DIURNAL-VARIATION IN THE DIRECTION OF MOOD SWITCHES IN PATIENTS WITH RAPID-CYCLING BIPOLAR DISORDER

Background: We assessed diurnal variation in the direction of mood swi tches in a sample of outpatients with rapid-cycling bipolar disorder w ho were on stable medication regimens. We predicted that patients woul d be more likely to switch from depression into mania or hypomania dur ing the daytime hours and from mania/hypomania into depression overnig ht. Method: Fifteen patients with rapid-cycling bipolar disorder compl eted self-rated mood scales twice a day: once shortly after awakening and once at bedtime. Using 3 months of data for each patient, we perfo rmed categorical analyses (McNemar chi-square) to study the direction of mood switches between each day's morning and evening rating and bet ween each evening rating and the subsequent morning rating. Results: A s predicted, switches that occurred between the morning and evening ra tings were more likely to be from depression into mania/hypomania or e uthymia (64.3%) than in the opposite direction (35.6%; p < .0001). Sim ilarly, switches that occurred between the evening rating and the next morning's ratings were more likely to be from mania/hypomania or euth ymia into depression (64.8%) than in the opposite direction (35.2%; p < .0001). Conclusion: Extended wakefulness, exposure to light, increas ed activity, and/or endogenous rhythms could contribute to the elevati on of mood during the course of the day. Sleep, darkness, reduced acti vity, and/or endogenous rhythms could contribute to the tendency to sw itch into depression overnight. Clinicians should attend to the time o f day that clinical assessments are performed in patients with rapid-c ycling bipolar disorder. Potential therapeutic implications include th e use of light or activity during depression and use of induced sleep or exposure to darkness during mania/hypomania.