Atypical contributions of reward decisions to momentary mood in individuals with methamphetamine use disorder.

BACKGROUND: Individuals with Methamphetamine use disorder (MUD) are often accompanied by severe mood dysregulation, leading to more frequent irrational decisions such as drug-seeking behavior. Existing research indicates that the impairment of the reward system is central to the development of addiction. However, it remains unclear how the abnormal reward processing affects the mood regulation abilities of individuals with MUD. In this study, we explored the cognitive and computational mechanisms through which the subjective mood of individuals with MUD is influenced by reward information during decision-making. METHODS: We recruited 76 male participants (27 with MUD, 49 healthy controls, HC) who completed a risk gambling task. In this task, participants were asked to choose between two options with certain or uncertain rewards. After every 2–3 gambling trials, participants also rated their momentary subjective happiness. We constructed multiple computational models to predict how various reward information (such as reward prediction error) influenced the short-term fluctuations in participants’ subjective mood during risk decisions. RESULTS: Individuals with MUD exhibited significantly more irrational decisions compared to the HC group. Computational modeling revealed that, compared to healthy controls, individuals with MUD showed a significantly weaker influence of various reward information (e.g., expected value, EV; reward prediction error, RPE) on their subjective mood. Importantly, the EV- and RPE-mood associations predict the degree of substance abuse. CONCLUSIONS: Our findings provide computational evidence that individuals with MUD lack effective regulation of mood by the reward system. This process leads to more substance abuse. These results shed new light on the mood issues in individuals with MUD from the perspective of reward processing, thereby helping to reduce drug use. CLINICAL TRIAL: Not applicable.