Background: Stabilization of rapid-cycling bipolar disorder is extremely difficult.
Methods: A refractory bipolar I rapid-cycling patient on valproate was treated with long "nights" (extended sleep in darkness) and daytime light therapy.
Results: Rapid cycling immediately stopped on initiation of a 10 hour dark/rest period. This was extended to 14 hours (plus a self-selected 1 hour midday nap) without problems. Depression gradually improved when midday light therapy was added; near-euthymia was attained after light therapy was shifted to the morning.
Conclusions: Nonpharmacological chronobiological treatments may be a means to interrupt rapid cycling.