Impulsive behaviour is a key characteristic of mania in bipolar disorder (BD). However, there is mixed evidence as to whether impulsivity is a trait feature of the disorder, present in the euthymic state in the absence of mania. The aim of this systematic review and meta-analysis was to examine whether impulsivity is elevated in euthymic BD in comparison to controls. Electronic databases were searched for papers published until April 2022 reporting data on a self-report or behavioural measure of impulsivity in a euthymic BD group and a healthy control group. In total, 46 studies were identified. Euthymic BD showed significantly higher levels of self-reported impulsivity compared to controls (large effect size). Euthymic BD also showed significantly higher levels of impulsivity on response inhibition and inattention tasks, with moderate and large effect sizes, respectively. Only two studies measured delay of gratification, finding no significant differences between groups. Our results suggest impulsivity may be a trait feature of BD, however longitudinal cohort studies are required to confirm whether elevated impulsivity is present before illness onset. Future research should establish whether cognitive interventions are beneficial in improving impulsivity in BD.
Keywords: bipolar disorder; delayed gratification; euthymia; impulsivity; inattention; response inhibition.