposal that LP has a closer kinship with affective disorder than with schizophrenia is part of a general theory of the sex differences in schizophrenia. In LP it becomes entangled with the organicity hypothesis, suggesting that neither of these explanations is adequate, and most of the evidence points to a unitary concept which views LP as a variant of a single disorder, namely schizophrenia, which, however, requires a broad definition. This concept has implications for fresh paths of enquiry.

Which characteristics of schizophrenia predate psychosis?

Neuropsychological and brain structural abnormalities are present in first onset schizophrenia; the balance of evidence is that in the majority of cases these are developmental in origin. A proportion of first degree relatives also show lateral ventricular enlargement, cortical volume decrease and possibly loss of the normal cerebral asymmetry; these findings suggest that certain families transmit a genetic defect in the control of neurodevelopment. On the contrary, decrement in left hippocampal volume appears to be secondary to perinatal hypoxia. High risk, follow-back and cohort studies all demonstrate that preschizophrenics as a group show deviant development; delayed milestones, lower IQ, solitary play, excessive anxiety, and minor neurological problems are all common. It seems likely, but not proven, that these are a manifestation of underlying neurodevelopmental disorder.

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.

Neurodevelopmental and neuroprogressive processes in schizophrenia. Antithetical or complementary, over a lifetime trajectory of disease?

The neurodevelopmental model of schizophrenia maintains ascendancy among current etiopathologic perspectives on schizophrenia. However, inconsistencies across studies and the absence thus far of pathognomic brain changes suggest the need for complex conceptualization of neurodevelopmental arrest, including some reconciliation with the competing neurodegenerative model of schizophrenia. This article critically reviews the preponderance of evidence for each model and provides an account of how these may interact or synergize to produce the characteristic clinical expression of schizophrenia.

Speaking behavior and speech sound characteristics in acute schizophrenia

Based on a sample of 45 hospitalized, acute-schizophrenic patients and 45 carefully matched controls, we investigated the non-verbal characteristics of schizophrenic speech by means of an 'acoustic' speech analysis and determined the extent to which speaking behavior and speech sound characteristics had adjusted toward normal values at the time of hospital release. Using a multivariate discriminant function derived from a previous study of chronic schizophrenics, totally 77 (85.6%) individuals of our patient and control sample could be correctly classified by a set of 12 acoustic variables at entry into study. At hospital release, the majority of patients (64.4%) still exhibited speech impairment although acute psychopathology had significantly improved. A configuration of 6 acoustic variables, assessed at the time point of entry into study, predicted at high reliability the severity of the negative syndrome at hospital release. Acute medication effects did not explain these findings, thus underlining the potential diagnostic relevance of the speech analysis method. With respect to the relationship between speech characteristics and acute psychopathology throughout the time course of recovery, our results suggest that changes in speaking behavior and speech sound characteristics may be distinct aspects of schizophrenia that can persist in a subgroup of patients over a long period, mostly beyond the time point of hospital release. Accordingly, the speech analysis method might become very useful in detailing the nature and severity of deficits in patients after remission of positive symptoms.

No neuropathologic evidence for an increased frequency of Alzheimer's disease among elderly schizophrenics

BACKGROUND

There is currently controversy as to the frequency of Alzheimer's disease (AD) in elderly persons with schizophrenia. Several studies have reported an increased frequency of AD in elderly schizophrenics, whereas others have found no increase. This issue is important because it has been hypothesized that medications used to treat schizophrenia may exacerbate AD histopathology.

METHODS

We examined autopsy cases from a state psychiatric hospital and a Veterans Affairs medical center. Charts were reviewed on 166 subjects to determine if the history warranted a DSM-IV diagnosis of schizophrenia. All subjects had complete gross and microscopic neuropathologic evaluations, which were reviewed for evidence of Alzheimer's disease.

RESULTS

Retrospective chart review identified 51 subjects over the age of 55 who met DSM-IV criteria for schizophrenia (mean age = 71.7 years, SD = 8.6, range 56-95 years). Of these 51, only I met neuropathologic criteria for AD, a frequency of 2%.

CONCLUSIONS

The frequency of subjects meeting neuropathologic criteria for Alzheimer's disease in our sample of schizophrenics was equal to or less than that found in the general population. Because institutionalized populations may contain an excess of elderly schizophrenic patients with severe behavioral pathologies, which may in turn reflect the presence of neurodegenerative processes such as Alzheimer's disease, our results may actually overestimate the frequency of Alzheimer's in the entire schizophrenic population. The frequency of Alzheimer's disease in the elderly with schizophrenia may be less than that in the general population.

The new antipsychotics, and their potential for early intervention in schizophrenia

Over almost four decades, few fundamentally different antipsychotic drugs evolved to challenge classical neuroleptics as the mainstay of the pharmacotherapy of schizophrenia. However, the recent re-emergence of clozapine, together with the emergence of risperidone, portends an increasing number of new antipsychotics which are now either traversing the stages of regulatory approval or else well-advanced in clinical development. This article first evaluates the significance of clozapine and risperidone; it then reviews some of the new antipsychotics and how they might be classified vis-a-vis potential advantages for patients, outlines putative mechanisms and new therapeutic targets, and considers whether such agents may act on any disease process inherent to schizophrenia. One fundamental issue is the extent to which the new antipsychotics might shift materially the risk benefit balance towards intervention, not just at the earliest possible stage following the onset of psychosis but at a yet earlier, 'prodromal' phase of the disorder where there is a considerably greater likelihood of 'treating' behavioural disturbances that prove not to be the harbingers of psychotic illness.

Parsing schizophrenia with neurocognitive tests: evidence of stability and validity

The stability and validity of a neurocognitive typology for schizophrenia were studied in 55 chronic patients who met DSMIII-R criteria for the illness. Subtypes were based on an earlier cluster analytic study by Heinrichs and Awad (1993) that utilized the following variables: IQ (WAIS-R), categories (Wisconsin Card Sorting Test), free recall intrusions (California Verbal Learning Test), and bilateral motor performance (Purdue Pegboard). Stability was examined by analyzing subtype assignment at the original assessment and 3 years later at follow-up. Stability over this interval was variable with an overall kappa of .45 and individual kappas from .12 to .66. Adjunct cognitive and clinical data gathered at follow-up provide evidence for the validity of several subtypes, especially in terms of their cognitive and functional differences. There was no evidence of symptom differences in this relatively asymptomatic medicated sample of patients. The results are discussed in terms of the possibility that several patterns of neurocognitive dysfunction may underlie schizophrenia, with implications for understanding the heterogeneity of the illness and its variable functional outcomes.

Effects of schizophrenia and aging on pupillographic measures of working memory

The amount of cognitive resources used to perform a task can be indexed as changes in pupil size. In a previous study, we examined pupillary response measures of slave store and central executive cognitive resources during a working memory task and found abnormally reduced utilization of these resources in schizophrenia. In the present study, multiple regression analyses were performed to examine the independent and combined effects of aging and schizophrenia on pupillary response and recall measures in a larger sample of community-dwelling schizophrenia patients. Schizophrenia was associated with a significant decline in working memory capacity, and an additional moderate decline was associated with aging, but these two factors did not interact. Baseline pupil size was significantly correlated with symptom severity, independent of medication. However, pupillary responses evoked by the working memory task and recall scores were not related to symptom severity. Results were consistent with an additive, rather than a synergistic, relationship between aging and schizophrenia, and suggested that working memory impairment in noninstitutionalized outpatients with schizophrenia may remain stable across symptom status and across the life span.

Executive (frontal) dysfunction and negative symptoms in schizophrenia: apparent gender differences in 'static' v. 'progressive' profiles

BACKGROUND

While executive (frontal lobe) dysfunction appears to be a core feature of schizophrenia, its relationship to psychopathology, age and duration of illness has yet to be explored systematically between the genders.

METHOD

Executive dysfunction, positive and negative symptoms were evaluated in 27 male and 21 female in-patients who were unusually well-matched on numerous demographic and clinical measures.

RESULTS

Measures of executive dyscontrol and negative symptoms were highly associated in both genders. However, while both executive dyscontrol and negative symptoms increased prominently with age/ duration of illness among women, no such relationship was evident among men.

CONCLUSIONS

The similarly prominent levels of current executive dyscontrol and negative symptoms in male and female patients appear to have emerged via processes that differ fundamentally between the genders; among males these deficits appear to emerge and become 'locked in' earlier in the course of illness and to show little subsequent increase, while among females these same deficits appear to be less evident early in the course but to increase in prominence thereafter.

Neuropsychological evidence supporting a neurodevelopmental model of schizophrenia: a longitudinal study

The stability of neuropsychological performance in schizophrenia and its relationship to clinical change was contrasted between 60 patients with schizophrenia (30 first-episode, 30 previously treated) and 38 healthy controls using a comprehensive neuropsychological battery and clinical scales administered at intake and at a 19-month follow-up. Consistent with the neurodevelopmental model of schizophrenia, patients demonstrated deficits in cognitive performance at initial testing and did not show decline at follow-up. There were no differences in neuropsychological performance over time between first-episode and previously treated patients, nor between male and female patients or controls. As expected, patients improved clinically with treatment with respect to both positive and negative symptoms. First-episode patients improved more on the positive symptoms of hallucination and delusion; male and female patients showed equivalent clinical improvement. Clinical improvement correlated positively with neuropsychological change, with improved negative symptomatology accounting for most of the significant correlations.

Cognitive function in schizophrenia--do neuroleptics make a difference?

Valid cognitive deficits in schizophrenia are now well characterised: general poor performance with disproportionate deficits in aspects of memory and executive function. Symptomatology, motivation, institutionalization, etc. cannot explain these deficits, which are of considerable importance for both the testing of theoretical models of schizophrenia and the determination of patients' functional outcome. The receptor blocking properties of neuroleptic treatments afford them the potential for interacting with monoaminergic, indoleaminergic, and cholinergic arousal systems in the brain and, hence, for modifying cognitive processes. However, the effects of conventional neuroleptics on cognition in schizophrenia are minor according to numerous studies. Atypical neuroleptics may, owing to their novel mechanisms of action, have the capacity to remediate cognitive impairment in schizophrenia: there is some evidence that clozapine has a "cognitive sparing" effect, but further research is needed in this area, particularly with other new drugs. Future studies should employ more appropriate methodology, particularly in terms of psychological/neurophysiological sophistication, patient evaluation, and applicability to real life, and should be hypothesis driven rather than purely empirical.

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.

Stability in cognitive dysfunctions in schizophrenic patients

The purpose of the present study was to classify cognitive dysfunctions in schizophrenic subjects according to a trait/state model. A sample of 15 patients was examined on 10 different cognitive measures in two distinctly different phases: an acute psychotic state and partial remission. To determine the degree of dysfunction at the two stages of illness, the schizophrenic patients were also compared to 14 non-psychiatric controls. Six of the 10 measures examined can be classified as cognitive deficits in schizophrenics. Four measures are possibly trait-dependent components: two backward masking scores and two long-term memory measures. A short-term memory measure is the only one that can be classified as an episode-linked factor. The other cognitive deficits found can be characterized as mediating vulnerability factors, i.e. they are more prominent in the acute psychotic state, but do not completely disappear during remission states.

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.

The varied outcomes of schizophrenia

OBJECTIVE

To review variations in outcomes in schizophrenia across individual, historical, and cross-cultural boundaries, as well as within specific domains of functioning.

METHOD

Research literature on the outcomes of schizophrenia appearing within the last 8 years was reviewed.

RESULTS

First, a review of follow-up studies published in the developed world suggests that heterogeneity in outcome across individuals with schizophrenia remains the rule, with affective symptoms, later and acute onset, and responsiveness to biological treatments predictive of good outcome. Negative symptoms are associated with poor outcome, cognitive impairments, and incapacity in social and work domains. Deterioration appears to occur within the first few months of onset if not already in the prodrome, with recent early-course studies finding longer duration of untreated psychosis associated with insidious onset, negative symptoms, social and work incapacity, and poor outcome. Second, a review of recent cross-cultural and historical studies provides evidence that outcome varies across time and place, schizophrenia having a more favourable outcome in the developing world and becoming a more benign disorder over the course of this century. Third, a review of studies of the domains of functioning within individuals identifies 4 relatively independent dimensions of depression and negative, psychotic, and disorganized symptoms. Cognitive deficits, which are associated with negative symptoms, also constitute a relatively stable dimension over time, showing neither marked deterioration nor improvement once established early in the course of disorder.

CONCLUSIONS

The early appearance and stability over time of negative symptoms and cognitive impairments call for assertive intervention efforts early in the course of disorder to prevent chronicity and prolonged disability.

Cognitive impairment and negative symptoms in geriatric chronic schizophrenic patients: a follow-up study

Cognitive impairment is increasingly recognized as an important aspect of schizophrenia. Since cognitive impairment has many features in common with the negative symptoms of the illness, it is possible that some of the characteristics attributed to negative symptoms are due to an association with cognitive impairments. In order to test this hypothesis, 174 chronically hospitalized geriatric schizophrenic patients were examined twice at a 1-year follow-up with ratings of the severity of their symptoms (using the Positive and Negative Syndrome Scale: PANSS) and assessments of cognitive functions with the Mini-Mental State Examination and a brief neuropsychological battery aimed at the typical impairments seen in dementia. Positive symptoms were unassociated with any of the cognitive variables, while negative symptom severity was correlated with each of the cognitive measures. In the cross-temporal analyses, cognitive impairments were more stable over time than negative symptom scores, but cognitive impairment did not predict the severity of any negative symptom over time. At each assessment, however, cognitive impairment was strongly correlated with each of the seven negative symptoms studied. These data indicate that cognitive impairments and negative symptoms are related, but discriminable, features in schizophrenia and that the considerable overlap between some negative symptoms and estimates of cognitive function may suggest a rethinking of the definition of some of these symptoms.

The neurodevelopmental theory of schizophrenia: evidence concerning structure and neuropsychology

Severe schizophrenics as a group show subtle abnormalities of cerebral structure. Cerebral ventricular enlargement is the best replicated finding, and this tends to be associated with impairment of neuropsychological performance. The idea that these abnormalities have a neurodevelopmental origin gains indirect support from the, admittedly less consistent, evidence of abnormalities of cerebral asymmetry and of neuronal migration in adult schizophrenics, as well as from the better established behavioural, psychomotor, and cognitive impairments reported in preschizophrenic children. However, the relationship between childhood and adult neuropsychological and brain structural findings has not been proven, and we don not know whether only some schizophrenia has a developmental origin, or whether patients differ only in the degree of developmental impairment that they show.

Clock drawing in schizophrenia

The Clock Drawing Test, a task sensitive to cognitive decline in neurological groups, was administered to 27 patients with schizophrenia. Clock drawings were scored for over-all global performance and the frequency of specific qualitative errors. Mean global performance scores indicated a small proportion of the sample was below the threshold typically used to identify dementia, and the patients displayed qualitative Clock Drawing deficits not fully represented in the global performance measure. Qualitative analyses indicated that size errors, graphic difficulty, and spatial planning problems were most common. Lastly, duration of illness was not related to global performance, suggesting that the latter might not reflect deterioration but the stable trajectory of impairment that may be constant through the schizophrenia illness.

Childhood behavioral characteristics and adult brain morphology in schizophrenia

It is well established that many schizophrenia patients manifest behavioral dysfunction long before the onset of clinical symptoms of illness. Some show signs of motor and socioemotional deficit as early as infancy. The present study examines the relations among childhood neuromotor, affective and behavior characteristics, and the association of these factors with adult brain morphology (MRI) in schizophrenia patients. Data on neuromotor functions and negative affect were obtained from coding of childhood films. Parents of patients provided information about six dimensions of childhood behavior problems. Analyses of data from patients and healthy siblings revealed that childhood neuromotor abnormalities and negative affect were associated with some of the behavioral dimensions. Among the patients, early childhood neuromotor deficits and negative affect were linked with greater ventricular enlargement in adulthood. The ratings of the behavior problem dimensions showed a complex relation with adult brain morphology, suggesting that externalized problems are linked with more abnormalities (smaller brain volume and larger ventricles), whereas internalized problems are associated with less abnormality. The findings are discussed in light of their implications for the developmental origins of brain abnormalities in schizophrenia.

Hippocampal age-related changes in schizophrenia: a proton magnetic resonance spectroscopy study

We have used proton magnetic resonance spectroscopy to study in vivo N-acetyl aspartate (NAA), choline and creatine in the hippocampi of 26 schizophrenics and 38 normal controls. Measurements of NAA suggest that age-related neuronal loss occurs at a similar rate in schizophrenics and controls. On the other hand, we observe in schizophrenics age-related choline abnormalities not present in controls. We suggest that these age-related changes may be related to an abnormal myelination process and contribute to the observed clinical deterioration associated with schizophrenia.

Cognitive dysfunction in chronic schizophrenia followed prospectively over 10 years and its longitudinal relationship to the emergence of tardive dyskinesia

Basic cognitive function was assessed at initial and at 5- and 10-year follow-up assessments among 41 primarily middle-aged in-patients manifesting the severest form of schizophrenia; additionally, the presence and severity of tardive dyskinesia was evaluated on each occasion. Overall, there was a modest but significant deterioration in cognitive function over the decade, particularly among older men. Longitudinally, patients with persistent tardive (orofacial) dyskinesia continued to show poorer cognitive function than those consistently without such movement disorder, though within neither group did cognitive function change over the decade. Those patients demonstrating prospectively the emergence of orofacial dyskinesia showed a marked deterioration in their cognitive function over the same time-frame within which their movement disorder emerged, but this decline did not progress further thereafter. There appears to exist some modes, progressive deterioration in cognitive function even late in the chronic phase of severe schizophrenic illness which appears to derive primarily from patients showing de novo emergence of tardive orofacial dyskinesia.

De ontwikkelingsneurologische theorie van schizofrenie: bewijsmateriaal betreffende structuur en neuropsychologic

Severe schizophrenics as a group show subtle abnormalities of cerebral structure. Cerebral ventricular enlargement is the best replicated finding, and this tends to be associated with impairment of neuropsychological performance. The idea that these abnormalities have a neurodevelopmental origin gains indirect support from the, admittedly less consistent, evidence of abnormalities of cerebral asymmetry and of neuronal migration in adult schizophrenics, as well as from the behavioural, psychomotor, and cognitive impairments reported in preschizophrenic children. However, the relationship between childhood and adult neuropsychological and brain structural findings has not been proven, and we do not know whether only some schizophrenics have a developmental origin, or whether patients differ only in the degree of developmental impairment that they show.

Neurological signs, age, and illness duration in schizophrenia

Although increased prevalence of neurological signs in schizophrenia may reflect the presence of subtle brain dysfunctions, it is not clear whether there is progressive deterioration in such neurological function as the illness advances. This study compared neurological signs in patients with different durations of illness, controlling for age and education level. No deterioration in neurological signs as a function of illness duration was observed. Although there was an increase in neurological signs with age, there was a parallel increase in a control group. In addition, no change in the profile of subgroups of neurological signs was detected. These data provide further evidence for the stability of neurological dysfunction in schizophrenia. The findings are discussed in the context of the developmental origin of neurological dysfunction in schizophrenia.

Prefrontal neuropsychological impairment and illness duration in schizophrenia: a study of 204 patients in Hong Kong

Previous studies investigating the progression of neuropsychological impairment in schizophrenia have yielded conflicting results. We compared prefrontal neuropsychological function and other cognitive performance in a larger sample of schizophrenic patients with different duration of illness. The inclusion of a normal control group also allowed the effect of age to be taken into account. Performance in the Wisconsin Card Sorting Test (WCST) and semantic fluency were both impaired at an early stage in the illness and did not significantly deteriorate as the illness duration increased. Against this background there was preliminary evidence for deterioration in verbal memory function. The data support a lack of progression in prefrontal dysfunction and in most other cognitive domains.

Symptom stability in geriatric chronic schizophrenic inpatients: a one-year follow-up study

The results of previous studies of symptom stability in schizophrenia suggest that negative symptoms manifest traitlike characteristics while positive symptoms fluctuate over time. Various prospective studies of chronic schizophrenic patients have found consistent results, regardless of the follow-up period, yet there is little research addressing symptomatology in geriatric schizophrenic patients. Since these patients have a very poor outcome and more severe negative symptoms, their symptoms might differ from younger patients. This study examined the course of symptomatology in 178 geriatric schizophrenic inpatients who were assessed twice at a 1-year interval with the Positive and Negative Syndrome Scale (PANSS). Intraclass correlations revealed that the distribution of negative symptoms was considerably more stable than that of positive symptoms over the interval, and subtypes based on negative symptoms were the only ones that manifested consistent stability over time. There was also a significant increase in negative symptom severity for the sample, with a slight decrease in positive symptom severity. Thus, even in chronic inpatients, with a very extended illness, positive symptom severity is not particularly stable within patients. These data indicate that the characteristics of negative and positive schizophrenic symptoms are similar in younger and geriatric schizophrenic patients, suggesting a continuity of the illness process. Tentative evidence for increasing severity of negative symptoms over a brief follow-up period suggests the possibility of a steady worsening of clinical state in very elderly patients who remained hospitalized.

Neuropsychological impairment in first-episode and chronic schizophrenic patients

Patients with first-episode (FE) schizophrenia (n = 40), with chronic schizophrenia (n = 40) and healthy controls (n = 40) matched for age, gender, education and parental socioeconomic status were administered a battery of standardized neuropsychological (NP) tests. Both patient groups showed generalized impairment relative to controls and the most pronounced deficits in visual-motor processing and attention (VSM). Compared with FE patients, chronic schizophrenics performed worse in VSM and abstraction/flexibility. Our findings suggest that NP deficits are fundamental manifestations of the illness, and that mainly frontally based dysfunctions are more prominent in chronic, kraepelinian patients.

Neuropsychological deficit in newly diagnosed patients with schizophrenia or schizophreniform disorder

Forty-six patients with schizophrenia or schizophreniform disorder admitted to hospital for the first time were compared with 21 healthy volunteers on neuropsychological tests reflecting prefrontal and left respectively right hemisphere function. The patients with schizophrenia or schizophreniform disorder had a poorer performance on neuropsychological tests (such as Wisconsin Card Sorting) compared with healthy volunteers. Both left and right hemisphere seemed to be involved. Especially poor performance was found on somewhat complicated tests requiring ability of analysis, abstraction and memory, thus indicating dysfunction of prefrontal and temporohippocampal regions. Signs of sulcal enlargement and size of lateral ventricles on computed tomographic scan correlated with poor test performance on some tests both in patients and in healthy volunteers. No correlations were found between performance on neuropsychological test and negative symptoms.

Neuropsychological assessment of schizophrenic patients during a psychotic episode: persistent cognitive deficit?

Neuropsychological test performance and clinical symptoms were assessed in 14 schizophrenic patients at admission to and discharge from an acute inpatient psychiatric service. Despite significant clinical improvement at discharge, no major change in cognitive performance was observed. Furthermore, patients at discharge were significantly impaired compared with normal control subjects case-matched for gender, age, handedness and level of education. The results suggest that some degree of cognitive impairment may be relatively independent from schizophrenic symptoms and that such impairment may represent part of a residual enduring "trait" vulnerability.

Preliminary report: cerebral blood flow abnormalities in older schizophrenic patients

We compared global and regional cerebral blood flow in 11 schizophrenic patients and 11 normal comparison subjects, all over the age of 45 years. The schizophrenic patients had lower global cortical uptake than the control subjects. Among the individual regions of interest, the schizophrenic patients had significant decrements in the left posterior frontal region and in the bilateral inferior temporal regions. The uptake did not correlate with age of onset or duration of schizophrenia, current daily neuroleptic dose, severity of psychopathology, or global cognitive impairment.