Altered learning under uncertainty in unmedicated mood and anxiety disorders

Anxiety is characterized by altered responses under uncertain conditions, but the precise mechanism by which uncertainty changes the behaviour of anxious individuals is unclear. Here we probe the computational basis of learning under uncertainty in healthy individuals and individuals with a mix of mood and anxiety disorders. Participants chose between four competing slot machines with fluctuating, reward/punishment outcomes during safety and stress. We predicted that anxious individuals under stress would learn faster about punishments, and exhibit choices that were more affected by them, formalising our predictions as parameters in reinforcement-learning accounts of behaviour. Overall, data suggest that anxious individuals are quicker to update their behaviour in response to negative outcomes (i.e. increased punishment learning-rates). When treating anxiety, it may therefore be more fruitful to encourage anxious individuals to integrate information over longer horizons when bad things happen, rather than try to blunt responses to negative outcomes.