Eric J. Tan

Speech disturbances and quality of life in schizophrenia: Differential impacts on functioning and life satisfaction

Speech disturbances in schizophrenia impact on the individuals communicative ability. Although they are considered a core feature of schizophrenia, comparatively little work has been done to examine their impact on the life experiences of patients. This study aimed to examine the relationship between schizophrenia speech disturbances, including those traditionally known as formal thought disorder (TD), and quality of life (QoL). It assessed effects on functioning (objective QoL) and satisfaction (subjective QoL) concurrently, while controlling for the influence of neurocognition and depression. Fifty-four patients with schizophrenia/schizoaffective disorder were administered the MATRICS Consensus Cognitive Battery (MCCB), the PANSS, MADRS (with separate ratings for negative TD [verbal underproductivity] and positive TD [verbal disorganisation and pressured speech]) and Lehmans QOLI assessing both objective and subjective QoL. Ratings of positive and negative TD, depression, and general neurocognition were entered into hierarchical regressions to explore their relationship with both life functioning and satisfaction. Verbal underproductivity was a significant predictor of objective QoL, while pressured speech had a trend association with subjective QoL. This suggests a differential relationship between speech disturbances and QoL. Verbal underproductivity seems to affect daily functioning and relations with others, while pressured speech is predictive of satisfaction with life. The impact of verbal underproductivity on QoL suggests it to be an important target for rehabilitation in schizophrenia.

Characterizing cognitive heterogeneity on the schizophrenia–bipolar disorder spectrum

BACKGROUND Current group-average analysis suggests quantitative but not qualitative cognitive differences between schizophrenia (SZ) and bipolar disorder (BD). There is increasing recognition that cognitive within-group heterogeneity exists in both disorders, but it remains unclear as to whether between-group comparisons of performance in cognitive subgroups emerging from within each of these nosological categories uphold group-average findings. We addressed this by identifying cognitive subgroups in large samples of SZ and BD patients independently, and comparing their cognitive profiles. The utility of a cross-diagnostic clustering approach to understanding cognitive heterogeneity in these patients was also explored. METHOD Hierarchical clustering analyses were conducted using cognitive data from 1541 participants (SZ n = 564, BD n = 402, healthy control n = 575). RESULTS Three qualitatively and quantitatively similar clusters emerged within each clinical group: a severely impaired cluster, a mild-moderately impaired cluster and a relatively intact cognitive cluster. A cross-diagnostic clustering solution also resulted in three subgroups and was superior in reducing cognitive heterogeneity compared with disorder clustering independently. CONCLUSIONS Quantitative SZ-BD cognitive differences commonly seen using group averages did not hold when cognitive heterogeneity was factored into our sample. Members of each corresponding subgroup, irrespective of diagnosis, might be manifesting the outcome of differences in shared cognitive risk factors.

Building a neurocognitive profile of thought disorder in schizophrenia using a standardized test battery

A core symptom of schizophrenia is thought disorder (TD). The cognitive abilities of semantic processing and executive function are argued to be etiologically linked to TD. However, there has been no comprehensive investigation of neurocognition in TD to date. The neurocognitive profile of 58 schizophrenia patients and 48 healthy controls was examined using the MATRICS Consensus Cognitive Battery and the D-KEFS Color-Word Interference Test. TD patients performed more poorly than non-TD patients on the cognitive domains of Verbal Learning and Inhibition, reflective of semantic and executive function respectively, confirming their critical roles over and above other cognitive deficits in schizophrenia.

Schizotypal Traits are Associated with Poorer Executive Functioning in Healthy Adults.

Previous research has shown mild forms of the neurocognitive impairments seen in schizophrenia among healthy individuals exhibiting high schizotypal traits. This study aimed to explore associations between schizotypy and cognitive performance in an adult community sample. Ninety-five females and 79 males completed the Oxford–Liverpool Inventory of Feelings and Experiences (O-LIFE), which measures four separable aspects of schizotypy: cognitive disorganization, unusual experiences, introvertive anhedonia, and impulsive non-conformity. Subsequently, participants were administered a neurocognitive battery incorporating measures of executive skills including inhibition, cognitive flexibility, reasoning, and problem solving along with measures of attention and processing speed and both verbal and spatial working memory. In line with predictions, the current study found that higher scores on the subscales of unusual experiences, cognitive disorganization, and impulsive non-conformity related to worse performance on a measure of inhibition. Additionally, as introvertive anhedonia increased, both attention and processing speed and reasoning and problem-solving performance became more impaired. In conclusion, this study extends schizotypy literature by examining the subscales of the O-LIFE, and enables inferences to be drawn in relation to cognitive impairment in schizophrenia.

Assessing the Relationship between Semantic Processing and Thought Disorder Symptoms in Schizophrenia

Aberrant semantic processing has been linked to the etiology of formal thought disorder (TD) symptoms in schizophrenia. In this cross-sectional study, two prominent theories, overactivation and disorganized structure of semantic memory (SM), were examined in relation to TD symptoms using the continuum approach across two established semantic tasks (direct/indirect semantic priming and categorical fluency). The aim was to examine the validity of the two TD theories in relation to TD symptoms in schizophrenia. Greater direct and indirect priming, fluency productivity and category errors were expected if the data supported the overactivation theory. Reduced fluency productivity and increased category errors would be characteristic of disorganized storage. Fifty-seven schizophrenia/schizoaffective disorder patients and 48 controls completed a clinical assessment and the semantic tasks. There was significantly reduced direct priming in patients compared to controls (p<.05), while indirect priming was not significantly different; there was no association between TD and degree of priming. Patients produced more category-inappropriate words (p<.005) than controls, which was related to increasing severity of circumstantiality. The pattern of results was more indicative of a disorganized SM storage problem in this sample. This phenomenon may underlie some TD symptoms in general schizophrenia. The findings strengthen the relationship between SM deficits and TD symptoms, though this appears to differ between individual symptoms. The authors discuss the value of the continuum approach in addressing research questions in TD etiology. Given low levels of TD in this study, replication of these findings in a sample with greater TD is desirable.

Does cognitive performance map to categorical diagnoses of schizophrenia, schizoaffective disorder and bipolar disorder? A discriminant functions analysis

OBJECTIVES Despite known overlaps in the pattern of cognitive impairments in individuals with bipolar disorder (BD), schizophrenia (SZ) and schizoaffective disorder (SZA), few studies have examined the extent to which cognitive performance validates traditional diagnostic boundaries in these groups. METHOD Individuals with SZ (n=49), schizoaffective disorder (n=33) and BD (n=35) completed a battery of cognitive tests measuring the domains of processing speed, immediate memory, semantic memory, learning, working memory, executive function and sustained attention. RESULTS A discriminant functions analysis revealed a significant function comprising semantic memory, immediate memory and processing speed that maximally separated patients with SZ from those with BD. Initial classification scores on the basis of this function showed modest diagnostic accuracy, owing in part to the misclassification of SZA patients as having SZ. When SZA patients were removed from the model, a second cross-validated classifier yielded slightly improved diagnostic accuracy and a single function solution, of which semantic memory loaded most heavily. CONCLUSIONS A cluster of non-executive cognitive processes appears to have some validity in mapping onto traditional nosological boundaries. However, since semantic memory performance was the primary driver of the discrimination between BD and SZ, it is possible that performance differences between the disorders in this cognitive domain in particular, index separate underlying aetiologies.

Characterising receptive language processing in schizophrenia using word and sentence tasks.

ABSTRACT Introduction. Language dysfunction is proposed to relate to the speech disturbances in schizophrenia, which are more commonly referred to as formal thought disorder (FTD). Presently, language production deficits in schizophrenia are better characterised than language comprehension difficulties. This study thus aimed to examine three aspects of language comprehension in schizophrenia: (1) the role of lexical processing, (2) meaning attribution for words and sentences, and (3) the relationship between comprehension and production. Methods. Fifty-seven schizophrenia/schizoaffective disorder patients and 48 healthy controls completed a clinical assessment and three language tasks assessing word recognition, synonym identification, and sentence comprehension. Poorer patient performance was expected on the latter two tasks. Results. Recognition of word form was not impaired in schizophrenia, indicating intact lexical processing. Whereas single-word synonym identification was not significantly impaired, there was a tendency to attribute word meanings based on phonological similarity with increasing FTD severity. Importantly, there was a significant sentence comprehension deficit for processing deep structure, which correlated with FTD severity. Conclusions. These findings established a receptive language deficit in schizophrenia at the syntactic level. There was also evidence for a relationship between some aspects of language comprehension and speech production/FTD. Apart from indicating language as another mechanism in FTD aetiology, the data also suggest that remediating language comprehension problems may be an avenue to pursue in alleviating FTD symptomatology.

On the nosology of formal thought disorder

Current diagnostic criteria for formal thought disorder (FTD) in schizophrenia (Diagnostic and Statistical Manual of Mental Disorders–Fifth Edition [DSM-5]; American Psychiatric Association, 2013) do not reflect (1) the general consensus in the literature for it being associated with neurocognitive deficits or (2) the distinction between positive and negative FTD. This situation should be rectified. In terms of nosology, FTD is currently classified as simply a psychotic feature in the DSM-5. Classification as a psychotic feature traditionally reflects the observations that FTD severity fluctuates between acute and chronic states, much like hallucinations. However, there is evidence suggesting that unlike psychotic symptoms, the impairments observed in patients with FTD never truly recover even when FTD is in remission, i.e., semantic memory deficits (Leeson et al., 2005). Problems with language production are also well-documented in FTD, with evidence suggesting that language comprehension problems are already present early in the illness (Wood et al., 2007). The aforementioned work on semantic and language impairments in FTD highlights an underlying continuity of FTD-related impairments. Such a situation is more akin to the classification for cognitive symptoms and differs from the transient nature of psychotic symptoms under which FTD is currently classified. Consequently, it might be time to consider revisiting the nosological debate surrounding FTD, and look at re-classifying it as a neurocognitive phenomenon. Another pertinent reason for change is that the current criteria do not account for the well-observed differences between positive and negative FTD, at both levels of underlying mechanisms and prognostic outcome. The change in nosology is important as it results in clearer diagnostic criteria that better reflect the nature of the symptom as well as schizophrenia itself. This in turn will help better inform treatment and rehabilitation options for individuals with FTD. While we acknowledge that these top-level changes unfortunately do not happen quickly, there are some measures that can be adopted in the interim. First, it would be beneficial to avoid use of the term ‘disorganised thoughts’ in positive symptom classifications of schizophrenia to avoid confusion with ‘thought disorder’. This would better facilitate the identification of FTD as being of a different nature. Second, distinctions between positive and negative FTD should continue to be recognised and adopted. Finally, continued examination of the cognitive mechanisms underlying individual FTD symptoms, particularly longitudinal work, would help in further fine-tuning the growing understanding of the disorder and strengthen the case for nosological change.

“How is cognitive remediation training perceived by people with schizophrenia? A qualitative study examining personal experiences”

Abstract Background: Meta-analytical findings have shown Cognitive Remediation (CR) effectiveness in augmenting cognitive and functional outcomes. Comparatively, a minimum amount of qualitative evidence has been reported to date. Aims: This study aimed to explore the subjective experience of participants undertaking a CR trial. Method: Twenty people with schizophrenia completed a questionnaire-facilitated interview, after having completed 20 h of CR. Thematic analysis was then used to identify codes and themes. Results: Three themes were identified. In relation to reported benefits, all participants found the training to be a positive experience, with 70% having identified cognitive improvements, 45% improved motivation or confidence and 20% improved social skills. The role of the cognitive trainer in being supportive, adaptive and instructive was consistently reported as important, and most participants commented positively about the group format. Fewer participants had observed a transfer to real life settings, with improved social skills, use of cognitive strategies or aspects of everyday living reported by 40% of participants. Conclusions: These data highlight that all participants reported participation in CR to be a positive experience, with many reporting observed benefits following participation. Key aspects of the training that contributed to this positive experience were also identified and may assist in the further development of this intervention.

Formal thought disorder and neurocognition in schizophrenia: The question of individual mechanisms

Formal thought disorder (FTD) is a core heterogeneous symptom of schizophrenia, with 18 distinct subtypes noted (Andreasen, 1986). These range from the paucity of poverty of speech, and the novelty of neologisms, to the rambling nature of circumstantiality. FTD has been associated with semantic and executive dysfunction (Stirling et al., 2006; Tan and Rossell, 2014), and to a lesser extent working memory and attentional impairments (Docherty et al., 1996). Presently there is almost no dedicated work on individual FTD symptoms. Given significant presentation differences between FTD symptoms, it is plausible to expect that their underlying mechanisms might differ (Tan and Rossell, 2015). We have previously demonstrated that individual FTD symptoms are differentially related to semantic memory and language impairments (Tan et al., 2015; Tan et al., 2016). This current study seeks to extend thiswork by concurrently investigating this relationship across multiple neurocognitive domains. Fifty-nine patients (M= 43.46, SD=10.67) with DSM-IV schizophrenia/schizoaffective disorder were recruited. Eight neurocognitive domains were investigated: Speed of Processing (SP), Attention/Vigilance (ATT), Working Memory (WM), Verbal Learning (VerL), Visual Learning (VisL), Reasoning and Problem Solving (RPS), and Social Cognition (SOC) from the MATRICS Consensus Cognitive Battery (Nuechterlein et al., 2008) and Inhibition/ Executive function (INHB) from the D-KEFS Colour-Word Interference Test (Delis et al., 2001). Domain z-scores were individually calculated based on previously collected HCmeans (see Tan and Rossell, 2014). Individual FTD symptom scores and a composite measure of general FTD severity (Global FTD score) from the Thought, Language and Communication Scale (TLC; Andreasen, 1986) were used. Only FTD symptoms present in N10% of the patients were examined (see Tan et al., 2015): poverty of speech (13.6%), pressure of speech (10.2%), tangentiality (23.7%), derailment (11.9%), circumstantiality (32.2%), loss of goal (15.3%), and perseveration (13.6%). Spearmans correlations were conducted, due to the ordinal nature of TLC ratings, with statistical significance levels Bonferroni-corrected for multiple comparisons at p ≤ 0.007. These data confirm a differential pattern of associations between individual FTD symptoms and neurocognitive variables (see Table 1). Each significant finding will be discussed. Pressure of speech was correlated with poor INHB performance; suggesting that the continuous uninterruptible diatribe may be related to an inability to limit or inhibit automated speech generation. The correlation between derailment andVisLwas initially puzzling, particularly given no associations with ATT or VerL (which seem logical cognitive candidates for speech distractibility). However, the VisL task requires additional capacities to the VerL task. Intact organisational ability is necessary to memorise the position of the 6 simple figures on the page,