Motivational deficits and cognitive test performance in schizophrenia.

Importance: Motivational and cognitive deficits are core features of schizophrenia, both closely linked with functional outcomes. Although poor effort and decreased motivation are known to affect performance on cognitive tests, the extent of this relationship is unclear in patients with schizophrenia.
Objective: To evaluate the association between intrinsic motivation and cognitive test performance in patients with schizophrenia.
Design, Setting, and Participants: Cross-sectional and 6-month prospective follow-up study performed at 57 sites in the United States, including academic and community medical treatment centers, participating in the Clinical Antipsychotic Trials of Intervention Effectiveness study. The primary sample included 431 stable patients with a DSM-IV diagnosis of schizophrenia currently receiving a stable medication regimen.
Interventions: Cognitive performance and intrinsic motivation were evaluated using a comprehensive neuropsychological test battery and a derived measure from the Heinrichs-Carpenter Quality of Life Scale, respectively. Symptom severity and functional status were also assessed.
Main Outcomes and Measures: The primary outcome variable was global neurocognition. Individual domains of cognition were also evaluated for their association with motivation.
Results: Level of intrinsic motivation was significantly and positively correlated with global cognitive test performance, a relationship that held for each domain of cognition evaluated (correlation range, 0.20-0.34; P < .001). This association was found to be reliable after statistically accounting for positive, negative, depressive, and overall symptom severity (P < .05) and after accounting for community functioning (P < .001). The relationship between motivation and cognitive performance also remained significant after controlling for antipsychotic dose (P < .05). Prospective increase in motivation during the 6-month follow-up was also found to be significantly related to improvement in global cognitive performance (P < .05).
Conclusions and Relevance: The present findings provide strong support for a robust and reliable relationship between motivation and cognitive performance and suggest that test performance is not purely a measure of ability. Future studies assessing cognition in patients with schizophrenia should consider potential moderating variables such as effort and motivation. Implications for the assessment and interpretation of cognitive impairment based on neuropsychological test measures in schizophrenia are discussed, especially in the case of clinical trials for cognition-enhancing treatments.
Trial Registration: clinicaltrials.gov Identifier: NCT00014001.