Motivation and cognitive performance are closely linked in patients with schizophrenia, research shows.
This suggests that performance in neurocognitive tests is “not purely a measure of ability”, say lead researcher Gagan Fervaha (University of Toronto, Ontario, Canada) and colleagues.
Fervaha et al identified the association among 431 patients who participated in the Clinical Antipsychotic Trials of Intervention Effectiveness (CATIE). They measured general trait-like motivation using the sense of purpose, motivation and curiosity items from the Intrapsychic Foundations subscale of the Heinrichs-Carpenter Quality of Life Scale.
“We wish to emphasize that […] the present results do not suggest that the full extent and degree of cognitive impairment in schizophrenia result from motivational impairments”, the researchers write in JAMA Psychiatry.
Nevertheless, they found a moderate effect size, with correlation coefficients ranging from about 0.20 to 0.34, where 1.00 is perfect correlation, and intrinsic motivation explaining between 6% and 16% of the variance in patients’ cognitive performance.
Each individual item of intrinsic motivation was significantly associated with each cognitive measure, although the strongest association was seen for processing speed. Reasoning and vigilance were the least affected by motivation.
The associations remained after adjusting for sociodemographical variables, illness severity, medical comorbidities, community functioning and duration of antipsychotic treatment.
In an accompanying editorial, Richard Keefe (Duke University Medical Center, Durham, North Carolina, USA) cautions against findings such as these “putting us back into the position of blaming people with schizophrenia for their illness”.
He highlights another of the team’s findings: that increased motivation also predicted neurocognitive improvement over 6 months of follow-up, albeit explaining only about 1% of the variance. He says this fits with the knowledge that cognitive impairment leads to functional disability before the onset of psychosis.
“The self-defeat that is generated from this cycle of prodromal impairment adds another important dimension to the cycle, which likely leads to further social isolation, the single strongest predictor of psychosis”, says Keefe.
He concludes: “Treatments that target these aspects of schizophrenia before psychosis emerges have the potential to interrupt the illness before it progresses on its devastating course.”
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