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

OBJECTIVES: To differentiate the relation between the structure and timing of rest‐activity patterns and symptoms of impulsivity and mood instability in bipolar disorder (BD), borderline personality disorder (BPD) and healthy controls (HC). METHODS: Eighty‐seven participants (31 BD, 21 BPD and 35 HC) underwent actigraph monitoring for 28 days as part of the Automated Monitoring of Symptom Severity (AMoSS) study. Impulsivity was assessed at study entry using the BIS‐11. Mood instability was subsequently longitudinally monitored using the digital Mood Zoom questionnaire. RESULTS: BPD participants show several robust and significant correlations between non‐parametric circadian rest‐activity variables and worsened symptoms. Impulsivity was associated with low interdaily stability (r = −0.663) and weak amplitude (r = −0.616). Mood instability was associated with low interdaily stability (r = −0.773), greater rhythm fragmentation (r = 0.662), weak amplitude (r = −0.694) and later onset of daily activity (r = 0.553). These associations were not present for BD or HCs. Classification analysis using actigraphic measures determined that later L5 onset reliably distinguished BPD from BD and HC but did not sufficiently discriminate between BD and HC. CONCLUSIONS: Rest‐activity pattern disturbance indicative of perturbed sleep and circadian function is an important predictor of symptom severity in BPD. This appears to validate the greater subjective complaints of BPD individuals that are sometimes regarded as exaggerated by clinicians. We suggest that treatment strategies directed towards improving sleep and circadian entrainment may in the future be investigated in BPD.