Background: Early recognition of the prodromal symptoms of bipolar disorder, combined with a patient action plan, may help to prevent relapses. Sleep disturbances are frequent warning signs of both mania and depression. This study used cross correlation analysis to characterize the relationship between mood, sleep and bedrest in longitudinal data.
Methods: Self-reported mood, sleep and bedrest (mean 169 +/- 59 days of data per patient) from 59 outpatients with bipolar disorder receiving standard treatment were analyzed. The cross correlation function was used to determine the latency between the changes in sleep and/or bedrest and mood for time shifts of between -7 and 7 days.
Results: For sleep and/or bedrest, a significant inverse correlation was found with the change in mood, most commonly with a time latency of one day. Sleep plus bedrest had the strongest relationship with a change in mood, with a significant correlation in 24 of 59 patients (41%) for the night before or night of a mood change. The patients with a significant cross-correlation between mood and sleep plus bedrest reported about two thirds of all large sleep changes of >3 h and three fourths of all large mood changes (>20 on 100-unit scale). Patients with a significant cross correlation were more likely to take benzodiazepines.
Conclusion: In most patients with a significant cross correlation between sleep and/or bedrest and mood, the mood change occurred on the day following the change in sleep and/or bedrest. Sleep changes from a previous pattern, especially those of more than 3 h, may indicate that a large mood change is imminent.