Origins of cognitive dysfunction in schizophrenia: clues from age at onset

First-Episode Psychosis Patients Who Deteriorated in the Premorbid Period Do Not Have Higher Polygenic Risk Scores Than Others: A Cluster Analysis of EU-GEI Data

Cluster studies identified a subgroup of patients with psychosis whose premorbid adjustment deteriorates before the onset, which may reflect variation in genetic influence. However, other studies reported a complex relationship between distinctive patterns of cannabis use and cognitive and premorbid impairment that is worthy of consideration. We examined whether: (1) premorbid social functioning (PSF) and premorbid academic functioning (PAF) in childhood and adolescence and current intellectual quotient (IQ) define different clusters in 802 first-episode of psychosis (FEP) patients; resulting clusters vary in (2) polygenic risk scores (PRSs) for schizophrenia (SCZ_PRS), bipolar disorder (BD_PRS), major depression (MD_PRS), and IQ (IQ_PRS), and (3) patterns of cannabis use, compared to 1,263 population-based controls. Four transdiagnostic clusters emerged (BIC = 2268.5): (1) high-cognitive-functioning (n = 205), with the highest IQ (Mean = 106.1, 95% CI: 104.3, 107.9) and PAF, but low PSF. (2) Low-cognitive-functioning (n = 223), with the lowest IQ (Mean = 73.9, 95% CI: 72.2, 75.7) and PAF, but normal PSF. (3) Intermediate (n = 224) (Mean_IQ = 80.8, 95% CI: 79.1, 82.5) with low-improving PAF and PSF. 4) Deteriorating (n = 150) (Mean_IQ = 80.6, 95% CI: 78.5, 82.7), with normal-deteriorating PAF and PSF. The PRSs explained 7.9% of between-group membership. FEP had higher SCZ_PRS than controls [F(4,1319) = 20.4, P < .001]. Among the clusters, the deteriorating group had lower SCZ_PRS and was likelier to have used high-potency cannabis daily. Patients with FEP clustered according to their premorbid and cognitive abilities. Pronounced premorbid deterioration was not typical of most FEP, including those more strongly predisposed to schizophrenia, but appeared in a cluster with a history of high-potency cannabis use.

Family history of psychosis and outcome of people with schizophrenia in rural China: 14-year follow-up study

OBJECTIVE

This study examined the differences in 14-year outcomes of persons with schizophrenia with and without family history of psychosis in a rural community in China.

METHODS

All participants with schizophrenia (n=510) aged 15 years and older were identified in a 1994 epidemiological investigation of 123,572 people and followed up in 2004 and 2008 in Xinjin County, Chengdu, China.

RESULTS

Individuals with positive family history of schizophrenia had significantly younger age of first onset than those with negative family history of schizophrenia in 1994 and 2004. Compared with individuals with negative family history of schizophrenia, those with positive family history of schizophrenia had significantly higher rate of homelessness and lower rate of death due to other reasons in 10-year (2004) and 14-year follow-up (2008). There were no significantly differences of mean scores on PANSS, SDSS and GAF in 2008 between positive and negative family history groups.

CONCLUSIONS

The positive family history of schizophrenia is strongly related to younger age of onset, and may predict a poorer long-term outcome (e.g., higher rate of homelessness) in persons with schizophrenia in the rural community. The findings have implications for further studies on specific family-related mechanisms on clinical treatment and rehabilitation, as well as for planning and delivering of community-based mental health services.

A Neurophysiological Perspective on a Preventive Treatment against Schizophrenia Using Transcranial Electric Stimulation of the Corticothalamic Pathway

Schizophrenia patients are waiting for a treatment free of detrimental effects. Psychotic disorders are devastating mental illnesses associated with dysfunctional brain networks. Ongoing brain network gamma frequency (30–80 Hz) oscillations, naturally implicated in integrative function, are excessively amplified during hallucinations, in at-risk mental states for psychosis and first-episode psychosis. So, gamma oscillations represent a bioelectrical marker for cerebral network disorders with prognostic and therapeutic potential. They accompany sensorimotor and cognitive deficits already present in prodromal schizophrenia. Abnormally amplified gamma oscillations are reproduced in the corticothalamic systems of healthy humans and rodents after a single systemic administration, at a psychotomimetic dose, of the glutamate N-methyl-d-aspartate receptor antagonist ketamine. These translational ketamine models of prodromal schizophrenia are thus promising to work out a preventive noninvasive treatment against first-episode psychosis and chronic schizophrenia. In the present essay, transcranial electric stimulation (TES) is considered an appropriate preventive therapeutic modality because it can influence cognitive performance and neural oscillations. Here, I highlight clinical and experimental findings showing that, together, the corticothalamic pathway, the thalamus, and the glutamatergic synaptic transmission form an etiopathophysiological backbone for schizophrenia and represent a potential therapeutic target for preventive TES of dysfunctional brain networks in at-risk mental state patients against psychotic disorders.

Association of KIBRA rs17070145 polymorphism with episodic memory in the early stages of a human neurodevelopmental disorder

A common T/C polymorphism within the ninth intron of the KIBRA gene (rs17070145) is thought to influence memory in humans. Since cognitive impairment, including memory, is a core feature of schizophrenia, we attempted to investigate this association in an independent sample of adolescent patients with early-onset schizophrenia (EOS; onset before age 18) probands and their healthy siblings. In a sample of 25 pairs of EOS proband-healthy full sibling, we sought to investigate the association of KIBRA with memory performance. Episodic memory was measured using immediate and delayed recall measures of the California Verbal Learning Test. EOS underperformed at immediate and delayed recall compared with siblings. In a combined analysis (TT vs. TC/CC) assuming a C dominant model of inheritance, we found a main effect of genotype where individuals with TT genotype outperformed non-TT-carriers at immediate and delayed recall. A genotype by group interaction showed that EOS with TT genotype did not show a memory advantage over siblings with TT or non-TT-carriers at immediate or delayed recall. Siblings with TT genotype showed enhanced immediate recall (not delayed recall) compared with non-TT-carriers. This study demonstrates an association between the KIBRA gene and episodic memory (immediate free recall) and suggests a differential effect of this genetic variant in EOS and healthy siblings.

A genome-wide linkage scan for distinct subsets of schizophrenia characterized by age at onset and neurocognitive deficits

BACKGROUND

As schizophrenia is genetically and phenotypically heterogeneous, targeting genetically informative phenotypes may help identify greater linkage signals. The aim of the study is to evaluate the genetic linkage evidence for schizophrenia in subsets of families with earlier age at onset or greater neurocognitive deficits.

METHODS

Patients with schizophrenia (n  =  1,207) and their first-degree relatives (n  =  1,035) from 557 families with schizophrenia were recruited from six data collection field research centers throughout Taiwan. Subjects completed a face-to-face semi-structured interview, the Continuous Performance Test (CPT), the Wisconsin Card Sorting Test, and were genotyped with 386 microsatellite markers across the genome.

RESULTS

A maximum nonparametric logarithm of odds (LOD) score of 4.17 at 2q22.1 was found in 295 families ranked by increasing age at onset, which had significant increases in the maximum LOD score compared with those obtained in initial linkage analyses using all available families. Based on this subset, a further subsetting by false alarm rate on the undegraded and degraded CPT obtained further increase in the nested subset-based LOD on 2q22.1, with a score of 7.36 in 228 families and 7.71 in 243 families, respectively.

CONCLUSION

We found possible evidence of linkage on chromosome 2q22.1 in families of schizophrenia patients with more CPT false alarm rates nested within the families with younger age at onset. These results highlight the importance of incorporating genetically informative phenotypes in unraveling the complex genetics of schizophrenia.

Attributional style of Egyptians with schizophrenia

The attributional style is one domain of social cognition that involves perceiving, interpreting, and generating responses to others' intentions and behaviours in different situations. This study describes the attributional style of Egyptians with schizophrenia. The study took place in a psychiatric hospital in Egypt. Eight psychiatric wards were randomly selected, and all participants (150) with a diagnosis of schizophrenia participated. Data were collected using the Ambiguous Intention Hostility Questionnaire (AIHQ), the attributional style interview schedule, and the sociodemographic/clinical data sheet. Participants' scores on the AIHQ varied significantly between different situations (intentional, accidental, and ambiguous). The attributional style of the studied participants regarding their perceived psychosocial problems tended to be related to specific causes. These causes were mostly externally attributed to other people and to circumstances, and were perceived not to persist in the future. It would seem that Egyptians with schizophrenia tend to blame other people for negative events if these events are perceived to cause intentional harm.

The impact of a family history of psychosis on age-at-onset and positive and negative symptoms of schizophrenia: a meta-analysis

The results of research on the relation of family history (FH) of psychosis with clinical presentation in schizophrenia have been mixed. To date, there have been no comprehensive reviews that have examined this body of research. The current review quantitatively evaluates research on the relation of FH with two aspects of schizophrenia, age-at-onset and symptom presentation. Studies investigating the influence of a FH on age-at-onset (N=15 studies), age-at-onset and sex (N=12 studies), and/or positive (N=11 studies) and negative symptoms (N=12 studies) in patients with schizophrenia were included in the meta-analyses. Results showed that FH has a small but significant impact on age-at-onset as well as negative symptoms. Of most interest was the finding that sex differences in age-at-onset are not observed in samples with a FH. Furthermore, there was a significant interaction between FH and sex with respect to negative symptoms. The findings of the current review are discussed in light of the diathesis-stress model. Theoretical assumptions and empirical research are reviewed to support the notion that FH influences susceptibility and presentation through similar mechanisms. Implications of the current findings, limitations of the review, and directions for future research are highlighted.

Dissociation of long-term verbal memory and fronto-executive impairment in first-episode psychosis

BACKGROUND

Verbal memory is frequently and severely affected in schizophrenia and has been implicated as a mediator of poor clinical outcome. Whereas encoding deficits are well demonstrated, it is unclear whether retention is impaired. This distinction is important because accelerated forgetting implies impaired consolidation attributable to medial temporal lobe (MTL) dysfunction whereas impaired encoding and retrieval implicates involvement of prefrontal cortex.

METHOD

We assessed a group of healthy volunteers (n=97) and pre-morbid IQ- and sex-matched first-episode psychosis patients (n=97), the majority of whom developed schizophrenia. We compared performance of verbal learning and recall with measures of visuospatial working memory, planning and attentional set-shifting, and also current IQ.

RESULTS

All measures of performance, including verbal memory retention, a memory savings score that accounted for learning impairments, were significantly impaired in the schizophrenia group. The difference between groups for delayed recall remained even after the influence of learning and recall was accounted for. Factor analyses showed that, in patients, all variables except verbal memory retention loaded on a single factor, whereas in controls verbal memory and fronto-executive measures were separable.

CONCLUSIONS

The results suggest that IQ, executive function and verbal learning deficits in schizophrenia may reflect a common abnormality of information processing in prefrontal cortex rather than specific impairments in different cognitive domains. Verbal memory retention impairments, however, may have a different aetiology.

Prospective memory deficits in subjects with schizophrenia spectrum disorders: a comparison study with schizophrenic subjects, psychometrically defined schizotypal subjects, and healthy controls

Memory impairment is one of the core deficits in schizophrenia. This study explored the memory profiles of schizophrenic and psychometrically defined schizotypal subjects. The study participants included 15 patients with schizophrenia, 41 schizotypal subjects, and 20 healthy controls. All of the participants completed verbal and visual memory, working memory, and prospective memory tasks. The results showed that patients with schizophrenia were impaired in all aspects of memory function, whereas the schizotypal subjects tended to show moderate to large impairment effect sizes in prospective memory. It is suggested that prospective memory be considered a potential endophenotype of schizophrenia.

Duration of Untreated Psychosis, Referral Route, and Age of Onset in an Early Intervention in Psychosis Service and a Local CAMHS

BACKGROUND

  The aim of this study was to investigate associations between demographic and clinical variables and duration of untreated psychosis (DUP) in a sample of cases of psychosis across an adult early intervention in psychosis service and a child and adolescent community team.

METHOD

  Cross-sectional baseline data for cases of psychosis across the two teams on the caseload at a given time point were collected, including age of onset, gender, ethnicity, referral route, and DUP.

RESULTS

  The median DUP across the entire sample was 91 days, while those patients with initial treatment for psychosis from the child and adolescent team had a median DUP of 69 days. Using multiple linear regression, there were two variables that showed a significant association with DUP: referral route (p < .001), and age of onset, with earlier age of onset associated with shorter DUP (p = .015).

CONCLUSION

  These findings are discussed in relation to possible explanatory factors, with particular focus on service-level variables and pathways to care. It is suggested that the involvement of child and adolescent teams is vital to the work of early intervention in psychosis services.

Schizophrenia, "Just the Facts": what we know in 2008 part 1: overview

For every disorder, there is a set of established findings and accepted constructs upon which further understanding is built. The concept of schizophrenia as a disease entity has been with us for a little more than a century, although descriptions resembling this condition predate this conceptualization. In 1988, for the inaugural issue of Schizophrenia Research, at the invitation of the founding editors, a senior researcher, since deceased (RJ Wyatt) published a summary of generally accepted ideas about the disorder, which he termed "the facts" of schizophrenia. Ten years later, in conjunction with two of the authors (MSK, RT), he compiled a more extensive set of "facts" for the purpose of evaluating conceptual models or theoretical constructs developed to understand the nature of schizophrenia. On the 20th anniversary of this journal, we update and substantially expand our effort to periodically summarize the current body of information about schizophrenia. We compile a body of seventy-seven representative major findings and group them in terms of their specific relevance to schizophrenia -- etiologies, pathophysiology, clinical manifestations, and treatments. We rate each such "fact" on a 0-3 scale for measures of reproducibility, whether primary to schizophrenia, and durability over time. We also pose one or more critical questions with reference to each "fact", answers to which might help better elucidate the meaning of that finding for our understanding of schizophrenia. We intend to follow this paper with the submission to the journal of a series of topic-specific articles, critically reviewing the evidence.

Toward a model of memory enhancement in schizophrenia: glucose administration and hippocampal function

Recognition of the need to treat cognitive deficits in schizophrenia is compelling and well established, with empirical findings and conceptual arguments related to cognitive enhancement appearing regularly in the literature. Cognitive enhancement itself, however, remains at an early stage. Biological approaches have centered on the development of antipsychotic medications that also improve cognition, but the results have so far remained modest. As a way to facilitate the development of cognitive enhancers in schizophrenia, this article focuses on adjunctive pharmacological approaches to antipsychotic medications and highlights the need for systematic explorations of relevant brain mechanisms. While numerous conceptual criteria might be employed to guide the search, we will focus on 4 points that are especially likely to be useful and which have not yet been considered together. First, the discussion will focus on deficits in a particular cognitive domain, verbal declarative memory. Second, we will review the current status of preclinical and clinical efforts to improve declarative memory using antipsychotic medications, which is the main, existing mode of treatment. Third, we will examine an example of an adjunctive intervention-glucose administration-that improves memory in animals and humans, modulates function in brain regions related to verbal declarative memory, and is highly amenable to translational research. Finally, a heuristic model will be outlined to explore how the intervention maps on to the underlying neurobiology of schizophrenia. More generally, the discussion underlines the promise of cognitive improvement in schizophrenia and the need to approach the issue in a programmatic manner.

The Consortium on the Genetics of Schizophrenia: neurocognitive endophenotypes

The Consortium on the Genetics of Schizophrenia (COGS) is a 7-site collaboration that examines the genetic architecture of quantitative endophenotypes in families with schizophrenia. Here we review the background and rationale for selecting neurocognitive tasks as endophenotypic measures in genetic studies. Criteria are outlined for the potential of measures as endophenotypic vulnerability markers. These include association with illness, state independence (ie, adequate test-retest stability, adequate between-site reliability, impairments in patients not due to medications, impairments observed regardless of illness state), heritability, findings of higher rates in relatives of probands than in the general population, and cosegregation within families. The COGS required that, in addition, the measures be "neurocognitive" and thus linked to neurobiology and that they be feasible in multisite studies. The COGS neurocognitive assessment includes measures of attention, verbal memory, working memory, and a computerized neurocognitive battery that also includes facial processing tasks. Here we describe data demonstrating that these neurobehavioral measures meet criteria for endophenotypic candidacy. We conclude that quantitative neurocognitive endophenotypes need further evidence for efficacy in identifying genetic effects but have the potential of providing unprecedented insight into gene-environment interaction related to dimensions of brain and behavior in health and disease.

Cognitive, emotional, and social processes in psychosis: refining cognitive behavioral therapy for persistent positive symptoms

Psychosis used to be thought of as essentially a biological condition unamenable to psychological interventions. However, more recent research has shown that positive symptoms such as delusions and hallucinations are on a continuum with normality and therefore might also be susceptible to adaptations of the cognitive behavioral therapies found useful for anxiety and depression. In the context of a model of cognitive, emotional, and social processes in psychosis, the latest evidence for the putative psychological mechanisms that elicit and maintain symptoms is reviewed. There is now good support for emotional processes in psychosis, for the role of cognitive processes including reasoning biases, for the central role of appraisal, and for the effects of the social environment, including stress and trauma. We have also used virtual environments to test our hypotheses. These developments have improved our understanding of symptom dimensions such as distress and conviction and also provide a rationale for interventions, which have some evidence of efficacy. Therapeutic approaches are described as follows: a collaborative therapeutic relationship, managing dysphoria, helping service users reappraise their beliefs to reduce distress, working on negative schemas, managing and reducing stressful environments if possible, compensating for reasoning biases by using disconfirmation strategies, and considering the full range of evidence in order to reduce high conviction. Theoretical ideas supported by experimental evidence can inform the development of cognitive behavior therapy for persistent positive symptoms of psychosis.

Development of visual motion perception in children of patients with schizophrenia and bipolar disorder: a follow-up study

The "dorsal-stream vulnerability" hypothesis claims that motion-sensitive areas in the dorsal occipito-parietal visual system are vulnerable to genetic and environmental factors which affect brain maturation and development. The aim of this study was to investigate the possibility that developmental anomalies of directional motion perception can be detected in children of mothers with schizophrenia and bipolar disorder. Motion and form coherence thresholds were measured in 36 children of mothers with schizophrenia, 28 children of mothers with bipolar disorder, and 30 children with negative family history at 7, 8-9, and 10-11 years of age. These tasks require the detection of direction of coherently moving dots embedded among randomly oscillating dots (motion task) and the detection of tangentially oriented line-segments embedded among randomly oriented segments (form task). Results revealed that the rate of development in the motion task was less pronounced in children of mothers with schizophrenia than that in children of mothers with bipolar disorder and in age-matched controls. The development of form perception was spared. Children of mothers with bipolar disorder showed an intact development in both motion and form perception tasks. These results suggest that the progressive developmental abnormality of motion-sensitive visual areas may be a characteristic feature of schizophrenia-vulnerability.

Gender and ethnic differences in urban and rural first-contact schizophrenia outpatients in Trinidad

This study investigated gender and ethnic differences in the rate of first contact outpatients with schizophrenia in the setting of a more-urban region (MUR) and a less-urban region (LUR) in Trinidad. In a prospective study, 134 first-contact patients with a diagnosis of schizophrenia were selected from two ecologically different regions.

RESULTS

Of this population, 56.7% were of African origin and 32.1% were of Indian descent. Gender differences were significant, with males accounting for 66.4% (n=89) of patients with schizophrenia (chi2 = 14.45, d.f. = 1, p = 0.0001). Further analysis by age categories revealed a significant male predominance at ages 20-24 (p = 0.0001) and 25-29 (p = 0.002). Young African males (15-19 y, p = 0.049) predominated in MUR compared with LUR. The results showed a marked presence of Afro-Trinidadian males in both outpatient clinics (p < 0.05). We conclude that gender and ethnicity are important variables in the presentation of schizophrenia in Trinidad, whereas neither rural nor urban environments appeared to influence the expression of schizophrenia.