Cognitive effort-based decision making in schizophrenia and bipolar disorder: Associations with clinical symptoms and cognitive performance

Individuals frequently make decisions about how much cognitive effort to expend for specific tasks. For a given reward, individuals with schizophrenia and bipolar disorder choose to exert less effort than comparison subjects, which contributes to motivational deficits common in these disorders. One component of motivation is an analysis in which potential rewards are discounted by the costs, such as effort, associated with that reward. Impairments in such a cost/benefit analysis are associated with cognitive deficits in schizophrenia. Prior work using mathematical discounting functions has modeled how individuals evaluate rewards against delay and probability costs, but no study has modeled effort-based discounting in schizophrenia and bipolar disorder. Using the Cognitive Effort Discounting task (CogED), the shape and slope of effort discounting curves was modeled across three groups of Veterans: those with schizophrenia (n = 35) those with bipolar disorder (n = 23) and controls (n = 32). Veterans with schizophrenia displayed a blunted discounting curve compared with controls and those with bipolar disorder, driven, in part, by the schizophrenia group assigning smaller subjective values to low effort, high reward tasks. Discounting rate was related to cognitive performance in both schizophrenia and bipolar patients, such that greater cognitive ability was associated with steeper discounting. The use of discounting models extends our understanding of effort-based decision-making in schizophrenia and bipolar disorder and supports the role of cognitive impairment as a contributor to decision making abnormalities in the two disorders.