Memory profiles in schizophrenia: categorization validity and stability

Disentangling Cognitive Heterogeneity in Psychotic Spectrum Disorders

Neuropsychological impairments represent a central feature of psychosis-spectrum disorders. It is characterized by a great both within- and between-subjects variability (i.e. cognitive heterogeneity), which needs to be better disentangled. The present study aimed to describe the distribution of performance on the Brief Assessment of Cognition in Schizophrenia (BACS) by using the Equivalent Scores, in order to balance statistical methodological problems. To do so, cognitive performance groups were branded, identifying the main factors contributing to cognitive heterogeneity. A sample of 583 patients with a diagnosis of Schizophrenia or Psychotic Disorder Not Otherwise Specified was enrolled and assessed for neurocognition and intellectual level. K-means cluster analysis was performed based on BACS Equivalent Scores. Differences among clusters were analyzed throughout Analysis of Variance and Discriminant Function Analysis in order to identify the most significant predictors of cluster membership. For each cognitive task, roughly 40% of patients displayed poor performance, while up to 63% displayed a symbol-coding deficit. K-means cluster analysis depicted three profiles characterized by "near-normal" cognition, widespread impairment, and "borderline" profile. Discriminant analysis selected Verbal IQ and diagnosis as predictors of cluster membership. Our findings support the usefulness of Equivalent Scores and cluster analysis to explain cognitive heterogeneity, and tailor better interventions.

A systematic review and narrative synthesis of data-driven studies in schizophrenia symptoms and cognitive deficits

To tackle the phenotypic heterogeneity of schizophrenia, data-driven methods are often applied to identify subtypes of its symptoms and cognitive deficits. However, a systematic review on this topic is lacking. The objective of this review was to summarize the evidence obtained from longitudinal and cross-sectional data-driven studies in positive and negative symptoms and cognitive deficits in patients with schizophrenia spectrum disorders, their unaffected siblings and healthy controls or individuals from general population. Additionally, we aimed to highlight methodological gaps across studies and point out future directions to optimize the translatability of evidence from data-driven studies. A systematic review was performed through searching PsycINFO, PubMed, PsycTESTS, PsycARTICLES, SCOPUS, EMBASE and Web of Science electronic databases. Both longitudinal and cross-sectional studies published from 2008 to 2019, which reported at least two statistically derived clusters or trajectories were included. Two reviewers independently screened and extracted the data. In this review, 53 studies (19 longitudinal and 34 cross-sectional) that conducted among 17,822 patients, 8729 unaffected siblings and 5520 controls or general population were included. Most longitudinal studies found four trajectories that characterized by stability, progressive deterioration, relapsing and progressive amelioration of symptoms and cognitive function. Cross-sectional studies commonly identified three clusters with low, intermediate (mixed) and high psychotic symptoms and cognitive profiles. Moreover, identified subgroups were predicted by numerous genetic, sociodemographic and clinical factors. Our findings indicate that schizophrenia symptoms and cognitive deficits are heterogeneous, although methodological limitations across studies are observed. Identified clusters and trajectories along with their predictors may be used to base the implementation of personalized treatment and develop a risk prediction model for high-risk individuals with prodromal symptoms.

Cognitive Reserve Profiles in Chronic Schizophrenia: Effects on Theory of Mind Performance and Improvement after Training

OBJECTIVES

Cognitive reserve (CR), defined as individual differences in the ability to cope with brain damage, seem to be associated to the several psychopathological features in psychiatric patients, such as the functional outcome. This study aims to identify different profiles of CR by combining intelligence quotient (IQ) and premorbid functioning, two measures independently associated to CR in previous works, as well as to explore CR effect on both Theory of Mind (ToM) baseline performance and improvement after socio-cognitive trainings.

METHODS

Sixty patients with chronic schizophrenia underwent a socio-cognitive rehabilitation. All patients were assessed for psychopathology, neurocognition, and ToM at baseline and post-treatment. CR profiles were explored with K-means cluster analysis, while differences between clusters in both baseline assessments and post-treatment ToM improvement, were analyzed by means of analysis of variance and repeated measures analysis of covariance.

RESULTS

The analysis revealed three CR profiles, respectively, characterized by low early premorbid functioning and mild intellectual impairment, average/high early premorbid functioning trend with moderate intellectual impairment and good early premorbid functioning associated to IQ within normal limits. Analyses showed a significant effect of CR on both baseline ToM performance and treatment outcome: patients with higher CR reached significantly better ToM scores.

CONCLUSIONS

These results underline the clinical relevance of defining CR profiles of patients to customize trainings: subjects with a lower CR may benefit from more intensive programs. A deeper knowledge about CR may considerably increase our understanding of individual differences and thus potentiate treatment outcome. (JINS, 2018, 24, 563-571).

Cluster analysis of cognitive deficits may mark heterogeneity in schizophrenia in terms of outcome and response to treatment

Cognitive impairments are central to schizophrenia, but their clinical utility for tagging heterogeneity in lifetime outcome and response to treatment is not conclusive. By exploiting four cognitive domains consistently showing large deficits in studies, we tested whether cluster analysis would define separate subsets of patients and then whether the disease heterogeneity marked by these clusters would be related to lifetime outcome and response to treatment. A total of 112 schizophrenia patients completed a neuropsychological evaluation. The PANSS, GAF-S and GAF-F were rated at the onset and endpoint of the illness trajectory. A blind judgment of the lifetime response to treatment was made. The first cluster presented near-normal cognitive performance. Two other clusters of severely impaired patients were identified: one generally impaired in the four cognitive domains and another selectively impaired in visual episodic memory and processing speed, each relating to a different lifetime evolution of disease and treatment response. Although the two impaired clusters were clinically indistinguishable in symptom severity and functioning at disease onset, patients with selective cognitive impairments demonstrated better improvement at outcome, whereas the generally impaired patients were more likely to be treatment refractory. The findings have implications for the management of patients and for clinical trials since particular combinations of cognitive deficits in patients would influence their treatment response.

Prospective memory impairments in schizophrenic patients

OBJECTIVE

Memory impairment is one of the most pervasive cognitive dysfunctions in schizophrenic patients. The aim of the current study was to conduct the most comprehensive assessment of how prospective memory (PM) is affected in schizophrenia in comparison with healthy controls.

METHODS

In this study, 30 first-episode schizophrenic patients who fulfilled the diagnostic criteria of the Diagnostic and Statistical Manual of Mental Disorders based on the diagnostic interview were recruited from eight regional psychiatric clinics in Iran. All participants were males (age 27-42). Moreover, 28 healthy controls were recruited from the same social-class as the patients. The Prospective and Retrospective Memory Questionnaire (PRMQ), PM tasks, and the Virtual Week Board Game were administered. Moreover, clinical symptoms were rated using the positive and negative symptoms scale.

RESULTS

The results showed that in all of the memory types, the group with dominant positive symptoms was superior to the group with dominant negative symptoms. In addition, the results showed that in all of the memory types, the control group had superiority to the schizophrenic group. The most considerable differences between groups were in time-based PM tasks, irregular event-based virtual week tasks, and retrospective tasks (PRMQ).

CONCLUSION

The current study confirmed that schizophrenic patients have severe PM deficits.

Cortical thickness in neuropsychologically near-normal schizophrenia

Schizophrenia is a severe psychiatric illness with widespread impairments of cognitive functioning; however, a certain percentage of subjects are known to perform in the normal range on neuropsychological measures. While the cognitive profiles of these individuals have been examined, there has been relatively little attention to the neuroanatomical characteristics of this important subgroup. The aims of this study were to statistically identify schizophrenia subjects with relatively normal cognition, examine their neuroanatomical characteristics relative to their more impaired counterparts using cortical thickness mapping, and to investigate relationships between these characteristics and demographic variables to better understand the nature of cognitive heterogeneity in schizophrenia. Clinical, neuropsychological, and MRI data were collected from schizophrenia (n = 79) and healthy subjects (n = 65). A series of clustering algorithms on neuropsychological scores was examined, and a 2-cluster solution that separated subjects into neuropsychologically near-normal (NPNN) and neuropsychologically impaired (NPI) groups was determined most appropriate. Surface-based cortical thickness mapping was utilized to examine differences in thinning among schizophrenia subtypes compared with the healthy participants. A widespread cortical thinning pattern characteristic of schizophrenia emerged in the NPI group, while NPNN subjects demonstrated very limited thinning relative to healthy comparison subjects. Analysis of illness duration indicated minimal effects on subtype classification and cortical thickness results. Findings suggest a strong link between cognitive impairment and cortical thinning in schizophrenia, where subjects with near-normal cognitive abilities also demonstrate near-normal cortical thickness patterns. While generally supportive of distinct etiological processes for cognitive subtypes, results provide direction for further examination of additional neuroanatomical differences.

Paternal age related schizophrenia (PARS): Latent subgroups detected by k-means clustering analysis

BACKGROUND

Paternal age related schizophrenia (PARS) has been proposed as a subgroup of schizophrenia with distinct etiology, pathophysiology and symptoms. This study uses a k-means clustering analysis approach to generate hypotheses about differences between PARS and other cases of schizophrenia.

METHODS

We studied PARS (operationally defined as not having any family history of schizophrenia among first and second-degree relatives and fathers' age at birth ≥ 35 years) in a series of schizophrenia cases recruited from a research unit. Data were available on demographic variables, symptoms (Positive and Negative Syndrome Scale; PANSS), cognitive tests (Wechsler Adult Intelligence Scale-Revised; WAIS-R) and olfaction (University of Pennsylvania Smell Identification Test; UPSIT). We conducted a series of k-means clustering analyses to identify clusters of cases containing high concentrations of PARS.

RESULTS

Two analyses generated clusters with high concentrations of PARS cases. The first analysis (N=136; PARS=34) revealed a cluster containing 83% PARS cases, in which the patients showed a significant discrepancy between verbal and performance intelligence. The mean paternal and maternal ages were 41 and 33, respectively. The second analysis (N=123; PARS=30) revealed a cluster containing 71% PARS cases, of which 93% were females; the mean age of onset of psychosis, at 17.2, was significantly early.

CONCLUSIONS

These results strengthen the evidence that PARS cases differ from other patients with schizophrenia. Hypothesis-generating findings suggest that features of PARS may include a discrepancy between verbal and performance intelligence, and in females, an early age of onset. These findings provide a rationale for separating these phenotypes from others in future clinical, genetic and pathophysiologic studies of schizophrenia and in considering responses to treatment.