The Relationship Between IQ, Memory, Executive Function, and Processing Speed in Recent-Onset Psychosis: 1-Year Stability and Clinical Outcome

Abstract

Studies commonly report poor performance in psychotic patients compared with controls on tasks testing a range of cognitive functions, but, because current IQ is often not matched between these groups, it is difficult to determine whether this represents a generalized deficit or specific abnormalities. Fifty-three first-episode psychosis patients and 53 healthy controls, one-to-one matched for sex, age, and full-scale current IQ, were compared on Wechsler Adult Intelligence Scale (WAIS) subtests representing indices of perceptual organization, verbal comprehension, processing speed, and working memory as well as other tests of executive function and episodic memory. The groups showed an equivalent pattern of performance on all WAIS subtests except digit symbol processing speed, on which the patients were significantly worse. Patients were also worse on measures where performance correlated with digit symbol score, namely working and verbal memory tasks. Standardized residual scores for each subtest were calculated for each patient using the difference between their actual subtest score and a predicted subtest score based on their full-scale IQ and the performance of controls. Scaled scores and residual scores were examined for relationships with clinical measures. Digit symbol–scaled score was significantly correlated with concurrent negative syndrome score at baseline, and digit symbol residual score significantly predicted residual negative symptoms at 1-year follow-up. In summary, our comparison of patients and controls precisely matched for IQ revealed that processing speed was attenuated in recent-onset schizophrenia, contributed significantly to working and episodic memory deficits, and was a prognostic factor for poor outcome at 1 year.

Cognitive course in first-episode psychosis and clinical correlates: A 4 year longitudinal study using the MATRICS Consensus Cognitive Battery

“…When investigating the clinical relevance of our cognitive findings we found poorer cognitive ability, specifically reasoning and problem solving and social cognition at illness onset, to predict greater negative symptom severity four years later. Longitudinally, performance on a variety of cognition domains at illness onset, such as processing speed, IQ, working memory and verbal learning, have been found to relate to the course of negative symptom severity (Leeson et al, 2010;Carlsson et al, 2006;Bora and Murray, 2013;González-Ortega et al, 2013). Taken together, these data support cognition at illness onset as a potential predictive indicator of illness course; however, there is yet heterogeneity as to which exact cognitive domain which relates to negative symptom severity.…”

Cognitive intervention in early psychosis — preserving abilities versus remediating deficits

“…In early illness stages, however, attentional set-shifting ability appears to be preserved or only minimally affected. A number of studies have found no differences between FEP patients and healthy controls on the IED task [12,[38][39][40], and a small study of pre-psychotic individuals also found no impairment in attentional set-shifting ability [41]. These findings are interesting when considered in the context of developmental trajectories of these tasks, as discussed below.…”

The relationship between intelligence and cognitive function in schizophrenic

“…[3] Leeson and his colleagues in his research also get the same results that intelligence significantly correlated with cognitive function, especially memory and executive function. [4] Beilen et al, in a study also get the same result, namely a clear link between the level of intelligence and memory function, attention and executive function of the cognitive function. According to him, intelligence and cognitive function may be difficult to distinguish.…”