S63. CLINICAL AND DEVELOPMENTAL CHARACTERISTICS OF COGNITIVE SUBGROUPS IN A TRANSDIAGNOSTIC SAMPLE OF SCHIZOPHRENIA, SCHIZOAFFECTIVE DISORDER AND BIPOLAR DISORDER
Authors: Bora Emre , Verim Burcu , Akgul Ozge , Ildız Ayşegül , Alptekin Köksal , Özerdem Ayşegül , Akdede Berna Binnur 
Published: May 2020

Abstract

Background
Evidence suggests that neurocognitive dysfunction is a transdiagnostic feature of individuals across continuum between schizophrenia and bipolar disorder. However, there is a significant heterogeneity of neuropsychological and social cognitive abilities in schizophrenia, schizoaffective disorder and bipolar disorder. In recent years, several studies have investigated cognitive subgroups in schizophrenia-bipolar disorder continuum using data-driven methods and found that bipolar disorder includes several subgroups including a severely impaired and a neurocognitively intact clusters. However, neurodevelopmental and clinical characteristics of cognitive subgroups are not clear.

Methods
147 clinically stable patients with schizophrenia, schizoaffective or bipolar disorder were assessed using clinical rating scales for current psychotic and affective symptoms, schizobipolar scale, and a comprehensive neuropsychological battery including measures of ToM (Hinting and Reading the mind from the Eyes (RMET) task)). Developmental history and premorbid academic functioning were also evaluated. The study also included 37 healthy controls. Neurocognitive subgroups were investigated using latent class analysis (LCA). The optimal number of clusters were determined based on Bayesian information criterion. Logistic regression analysis were conducted to investigate the predictors of the membership to globally impaired subgroup.

Results
LCA revealed two neurocognitive clusters including generally impaired (n=89, 60.5 %) and near-normal cognitive functioning (n=58, 39.5 %) subgroups. The generally impaired subgroup significantly underperformed both groups in memory, executive functions, processing speed, attention and both aspects of ToM. The near-normal cognitive functioning subgroup did not significantly underperformed healthy controls except RMET (p=0.01). The generally impaired subgroup had a history of increased number of developmental abnormalities (p=0.03) and more severe disorganised speech (p=0.02) compared to the near-normal cognitive functioning group. The near-normal subgroup had a significantly higher percentage of individuals with a history of good academic performance in childhood than the globally impaired group (p=0.002). Compared to the near-normal subgroup, the globally impaired subgroup was significantly older (p&lt;0.001) and had mothers who were less educated (p=0.02). While relatively higher percentage of patients with bipolar disorder than schizophrenia were members of the near-normal functioning subgroup (and opposite for the generally impaired subgroup), the between-group difference was not significant. Logistic regression analysis suggested that both the number of neurodevelopmental abnormalities (p=0.02) and disorganised speech (p=0.05) were significant predictors of being included in the globally cognitive impaired subgroup (Log likelihood=144. 4, R2=0.23, p=0.003, percentage correctly identified as globally impaired 81.1 %).

Discussion
History of developmental abnormalities and persistent disorganisation rather than diagnosis are the significant predictors of the subgroup of individuals with global cognitive impairment in schizophrenia-bipolar disorder continuum. Studies investigating neurobiological and genetic underpinnings of the relationship between cognitive impairment, neurodevelopmental abnormalities and persistent disorganised speech might be important to develop a more valid classification of disorders presenting with psychotic and mood symptoms.