Reinforcement learning impairment in individuals with euthymic bipolar I disorder with a history of psychosis

Reinforcement-learning (RL) impairment is an important determinant of functional outcome in bipolar-disorder (BD). This study examined RL in 38 euthymic bipolar-I-disorder (BD-I) individuals aged 16-40 years who were treated within three years from first-episode mania with psychosis and 40 demographically-matched healthy-controls using a computerized RL-paradigm, which investigated rapid and gradual learning, and reward-driven and punishment-driven learning. Symptom severity and cognitive functions were assessed. Our results showed that BD-I individuals displayed lower lose-shift scores than controls (p = 0.03). There were no group differences in other rapid RL measures. Regarding overall RL, a repeated-measures ANOVA revealed main effect of group (F1,76 = 6.5, p = 0.03; controls performed better than patients), block (F2.87,218.45 = 43.7, p < 0.001; performance improving over time) and probability (F1,76 = 15.6, p < 0.001; better performance in 90% than in 80% condition). Post-hoc analysis revealed that controls performed better than BD-I individuals on loss-avoidance stimuli (p = 0.02). Better performance of controls relative to BD-I individuals on gain stimuli approached statistical significance (p = 0.06). No correlations of RL measures with symptoms, cognition or antipsychotic dose were observed. In conclusion, this study is among the few to examine RL impairment in euthymic BD-I with history of psychosis at a relatively early illness stage, and indicates that BD-I individuals displayed punishment-driven learning (i.e., negative RL) deficits compared with controls. Diminished punishment-sensitivity may indicate vulnerability to maladaptive behaviors, particularly in response to negative events or stress, and poorer functional impairment. Further research is required to clarify longitudinal trajectory of punishment-insensitivity and its relationship with psychosis and functional outcomes in the early-stage of BD.