Restructuring mood in cyclothymia using cognitive behavior therapy: an intensive time-sampling study.

Hypotheses predicting how cognitive behavioral therapy (CBT) would change the daily pattern of mood and sleep in a patient with cyclothymia were formulated based on circadian processes. Using a prospective single-case experimental design, the patient provided mood ratings every 4 hours and sleep reports daily for 49 weeks, including a 4-week baseline, a 20-session CBT intervention, and a follow-up period. Improvements in mood during and after therapy were accounted for by reduced daily mood variability and extended sleep. The patient's energy at different times of day was explained by adjusting the endogenous rhythm in a mathematical circadian model. Treatment of cyclothymia and related bipolar disorders may be enhanced by integrating understanding of circadian mood regulation into CBT treatment.