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The validity and significance of normal range neurocognition in schizophrenia remain unclear and controversial. We assessed whether normal range patients and controls demonstrate evidence of decline relative to premorbid ability and differ in performance profiles across measures, including those external to the normality criterion. In addition, we compared below normal range healthy control participants with patients at the same ability level. Performance normality was defined as a MATRICS Consensus Cognitive Battery (MCCB) composite T score between 40 and 60. Patients (n = 17) and controls (n = 24) meeting the criterion were compared on MCCB domain scores and on independent measures of reading ability, probabilistic and social reasoning. Patients (n = 19) and controls (n = 20) scoring below 40 on the MCCB composite were compared on the same set of measures. Cognitively normal range patients and controls did not differ on estimated premorbid ability or decline and differed only on the Processing Speed domain of the MCCB. Performance did not differ across other domains or on social and probabilistic reasoning tasks. Cognitively below normal range patients and controls showed marked discrepancies between premorbid and current ability, but there were no group differences. In addition, below normal range groups did not differ on any MCCB domain score or in terms of external cognitive measures. Cognitively normal range schizophrenia patients may be largely indistinguishable from normal range controls, with the exception of processing speed performance. More typical schizophrenia patients below the normal range may be indistinguishable from low-performing controls even in terms of processing speed.

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Recent reports suggest that cognition is relatively preserved in some schizophrenia patients. However, little is known about the functional advantage these patients may demonstrate. The purpose of this study was to identify cognitively normal patients with a recently developed test battery and to determine the functional benefit of this normality relative to cognitively impaired patients. Average-range cognitive ability was defined by the Measurement and Treatment Research to Improve Cognition in Schizophrenia (MATRICS) Consensus Cognitive Battery (MCCB) composite score (T≥40) and applied to 100 patients with schizophrenia or schizoaffective disorder and to 81 non-psychiatric research participants. With group assignment adjusted for demographic variables, this procedure yielded 14 cognitively normal patients, 21 cognitively impaired patients, and 21 healthy adults with normal-range MCCB scores. Cognitively normal patients were indistinguishable from controls across all MCCB scales. Furthermore, their performance was superior to impaired patients on all scales except Social Cognition. Cognitively normal patients were also superior to impaired patients on a summary index of simulated life skills and functional competence. Nevertheless, both patient groups were equally disadvantaged relative to controls in independent community living. These findings suggest that normal-range cognition exists in schizophrenia, but fails to translate into enhanced community outcome.

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OBJECTIVE: The main purpose of this investigation was to identify patterns of intellectual performance in schizophrenia patients suggesting preserved, deteriorated, and premorbidly impaired ability, and to determine clinical, cognitive, and functional correlates of these patterns. METHOD: We assessed 101 patients with schizophrenia or schizoaffective disorder and 80 non-psychiatric control participants. The "preserved" performance pattern was defined by average-range estimated premorbid and current IQ with no evidence of decline (premorbid-current IQ difference <10 points). The "deteriorated" pattern was defined by a difference between estimated premorbid and current IQ estimates of 10 points or more. The premorbidly "impaired" pattern was defined by below average estimated premorbid and current IQ and no evidence of decline greater than 10 points. Preserved and deteriorated patterns in healthy controls were also identified and studied in comparison to patient findings. The groups were compared on demographic, neurocognitive, clinical and functionality variables. RESULTS: Patients with the preserved pattern outperformed those meeting criteria for deteriorated and compromised intellectual ability on a composite measure of neurocognitive ability as well as in terms of functional competence. Patients demonstrating the deteriorated and compromised patterns were equivalent across all measures. However, "preserved" patients failed to show any advantage in terms of community functioning and demonstrated cognitive impairments relative to control participants. CONCLUSIONS: Our results suggest that proposed patterns of intellectual decline and stability exist in both the schizophrenia and general populations, but may not hold true across other cognitive abilities and do not translate into differential functional outcome.

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It has been well established that neurocognitive deficits are a core feature in schizophrenia and predict difficulties in functional independence. However, few studies have assessed the longitudinal stability of cognition and key aspects of functional outcome concurrently. Even less attention has been directed at the contingency of cognitive change on real world outcome changes. Accordingly, this study will assess the extent to which significant changes in cognition and community status are independent or related. As a point of comparison, the stability of clinical symptom status and the relationship between symptom and outcome change are evaluated. Symptoms, cognitive abilities, and community outcome was assessed in 128 patients with schizophrenia at baseline and again one year later. Intraclass correlation coefficients were used to index stability and reliable change index analyses quantified the prevalence of significant improvement or deterioration in each of the three illness features. Results from these analyses revealed that symptom status, cognitive functioning, and community outcome are similarly stable in treated schizophrenia outpatients. A small proportion of the sample demonstrated significant improvement or deterioration in these domains, with only weak evidence that such change was predicted by changes in symptoms or cognition. Further, there was no strong evidence of a preferential relationship for cognition relative to symptoms in relation to functional outcome. These results shed light on the strength and nature of the cognition-real world outcome relationship in schizophrenia and have implications for pharmacological and behavioral interventions aimed at improving real world outcome.

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This study examined the reliability and validity of a new performance-based measure of functional competence for individuals with serious mental illness, the Canadian Objective Assessment of Life Skills (COALS). The COALS assesses both routinized procedural knowledge routines (PKR) and executive operations (EXO) in order to capture functional outcome variance. The COALS was administered to 101 outpatients with schizophrenia and schizoaffective disorder and 80 non-psychiatric controls. One month later, 95 patients and 63 controls completed a follow-up assessment. Measures of psychopathology, neurocognition, functionality and community adjustment were also administered. Results indicated that the COALS summary scores had good test-retest reliability for patient data. Further, the COALS correlated with other measures of functionality and with negative symptoms, but was independent of positive symptoms, demonstrating concurrent and discriminant validity. The overall COALS summary score added incremental validity to the prediction of community independence over and above the contribution of symptoms, intellectual ability and neurocognitive performance. Inclusion of EXO scores provided incremental validity not available with PKR scores alone. The COALS increases the number of functional competence instruments and offers the advantage of specific validity while incorporating important distinctions in cognitive performance.

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