Correspondence: Actigraphic patterns, impulsivity and mood instability in bipolar disorder, borderline personality disorder and healthy controls.

We would like to commend McGowan and colleagues for their study addressing shared core symptoms of Borderline Personality Disorder (BPD) and Bipolar Disorder (BD) (1). These researchers established significant correlations between dysregulated circadian rest-activity variables (including low interdaily stability and weak amplitude) and symptoms of impulsivity and mood instability among their study participants with BPD. These patterns were neither observed in participants with BD nor in healthy controls. The authors suggest further investigation of sleep symptoms as a future research objective for patients with BPD.