Effort discounting and its association with negative symptoms in schizophrenia

Introduction. Deficits in the initiation and persistence of goal-directed behaviour are key aspects of schizophrenia. In this study, the association between these motivational deficits and discounting of reward value in function of increasing physical effort costs was investigated. Methods. Effort-based decision-making was investigated in 40 patients with a DSM-IV diagnosis of schizophrenia and 30 age- and sex-matched healthy control subjects by means of an effort discounting task. To assess negative symptom severity, we made use of the Scale for the Assessment of Negative Symptoms as well as objective measurements of hedonic response to stimuli and motor activity levels. Results. Patients as well as control subjects discounted the subjective value of rewards significantly with increasing physical effort costs. However, we failed to find a difference in the discounting curves between patients and controls. Furthermore, effort discounting was not associated with any of the negative symptoms measures. Conclusions. Physical effort discounting was not found to be associated with motivational symptoms in schizophrenia if other decision costs are constant. However, recent findings show that more cognitive effort and/or an interaction between effort and other decision costs (e.g. temporal delay or uncertainty) are associated with negative symptoms in schizophrenia. This should be investigated further in future research.