Working memory interacts with emotion regulation to predict symptoms of mania

•Performance on a working memory task was not correlated with use of emotion regulation strategies in euthymic bipolar disorder.•Working memory and expressive suppression interacted to predict higher mania symptoms at 12-month follow-up.•At lower levels of working memory, low use of suppression was associated with greater symptoms of mania at follow-up. Although neurocognitive deficits and emotion regulation are closely linked within unipolar depression, little research has tested links between these two variables within bipolar disorder. The present study tested whether working memory is related to individual differences in emotion regulation strategies in bipolar disorder and whether working memory and emotion regulation can explain variability in symptoms over time. Fifty-nine euthymic adults with bipolar I disorder completed a working memory span task, symptom interviews assessing depression and mania, and questionnaires assessing brooding rumination, reappraisal, and suppression. At baseline, working memory was unrelated to emotion regulation. Symptom interviews were repeated at six months (n = 41) and 12 months (n = 36) follow-up. At 12 months, baseline working memory significantly interacted with baseline suppression to predict higher mania. Tests of simple slopes showed that at lower working memory levels, low use of suppression was associated with significantly greater mania symptoms. These results help to clarify previous inconsistent findings regarding cognitive functioning and emotion regulation strategies in bipolar disorder, suggesting that deficits in both domains combine to predict outcomes.