Neuropsychological Profile in Patients with Schizotypal Personality Disorder or Schizophrenia

Cognitive and prepulse inhibition deficits in psychometrically high schizotypal subjects in the general population: relevance to schizophrenia research

Schizophrenia and schizotypal personality disorder share common clinical profiles, neurobiological and genetic substrates along with Prepulse Inhibition and cognitive deficits; among those, executive, attention, and memory dysfunctions are more consistent. Schizotypy is considered to be a non-specific "psychosis-proneness," and understanding the relationship between schizotypal traits and cognitive function in the general population is a promising approach for endophenotypic research in schizophrenia spectrum disorders. In this review, findings for executive function, attention, memory, and Prepulse Inhibition impairments in psychometrically defined schizotypal subjects have been summarized and compared to schizophrenia patients and their unaffected first-degree relatives. Cognitive flexibility, sustained attention, working memory, and Prepulse Inhibition impairments were consistently reported in high schizotypal subjects in accordance to schizophrenia patients. Genetic studies assessing the effects of various candidate gene polymorphisms in schizotypal traits and cognitive function are promising, further supporting a polygenic mode of inheritance. The implications of the findings, methodological issues, and suggestions for future research are discussed.

A systematic review and meta-analysis of the psychosis continuum: evidence for a psychosis proneness-persistence-impairment model of psychotic disorder

A systematic review of all reported incidence and prevalence studies of population rates of subclinical psychotic experiences reveals a median prevalence rate of around 5% and a median incidence rate of around 3%. A meta-analysis of risk factors reveals associations with developmental stage, child and adult social adversity, psychoactive drug use, and also male sex and migrant status. The small difference between prevalence and incidence rates, together with data from follow-up studies, indicates that approximately 75-90% of developmental psychotic experiences are transitory and disappear over time. There is evidence, however, that transitory developmental expression of psychosis (psychosis proneness) may become abnormally persistent (persistence) and subsequently clinically relevant (impairment), depending on the degree of environmental risk the person is additionally exposed to. The psychosis proneness-persistence-impairment model considers genetic background factors impacting on a broadly distributed and transitory population expression of psychosis during development, poor prognosis of which, in terms of persistence and clinical need, is predicted by environmental exposure interacting with genetic risk.

Does reactivity to stress cosegregate with subclinical psychosis? A general population twin study

OBJECTIVE

This study assessed the relationship between stress reactivity (trait 1) and psychosis (trait 2) across genetically related persons (cross-twin, cross-trait design) to examine whether stress reactivity is an uncontaminated and unconfounded familial marker of psychosis risk.

METHOD

Reactivity to stress and subclinical psychotic experiences were assessed in 289 female, general population twin-pairs. Cross-trait, within-twin associations investigating the association between stress reactivity and subclinical psychotic experiences in each person, were calculated. In addition, cross-trait, cross-twin associations were calculated to assess whether stress reactivity in one twin was moderated by subclinical psychotic experiences in the co-twin.

RESULTS

Cross-trait, within-twin analyses showed significant associations between stress reactivity and subclinical psychotic experiences in each person. In addition, the cross-trait cross-twin analyses showed that stress reactivity in twin 1 was significantly moderated by subclinical experiences in the co-twin.

CONCLUSION

The results suggest that the psychosis phenotype cosegregates with increased emotional reactivity to stress in daily life.

Recent advances in the biological study of personality disorders

While it is premature to provide a simple model for the vulnerability to the development of either borderline (BPD) or schizotypal (SPD) personality disorder, it is clear that these heritable disorders lend themselves to fruitful neurobiological exploration. The most promising findings in BPD suggest that a diminished top-down control of affective responses, which is likely to relate to deceased responsiveness of specific midline regions of prefrontal cortex, may underlie the affective hyperresponsiveness in this disorder. In addition, genetic and neuroendocrine and molecular neuroimaging findings point to a role for serotonin in this affective disinhibition. Clearly SPD falls within the schizophrenia spectrum, but precisely the nature of what predicts full-blown schizophrenia as opposed to the milder symptoms of SPD is not yet clear.

Borderline Personality Disorder: What do We Know? Diagnosis, Course, Co-Morbidity, and Aetiology

Evidence regarding the diagnostic dilemmas, course, co-morbidity, and aetiology of Borderline Personality Disorder (BPD) is reviewed. After considering problems that the clinician and researcher face in using BPD as a diagnostic category, I argue that current evidence indicates that there is reason to be more optimistic about the course of BPD. Emerging dilemmas in considering co-morbidity in the BPD patient are considered. Aetiological factors are presented in support of a ‘multiple pathways’ model of aetiology where characterological and temperamental characteristics interact in complex idiosyncratic ways.

Essential polyunsaturated fatty acids and social cognition in schizophrenia

Abnormal metabolism of essential polyunsaturated fatty acids (EPUFAs), a component of phospholipids in neural membranes, has been suggested to be related to the pathophysiology of schizophrenia. The purpose of this study was to examine the relationship between EPUFA concentrations in erythrocyte membranes, a peripheral measure of phospholipid composition in the brain, and clinical variables, such as cognitive performance relevant to social functions, in patients with schizophrenia. Erythrocyte membrane levels of EPUFAs, saturated fatty acids, and monounsaturated acids were measured in 25 patients with schizophrenia and 32 age- and gender-matched 32 normal volunteers. The script tasks, a measure of social cognition, and the Brief Psychiatric Rating Scale were administered to the patients. The levels of EPUFAs, but not those of saturated or monosaturated fatty acids, were significantly lower in patients than in normal controls. The degree of a decrease in EPUFA levels was positively correlated with severity of positive symptoms and impairment of frequency judgment performance on the script tasks, while no such correlations were found with negative symptoms, attention as measured by the Wechsler Adult Intelligence Scale-Revised-Digit Span, or verbal memory as measured by the Auditory Verbal Learning Test. These results provide the first suggestion for a contribution of decreased levels of EPUFAs to impaired social cognition, as represented by event schema, in patients with schizophrenia.

Exophenotypical profile of adolescents with sustained attention deficit: A 10-year follow-up study

We aimed to explore prospectively the relationship between the presence of sustained attention deficit (SAD) in early adolescence and exophenotypical measures of vulnerability to schizophrenia spectrum disorders (personality and psychosocial measures) in early adulthood. Two cohorts of community adolescents were selected in 1993 according to the presence or absence of a CPT-linked SAD. In 2003, both cohorts (Index: n=42, and

CONTROL

n=38) were administered the O-LIFE, the SCID-II, the DOI battery and the COPE scale, among other tests. T-tests were used to compare both cohorts. Index subjects showed a higher level of negative schizotypy, avoidant, depressive and narcissistic personality traits, as well as more asocial behavior and poorer use of coping resources than CONTROL subjects did. A SAD in early adolescence may be associated with coping and social deficits, negative schizotypy, and personality traits indicative of emotional disturbance in adulthood. Our results suggest that SAD in early adolescence might be an indicator of psychopathology in adulthood and give support to dimensional models of psychopathology.

Schizotypal disorder and schizophrenia: a profile analysis of neuropsychological functioning in Japanese patients

This study compares neuropsychological functioning in a Japanese schizophrenia spectrum disorder group and a group of healthy Japanese volunteers. Participants were 37 patients diagnosed with schizophrenia, 28 schizotypal patients, and 99 psychiatrically-normal volunteers. A wide range of cognitive measures were examined. All participants completed a Japanese version of a neuropsychological battery assessing executive function, working memory, processing speed, language, verbal memory, and spatial organization. Comparisons of neuropsychological function demonstrated similarities and differences between patients diagnosed with schizotypal disorder and those diagnosed with schizophrenia. Impairments in verbal memory, language, and processing speed were common to both patient groups and may represent a vulnerability to schizophrenia. Impairments in aspects of working memory, spatial organization and executive function were preferentially observed in schizophrenia and may be features of the overt manifestation of psychosis. Possible differences in the contributions of prefrontal and temporo-limbic structures provide direction for further studies.

The impact of subclinical psychosis on the transition from subclinicial mania to bipolar disorder

BACKGROUND

In the general population, symptoms of mania and psychosis are more broadly distributed than their associated clinical syndromes. Little is known, however, about how these subclinical population phenotypes co-vary with and impact on each other.

METHOD

In a representative population cohort of 7076 adults, prevalence of mania and psychosis symptoms and syndromes were assessed with the CIDI at baseline, at one (T1) and two years later (T2). The degree of comorbidity between subclinical mania and subclinical psychosis was examined, as well as the impact of subclinical comorbidity on social impairment and transition from subclinical mania to onset of bipolar disorder.

RESULTS

The lifetime prevalence of at least one manic and one psychotic symptom was 4.1% and 4.2% respectively. Excluding individuals with any lifetime DSM-III-R bipolar or psychotic disorder (n=218), these prevalences were 2.3% (subclinical mania) and 2.8% (subclinical psychosis). Individuals with subclinical mania had a 17% risk of subclinical psychosis, compared with 2.3% in those without (P<0.000). Comorbid subclinical psychosis in individuals with subclinical mania was much more predictive of a future diagnosis of bipolar disorder (positive predictive values of 3% versus 10% respectively).

CONCLUSION

Subclinical phenotypes of mania and psychosis are more prevalent than their clinical counterparts and cluster together. The risk factors for psychosis may facilitate the formation of more "toxic" combinations of subclinical mania and subclinical psychosis with a higher probability of transition to bipolar disorder. A better understanding of this pathway is crucial for the development of early interventions.

Impairment of memory organization in patients with schizophrenia or schizotypal disorder

Verbal learning and the organization of memory in patients with schizophrenia or schizotypal disorder were compared with normal subjects. Three indices of memory organization (semantic clustering, serial clustering, and subjective clustering) were calculated from participants' responses on the Japanese Verbal Learning Test. Schizophrenic and schizotypal patients showed similar decrements in semantic organization compared with normal subjects. Neither patient group showed any effect of learning on their use of semantic organization, although both groups recalled more items as the number of trials increased. These results suggest that impairment of memory organization is a common characteristic of schizophrenia spectrum disorders.

Impairment of event schema in patients with schizophrenia: examination of script for shopping at supermarket

The purpose of this study was to examine event schema, the conceptualization of past experience based on script theory, in Japanese patients with schizophrenia. Subjects comprised 25 patients meeting DSM-IV criteria for schizophrenia and 31 normal individuals who gave informed consent. This experiment used three script tasks measuring free recall, frequency judgment, and sequencing of events encountered when shopping at a supermarket. Patients with schizophrenia performed significantly worse than did control subjects on all tasks. In particular, patients committed more errors when judging the events that "occasionally happen" in the frequency judgment task. On the other hand, these patients judged "seldom occurring events" relatively well. Patients with schizophrenia made more errors than normal people in the free recall task. Specifically, patients made more intrusion errors and failed to close scripts. There was a negative correlation between scores the Scale for the Assessment of Positive Symptoms and performance on the free recall task. The results of the present study suggest that event schemas (semantic structure) in patients with schizophrenia are impaired which may be associated with positive symptoms and frontal lobe dysfunction.

Evidence for instrument and family-specific variation of subclinical psychosis dimensions in the general population

It is unknown to what degree dimensions of schizotypy (subclinical psychosis) show independent, family-specific variation in the general population. Psychologists administered the Community Assessment of Psychic Experiences, the Structured Interview for Schizotypy-Revised (SIS-R), and the Brief Psychiatric Rating Scale to 257 subjects pertaining to 82 general population families. All 3 instruments showed family-specific variation for positive and negative subclinical psychosis dimensions with between-families proportions of total variance between 10% and 40%. However, only the SIS-R showed family-specific variation of the negative dimension independent of its correlation with the positive dimension. The positive dimension of subclinical psychosis shows familial-specific variation in samples unselected for psychiatric disorder, suggesting dimensional liability in the population. The SIS-R additionally captures family-specific variation in the negative domain.

Differential contributions of prefrontal and temporolimbic pathology to mechanisms of psychosis

Common abnormalities within the schizophrenia spectrum may be essential for the pathogenesis of schizophrenia, but additional pathological changes may be required for the development of full-blown schizophrenia. Clarifying the neurobiological similarities and differences between established schizophrenia and a milder form of schizophrenia spectrum disorder would potentially discriminate the pathophysiological mechanisms underlying the core features of the schizophrenia spectrum from those associated with overt psychosis. High-resolution MRIs were acquired from 25 patients with schizotypal disorder, 53 patients with schizophrenia and 59 healthy volunteers matched for age, gender, handedness and parental education. Volumetric measurements of the medial temporal structures and the prefrontal cortex subcomponents were performed using consecutive 1-mm thick coronal slices. Parcellation of the prefrontal cortex into subcomponents was performed according to the intrinsic anatomical landmarks of the frontal sulci/gyri. Compared with the controls, the bilateral volumes of the amygdala and the hippocampus were reduced comparably in the schizotypal and schizophrenia patients. The parahippocampal gyrus volume did not differ significantly between diagnostic groups. Total prefrontal grey matter volumes were smaller bilaterally in the schizophrenia patients than in the controls and the schizotypal patients, whereas the schizotypal patients had larger prefrontal grey matter than the controls in the right hemisphere. In the schizophrenia patients, grey matter volumes of the bilateral superior frontal gyrus, left middle frontal gyrus, bilateral inferior frontal gyrus and bilateral straight gyrus were smaller than those in the controls. The schizophrenia patients also had reduced grey matter volumes in the right superior frontal gyrus, bilateral middle frontal gyrus and right inferior frontal gyrus relative to the schizotypal patients. Compared with the controls, the schizotypal patients had larger volumes of the bilateral middle frontal gyrus and smaller volumes of the right straight gyrus. There were no significant between-group differences in volumes of the ventral medial prefrontal cortex or the orbitofrontal cortex. These findings suggest that volume reductions in the amygdala and hippocampus are the common morphological substrates for the schizophrenia spectrum, which presumably represent the vulnerability. Additional widespread involvement of the prefrontal cortex in schizophrenia may lead to the loss of inhibitory control in other brain regions and suggests (although it is not specifically be related to) its critical role in the manifestation of overt psychosis.

Disorganization of semantic memory underlies alogia in schizophrenia: an analysis of verbal fluency performance in Japanese subjects

Patients with schizophrenia exhibit impaired semantic memory as well as deficits in a wide range of language-related functions, such as verbal fluency, comprehension and production of complex sentences. Since language and memory disturbances may underlie some of the psychotic symptoms of schizophrenia, the present study investigated the specific association between alogia (i.e. poverty of speech, poverty of content of speech, blocking, and increased latency of response) and semantic memory organization using the category fluency task (CFT) as a measure of verbal fluency. Thirty-eight patients with schizophrenia and an equal number of normal controls entered the study. Semantic structure was derived from multidimensional scaling analysis using sequential word outputs from the CFT. Patients with schizophrenia revealed disorganized semantic structure (e.g. irregular association of category members) compared with controls, consistent with previous reports. The patients were then divided into two groups, i.e. alogia- and non-alogia subjects, based on the Alogia scores from the Scale for the Assessment of Negative Symptoms (SANS). The symptom-based analysis showed that the semantic structure for the alogia group (Alogia score < or =2) was more disorganized than that for the non-alogia group (Alogia score <1) although the number of words produced did not differ between the two groups. The results of cluster analysis revealed the presence of bizarre coherence specifically in the alogia group. These results indicate that semantic memory disorganization may contribute to the symptom of alogia in schizophrenia. In addition, this is one of the few studies that examined verbal fluency in Japanese patients with schizophrenia and suggest that the language abnormalities in schizophrenia are universal.

How does studying schizotypal personality disorder inform us about the prodrome of schizophrenia?

An increasing emphasis in the schizophrenia literature has been on the prodromal phase of the illness. The study of schizophrenia spectrum illness, including schizotypal personality disorder, has added important insight into the etiology, neuropathology, and treatment of schizophrenia, which can facilitate early identification, intervention, and perhaps prevention of the illness. The heterogeneity of the schizophrenia spectrum makes its definition elusive at best. The primary aim of the Cognitive Assessment and Risk Evaluation Program at the authors' institution is to combine the current knowledge of clinical and demographic risk factors for schizophrenia with the rapidly emerging data on vulnerability markers, or endophenotypes, that are associated with schizophrenia. The use of brain-based vulnerability markers may help to identify neurobiologically and clinically meaningful subgroups within this heterogeneous population of individuals in the early stages of schizophrenia. Another important aim of the Cognitive Assessment and Risk Evaluation program is to thoroughly assess those individuals who have not converted to psychosis to understand potential protective factors, reduce the rate of false positives, and decrease disability. The current review details a strategy for researching the schizophrenia prodrome by using information gained from research in schizotypal personality disorder.