Abstract
Motivational impairments are common to many psychiatric conditions, yet associations between psychiatric symptoms and willingness to exert cognitive effort have been inconsistent. Previous studies have mostly analyzed cognitive effort at the moment when people choose to engage in an effortful task, overlooking fatigue before the choice and how the task is executed after the choice. Here we examined this process during a 75-min online experiment involving 529 adults with psychiatric profiles spanning a broad range of symptoms. Participants repeatedly chose between resting and performing a demanding working-memory task, carried out the selected activity, and reported their fatigue. We derived continuous transdiagnostic symptom dimensions and modeled fatigue, effort selection, and task performance across time. Across participants, fatigue accumulated over time, and higher pre-choice fatigue predicted effort avoidance despite high overall task accuracy. Higher anxious-depression scores were associated with greater initial fatigue, faster fatigue accumulation, and a progressively steeper decline in high-effort choices. By contrast, higher compulsivity/intrusive thought scores were associated with more frequent high-effort choices but lower accuracy after effort was selected. Motivational dysfunction therefore did not reduce to a general reluctance to exert effort, but emerged through distinct alterations in fatigue accumulation, effort selection, and task execution. A dynamic, process-based account that separates these stages may help reconcile inconsistent findings in effort-based mental health research.