Multiple sclerosis reduces sensitivity to immediate reward during decision making

Individuals with multiple sclerosis (MS) often face important health-related and financial decisions that involve trade-offs between short-term and long-term benefits, yet decision making is rarely studied in MS patients. The temporal discounting paradigm is a useful tool for investigating such time-dependent choices in humans. Here, we investigated whether patients with relapsing-remitting MS differed from healthy controls when making choices between hypothetical monetary rewards available at different points in time. Participants were tested in two conditions: in one, the choice was between a smaller amount of money available immediately and a larger amount of money available at a later date; in the other, a fixed delay of 60 days was added to both options. We found that, compared with healthy controls, MS patients favored less the sooner reward in the condition involving an immediate reward, whereas no difference between MS patients and the control group emerged in the condition involving only delayed rewards. Moreover, the decreased immediacy bias was corroborated by lower scores at scale that assesses responsiveness to rewards in MS patients. Taken together, these findings indicate reduced sensitivity to immediate reward and a consequent stronger willingness to defer gratification in MS individuals.