Sleep disturbance and impulsivity are key components of mood vulnerability in bipolar disorder (BD), but few studies have assessed the association between these two symptoms among patients with BD.

Forty-seven euthymic patients with bipolar I disorder (BDI) or bipolar II disorder (BDII) and 58 age- and sex-matched healthy controls were enrolled in this cross-sectional study. Trait impulsivity was measured using the Barratt Impulsiveness Scale Version 11 (BIS-11), which yielded 3 second-order factors: attention, motor, and non-planning. Subjective sleep quality was assessed using the self-reported Pittsburgh Sleep Quality Index (PSQI). General linear models (GLMs) were used to assess the associations between subjective poor sleep and trait impulsivity with multiple testing corrections.

Patients with BD scored higher in BIS-11 and PSQI than healthy controls. PSQI total scores positively correlated with BIS-11 total scores, while sleep disturbance and daytime dysfunction were associated with attentional impulsiveness after controlling for covariates. Participants with higher PSQI total scores (>10) had higher scores in BIS-11 total, attention, and non-planning than those with low PSQI scores (≤5).

These findings support the hypothesis that poor sleep quality might lead to impulsivity and add to the growing evidence that improving sleep quality may be a therapeutic target for patients with BD.

Patients with bipolar disorder (BD) frequently exhibit impulsive behaviors independent of their mood state, and trait impulsivity is increasingly recognized as a crucial BD biomarker. This study aimed to investigate structural correlates of trait impulsivity measured using the Barratt Impulsiveness Scale (BIS) in healthy controls (HCs) and patients with BD.

We recruited 59 patients diagnosed with BD I or BD II (35.3 ± 8.5 years) and 56 age- and sex-matched HCs (33.9 ± 7.4 years). Participants underwent structural magnetic resonance imaging and clinical evaluations, and their BIS scores were evaluated. An automated surface-based method (FreeSurfer) was used to measure cortical thickness and generate thickness maps for each participant. Brain-wise regression analysis of the association between cortical thickness and BIS scores was performed separately for BD and HC groups by using a general linear model.

Patients with BD obtained significantly higher BIS scores than HCs. In HCs, higher BIS scores were associated with a thinner cortex in the left inferior, middle and medial frontal cortices. By contrast, in BD patients, higher BIS scores were associated with a thicker cortex in the right insula. Patients with BD showed a thinner cortex than HCs in all these four structures.

The findings indicate that the left prefrontal cortex plays a cardinal role in trait impulsivity of healthy individuals. Patients with BD have a different structural correlate of trait impulsivity in the right insula. However, the use of various psychotropics in patients with BD may limit our interpretation of BD findings.