Antidepressant response to sleep deprivation as a function of time into depressive episode in rapidly cycling bipolar patients.

Three patients with treatment-resistant rapidly cycling bipolar disorder were studied with multiple sleep deprivations (SD) during several depressive episodes to assess the effect of phase or duration of a depressive episode on SD response. There was little response to SD early in a depressive episode, but responses were often robust late in an episode, sometimes triggering its termination. In 2 subjects, the duration of antidepressant response to SD increased linearly as time into episode increased. Neither the number of SD given in an episode nor the medication status of the patients appeared to account for the observed increases in antidepressant response. These results suggest that the neurobiological substrates underlying depression may change over the course of an episode, resulting in an increased responsivity to sleep deprivation later compared with earlier in the course of an episode in rapidly cycling patients. The generalizability of these findings to unipolar patients remains to be explored.