Examining cognition across the bipolar/schizophrenia diagnostic spectrum

Abstract

Background: Cognitive impairments are well-established features of schizophrenia whereas there is ongoing debate about nature and degree of cognitive performance in schizoaffective disorder and bipolar disorder. We hypothesised that there is a spectrum of increasing impairment from bipolar disorder to schizoaffective-bipolar type to schizoaffective-depressive type and schizophrenia. Method: Performance on the MATRICS Consensus Cognitive Battery was compared between participants with schizophrenia (N=558), schizoaffective-depressive type (N=112), schizoaffective-bipolar type (N=76), bipolar disorder (N=78) and healthy participants (N=103) using analysis of covariance with post-hoc comparisons. An ordinal logistic regression was conducted to examine whether cognitive impairments followed the hypothesised spectrum from bipolar disorder (least severe) to schizophrenia (most severe). In addition to categorical diagnoses we addressed the influence of symptom domains, examining the association between cognition and mania, depression and psychosis. Results: Cognitive impairments increased in severity from bipolar disorder to schizoaffective-bipolar to schizophrenia/schizoaffective-depressive. Participants with schizophrenia and schizoaffective-depressive displayed equivalent performance (d=0.07,p=0.90). The results of the ordinal logistic regression were consistent with a spectrum of deficits from bipolar disorder to schizoaffective-bipolar type to schizophrenia/schizoaffective-depressive type (OR=1.98, p=2.4x10-16). In analyses of the associations between symptom dimensions and cognition, higher scores on the psychosis dimension were associated with poorer performance (B=0.015 p=3.2 x 10-16). Limitations: There were fewer participants with schizoaffective disorder and bipolar disorder than schizophrenia. Despite this, our analyses were robust to differences in the group sizes and we were able to detect differences between groups. Conclusion: Cognitive impairments represent a symptom dimension that cuts across traditional diagnostic boundaries.

Validity and utility of Hierarchical Taxonomy of Psychopathology (HiTOP): I. Psychosis superspectrum

“…In schizophrenia, schizoaffective disorder, bipolar I disorder, and schizotypal personality disorder, cognitive deficits were doc­u­mented in all domains: sensorimotor, attention, learning and memory, executive functions, language, and social cognition 180‐184 . These deficits were most pronounced in schizophrenia, but the other disorders showed a similar, although less extreme, profile of cognitive impairment 185‐188 . With regard to dimensions, negative and disorganized symptoms were linked to all aforementioned deficits, whereas reality distortion was essentially unrelated to cognitive impairment 189‐191 .…”

Let’s Talk about the Association between Schizophrenia Polygenic Risk Scores and Cognition in Patients and the General Population: A Review

“…But there is one exception: Whalley et al [34] investigated the association between SZ-PRS and some specific cognitive functions exclusively in individuals with MDD. Even though the results did not reveal any significant association, this might be an interesting new approach in the future, in order to further investigate the affective-to-psychotic continuum regarding the effects of genetics on cognitive symptoms [9,10] .…”

“…Therefore, researchers have questioned the Kraepelinian dichotomy and proposed a continuum model from MDD and BD over SA to SZ [9] . A recent study investigated cognitive performance within a continuum approach, showing a decrease of cognitive abilities in the direction from BD to SZ [10] .…”

Cognitive and clinical predictors of community functioning across the psychoses

“…Across the psychoses, comparisons of patients by diagnosis have demonstrated both overlapping and distinct aspects of cognitive impairment, and diagnostic group comparisons have yielded some inconsistent findings. For example, some studies report few or no significant group differences in cognitive performance by diagnoses (Dickerson, Sommerville, Origoni, Ringel, & Parente, ; Lewandowski, Cohen, Keshavan, & Ongür, ; Owoso et al, ), whereas other reports support the notion of a “spectrum” of cognitive impairment across diagnostic groups, typically ranging from lowest impairment in patients with BD, to moderate impairment in patients with schizoaffective disorder (SZA)–bipolar subtype, to more severe impairment in patients with SZ and SZA–depressive subtype (Hill et al, ; Lynham et al, ; McIntosh, Harrison, Forrester, Lawrie, & Johnstone, ; Szoke et al, ). Similarly, some findings show global impairments in patients with primary psychosis and more selective impairments in patients with affective disorders (Laes & Sponheim, ; Reichenberg et al, ).…”

“…In both affective and non‐affective psychosis, cognitive impairment persists during clinical remission/euthymia (Buckley, Harvey, Bowie, & Loebel, ; Caspi et al, ; Szmulewicz et al, ). However, clinical symptoms may be associated with cognition, suggesting that state symptomatology may exacerbate cognitive impairments (Lynham et al, ). For example, in patients with SZ, more severe negative symptoms have been found to be associated with cognitive impairment (e.g., Ventura, Hellemann, Thames, Koellner, & Nuechterlein, ).…”