Schizophrenia and frontotemporal dementia: shared causation?

Integrating Electronic Health Records and Polygenic Risk to Identify Genetically Unrelated Comorbidities of Schizophrenia That May Be Modifiable

Background

Patients with schizophrenia have substantial comorbidity that contributes to reduced life expectancy of 10 to 20 years. Identifying modifiable comorbidities could improve rates of premature mortality. Conditions that frequently co-occur but lack shared genetic risk with schizophrenia are more likely to be products of treatment, behavior, or environmental factors and therefore are enriched for potentially modifiable associations.

Methods

Phenome-wide comorbidity was calculated from electronic health records of 250,000 patients across 2 independent health care institutions (Vanderbilt University Medical Center and Mass General Brigham); associations with schizophrenia polygenic risk scores were calculated across the same phenotypes in linked biobanks.

Results

Schizophrenia comorbidity was significantly correlated across institutions (r = 0.85), and the 77 identified comorbidities were consistent with prior literature. Overall, comorbidity and polygenic risk score associations were significantly correlated (r = 0.55, p = 1.29 × 10-118). However, directly testing for the absence of genetic effects identified 36 comorbidities that had significantly equivalent schizophrenia polygenic risk score distributions between cases and controls. This set included phenotypes known to be consequences of antipsychotic medications (e.g., movement disorders) or of the disease such as reduced hygiene (e.g., diseases of the nail), thereby validating the approach. It also highlighted phenotypes with less clear causal relationships and minimal genetic effects such as tobacco use disorder and diabetes.

Conclusions

This work demonstrates the consistency and robustness of electronic health record-based schizophrenia comorbidities across independent institutions and with the existing literature. It identifies known and novel comorbidities with an absence of shared genetic risk, indicating other causes that may be modifiable and where further study of causal pathways could improve outcomes for patients.

Identifying modifiable comorbidities of schizophrenia by integrating electronic health records and polygenic risk

Patients with schizophrenia have substantial comorbidity contributing to reduced life expectancy of 10-20 years. Identifying which comorbidities might be modifiable could improve rates of premature mortality in this population. We hypothesize that conditions that frequently co-occur but lack shared genetic risk with schizophrenia are more likely to be products of treatment, behavior, or environmental factors and therefore potentially modifiable. To test this hypothesis, we calculated phenome-wide comorbidity from electronic health records (EHR) in 250,000 patients in each of two independent health care institutions (Vanderbilt University Medical Center and Mass General Brigham) and association with schizophrenia polygenic risk scores (PRS) across the same phenotypes (phecodes) in linked biobanks. Comorbidity with schizophrenia was significantly correlated across institutions (r = 0.85) and consistent with prior literature. After multiple test correction, there were 77 significant phecodes comorbid with schizophrenia. Overall, comorbidity and PRS association were highly correlated (r = 0.55, p = 1.29×10-118), however, 36 of the EHR identified comorbidities had significantly equivalent schizophrenia PRS distributions between cases and controls. Fifteen of these lacked any PRS association and were enriched for phenotypes known to be side effects of antipsychotic medications (e.g., "movement disorders", "convulsions", "tachycardia") or other schizophrenia related factors such as from smoking ("bronchitis") or reduced hygiene (e.g., "diseases of the nail") highlighting the validity of this approach. Other phenotypes implicated by this approach where the contribution from shared common genetic risk with schizophrenia was minimal included tobacco use disorder, diabetes, and dementia. This work demonstrates the consistency and robustness of EHR-based schizophrenia comorbidities across independent institutions and with the existing literature. It identifies comorbidities with an absence of shared genetic risk indicating other causes that might be more modifiable and where further study of causal pathways could improve outcomes for patients.

Strategies for Treatment of Disease-Associated Dementia Beyond Alzheimer's Disease: An Update

Memory, cognition, dementia, and neurodegeneration are complexly interlinked processes with various mechanistic pathways, leading to a range of clinical outcomes. They are strongly associated with pathological conditions like Alzheimer's disease, Parkinson's disease, schizophrenia, and stroke and are a growing concern for their timely diagnosis and management. Several cognitionenhancing interventions for management include non-pharmacological interventions like diet, exercise, and physical activity, while pharmacological interventions include medicinal agents, herbal agents, and nutritional supplements. This review critically analyzed and discussed the currently available agents under different drug development phases designed to target the molecular targets, including cholinergic receptor, glutamatergic system, GABAergic targets, glycine site, serotonergic targets, histamine receptors, etc. Understanding memory formation and pathways involved therein aids in opening the new gateways to treating cognitive disorders. However, clinical studies suggest that there is still a dearth of knowledge about the pathological mechanism involved in neurological conditions, making the dropouts of agents from the initial phases of the clinical trial. Hence, a better understanding of the disease biology, mode of drug action, and interlinked mechanistic pathways at a molecular level is required.

Genetic Spectrum and Clinical Heterogeneity of Chinese Frontotemporal Dementia Patients: Data from PUMCH Dementia Cohort

Background:

There are relatively few data on the genetic spectrum of Chinese frontotemporal dementia (FTD) population.

Objective:

With the dementia cohort of Peking Union Medical College Hospital, we aim to illustrate the genetic spectrum of FTD patients, as well as the phenotypic heterogeneity of FTD-gene variant carriers.

Methods:

204 unrelated, clinically diagnosed FTD patients of Chinese ancestry were enrolled. All the participants received demographic survey, history inquiry, physical examination, cognitive assessment, blood biochemical test, brain CT/MRI, and gene sequencing.

Results:

56.4% (115/204) participants were clinically diagnosed with behavioral variant of FTD, 20.6% (42/204) with nonfluent/agrammatic variant primary progressive aphasia (PPA), 20.1% (41/204) with semantic variant PPA, and 2.9% (6/204) with mixed variant PPA. 11.8% (24/204) subjects harbored the potential causative variants in FTD-related genes, including the MAPT (n = 7), TBK1 (n = 7), GRN (n = 2), TBK1+GRN (n = 1), VCP (n = 1), TARDBP (n = 1), UBQLN2 (n = 1), SQSTM1 (n = 1), DCTN1 (n = 1), HNRNPA1 (n = 1), and C9orf72 GGGGCC repeats (n = 1). The TBK1 T31fs, T457fs, K622fs, c.359-1G>A, the VCP P188T, and the GRN P50fs, P439fs were novel pathogenic/likely pathogenic variants. The TBK1 carriers showed a later disease onset and a higher incidence of parietal atrophy relative to the MAPTcarriers.

Conclusion:

There is genetic and clinical heterogeneity among Chinese FTD population. The TBK1 has a high mutation frequency in Chinese FTD patients.

Overlap of Neuroanatomical Involvement in Frontotemporal Dementia and Primary Psychiatric Disorders: A Meta-analysis

BACKGROUND

Despite significant symptomatic overlap between behavioral variant frontotemporal dementia (bvFTD) and primary psychiatric disorders (PPDs), a potential overlap in their structural anatomical changes has not been studied systematically.

METHODS

In this magnetic resonance imaging-based meta-analysis, we included studies on bvFTD, schizophrenia, bipolar disorder, and autism spectrum disorder that 1) used voxel-based morphometry analysis to assess regional gray matter volumes (GMVs) and 2) reported the coordinates of the regional GMV. Separate analyses were performed comparing clusters of coordinate-based changes in the GMVs (n = 24,183) between patients and control subjects, and overlapping brain regions between bvFTD and each PPD were examined.

RESULTS

We found that GMV alterations in the prefrontal and anterior cingulate cortices, temporal lobe, amygdala, and insula comprise the transdiagnostic brain alterations in bvFTD and PPD.

CONCLUSIONS

Our meta-analysis revealed significant anatomical overlap that paves the way for future investigations of shared pathophysiological pathways, and our cross-disorder approach would provide new insights to better understand the relationship between bvFTD and PPD.

Shared genetic links between frontotemporal dementia and psychiatric disorders

BACKGROUND

Epidemiological and clinical studies have suggested comorbidity between frontotemporal dementia (FTD) and psychiatric disorders. FTD patients carrying specific mutations were at higher risk for some psychiatric disorders, and vice versa, implying potential shared genetic etiology, which is still less explored.

METHODS

We examined the genetic correlation using summary statistics from genome-wide association studies and analyzed their genetic enrichment leveraging the conditional false discovery rate method. Furthermore, we explored the causal association between FTD and psychiatric disorders with Mendelian randomization (MR) analysis.

RESULTS

We identified a significant genetic correlation between FTD and schizophrenia at both genetic and transcriptomic levels. Meanwhile, robust genetic enrichment was observed between FTD and schizophrenia and alcohol use disorder. Seven shared genetic loci were identified, which were mainly involved in interleukin-induced signaling, synaptic vesicle, and brain-derived neurotrophic factor signaling pathways. By integrating cis-expression quantitative trait loci analysis, we identified MAPT and CADM2 as shared risk genes. MR analysis showed mutual causation between FTD and schizophrenia with nominal association.

CONCLUSIONS

Our findings provide evidence of shared etiology between FTD and schizophrenia and indicate potential common molecular mechanisms contributing to the overlapping pathophysiological and clinical characteristics. Our results also demonstrate the essential role of autoimmunity in these diseases. These findings provide a better understanding of the pleiotropy between FTD and psychiatric disorders and have implications for therapeutic trials.

Cognitive Trajectories in Comorbid Dementia With Schizophrenia or Bipolar Disorder: The South London and Maudsley NHS Foundation Trust Biomedical Research Centre (SLaM BRC) Case Register

OBJECTIVES

We aimed to compare trajectories of cognitive performance in individuals diagnosed with dementia with and without severe mental illness (SMI).

DESIGN

Retrospective cohort study.

SETTING

We used data from a large longitudinal mental healthcare case register, the Clinical Record Interactive Search (CRIS), at the South London and Maudsley NHS Foundation Trust (SLaM) which provides mental health services to four south London boroughs.

PARTICIPANTS

Our sample (N = 4718) consisted of any individual who had a primary or secondary diagnosis of dementia from 2007 to 2018, was 50 years old or over at first diagnosis of dementia and had at least 3 recorded Mini-Mental State Examination (MMSE) scores.

MEASUREMENTS

Cognitive performance was measured using MMSE. Linear mixed models were fitted to explore whether MMSE trajectories differed between individuals with or without prior/current SMI diagnoses. Models were adjusted by socio-demographics, cardiovascular risk, smoking, and medication.

RESULTS AND CONCLUSIONS

Our results showed differences in the rate of change, where individuals with comorbid SMI had a faster decline when compared with those that have dementia without comorbid SMI. However, this association was partially attenuated when adjusted by socio-demographics, smoking and cardiovascular risk factors; and more substantially attenuated when medication was included in models. Additional analyses showed that this accelerated decline might be more evident in individuals with bipolar disorders. Future research to detangle the potential biological underlying mechanisms of these associations is needed.

Neurophysiological Correlates of Positive and Negative Symptoms in Frontotemporal Dementia

BACKGROUND

The neural correlates of behavioral symptoms in frontotemporal dementia (FTD) are still to be elucidated. Neurotransmitter abnormalities could be correlated to the pathophysiology of negative and positive symptoms in FTD.

OBJECTIVE

To evaluate if the imbalance between inhibitory and excitatory cortical circuits, evaluated with transcranial magnetic stimulation (TMS), correlate with the magnitude of negative and positive symptoms, as measured by Frontal Behavioral Inventory (FBI) scores, in patients with FTD.

METHODS

Paired-pulse TMS was used to investigate the activity of different intracortical circuits in 186 FTD patients (130 bvFTD, 35 avPPA, 21 svPPA). We applied short interval intracortical inhibition (SICI - GABAAergic transmission), intracortical facilitation (ICF - glutamatergic transmission), long interval intracortical inhibition (LICI - GABABergic transmission), and short latency afferent inhibition (SAI - cholinergic transmission). Linear and stepwise multiple regression analysis were used to determine the contribution of each neurophysiological measures to the total variance of FBI scores.

RESULTS

At the stepwise multivariate analysis, we observed a significant negative correlation between FBI-A scores (negative symptoms) and ICF (β = -0.57, p < 0.001, adjusted R2 = 0.32). For FBI-B scores (positive symptoms), we observed a significant positive correlation for SICI (β = 0.84, p < 0.001, adjusted R2 = 0.56). Significant correlations were observed for single items of the FBI-A score with ICF and FBI-B scores with SICI, with a medium-large size effect for several items.

CONCLUSIONS

The present study shows that the imbalance between inhibitory and excitatory intracortical circuits, evaluated with TMS, correlated with the magnitude of negative and positive symptoms in FTD, respectively.

Is that schizophrenia or frontotemporal dementia? Supporting clinicians in making the right diagnosis

Schizophrenia (SCH) and frontotemporal dementia (FTD) are neurobehavioral syndromes characterized by a profound alteration in personal and social conduct. Differential diagnosis between SCH and FTD remains a challenge. In this short narrative review, we summarize evidences regarding similarities and differences between these disorders to support clinicians in making the right diagnosis. Reports of FTD misdiagnosed as schizophrenia or schizophrenia-like psychosis are frequently reported in the literature. The behavioural variant of FTD (bvFTD) along with familial FTD characterized by delusions and hallucinations represent the medical conditions that best illustrate overlaps between psychiatry and neurology. Neuropsychological patterns of core deficits and anatomical and physiological brain alterations primarily concur in differencing such disorders while additional research on genetic alterations and their reflection on clinical phenotypes should be implemented in the near future. In some cases, a correct diagnosis should be made within an interdisciplinary clinical setting by complementary competences and follow-up visits to evaluate pathology evolution.

Autism and psychosis as diametrical disorders of embodiment

Humans have evolved an elaborate system of self-consciousness, self-identity, self-agency, and self-embodiment that is grounded in specific neurological structures including an expanded insula. Instantiation of the bodily self has been most-extensively studied via the 'rubber hand illusion', whereby parallel stimulation of a hidden true hand, and a viewed false hand, leads to the felt belief that the false hand is one's own. Autism and schizophrenia have both long been regarded as conditions centrally involving altered development of the self, but they have yet to be compared directly with regard to the self and embodiment. Here, we synthesize the embodied cognition literature for these and related conditions, and describe evidence that these two sets of disorders exhibit opposite susceptibilities from typical individuals to the rubber hand illusion: reduced on the autism spectrum and increased in schizophrenia and other psychotic-affective conditions. Moreover, the opposite illusion effects are mediated by a consilient set of associated phenomena, including empathy, interoception, anorexia risk and phenotypes, and patterns of genetic correlation. Taken together, these findings: (i) support the diametric model of autism and psychotic-affective disorders, (ii) implicate the adaptive human system of self-embodiment, and its neural bases, in neurodevelopmental disorders, and suggest new therapies and (iii) experimentally ground Bayesian predictive coding models with regard to autism compared with psychosis. Lay summary: Humans have evolved a highly developed sense of self and perception of one's own body. The 'rubber hand illusion' can be used to test individual variation in sense of self, relative to connection with others. We show that this illusion is reduced in autism spectrum disorders, and increased in psychotic and mood disorders. These findings have important implications for understanding and treatment of mental disorders.

Protein misassembly and aggregation as potential convergence points for non-genetic causes of chronic mental illness

Chronic mental illnesses (CMI), such as schizophrenia or recurrent affective disorders, are complex conditions with both genetic and non-genetic elements. In many other chronic brain conditions, including Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis and frontotemporal dementia, sporadic instances of the disease are more common than gene-driven familial cases. Yet, the pathology of these conditions can be characterized by the presence of aberrant protein homeostasis, proteostasis, resulting in misfolded or aggregated proteins in the brains of patients that predominantly do not derive from genetic mutations. While visible deposits of aggregated protein have not yet been detected in CMI patients, we propose the existence of more subtle protein misassembly in these conditions, which form a continuum with the psychiatric phenotypes found in the early stages of many neurodegenerative conditions. Such proteinopathies need not rely on genetic variation. In a similar manner to the established aberrant neurotransmitter homeostasis in CMI, aberrant homeostasis of proteins is a functional statement that can only partially be explained by, but is certainly complementary to, genetic approaches. Here, we review evidence for aberrant proteostasis signatures from post mortem human cases, in vivo animal work, and in vitro analysis of candidate proteins misassembled in CMI. The five best-characterized proteins in this respect are currently DISC1, dysbindin-1, CRMP1, TRIOBP-1, and NPAS3. Misassembly of these proteins with inherently unstructured domains is triggered by extracellular stressors and thus provides a converging point for non-genetic causes of CMI.

An integrative functional genomics framework for effective identification of novel regulatory variants in genome-phenome studies

BACKGROUND

Genome-phenome studies have identified thousands of variants that are statistically associated with disease or traits; however, their functional roles are largely unclear. A comprehensive investigation of regulatory mechanisms and the gene regulatory networks between phenome-wide association study (PheWAS) and genome-wide association study (GWAS) is needed to identify novel regulatory variants contributing to risk for human diseases.

METHODS

In this study, we developed an integrative functional genomics framework that maps 215,107 significant single nucleotide polymorphism (SNP) traits generated from the PheWAS Catalog and 28,870 genome-wide significant SNP traits collected from the GWAS Catalog into a global human genome regulatory map via incorporating various functional annotation data, including transcription factor (TF)-based motifs, promoters, enhancers, and expression quantitative trait loci (eQTLs) generated from four major functional genomics databases: FANTOM5, ENCODE, NIH Roadmap, and Genotype-Tissue Expression (GTEx). In addition, we performed a tissue-specific regulatory circuit analysis through the integration of the identified regulatory variants and tissue-specific gene expression profiles in 7051 samples across 32 tissues from GTEx.

RESULTS

We found that the disease-associated loci in both the PheWAS and GWAS Catalogs were significantly enriched with functional SNPs. The integration of functional annotations significantly improved the power of detecting novel associations in PheWAS, through which we found a number of functional associations with strong regulatory evidence in the PheWAS Catalog. Finally, we constructed tissue-specific regulatory circuits for several complex traits: mental diseases, autoimmune diseases, and cancer, via exploring tissue-specific TF-promoter/enhancer-target gene interaction networks. We uncovered several promising tissue-specific regulatory TFs or genes for Alzheimer's disease (e.g. ZIC1 and STX1B) and asthma (e.g. CSF3 and IL1RL1).

CONCLUSIONS

This study offers powerful tools for exploring the functional consequences of variants generated from genome-phenome association studies in terms of their mechanisms on affecting multiple complex diseases and traits.

Occurrence and co-occurrence of hallucinations by modality in schizophrenia-spectrum disorders

It is not only unclear why hallucinations in schizophrenia occur with different prevalence by modality, but also to what extent they do. Reliable prevalence estimates of hallucinations by modality in schizophrenia are currently lacking, particularly for non-auditory hallucinations. Studies have also tended to report lifetime, not point prevalence by modality. This study assessed the prevalence and co-occurrence of hallucinations, for both lifetime and point prevalence, across the auditory, visual, olfactory, and tactile modalities, in people diagnosed with chronic schizophrenia-spectrum disorders in Ireland (N=693) and Australia (N=218). Lifetime prevalence was 64-80% auditory, 23-31% visual, 9-19% tactile, and 6-10% olfactory. Past month prevalence was 23-27% auditory, 5-8% visual, 4-7% tactile, and 2% olfactory. The majority of participants had only hallucinated in one modality, with this nearly always being the auditory. Approximately one-third had hallucinated in two modalities, most commonly the auditory and visual. Most currently hallucinating patients also hallucinated in a single modality, again, nearly always the auditory. Whereas 30-37% of patients with lifetime auditory hallucinations had experienced visual hallucinations, 83-97% of patients with experience of visual hallucinations had experienced auditory hallucinations. These findings help delineate the modality distribution of hallucinations in schizophrenia, and provide an explanatory target for theoretical models.

[Reconciliating neurology and psychiatry: The prototypical case of frontotemporal dementia]

Frontotemporal degeneration (FTD) in its behavioral variant (bvFTD) is probably one of the conditions that best illustrates the links between psychiatry and neurology. It is indeed admitted that between a third and half of patients with this condition, especially in early-onset forms, receive an initial diagnosis of psychiatric disorder (depression, schizophrenia, bipolar disorder) and are then referred to a psychiatric ward. BvFTD can thus be considered a neurological disorder with a psychiatric presentation. Among psychiatric symptoms reported in this disease, psychotic symptoms (hallucinations, delusions, especially of persecution), which have long been underestimated in bvFTD and are not part of the current diagnostic criteria, are present in about 20% of cases and may be inaugural. They are particularly common in the genetic forms related to a mutation in the C9orf72 gene (up to 50%), and to a lesser extent in the GRN gene (up to 25%). C9orf72 gene mutation is often associated with a family history of dementia or motor neuron disease but also of psychiatric disorders. It has also been described in sporadic presentation forms. Sometimes, the moderate degree of brain atrophy on MRI described in patients carrying this mutation may complicate the differential diagnosis with late-onset psychiatric diseases. In the present article, we underline the importance of considering that psychiatric - especially psychotic - symptoms are not rare in bvFTD, which should lead to a revision of the diagnostic criteria of this disease by taking greater account of this fact. We also propose a diagnostic chart, based on concerted evaluation by neurologists and psychiatrists for cases of atypical psychiatric symptoms (late-onset or pharmacoresistant troubles) leading to consider the possibility of a neurological disorder, in order to shed a new light on these difficult clinical situations. In the field of research, bvFTD may constitute a model to explore the neural basis of certain psychiatric disorders, and a possible molecular link between bvFTD and psychoses, which could eventually lead to new therapeutic approaches, has been recently suggested. Thus, bvFTD illustrates how the links between neurology and psychiatry are close and tend to evolve with the progress of scientific knowledge. It is necessary to strengthen collaboration between the two disciplines both to improve the care - diagnosis and management of these patients - and to promote the emergence of innovative clinical research.

Psychotic symptoms in frontotemporal dementia

Although psychotic features have long been recognized in association with frontotemporal dementia (FTD), recent genetic discoveries enabling further subtyping of FTD have revealed that psychotic symptoms are frequent in some forms of FTD. Hallucinations and delusions can even precede onset of other cognitive or behavioural symptoms in patients with FTD. In this review, we explore the frequency and types of psychotic symptoms reported in patients with FTD, as well as in other neuropsychiatric disorders, to aid practitioners' consideration of these features in the diagnosis of FTD and related disorders.

Frontotemporal Dementia and Psychiatric Illness: Emerging Clinical and Biological Links in Gene Carriers

OBJECTIVE

To describe psychiatric presentations in individuals with genetic mutations causing frontotemporal dementia (FTD).

DESIGN

Case descriptions from five carriers of FTD-related gene mutations with symptoms associated with non-neurodegenerative psychiatric disease.

SETTING

A comprehensive research program investigating genetic and non-genetic FTD at the University of California, San Francisco Memory and Aging Center.

PARTICIPANTS

Three proband and two non-proband gene carriers.

MEASUREMENTS

Medical history and neurological examination, neuropsychological testing, magnetic resonance and/or positron emission tomography imaging, and a genetic analysis to screen for dementia-related mutations. Genetic status was unknown at the time of initial evaluation.

RESULTS

The chosen cases are illustrative of the variety of presentations of psychiatric symptoms in FTD gene carriers. In some cases, a non-neurodegenerative psychiatric illness was diagnosed based on specific symptoms, but the diagnosis may have been inappropriate based on the overall syndrome. In other cases, symptoms closely resembling those seen in non-neurodegenerative psychiatric illness did occur, in some cases immediately preceding the development of dementia, and in other cases developing a decade prior to dementia symptoms.

CONCLUSIONS

Psychiatric symptoms in FTD gene carriers can be very similar to those seen in non-neurodegenerative psychiatric illness. Psychiatric symptoms with atypical features (e.g., late-life onset, insidiously worsening course) should prompt careful assessment for neurodegenerative disease. Guidelines for such an assessment should be established.

The frontotemporal dementias

Frontotemporal dementia (FTD) is a heterogeneous group of hereditary and sporadic neurodegenerative disorders affecting frontotemporal areas. FTD, a leading cause of young-onset dementia, is often initially mistaken for primary psychiatric disorders. Based on early and predominant symptoms, different clinical syndromes can be distinguished: the behavioral variant and 2 variants of progressive aphasia; semantic dementia and progressive nonfluent aphasia. Neuropathological classification is based on protein accumulation in the brain. Pathogenic mutations in different genes have been identified. Specific pharmacological treatment is the main research goal. Meanwhile the management must focus on early correct diagnosis, symptom alleviation, caregiver support and educational interventions.

Psychotic symptoms in frontotemporal dementia: a diagnostic dilemma?

BACKGROUND

Frontotemporal dementia (FTD) constitutes a spectrum of neurodegenerative disorders associated with degeneration of, predominantly, the frontal and temporal lobes. The clinical heterogeneity is evident, and early diagnosis is a challenge. The primary objectives were to characterize psychotic symptoms, initial clinical diagnoses and family history in neuropathologically verified FTD-patients and to analyze possible correlations with different neuropathological findings.

METHODS

The medical records of 97 consecutive patients with a neuropathological diagnosis of frontotemporal lobar degeneration (FTLD) were reevaluated. Psychotic symptoms (hallucinations, delusions, paranoid ideas), initial diagnosis and family history for psychiatric disorders were analyzed.

RESULTS

Psychotic symptoms were present in 31 patients (32%). There were no significant differences in age at onset, disease duration or gender between patients with and without psychotic symptoms. Paranoid ideas were seen in 20.6%, and hallucinations and delusions in 17.5% in equal measure. Apart from a strong correlation between psychotic symptoms and predominantly right-sided brain degeneration, the majority of patients (77.4%) were tau-negative. Only 14.4% of the patients were initially diagnosed as FTD, while other types of dementia were seen in 34%, other psychiatric disorders in 42%, and 9.2% with other cognitive/neurological disorders. The patients who were initially diagnosed with a psychiatric disorder were significantly younger than the patients with other initial clinical diagnoses. A positive heredity for dementia or other psychiatric disorder was seen in 42% and 26% of the patients respectively.

CONCLUSIONS

Psychotic symptoms, not covered by current diagnostic criteria, are common and may lead to clinical misdiagnosis in FTD.

Neurocognitive similarities between severe chronic schizophrenia and behavioural variant frontotemporal dementia

This study focuses on a group of patients with chronic schizophrenia who have a more severe form of the disorder, as indicated by socio-functional decline, treatment resistance, and recurrent hospitalisation. Previous research has suggested that the pattern and severity of cognitive deficits in people with severe chronic schizophrenia is similar to that observed in behavioural variant frontotemporal dementia (bvFTD). In the current study, we compared neurocognitive performance in 16 cognitive domains in 7 inpatients with severe chronic schizophrenia, 13 community-dwelling outpatients with chronic schizophrenia, 12 patients with bvFTD, and 18 healthy controls. Our findings revealed more similar cognitive profiles between the schizophrenia inpatient and bvFTD groups compared to the schizophrenia outpatient group, who outperformed the former groups. The current results provide preliminary evidence for a distinct schizophrenia subgroup, distinguishable from other chronic schizophrenia patients by poorer clinical and functional status, who have levels of cognitive impairment comparable to those seen in bvFTD patients.

The effect of deficient muscarinic signaling on commonly reported biochemical effects in schizophrenia and convergence with genetic susceptibility loci in explaining symptom dimensions of psychosis

With the advent of DSM 5 criticism has generally centered on a lack of biological validity of the diagnostic criteria. Part of the problem in describing a nosology of psychosis is the tacit assumption of multiple genetic causes each with an incremental loading on the clinical picture that fails to differentiate a clear underlying pathophysiology of high impact. The aim of this paper is to consolidate a primary theory of deficient muscarinic signaling underlying key clinical features of schizophrenia and its regulation by several important genetic associations including neuregulin, DISC and dysbindin. Secondary reductions in markers for GABAergic function and changes in the levels of interneuron calcium binding proteins parvalbumin and calbindin can be attributed to dysfunctional muscarinic transduction. A parallel association exists for cytokine production. The convergent pathway hypothesis is likewise used to model dopaminergic and glutamatergic theories of schizophrenia. The negative symptom dimension is correlated with dysfunction of Akt and ERK transduction, a major point of convergence. The present paradigm predicts the importance of a recent finding of a deletion in a copy number variant of PLCB1 and its potential use if replicated, as one of the first testable biological markers differentiating schizophrenia from bipolar disorder and further subtyping of schizophrenia into deficit and non-deficit. Potential limitations of PLCB1 as a prospective marker are also discussed.

Comparing neurocognition in severe chronic schizophrenia and frontotemporal dementia

OBJECTIVE

Previous research has suggested cognitive similarities between schizophrenia and frontotemporal dementia. In the current study, we compared neurocognition in a group of hospitalised patients with chronic schizophrenia, who may have a more severe form of schizophrenia resembling Emil Kraepelin's dementia praecox, with patients with frontotemporal dementia. We hypothesised minimal group differences in cognitive performance, and a large overlap in between-group score distributions in each cognitive domain.

METHODS

Retrospective neuropsychological data for 26 patients with severe chronic schizophrenia and 34 patients with frontotemporal dementia (behavioural variant) was collated. Neuropsychological measures were categorised into 16 cognitive domains. Raw scores were converted into standardised z-scores for each measure, which were then averaged across measures within each domain. In addition to difference analysis, equivalence testing was utilised, whereby overlap percentages were computed to reflect the amount of score distribution overlap in each domain between groups.

RESULTS

A statistically significant difference was observed only in the executive function sub-domain of Switching. Small-to-moderate and moderate effect sizes were noted in four other domains. Equivalence testing showed more than 85% of overlap in score distribution in most domains.

CONCLUSIONS

Our findings suggest that some patients with severe chronic schizophrenia have cognitive deficits similar in degree and pattern to patients with frontotemporal dementia. The few differences observed between both groups of patients are important for differential diagnostic purposes. One limitation is the retrospective nature of the study. Suggestions for future research include longitudinal follow-up studies of these two patient populations and studies of aspects beyond neurocognition. An implication of our findings is that the 'dementia of schizophrenia' concept may be applicable to patients with severe chronic schizophrenia.

Negative symptoms, past and present: a historical perspective and moving to DSM-5

The diagnosis of schizophrenia includes "positive" and "negative" symptoms. These titles were developed to respectively reflect if the symptoms are additions to normal experiences, such as delusions and hallucinations, or if they refer to the absence or the loss of normal emotional function or behavior. This paper describes the history of the negative symptom concept, from its origins up to the considerations for the DSM-5, including the steps that produced the current conceptualizations. The DSM-5 only includes deficits in emotional expression and avolition as negative symptoms, which can be assessed from interview information. Factor analyses show they encompass most other negative symptom items. In addition to using these negative symptoms in a categorical manner to make a diagnosis, the DSM-5 has quantitative severity ratings of the negative symptoms, along with ratings of delusions, cognitive symptoms, motor symptoms, disorganization, depression and mania. With this approach, the different symptom domains, including negative symptoms, can be measured and tracked over time. Another change in the DSM-5 is the dropping of the schizophrenia subtypes that have been included in earlier volumes, as they were not useful in treatment decisions or prognosis. An intended outcome of these changes in DSM-5 is for clinicians to directly treat the individual psychopathological domains of the disorder for optimizing individual outcomes. Finally, this paper includes descriptions of the negative symptom items from over a dozen different scales.