Much of the Neurocognitive Impairment in Schizophrenia is Due to Factors Other Than Schizophrenia Itself: Implications for Research and Treatment

Abstract

Abstract Patients with schizophrenia perform worse on neuropsychological tasks than controls. While most experts ascribe poor performance to neurocognitive impairment, an emerging literature is identifying important nonspecific mediators of neurocognitive test performance, some of which can be accounted for in trials (eg, motivation, effort, defeatist performance beliefs, stress, anxiety, physical inactivity). Other factors are harder, if not impossible, to control when patients are compared to non-clinical participants (eg, hospitalization, medication effects, distraction due to positive symptoms). Effect sizes of neurocognitive performance differences are usually not adjusted for these confounders, and the level of neurocognitive impairment due to schizophrenia is thus likely exaggerated. We suggest some ways for researchers to account for the effects of these mediators. Secondary influences that negatively affect neurocognitive performance should not be treated as mere noise. They give important insight into causal mechanisms and may inform more effective treatments that go beyond cognitive remediation.