Differential Profiles of Delay Discounting in Affective and Non-Affective Psychotic Disorders

Motivational impairments are common in psychotic disorders and have implications for functioning and recovery. A key underlying mechanism is reward processing, which crucially relies on value representation (the mental representation of the subjective value of a reward). Previous studies have found altered value representation in people with psychosis using a delay discounting task, but results have been mixed, especially in affective psychosis. It is also inconclusive how value representation relates to other constructs such as symptoms and cognition.

A total of 71 participants with schizophrenia spectrum disorders (SZ), 77 with psychotic mood disorders (MP), and 42 healthy control participants (HC) performed a delay discounting task. Using hierarchical Bayesian analysis, we derived three computational parameters from the task: discounting rate (how quickly delayed rewards lose subjective value), time sensitivity (subjective perception of time), and inverse temperature (choice consistency in relation to subjective value of rewards).

We found a stronger preference for immediate over delayed reward in SZ compared to HC, and a larger difference between the perception of near and far future. Compared to HC, MP made more choices that were consistent with their perceived differences between immediate and delayed rewards, which further correlated with lower behavioral activation. In both groups, higher discounting rate correlated with lower choice consistency.

Reward processing dysfunctions may manifest in different ways in different psychotic disorders and may be due to differing underlying mechanisms, which has important implications for targeted intervention development.