Two subgroups of schizophrenia identified by systematic cognitive neuropsychiatric mapping

The relationship between human development and prevalence of deficit schizophrenia: Results from a systematic review and meta-analysis

This study examined the relationship between the prevalence of deficit schizophrenia (DS) and a country's Human Development Index (HDI). A systematic review and meta-analysis of the literature published in the last decade were conducted to acquire data on the worldwide prevalence of deficit syndrome in schizophrenia cohorts and examine the correlation between DS prevalence and the HDI of the countries in the review. Twenty-six studies meeting our eligibility criteria provided prevalence data on DS in 14 countries with both low-to-middle and high-incomes, ranging from 14.34%-to 61.57%. The pooled prevalence of DS was 32.19% (95% CI = 26.17 to 38.52). Statistical analysis yielded a correlation coefficient (r) of -0.518 (95% CI = -0.754 to -0.164; p = 0.007), indicating a moderate inverse correlation between DS prevalence and HDI. This relationship remained significant in partial correlation analysis after controlling for potential sources of bias in the DS estimates (r = -0.489, p = 0.013). Our results show that schizophrenia cohorts from low-to-middle-income countries are more prone to primary and enduring negative symptoms, and contribute to the emerging evidence questioning the axiom that schizophrenia in the developing world has a better course than in high-income countries.

Eye movement characteristics in male patients with deficit and non-deficit schizophrenia and their relationships with psychiatric symptoms and cognitive function

BACKGROUND

The cognitive impairment pattern of deficit schizophrenia (DS) is centered on an impaired attention function. Previous studies have suggested that the exploratory eye movement (EEM) tests reflect attention deficits in patients with schizophrenia. However, no study has investigated the characteristics of eye movement in DS in the Chinese Han population. This study aimed to investigate the pattern of eye movement characteristics in DS patients and to examine whether eye movement characteristic is associated with serious negative symptoms and cognitive decline in this schizophrenia subtype.

METHODS

A total of 86 male patients [37 DS and 49 non-deficit schizophrenia (NDS)] and 80 healthy controls (HC) participated in this study. Clinical symptoms were assessed using the Scale for the Assessment of Positive Symptoms (SAPS) and Scale for the Assessment of Negative Symptoms (SANS). Cognitive function was assessed using the Mattis Dementia Rating Scale (MDRS-2). Eye movement data of subjects were collected using an eye movement tracking analyzer.

RESULTS

There were significant differences in the overall eye movement data and cognitive test scores among the three groups (all P < 0.001). Both DS and NDS schizophrenia subgroups showed more severe eye movement and cognitive impairment compared with the control group. The number of eye fixations (NEF), total of eye scanning length (TESL), and cognitive function in DS patients were significantly lower than those in NDS patients. The discriminant analysis (D score) was higher than that of the control group (P < 0.001). In the DS group, the inattention factor of SANS was negatively correlated with the attention factor (r = - 0.545, P = 0.001) and structure factor of cognitive (r = - 0.389, P = 0.023), the affective flattening factor of SANS was negatively correlated with TESL (r = - 0.353, P = 0.041) and initiation/retention factor of cognitive (r = - 0.376,P = 0.028). TESL was found to positively correlate with the MDRS-2 total score (r = 0.427, P = 0.012), attention factor (r = 0.354, P = 0.040), and memory factor (r = 0.349, P = 0.043) in the DS group, whereas the mean of eye scanning length (MESL) positively correlated with cognitive impairments in the NDS group. The negative symptoms showed no significant correlation with cognition in the NDS group.

CONCLUSIONS

Total of eye scanning length may be a characteristic eye movement symptom in DS patients, which is associated with serious negative symptoms and cognitive impairment in this schizophrenia subtype.

Deficit syndrome in Chinese patients with first-episode drug naïve schizophrenia: Prevalence, demographic and clinical characteristics

BACKGROUND

Deficit syndrome (DS) is a common subgroup of schizophrenia. However, few studies have examined the prevalence and risk factors for DS in Chinese Han patients with schizophrenia. The aim of this study was to assess prevalence, demographic and clinical characteristics of DS in Chinese Han patients with first-episode drug naïve (FEDN) schizophrenia.

METHODS

In total, 235 patients with schizophrenia were recruited, and clinical and demographic data were collected. The Positive and Negative Syndrome Scale (PANSS) was utilized for the psychopathological symptoms, and the 17-item Hamilton Depression Rating Scale (HDRS-17) for depressive symptoms. The Proxy for the Deficit Syndrome (PDS) was adopted to identify DS.

RESULTS

The prevalence of DS in the cohort of first-episode schizophrenia patients was 23.0%. Compared to those patients without DS, patients with DS had younger age, lower education level, and were more likely to be single. Further, DS patients had significantly lower scores of positive symptoms, general psychopathology, and depression than non-DS patients. Patients with DS had fewer suicide attempts, but they had more severe negative symptoms and cognitive impairment (all p < 0.05). Multiple regression showed that poor cognitive functioning, lower levels of depression and younger age at onset were predictors of DS.

CONCLUSIONS

Chinese Han patients with FEDN schizophrenia have high prevalence of DS. Some demographic and clinical parameters may be associated with DS.

Olfactory Impairment in Children and Adolescents With Obsessive-Compulsive Disorder

In this study, we aimed to examine the olfactory function of adolescents with obsessive-compulsive disorder (OCD). We investigated olfactory function of 50 adolescents with OCD and 50 healthy controls (min-max, 12-17 years) by the "Sniffin' Sticks" extended test. OCD and depression symptomatology were assessed with the Maudsley Obsessive-Compulsive Inventory (MOCI) and the Children's Depression Inventory (CDI). Adolescents with OCD had lower olfactory performance than healthy controls. The patients who responded positively to the treatment exhibited performance superior to the patients with partial response and those untreated. All olfactory measurements were significantly inversely correlated with MOCI and CDI total scores and OCD duration. Our results show that OCD has a significant impact on all olfactory tests, and olfactory impairment is related to symptom severity, duration, and course of OCD. The decrease in olfactory function may be a noninvasive state marker for OCD. Further investigations in longitudinal studies are required to confirm our results.

Characterization of deficit schizophrenia and reliability of the bidimensional model of its negative symptomatology

Background: Cumulative evidence has demonstrated important differences between deficit (DS) and non-deficit (NDS) schizophrenia, suggesting that DS may be a separate disease. However, most data come from the same research groups and more replication is needed to validate this hypothesis.Aims: Our study aimed to examine the distribution of DS, to compare their characteristics with NDS patients and to analyze the reliability of the two-factor structure of its negative symptomatology in a Spanish clinical sample.Methods: Sixty clinically stabilized patients with schizophrenia were evaluated. The Schedule for the Deficit Syndrome was used for DS/NDS categorization. Patient characteristics included age, gender, education, age at onset of psychosis, duration of illness, family history of psychosis, type of antipsychotic regimen, schizophrenia subtype and severity of the disease.Results: DS prevalence was 28.3%. Bivariate analysis revealed statistical differences between DS and NDS in terms of years of education and schizophrenia subtype. Factor analysis replicated the two-factor solution consisting of the 'Expressive deficit' and 'Avolition-apathy' domains reported in previous studies.Conclusions: Our results were consistent with the published data and indicated that the DS profile in the Spanish population is similar to that in other populations, which would corroborate the homogeneity of DS within the schizophrenia spectrum and contribute to the hypothesis that DS constitutes a separate disease.

Significant repetition probability effects in schizophrenia

BACKGROUND

A growing body of evidence suggests that the comparison of expected and incoming sensory stimuli (the prediction-error (ε) processing) is impaired in schizophrenia patients (SZ). For example, in studies of mismatch negativity, an ERP component that signals ε, SZ patients show deficits in the auditory and visual modalities. To test the role of impaired ε processing further in SZ, using neuroimaging methods, we applied a repetition-suppression (RS) paradigm.

METHODS

Patients diagnosed with SZ (n = 17) as well as age- and sex- matched healthy control subjects (HC, n = 17) were presented with pairs of faces, which could either repeat or alternate. Additionally, the likelihood of repetition/alternation trials was modulated in individual blocks of fMRI recordings, testing the effects of repetition probability (P(rep)) on RS.

RESULTS

We found a significant RS in the fusiform and occipital face areas as well as in the lateral occipital cortex that was similar in healthy controls and SZ patients SZ. More importantly, we observed similar P(rep) effects (larger RS in blocks with high frequency of repetitions than in blocks with low repetition likelihood) in both the control and the patient group.

CONCLUSION

Our findings suggest that repetition_probability modulations affect the neural responses in schizophrenia patients and healthy participants similarly. This suggests that the neural mechanisms determining perceptual inferences based on stimulus probabilities remain unimpaired in schizophrenia.

Is the Prevalence of the Deficit Syndrome in Schizophrenia Higher than Estimated? Results of a Meta-Analysis

The primary and enduring presence of negative symptoms observed in a relatively homogeneous subgroup of patients with schizophrenia led to the concept of deficit syndrome (DS). Until date, it is considered that 20-25% of schizophrenia cohorts have DS. The aim of this meta-analysis was to determine the current prevalence of DS, including international and most recent studies. Thirteen observational studies met the inclusion criteria, comprising 2092 patients from eight countries. Pooled proportion of the DS subgroup was 32.64%, higher than previously reported. Based on our outcomes, up to one-third of patients with schizophrenia might have idiopathic and stable negative symptoms. This significant proportion of patients should be well represented in clinical trial's samples.

Biclustered Independent Component Analysis for Complex Biomarker and Subtype Identification from Structural Magnetic Resonance Images in Schizophrenia

Clinical and cognitive symptoms domain-based subtyping in schizophrenia (Sz) has been critiqued due to the lack of neurobiological correlates and heterogeneity in symptom scores. We, therefore, present a novel data-driven framework using biclustered independent component analysis to detect subtypes from the reliable and stable gray matter concentration (GMC) of patients with Sz. The developed methodology consists of the following steps: source-based morphometry (SBM) decomposition, selection and sorting of two component loadings, subtype component reconstruction using group information-guided ICA (GIG-ICA). This framework was applied to the top two group discriminative components namely the insula/superior temporal gyrus/inferior frontal gyrus (I-STG-IFG component) and the superior frontal gyrus/middle frontal gyrus/medial frontal gyrus (SFG-MiFG-MFG component) from our previous SBM study, which showed diagnostic group difference and had the highest effect sizes. The aggregated multisite dataset consisted of 382 patients with Sz regressed of age, gender, and site voxelwise. We observed two subtypes (i.e., two different subsets of subjects) each heavily weighted on these two components, respectively. These subsets of subjects were characterized by significant differences in positive and negative syndrome scale (PANSS) positive clinical symptoms (p = 0.005). We also observed an overlapping subtype weighing heavily on both of these components. The PANSS general clinical symptom of this subtype was trend level correlated with the loading coefficients of the SFG-MiFG-MFG component (r = 0.25; p = 0.07). The reconstructed subtype-specific component using GIG-ICA showed variations in voxel regions, when compared to the group component. We observed deviations from mean GMC along with conjunction of features from two components characterizing each deciphered subtype. These inherent variations in GMC among patients with Sz could possibly indicate the need for personalized treatment and targeted drug development.

A New Division of Schizophrenia Revealed Expanded Bilateral Brain Structural Abnormalities of the Association Cortices

The phenomenological and, consequently, pathophysiological heterogeneity of schizophrenia may be substantially decreased by determining etiologically valid subgroups. In a cross-sectional study, we analyzed the brain structural impairments of outpatients with schizophrenia using concurrent subgrouping methods, partly to enhance the extensity of exploration, and partly to estimate the validation of the divisions. High resolution T1-weighted MR images were obtained for 21 patients and 13 healthy controls. Localized gray matter volumetric deficits were defined with optimized voxel-based morphometry. Employing two concurrent methods (i.e., the widely known deficit-non-deficit division vs. the neurocognitive clusters we identified earlier) the patient group was iteratively divided into two subgroups, and their volumetric peculiarities were compared with one another and with healthy controls. Our division revealed more significant differences demonstrating bilateral brain structural deficits, which affected the association cortices, primarily the heteromodal fields and partly the unimodal fields. This is the first study that showed that abnormalities of the association cortices can be bihemispherial and expanded in schizophrenia, even in the cases of outpatients living integrated in society. Our result suggests that the extended association cortex abnormalities could constitute substantial and determining neurological substrates in the phenomenology and aetiopathogenesis of schizophrenia, at least in a subgroup of patients with more unfavorable neurocognitive characteristics.

Premorbid, clinical and cognitive correlates of primary negative symptoms in first-episode psychosis

Negative symptoms are a core psychopathological dimension of psychotic disorders. Previous research on primary negative symptoms (PNS) mostly focused on chronic samples. Data regarding premorbid, clinical and cognitive correlates of PNS in the early illness course are limited and inconsistent. In this study, we assessed 355 Hong Kong Chinese adult patients presenting with first-episode psychosis (FEP) to early intervention service with an aim to examine the prevalence of PNS and its relationships with premorbid adjustment, clinical and cognitive profiles. PNS was defined as the presence of clinically significant negative symptoms excluding depression, positive symptoms and extrapyramidal signs. Results showed that 14.6% of patients exhibited PNS at service entry. PNS group had poorer premorbid social functioning, lower level of insight, and worse performance in Modified Wisconsin Card Sorting and digit symbol tests than non-PNS group. Logistic regression analysis showed that premorbid social functioning and digit symbol test score were independently associated with PNS. Our findings thus indicate that PNS are frequently observed in FEP patients. Deficits in proceeding speed, alongside impaired premorbid social functioning, might be specifically related to PNS in the early illness stage.

Neurocognitive Impairments in Deficit and Non-Deficit Schizophrenia and Their Relationships with Symptom Dimensions and Other Clinical Variables

Background

Deficit schizophrenia (DS) has been proposed as a pathophysiologically distinct subgroup within schizophrenia. Earlier studies focusing on neurocognitive function of DS patients have yielded inconsistent findings ranging from substantial deficits to no significant difference relative to non-deficit schizophrenia patients (NDS). The present study investigated the severity and characteristic patterns of neurocognitive impairments in DS and NDS patients and their relationships with clinical variables.

Methods

Attention, ideation fluency, cognitive flexibility and visuospatial memory function were assessed in 40 DS patients, 57 NDS patients, and 52 healthy controls by a comprehensive neuropsychological battery.

Results

Both schizophrenia subgroups had overall more severe cognitive impairments than controls while DS performed worse on every neuropsychological measure except the Stroop interference than the NDS patients with age and education as the covariates. Profile analysis found significantly different patterns of cognitive profiles between two patients group mainly due to their differences in attention and cognitive flexibility functions. Age, education, illness duration and negative symptoms were found to have the correlations with cognitive impairments in the NDS group, while only age and the negative symptoms were correlated with the cognitive impairments in the DS group. Multiple regression analyses revealed that sustained attention and cognitive flexibility were the core impaired cognitive domains mediating other cognitive functions in DS and NDS patients respectively.

Conclusions

DS patients exemplified worse in almost all cognitive domains than NDS patients. Sustained attention and cognitive flexibility might be the key impaired cognitive domains for DS and NDS patients respectively. The present study suggested the DS as a specific subgroup of schizophrenia.

Brain structural imaging correlates of olfactory dysfunction in obsessive-compulsive disorder

Olfactory dysfunction has been described in obsessive-compulsive disorder (OCD). Brain regions involved in smell processing partially overlap with structures included in the neurobiological models of OCD, although no previous studies have analyzed the neuroanatomical correlates of olfactory dysfunction in this disorder. The aim of our study was to examine the association between regional gray matter volume, as assessed by a voxel-based morphometry analysis of magnetic resonance images (MRI), and olfactory function, as assessed by the Sniffin' Sticks test (SST). Olfactory function was assessed in 19 OCD patients and 19 healthy volunteers. All participants were also scanned in a 1.5-T magnet to obtain T1-weighted anatomical MRIs, which were pre-processed and analyzed with SPM8. Three different correlation models were used to study the association between regional gray matter volumes and olfactory function in the domains assessed by the SST: detection threshold, discrimination, and identification. OCD patients showed a significant impairment in all the domains assessed by the SST. Voxel-based mapping revealed a positive association in healthy controls between detection threshold and the gray matter content of a left anterior cingulate cortex cluster. In OCD patients, a positive correlation was observed between identification errors and the gray matter volume of the left medial orbital gyrus. In a post hoc analysis, these two gray matter regions were shown to be enlarged in OCD patients. Our findings support the idea that olfactory dysfunction in OCD is associated with volumetric changes in brain areas typically implicated in the neurobiology of the disorder.

General and domain-specific neurocognitive impairments in deficit and non-deficit schizophrenia

Earlier studies suggested more severe overall cognitive impairments in deficit versus non-deficit schizophrenia; however, the specific contribution of different cognitive domains to this overall cognitive impairment remains unclear. The purpose of this study was to compare the two subtypes in general cognitive functioning as well as in individual cognitive domains using the composite score approach. One hundred and forty-three patients fulfilling the criteria for the deficit syndrome were compared with 123 patients diagnosed with non-deficit schizophrenia. Neurocognitive functioning was assessed by a neuropsychological test battery measuring the domains of sustained vigilance/attention, working memory, short-term memory, verbal memory, cognitive flexibility, and ideation fluency. Using the raw neuropsychological measures, we calculated a global index of cognitive impairment and domain-specific composite z-scores. Association between these composite scores and the deficit syndrome was examined by logistic regression analysis. After adjusting for relevant covariates including sex, age, education, smoking, and antipsychotic dose, results indicated a significant increase in the likelihood of deficit syndrome as a function of global (OR = 5.40; 95% CI 3.02-9.65) as well as domain-specific impairments (OR > 2 for all individual domains except for short-term memory). Cognitive flexibility was an independent predictor (OR = 2.92; 95% CI 1.47-5.80), whereas other cognitive domains demonstrated no unique contribution to the general cognitive impairment. Patients with deficit schizophrenia suffer from a more severe degree of neurocognitive impairment, which is qualitatively similar to the dysfunction seen in non-deficit schizophrenia. However, our results indicate that cognitive flexibility is specifically impaired in deficit versus non-deficit patients and may therefore represent a core feature of this subtype.

Olfactory identification and discrimination in obsessive-compulsive disorder

BACKGROUND

Neuroimaging and neuropsychological data from patients with an obsessive-compulsive disorder (OCD) indicate the dysfunction of the orbitofrontal cortex (OFC). Olfactory processing has been associated with OFC function, although results from OCD studies regarding this sensory modality have been inconclusive. No previous study has analyzed both odor discrimination and identification capacity in OCD patients using "Sniffin' Sticks" tests. The aim of our study was to assess odor threshold, identification, discrimination, and nonverbal memory in OCD patients, in order to determine whether these functions were affected.

METHODS

Olfactory function was measured in 29 OCD patients and 29 healthy volunteers (HV) using the "Sniffin' Sticks" test and their nonverbal memory was scored with the Rey-Osterrieth Complex Figure Test.

RESULTS

OCD patients showed significant impairment in their odor performance and in their execution of the nonverbal memory task compared to HV. No statistical associations were found between the deficits in the two areas. The severity of depressive and obsessive-compulsive symptoms did correlate with olfactory identification.

CONCLUSION

Our findings support the hypothesis that olfactory and memory dysfunctions in OCD reflect different neurobiological alterations of the disorder, and point to the modulation effect of depressive and obsessive-compulsive symptoms on odor performance.

The N1 auditory evoked potential component as an endophenotype for schizophrenia: high-density electrical mapping in clinically unaffected first-degree relatives, first-episode, and chronic schizophrenia patients

The N1 component of the auditory evoked potential (AEP) is a robust and easily recorded metric of auditory sensory-perceptual processing. In patients with schizophrenia, a diminution in the amplitude of this component is a near-ubiquitous finding. A pair of recent studies has also shown this N1 deficit in first-degree relatives of schizophrenia probands, suggesting that the deficit may be linked to the underlying genetic risk of the disease rather than to the disease state itself. However, in both these studies, a significant proportion of the relatives had other psychiatric conditions. As such, although the N1 deficit represents an intriguing candidate endophenotype for schizophrenia, it remains to be shown whether it is present in a group of clinically unaffected first-degree relatives. In addition to testing first-degree relatives, we also sought to replicate the N1 deficit in a group of first-episode patients and in a group of chronic schizophrenia probands. Subject groups consisted of 35 patients with schizophrenia, 30 unaffected first-degree relatives, 13 first-episode patients, and 22 healthy controls. Subjects sat in a dimly lit room and listened to a series of simple 1,000-Hz tones, indicating with a button press whenever they heard a deviant tone (1,500 Hz; 17% probability), while the AEP was recorded from 72 scalp electrodes. Both chronic and first-episode patients showed clear N1 amplitude decrements relative to healthy control subjects. Crucially, unaffected first-degree relatives also showed a clear N1 deficit. This study provides further support for the proposal that the auditory N1 deficit in schizophrenia is linked to the underlying genetic risk of developing this disorder. In light of recent studies, these results point to the N1 deficit as an endophenotypic marker for schizophrenia. The potential future utility of this metric as one element of a multivariate endophenotype is discussed.