Anxiety associated with perceived uncontrollable stress enhances expectations of environmental volatility and impairs reward learning

navoidable stress elicits perceived lack of controllability and learned helplessness, which is a risk-factor for depression. Stress, anxiety, and depression can all alter reward learning. In a preregistered study during the first-wave of the COVID-19 pandemic, we used self-reported measures of depression, anxiety, uncontrollable stress, and COVID-19 risk from 427 online participants to predict performance in a three-armed-bandit probabilistic reward learning task. As hypothesised, uncontrollable stress predicted impaired learning of optimal choices. Uncontrollable stress also predicted a greater proportion of probabilistic errors following negative feedback for correct choices, which reflected interpretation of ambiguous negative feedback as a change in task reward contingencies. Moreover, this effect of uncontrollable stress on probabilistic errors was mediated by state anxiety. A parameter from the best-fitting hidden Markov model that estimates expected beliefs that the identity of the optimal choice will shift across images, mediated effects of state anxiety on probabilistic errors and learning deficits. Our findings show that following uncontrollable stress, anxiety promotes an overly volatile representation of the reward structure of uncertain environments, impairing reward attainment, which is a potential path to anhedonia in depression