Abnormal hedonic process in patients with stable schizophrenia: Relationships to negative symptoms and social functioning

Background: Anhedonia is a deficit of dynamic reward process, and a large proportion of schizophrenia patients continue to experience anhedonia even during the stable phase. However, few studies have examined the multiple aspects of performance in reward processing in patients with stable schizophrenia and evidence suggests that physical and cognitive effort may involve different neural mechanisms.

Methods: Parallel measures of effort-based expenditure for reward tasks (EEfRT) and self-report questionnaires of pleasure were applied in 61 patients with stable schizophrenia (SSZ) and 46 healthy controls (HCs), and percentages of hard task choices (HTC%) were used to assess motivation in reward processing. Negative symptoms, neurocognitive and social function were evaluated in SSZ patients, and associations with performance in reward tasks were explored.

Results: SSZ patients reported more severe consummatory and anticipatory anhedonia and social anhedonia. HTC% in reward tasks of SSZ patients were significantly lower than that of HCs, especially in cognitive-effort tasks. HTC% in cognitive tasks were correlated with motivation and pleasure dimension of negative symptoms, whereas HTC% in physical tasks were associated with expression dimension. Anticipatory anhedonia and negative symptoms were correlated with Personal and Social Performance Scale (PSP) scores.

Conclusion: Patients with stable schizophrenia have social anhedonia, physically consummatory and anticipatory anhedonia and reduced reward motivation. They are less willing to make cognitive effort than physical effort for reward. The different associations of physical and cognitive effort with negative symptoms indicate physical and cognitive effort may represent disparate neuropsychological processes. Anticipatory anhedonia is closely related to social functioning.