Investigation of effor expenditure for the reward and effort based decision making in recent onset schizophrenia patients

Introduction: Schizophrenia is a chronic and disabling disorder that leads to impairment in functioning. Negative symptoms of schizophrenia have been conceptualized as an essential part of schizophrenia for many years, and are defined as the absence or reduction of behaviors normally present in the general population. Negative symptoms play a key role in the functional consequences of the disorder and impair patients' quality of life. There is increasing evidence that there are the reward processing deficits in patients with schizophrenia, such as reward learning, reward prediction, reward valuation and effort computation, and that these deficits are usually associated with negative symptoms. Various paradigms have been utilized to measure how much effort a person puts for varying degrees of reward and to evaluate effort based decision making strategies under different reward circumstances. Of these paradigms, the most valid is the Effort Expenditure for the Rewards Task (EEfRT). The aim of this study is to investigate whether there is a difference between effort based decision making attitudes of schizophrenia patients and healthy controls, and the relationship between effort based decision making and clinical features, especially negative symptoms, in schizophrenia patients. Methods: Thirty-one recent-onset schizophrenia patients followed-up at the Istanbul University Istanbul Faculty of Medicine Department of Psychiatry and 30 healthy controls were included in the study. The effort performances of all participants were evaluated with EEfRT, and their cognitive performances were evaluated with the Brief Cognitive Assessment Tool for Schizophrenia which consisted of Trail Making Test-B, Digit Symbol Coding Test and Category Fluency Test. Clinical characteristics of patients in the schizophrenia group were assessed with Brief Negative Symptoms Scale (BNSS), Positive and Negative Syndrome Scale (PANSS), Scale for the Assessment of Negative Symptoms (SANS), Self-Evaluation of Negative Symptoms Scale (SNS), Scale for the Assessment of Positive Symptoms (SAPS), Calgary Depression Scale for Schizophrenia (CDSS), Extrapyramidal Symptom Rating Scale (ESRS) and Personal and Social Performance Scale (PSP). Correlations with negative symptoms were examined both continuously by using negative symptom scale scores and categorically by forming schizophrenia groups consisting of patients with and without 4 Persistent Negative Symptoms (PNS). Data was analysed by repeated measures ANOVA and Spearman correlation analyses. Results: Results of this study showed that effort allocation for rewards was generally worse in patients with schizophrenia when compared to healthy controls. This difference was more pronounced when the reward magnitude and probability to obtain reward were highest. In the patient group, effort expenditure was negatively correlated with total negative symptoms scores and motivation-pleasure deficits sub-scores; whereas it was positively correlated with cognitive performance. Positive, depressive, extrapyramidal symptoms and functioning were not found to be associated with effort expenditure. The comparison between the negative symptom scales yielded that the BNSS and PANSS negative subscale best reflected the effort related decision-making processes. The relationship between EEfRT performances and negative symptom scale scores was more prominent when reward magnitude and probability of obtaining the reward were moderate. This was also true when negative symptoms were investigated categorically; patients with PNS performed worse than patients without PNS when the reward magnitude was moderate. Conclusions: Patients with schizophrenia are less willing to exert effort for rewards compared to controls, and this is negatively associated with motivation-pleasure deficits domain of negative symptoms. When examined both continuously and categorically, the relationship between negative symptoms and the effort exerted for rewards is especially evident in cases where it is less certain to obtain the reward and the reward is moderate.